Parkinson’s disease is characterized by synucleinopathy-associated neurodegeneration.Previous studies have shown that glucagon-like peptide-1(GLP-1)has beneficial effects in a mouse model of Parkinson’s disease indu...Parkinson’s disease is characterized by synucleinopathy-associated neurodegeneration.Previous studies have shown that glucagon-like peptide-1(GLP-1)has beneficial effects in a mouse model of Parkinson’s disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.However,the effect of GLP-1 on intrinsic synuclein malfunction remains unclear.In this study,we investigated the effect of Lactococcus lactis MG1363-pMG36e-GLP-1 on parkinsonism in SncaA53T transgenic mice and explored the underlying mechanisms.Our data showed that Lactococcus lactis MG1363-pMG36e-GLP-1 inhibited dopaminergic neuronal death,reduced pathological aggregation ofα-synuclein,and decreased movement disorders in SncaA53T transgenic mice.Furthermore,Lactococcus lactis MG1363-pMG36e-GLP-1 downregulated lipopolysaccharide-related inflammation,reduced cerebral activation of microglia and astrocytes,and promoted cell survival via the GLP-1 receptor/PI3K/Akt pathway in the substantia nigra.Additionally,Lactococcus lactis MG1363-pMG36e-GLP-1 decreased serum levels of pro-inflammatory molecules including lipopolysaccharide,lipopolysaccharide binding protein,interleukin-1β,and interleukin-6.Gut histopathology and western blotting further revealed that Lactococcus lactis MG1363-pMG36e-GLP-1 increased the expression of gut integrity-related proteins and reduced lipopolysaccharide-related inflammation by reversing gut dysbiosis in SncaA53T transgenic mice.Our findings showed that the beneficial effect of Lactococcus lactis MG1363-pMG36e-GLP-1 on parkinsonism traits in SncaA53T transgenic mice is mediated by microglial polarization and the reversal of dysbiosis.Collectively,our findings suggest that Lactococcus lactis MG1363-pMG36e-GLP-1 is a promising therapeutic agent for the treatment of Parkinson’s disease.展开更多
Among the low-cost nitrogen sources(dry spent yeast or DSY,rice bran,and soybean meal),DSY was identified as the most suitable supplement for lactic acid fermentation from sweet sorghum juice by Lactococcus lactis IO-...Among the low-cost nitrogen sources(dry spent yeast or DSY,rice bran,and soybean meal),DSY was identified as the most suitable supplement for lactic acid fermentation from sweet sorghum juice by Lactococcus lactis IO-1.However,lactic acid concentration(PL)using DSY was~22%lower than the control nitrogen source,yeast extract(YE).Statistical analysis using YE as a control nitrogen source revealed optimal conditions of 74.70 g/L of initial sugar and 15.20 g/L of YE,achieving a PL of 71.95 g/L and a 91.63%sugar consumption(SC).When DSY(22.61 g/L)containing an equivalent nitrogen content to the optimal YE was tested,PL and SC decreased to 55.13 g/L and 72.33%,respectively.Increasing DSY to 33.92 g/L(1.5 times)improved lactic acid productivity(QL)by~31%but did not enhance PL or SC.However,supplementing 33.92 g/L of DSY with 7.60 g/L of YE enhanced lactic acid production by~19-53%,achieving a PL of 70.11 g/L,SC of 92.33%,QL of 2.34 g/L⋅h,with a high lactic acid yield(YL/S),1.02 g/g.Scale-up fermentation in a 7.5-L fermenter demonstrated comparable results to those using 15.20 g/L of YE alone.These findings demonstrate that sweet sorghum juice supplemented with DSY and reduced YE is a promising medium for efficient lactic acid production,offering significant cost reduction potential for industrial applications while maintaining high productivity and yield.展开更多
Microbial food is an important direction of sustainable food development in the future.Microorganisms such as lactic acid bacteria(LAB)are important sources of natural radioprotectors.Moderate environmental stress can...Microbial food is an important direction of sustainable food development in the future.Microorganisms such as lactic acid bacteria(LAB)are important sources of natural radioprotectors.Moderate environmental stress can induce stress response and improve biological activity of LAB.In the previous study,Lactococcus lactis subsp.lactis IL1403(L.lactis IL1403)cell-free extract induced by ionizing radiation(IR)of 500 Gy(IR-CFE)presented the stronger radioprotective effect than untreated cell-free extract in mice.To explore the radioprotective active substances of IR-CFE,the key protein was screened by proteomics and its radioprotective effect in vivo was further evaluated.The Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment showed that two-component systems(TCS)were enhanced to adapt the IR induction.Meanwhile,the protein LlrG belonged to TCS was screened by the protein-protein interaction.Furthermore,the recombinant protein LlrG(rLlrG)could markedly alleviate the ^(60)Coγ-induced damage to the hematopoietic system,oxidative stress and inflammation in mice,thereby exerting its radioprotective function.These results suggested LlrG protein not only played an important role in the adaptation of L.lactis IL1403 to IR environment,but also exerted a good radioprotective effect,which could be applied in the development of protein-based radioprotectors.展开更多
Salmonella grows better under aerobic conditions as a facultative anaerobic foodborne pathogenic bacteria.The oxygen-scavenging activity of Lactococcus lactis in the intestinal tract is a promising strategy for preven...Salmonella grows better under aerobic conditions as a facultative anaerobic foodborne pathogenic bacteria.The oxygen-scavenging activity of Lactococcus lactis in the intestinal tract is a promising strategy for preventing Salmonella infection.In this study,the aerobic respiration requirement and preventive mechanism of L.lactis subsp.lactis KLDS 4.0325 in murine models infected by Salmonella enterica subsp.enterica serovar Typhimurium(S.Typhimurium)SL1344 were investigated.Results indicate that L.lactis KLDS 4.0325 is capable of aerobic respiratory metabolism in the host intestine when exogenous heme exists,and decrease intestinal oxygen concentration,which in turn trigger autophagy of intestinal cells to reduce S.Typhimurium load,improve gut microbiota composition,alleviate intestinal barrier injury and inflammation response.These results suggest that aerobic respiration L.lactis KLDS 4.0325 can prevent S.Typhimurium infection in a new way in which by restoring intestinal cell hypoxia,maintaining immune balance and regulating intestinal flora.展开更多
Lactococcus lactis,a major starter culture in the dairy industry,has been widely applied in food fermentation.While current research has primarily focused on evaluating its role during fermentation,genomic investigati...Lactococcus lactis,a major starter culture in the dairy industry,has been widely applied in food fermentation.While current research has primarily focused on evaluating its role during fermentation,genomic investigations into its genetic diversity and functional adaptability remain limited.In this study,199 L.lactis strains isolated from Chinese traditional artisanal cheeses(72 bovine,71 goat,and 56 yak milk cheese isolates)were subjected to comparative genomic analysis.Genomic characteristic analysis indicated that bovine milk strains possess larger genomes and the highest number of unique genes.Functional characterization further demonstrated notable differences in carbohydrate metabolism among strains from different sources,with yak milk strains enriched in enzymes involved in complex polysaccharide degradation,including members of the carbohydrate esterases family.Moreover,strains from different sources exhibit distinct strategies for lactose hydrolysis and metabolic utilization,reflecting adaptive evolution to their specific nutritional niches.Analysis of the antibiotic resistance profile suggests that L.lactis predominantly harbors glycopeptide and lincosamide resistance genes,encompassing four distinct resistance mechanisms.Collectively,this study reveals the genetic diversity and adaptive evolution of L.lactis strains from different sources and identifies key genes associated with carbohydrate degradation,lactose metabolism,and antibiotic resistance,providing concrete genetic evidence for the selection of efficient and safe industrial fermentation strains.展开更多
[Objective]The aim was to clone TapⅡchalcone isomerases（CHI1 A） from soybean specially and construct expression vector of PNZ8149-CHI1 A,and then transform it into Lactococcus Lactis NICE systers.[Method]Chalcone i...[Objective]The aim was to clone TapⅡchalcone isomerases（CHI1 A） from soybean specially and construct expression vector of PNZ8149-CHI1 A,and then transform it into Lactococcus Lactis NICE systers.[Method]Chalcone isomerases（CHI1 A） was cloned by RTPCR method,and it was sequenced after cloning into pMD18-T vectors,and recombined to expression vector PNZ8149-CHI1 A,then it was transformed into Lactococcus Lactis NZ3900[Result]The sequencing results indicated that the cloned fragment of CHI1 A contained 670 nucleotides,and shared a sequence homology of 92% with that from Genbank accession number AF595413（CHI1 A）.CHI1 A was transformed into NICE expression system successfully by identification of PCR and digestion.[Conclusion]The foundation of using the microorganism fermentation method to produce flavonoids was laid by construction of efficient induction expression vector with chalcone isomerases CHI1 A.展开更多
Objective To construct four recombinant Lactococcus lactis strains exhibiting high β-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion....Objective To construct four recombinant Lactococcus lactis strains exhibiting high β-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion. Methods The gene fragments encoding β-galactosidase from two strains of Loctobacillus bulgaricus, wch9901 isolated from yogurt and 1.1480 purchased from the Chinese Academy of Sciences, were amplified and inserted into lactococcal expression vector pMG36e. For fusion expression, the open reading frame of the β-galactosidase gene was amplified, while for non-fusion expression, the open reading frame of the β-galactosidase gene was amplified with its native Shine-Dalgarno sequence upstream. The start codon of the β-galactosidase gene partially overlapped with the stop codon of vector origin open reading frame. Then, the recombinant plasmids were transformed into Escherichia coli DH5α and Lactococcus lactis subsp, lactis MG1363 and confirmed by determining β-galactosidase activities. Results The non-fusion expression plasmids showed a significantly higher β-galactosidase activity in transformed strains than the fusion expression plasmids. The highest enzyme activity was observed in Lactococcus lactis transformed with the non-fusion expression plasmids which were inserted into the β-galactosidase gene from Lactobacillus bulgaricus wch9901. The β-galactosidase activity was 2.75 times as high as that of the native counterpart. In addition, β-galactosidase expressed by recombinant plasmids in Lactococcus lactis could be secreted into the culture medium. The highest secretion rate （27.1%） was observed when the culture medium contained 20 g/L of lactose. Conclusion Different properties of the native bacteria may have some effects on the protein expression of recombinant plasmids. Non-fusion expression shows a higher enzyme activity in host bacteria. There may be a host-related weak secretion signal peptide gene within the structure gene of Lb. bulgaricus β-galactosidase, and its translation product may introduce the enzyme secretion out of cells in special hosts.展开更多
Objective This study is to examine the secretion effects of β-galactosidase in Lactococcus lactis.Methods The usp45 and β-galactosidase genes were cloned and inserted into plasmid pMG36e to obtain the recombinant pl...Objective This study is to examine the secretion effects of β-galactosidase in Lactococcus lactis.Methods The usp45 and β-galactosidase genes were cloned and inserted into plasmid pMG36e to obtain the recombinant plasmid pMG36e-usp-lacZ.This recombinant plasmid was transformed into both Escherichia coli DH5α and L.lactis MG1363.The enzyme activity,gene sequencing,SDS-PAGE and hereditary stability were assessed and studied.Results The lacZ gene inserted into plasmids pMG36e-usp-lacZ was 99.37% similar to the GenBank sequence,and SDS-PAGE revealed an evident idio-strap at 116 KDa between L.lactis MG1363/pMG36eusp-lacZ in both supernatant and cell samples.β-Galactosidase activity measured 0.225 U/mL in L.lactis pMG36e-usp-lacZ transformants,and its secretion rate was 10%.The plasmid pMG36e-usp-lacZ appeared more stable in MG1363.Conclusion The authors concluded that these new recombinant bacteria well expressed and secreted β-galactosidase,indicating that the β-galactosidase expression system was successfully constructed,and this might provide a new solution for management of lactose intolerance specifically and promote the use of gene-modified organisms as part of the food-grade plasmid in general.展开更多
AIM： To construct the recombinant Lactococcus/actis as oral delivery vaccination against malaria. METHODS： The C-terminal 19-ku fragments of MSP1 （MSP-119） of Plasmodium yoelii265-BY was expressed in L. lactis and...AIM： To construct the recombinant Lactococcus/actis as oral delivery vaccination against malaria. METHODS： The C-terminal 19-ku fragments of MSP1 （MSP-119） of Plasmodium yoelii265-BY was expressed in L. lactis and the recombinant L. lact/s was administered orally to BALB/c and C57BL/6 mice. After seven interval vaccinations within 4 wk, the mice were challenged with P. yoelii 265-BY parasites of erythroo/tic stage. The protective efficacy of recombinant L. lactiswas evaluated. RESULTS： The peak parasitemias in average for the experiment groups of BALB/c and C57BL/6 mice were 0.8± 0.4% and 20.8±26.5%, respectively, and those of their control groups were 12.0±0.8% and 60.8±9.6%, respectively. None of the BALB/c mice in both experimental group and control group died during the experiment. However, all the C57BL/6 mice in the control group died within 23 d and all the vaccinated mice survived well. CONCLUSION： The results imply the potential of recombinant L. lactis as oral delivery vaccination against malaria.展开更多
To evaluate the specific immune responses induced by recombinant Lactococcus lactis（L.lactis） which expresses porcine epidemic diarrhea virus（PEDV） S1 protein through oral administration,the spike gene fragment of...To evaluate the specific immune responses induced by recombinant Lactococcus lactis（L.lactis） which expresses porcine epidemic diarrhea virus（PEDV） S1 protein through oral administration,the spike gene fragment of PEDV was amplified from PEDV SDLY strain to construct p MG36 e-S1 recombinant plasmid.The recombinant plasmid was then electro-transferred into competent cells of L.lactis MG1363,to prepare the recombinant L.lactis expressing S1 protein of PEDV.The expression of target protein was identified by SDS-PAGE and Western-blot.New Zealand white rabbits were orally administered with the recombinant strain;the antibody titer in intestinal mucosa and serum was detected by neutralizing test;and the specific Ig G in serum was evaluated by indirect ELISA.The results showed that the recombinant L.lactis could effectively induce high level of Ig G in serum and high level of mucosal immune antibody.The recombinant L.lactis is qualified to be a potential oral vaccine because it could successfully stimulate both humoral and mucosal immune responses against PEDV.展开更多
Objective:To determine the inhibition mechanisms of secretome protein extracted from Paenibacillus polymyxa Kp10(Kp10)and Lactococcus lactis Gh1(Gh1)against methicillin-resistant Staphylococcus aureus(MRSA)and vancomy...Objective:To determine the inhibition mechanisms of secretome protein extracted from Paenibacillus polymyxa Kp10(Kp10)and Lactococcus lactis Gh1(Gh1)against methicillin-resistant Staphylococcus aureus(MRSA)and vancomycin-resistant Enterococcus(VRE).Methods:The sensitivity and viability of MRSA and VRE treated with secretome proteins of Kp10 and Gh1 were determined using minimal inhibitory concentration,minimum bactericidal concentration,and time-to-kill assays.The morphological changes were observed using scanning electron microscopy and transmission electron microscopy.To elucidate the antimicrobial mechanism of secretome protein of Kp10 and Gh1 against MRSA and VRE,2D gel proteomic analysis using liquid chromatography-mass spectrometry was run by comparing upregulated and downregulated proteins,and the proton motive force study including the efflux of ATP,pH gradient,and the membrane potential study were conducted.Results:MRSA and VRE were sensitive to Kp10 and Gh1 secretome protein extracts and displayed apparent morphological and internal composition changes.Several proteins associated with cellular component functions were either downregulated or upregulated in treated MRSA and VRE by changing the membrane potential gradient.Conclusions:Kp10 and Gh1 secretome proteins reduce the growth of VRE and MRSA by damaging the cell membrane.Cell division,cell wall biosynthesis,and protein synthesis are involved in the inhibition mechanism.展开更多
[Objective]The paper was to study the improvement of poplar bark extract on intestinal Lactococcus lactis of white feather broilers.[Method]Totally 450 Ross 308 white-feather broilers were randomly divided into five g...[Objective]The paper was to study the improvement of poplar bark extract on intestinal Lactococcus lactis of white feather broilers.[Method]Totally 450 Ross 308 white-feather broilers were randomly divided into five groups:control group,low dose group,medium dose group,high dose group,and antibiotic group(oxytetracycline hydrochloride).The feeding duration was 45 d.The probiotics were screened and isolated through homology,and the physiological and biochemical characteristics of chicken intestinal bacteria in different groups were compared to determine the properties of bacterial strain.The drug resistance,antibacterial ability,proliferation ability,acid resistance and bile salt resistance of isolated strain were tested,and a strain of L.lactis was obtained.[Result]The isolated L.lactis was sensitive to other drugs except natural tetracyclines,and there was no significant difference among the four groups except oxytetracycline group;as the concentration of extract increased,the inhibition of L.lactis against Salmonella sp.increased;the medium dose extract had the largest increase in the ability to tolerate the proliferation of L.lactis.[Conclusion]Feeding poplar bark extract will produce positive effects on the physiological characters of intestinal L.lactis in broiler chicken,which will provide potential probiotic strain for chicken production.展开更多
Oxidative stress has been strongly related with Alzheimer disease pathogenesis. We determined the effects of watermelon powder (WMP) and Lactococcus lactis subsp lactis (LAL) supplementation on the generated Aβ42-ind...Oxidative stress has been strongly related with Alzheimer disease pathogenesis. We determined the effects of watermelon powder (WMP) and Lactococcus lactis subsp lactis (LAL) supplementation on the generated Aβ42-induced phenotypes in a Drosophila melanogaster model of AD. Enhanced Aβ42 expression in D. melanogaster neurons can diminish lifespan and flight ability. We have observed longevity methods to assay the effects of WMP and LAL on D. melanogaster survival. Furthermore, flies expressing Aβ42 in their body fed WMP and LAL had up to 90 days, or 35% longer median lifespan than those fed a control diet. In addition, synergistic effect of WMP and LAL improved Aβ42-induced flight impairments in the Drosophila wing tissues. Our microscope experiments revealed that individuals fed synergistic effect of WMP and LAL had ameliorated Aβ42 expression as well as increment of flight ability than Aβ42-induced flies. We propose that WMP is typically rich in L-citrulline and LAL, rich in naturally occurring probiotics and antioxidants, and that it promotes the survival of neurons in brain and wing muscle tissues with increased levels of Aβ42 via a protective cell survival mechanism.展开更多
This study evaluated the probiotic potential of Lactococcus lactis strain DMLL15,previously selected as a starter candidate based on safety and enzymatic activity.Antifungal efficacy was further investigated.Strain DM...This study evaluated the probiotic potential of Lactococcus lactis strain DMLL15,previously selected as a starter candidate based on safety and enzymatic activity.Antifungal efficacy was further investigated.Strain DML15 exhibited 98.44%bile tolerance and 89.70%acid tolerance under conditions of 0.3%(w/v)oxgall and pH 2.5,respectively,and showed 86.46%mucin-binding ability.These results were significantly superior to those of the reference strain L.lactis KACC 13877^(ᵀ),which showed 88.93%,87.59%,and 80.83%,respectively.In addition,antifungal activity was observed against Cladosporium herbarum KACC 47604,Clonostachys rosea KACC 40320,and Epicoccum nigrum KACC 47166,with inhibition zones of 4.58±0.15 mm,3.55±0.55 mm,and 6.38±0.35 mm,respectively.These activities were higher than those of the reference strain L.lactis KACC 13877^(ᵀ).Whole-genome analysis identified genes associated with safety,enzymatic activity,health benefits,and antimicrobial activity.Notably,strain DMLL15 uniquely harbors an exopolysaccharide biosynthesis operon(AAE362_RS00370-AAE362_RS00440)that may enhance survival under acidic or bile-rich conditions,as well as genes encoding endothelin-converting enzyme,RecA proteins,neutral endopeptidases,and the oligopeptide-binding protein OppA.In addition,the strain possesses the nisin operon,contributing to its antimicrobial po-tential.These genomic insights,together with functional assessments,support the use of strain DMLL15 as a starter culture and probiotic candidate for food applications.展开更多
The ability of Lactococcus lactis to grow under moderate oxygen conditions enables its expansion from the food industry to microbial cell factories.While leveraging known antioxidative regulatory mechanisms represents...The ability of Lactococcus lactis to grow under moderate oxygen conditions enables its expansion from the food industry to microbial cell factories.While leveraging known antioxidative regulatory mechanisms represents a promising strategy for engineering robust strains under high oxygen conditions,the complete genetic basis of oxygen tolerance in L.lactis remains incompletely understood.Here,we identified and characterized a novel antioxidative system and its corresponding regulatory mechanism in L.lactis N8.Genetic analyses demonstrated that RmaH,a MarR-family transcriptional regulator,is essential for mediating the oxidative stress response.Transcriptomic and qPCR analysis further revealed that RmaH acts as a transcriptional repressor of dps,which encodes a DNA-binding protein from starved cells(Dps).In vitro and in vivo protein-DNA binding assays confirmed that RmaH specifically binds to the coding sequence(CDS)of dps,with DNase I footprinting precisely identifying the binding motif(TGTAAG-12nt-CTTTCA).Finally,functional investigations revealed that under oxygen conditions,RmaH expression was suppressed,leading to upregulated dps expression.Dps thereby confers cellular protection via two distinct mechanisms:physically shielding DNA from hydroxyl radicals and inhibiting the Fenton reaction through its ferroxidase activity.Collectively,our findings elucidated a previously uncharacterized RmaH-Dps regulatory pathway that enhances oxygen tolerance in L.lactis,providing both mechanistic insight and a potential target for engineering industrially robust strains.展开更多
Lactococcus lactis is used as a starter for fermented milk,particularly in traditional cheese products.In this study,the anti-Listeria monocytogenes(Lm)activity of 32 coast-isolated Lc.lactis strains was compared to t...Lactococcus lactis is used as a starter for fermented milk,particularly in traditional cheese products.In this study,the anti-Listeria monocytogenes(Lm)activity of 32 coast-isolated Lc.lactis strains was compared to that of the typical nisin A-producing strain NBRC 12007 using the overlay plate assay,to identify a novel Lc.lactis starter with beneficial properties.The 10 isolates exhibited anti-Lm activity greater than that of NBRC 12007.Among them,the isolate Nagasaki-SU6 was selected based on its anti-Lm and cow-and soymilk fermentation activity.Cow-and soymilk were inoculated with 7 log CFU/mL Lm,with or without fermentation using NBRC 12007 and Nagasaki-SU6 at 37◦C for 48 h.The fermentation and anti-Lm activities of Nagasaki-SU6 were significantly greater than those of NBRC 12007.In the case of soymilk fermented with Nagasaki-SU6,the Lm viable count decreased by 2.8 log CFU/mL The fermented samples were inoculated with Lm and stored at 10◦C for 14 d.In Nagasaki-SU6 fermented samples,Lm growth was suppressed both in fermented cow milk and reduced in soymilk.Whole genome sequencing revealed the presence of nisin Z and sucrose PTS pathway genes in Nagasaki-SU6.However,the type and number of drug resistance and virulence genes in Nagasaki-SU6 did not differ from those in the type strain and NBRC 12007.These results suggest that Nagasaki-SU6 can be used as a desirable starter not only in cow milk but also in plant-based milk alternatives.展开更多
Nisin is a ribosomally synthesized and post-translationally modified peptide(RiPP)bacteriocin produced by Lactococcus lactis that holds significant value in food preservation and medicine.Although extensive research h...Nisin is a ribosomally synthesized and post-translationally modified peptide(RiPP)bacteriocin produced by Lactococcus lactis that holds significant value in food preservation and medicine.Although extensive research has centred on optimizing its native biosynthetic machinery,the possibility of metabolic competition between nisin biosynthesis and other secondary metabolic processes,such as those encoded by nonribosomal synthesis pathways,has been overlooked.In this study,we reveal that a nonribosomal peptide synthetase-polyketide synthase(NRPS-PKS)gene cluster in L.lactis acts as a potent negative regulator of nisin biosynthesis.Comparative transcriptomics revealed a striking inverse correlation in the expression of the two gene clusters.Genetic disruption of the NRPS-PKS cluster or its specific regulatory genes(npkK and npkR)dramatically increased nisin production by 8.1%,an effect that was reversible upon genetic complementation.Moreover,high-producing NRPS-PKS knockout mutants exhibited altered sensitivity to a broad spectrum of stressors.We further identi-fied the global carbon catabolite regulator CcpA as a key mediator of this interaction.Integrated transcriptomic and proteomic analyses suggested that the NRPS-PKS pathway exerts its suppressive effect primarily by competing for essential cellular resources-precursor amino acids,ATP,and the lipid carrier undecaprenyl-phosphate-thereby starving the nisin biosynthetic machinery.Our work uncovers a competitive dynamic between ribosomal and non-ribosomal biosynthetic systems and provides a novel metabolic engineering strategy for enhancing industrial nisin production by targeting the NRPS-PKS cluster for inactivation.展开更多
A novel strain of Lactococcus lactis grx602,exhibiting both intracellular and extracellular lipase activity,was isolated from raw milk using a selective medium with butter as the sole carbon source.Both intracellular ...A novel strain of Lactococcus lactis grx602,exhibiting both intracellular and extracellular lipase activity,was isolated from raw milk using a selective medium with butter as the sole carbon source.Both intracellular and extracellular lipase activity shared identical optimal reaction conditions including substrate,pH,temperature and NaCl concentration.Fermentation with L.lactis grx602 modified the fatty acids profile and raised the acid value by 0.48 mg/mL.L.lactis grx602 also demonstrated promising probiotic traits,including acid tolerance,bile salt resistance,and cholesterol-lowering ability.When applied to prepare Lg-sour cream,L.lactis grx602 significantly enhanced the key quality attributes,including physicochemical properties,structural integrity,flavor profile,and nutritional value.The comprehensive performance of L.lactis grx602 indicated its substantial potential as a multifunctional starter culture for developing functional dairy products.展开更多
Sufu,a traditional fermented soybean curd,is prone to contamination by Bacillus cereus.In this study,133 lactic acid bacteria(LAB)strains were initially screened from spring and winter Mao-tofu samples for their abili...Sufu,a traditional fermented soybean curd,is prone to contamination by Bacillus cereus.In this study,133 lactic acid bacteria(LAB)strains were initially screened from spring and winter Mao-tofu samples for their ability to inhibit the growth of B.cereus ATCC 14579T.Among these strains,five Lactococcus lactis strains exhibited a good safety profile and were capable of growing in pH 4-9 and salt concentrations of 6%-8%.Antimicrobial experiments conducted on the B.cereus group from sufu factories showed that L.lactis LJL7m20 strain had the strongest inhibitory effect.Whole-genome sequencing revealed the presence of three genes associated with high osmotic stress response and eight distinct two-component systems that may contribute to the strain’s tolerance,enhancing its survival in high-salt environments.The strain was further identified as L.lactis subsp.lactis through a combination of phenotypic and genotypic analysis.Additionally,bacteriocins nisin Z and nisin A/Q were identified using the BAGEL4 and antiSMASH databases.ELISA further confirmed the strain’s ability to produce nisin.A fermentation validation study demonstrated that inoculation with the strain contributed to reduce the number of B.cereus group in sufu pehtzes.This study provides a theoretical foundation for the use of new biocontrol bacteria to improve the safety of traditional fermented soybean foods.展开更多
基金supported by grants from the Jiangxi Provincial Natural Science Foundation,No.20242BAB26134(to XF)the National Natural Science Foundation of China,Nos.82060638(to TC),82060222(to XF),82460237(to XF)+1 种基金the Major Disciplines of Academic and Technical Leaders Project of Jiangxi Province,Nos.20194BCJ22032(to TC),20213BCJL22049(to XF)Science and Technology Plan of Jiangxi Health Planning Committee,No.202210390(to XF).
文摘Parkinson’s disease is characterized by synucleinopathy-associated neurodegeneration.Previous studies have shown that glucagon-like peptide-1(GLP-1)has beneficial effects in a mouse model of Parkinson’s disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.However,the effect of GLP-1 on intrinsic synuclein malfunction remains unclear.In this study,we investigated the effect of Lactococcus lactis MG1363-pMG36e-GLP-1 on parkinsonism in SncaA53T transgenic mice and explored the underlying mechanisms.Our data showed that Lactococcus lactis MG1363-pMG36e-GLP-1 inhibited dopaminergic neuronal death,reduced pathological aggregation ofα-synuclein,and decreased movement disorders in SncaA53T transgenic mice.Furthermore,Lactococcus lactis MG1363-pMG36e-GLP-1 downregulated lipopolysaccharide-related inflammation,reduced cerebral activation of microglia and astrocytes,and promoted cell survival via the GLP-1 receptor/PI3K/Akt pathway in the substantia nigra.Additionally,Lactococcus lactis MG1363-pMG36e-GLP-1 decreased serum levels of pro-inflammatory molecules including lipopolysaccharide,lipopolysaccharide binding protein,interleukin-1β,and interleukin-6.Gut histopathology and western blotting further revealed that Lactococcus lactis MG1363-pMG36e-GLP-1 increased the expression of gut integrity-related proteins and reduced lipopolysaccharide-related inflammation by reversing gut dysbiosis in SncaA53T transgenic mice.Our findings showed that the beneficial effect of Lactococcus lactis MG1363-pMG36e-GLP-1 on parkinsonism traits in SncaA53T transgenic mice is mediated by microglial polarization and the reversal of dysbiosis.Collectively,our findings suggest that Lactococcus lactis MG1363-pMG36e-GLP-1 is a promising therapeutic agent for the treatment of Parkinson’s disease.
基金supported by Research Program Funding,from Research and Innovation Department,Khon Kaen University(RP68-6-FerVAAP-001),ThailandThe authors also thank Beer Thip Brewery Co.,Ltd.,Phra Nakhon Si Ayutthaya,Thailand for providing dried spent yeast(DSY).
文摘Among the low-cost nitrogen sources(dry spent yeast or DSY,rice bran,and soybean meal),DSY was identified as the most suitable supplement for lactic acid fermentation from sweet sorghum juice by Lactococcus lactis IO-1.However,lactic acid concentration(PL)using DSY was~22%lower than the control nitrogen source,yeast extract(YE).Statistical analysis using YE as a control nitrogen source revealed optimal conditions of 74.70 g/L of initial sugar and 15.20 g/L of YE,achieving a PL of 71.95 g/L and a 91.63%sugar consumption(SC).When DSY(22.61 g/L)containing an equivalent nitrogen content to the optimal YE was tested,PL and SC decreased to 55.13 g/L and 72.33%,respectively.Increasing DSY to 33.92 g/L(1.5 times)improved lactic acid productivity(QL)by~31%but did not enhance PL or SC.However,supplementing 33.92 g/L of DSY with 7.60 g/L of YE enhanced lactic acid production by~19-53%,achieving a PL of 70.11 g/L,SC of 92.33%,QL of 2.34 g/L⋅h,with a high lactic acid yield(YL/S),1.02 g/g.Scale-up fermentation in a 7.5-L fermenter demonstrated comparable results to those using 15.20 g/L of YE alone.These findings demonstrate that sweet sorghum juice supplemented with DSY and reduced YE is a promising medium for efficient lactic acid production,offering significant cost reduction potential for industrial applications while maintaining high productivity and yield.
基金supported by the National Natural Science Foundation of China(32172211,32572557)the Key Science Research Projects of Higher Education Institutions in Henan Province(21A530006)+3 种基金the Key Research and Development and Promotion Projects of Henan Province(232102310293)the Henan Provincial Natural Science Foundation General Program(252300421403)the Zhongyuan Sci-Tech Innovation Leading Talents(254200510040)the Innovative Research Team(in Science and Technology)in University of Henan Province(26IRTSTHN030).
文摘Microbial food is an important direction of sustainable food development in the future.Microorganisms such as lactic acid bacteria(LAB)are important sources of natural radioprotectors.Moderate environmental stress can induce stress response and improve biological activity of LAB.In the previous study,Lactococcus lactis subsp.lactis IL1403(L.lactis IL1403)cell-free extract induced by ionizing radiation(IR)of 500 Gy(IR-CFE)presented the stronger radioprotective effect than untreated cell-free extract in mice.To explore the radioprotective active substances of IR-CFE,the key protein was screened by proteomics and its radioprotective effect in vivo was further evaluated.The Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment showed that two-component systems(TCS)were enhanced to adapt the IR induction.Meanwhile,the protein LlrG belonged to TCS was screened by the protein-protein interaction.Furthermore,the recombinant protein LlrG(rLlrG)could markedly alleviate the ^(60)Coγ-induced damage to the hematopoietic system,oxidative stress and inflammation in mice,thereby exerting its radioprotective function.These results suggested LlrG protein not only played an important role in the adaptation of L.lactis IL1403 to IR environment,but also exerted a good radioprotective effect,which could be applied in the development of protein-based radioprotectors.
基金supported by the National Natural Science Foundation of China(32072190 and 32101929)Academic Backbone Plan of Northeast Agricultural University(20XG12)。
文摘Salmonella grows better under aerobic conditions as a facultative anaerobic foodborne pathogenic bacteria.The oxygen-scavenging activity of Lactococcus lactis in the intestinal tract is a promising strategy for preventing Salmonella infection.In this study,the aerobic respiration requirement and preventive mechanism of L.lactis subsp.lactis KLDS 4.0325 in murine models infected by Salmonella enterica subsp.enterica serovar Typhimurium(S.Typhimurium)SL1344 were investigated.Results indicate that L.lactis KLDS 4.0325 is capable of aerobic respiratory metabolism in the host intestine when exogenous heme exists,and decrease intestinal oxygen concentration,which in turn trigger autophagy of intestinal cells to reduce S.Typhimurium load,improve gut microbiota composition,alleviate intestinal barrier injury and inflammation response.These results suggest that aerobic respiration L.lactis KLDS 4.0325 can prevent S.Typhimurium infection in a new way in which by restoring intestinal cell hypoxia,maintaining immune balance and regulating intestinal flora.
基金supported by the National Key Research and Development Project(2022YFD2100703)the National Natural Science Foundation of China(32394051 and U23A20259)the Fundamental Research Funds for the Central Universities(JUSRP622013).
文摘Lactococcus lactis,a major starter culture in the dairy industry,has been widely applied in food fermentation.While current research has primarily focused on evaluating its role during fermentation,genomic investigations into its genetic diversity and functional adaptability remain limited.In this study,199 L.lactis strains isolated from Chinese traditional artisanal cheeses(72 bovine,71 goat,and 56 yak milk cheese isolates)were subjected to comparative genomic analysis.Genomic characteristic analysis indicated that bovine milk strains possess larger genomes and the highest number of unique genes.Functional characterization further demonstrated notable differences in carbohydrate metabolism among strains from different sources,with yak milk strains enriched in enzymes involved in complex polysaccharide degradation,including members of the carbohydrate esterases family.Moreover,strains from different sources exhibit distinct strategies for lactose hydrolysis and metabolic utilization,reflecting adaptive evolution to their specific nutritional niches.Analysis of the antibiotic resistance profile suggests that L.lactis predominantly harbors glycopeptide and lincosamide resistance genes,encompassing four distinct resistance mechanisms.Collectively,this study reveals the genetic diversity and adaptive evolution of L.lactis strains from different sources and identifies key genes associated with carbohydrate degradation,lactose metabolism,and antibiotic resistance,providing concrete genetic evidence for the selection of efficient and safe industrial fermentation strains.
文摘[Objective]The aim was to clone TapⅡchalcone isomerases（CHI1 A） from soybean specially and construct expression vector of PNZ8149-CHI1 A,and then transform it into Lactococcus Lactis NICE systers.[Method]Chalcone isomerases（CHI1 A） was cloned by RTPCR method,and it was sequenced after cloning into pMD18-T vectors,and recombined to expression vector PNZ8149-CHI1 A,then it was transformed into Lactococcus Lactis NZ3900[Result]The sequencing results indicated that the cloned fragment of CHI1 A contained 670 nucleotides,and shared a sequence homology of 92% with that from Genbank accession number AF595413（CHI1 A）.CHI1 A was transformed into NICE expression system successfully by identification of PCR and digestion.[Conclusion]The foundation of using the microorganism fermentation method to produce flavonoids was laid by construction of efficient induction expression vector with chalcone isomerases CHI1 A.
基金a scientific research grant from Health Bureau of Sichuan Province (No. F0201)
文摘Objective To construct four recombinant Lactococcus lactis strains exhibiting high β-galactosidase activity in fusion or non-fusion ways, and to study the influence factors for their protein expression and secretion. Methods The gene fragments encoding β-galactosidase from two strains of Loctobacillus bulgaricus, wch9901 isolated from yogurt and 1.1480 purchased from the Chinese Academy of Sciences, were amplified and inserted into lactococcal expression vector pMG36e. For fusion expression, the open reading frame of the β-galactosidase gene was amplified, while for non-fusion expression, the open reading frame of the β-galactosidase gene was amplified with its native Shine-Dalgarno sequence upstream. The start codon of the β-galactosidase gene partially overlapped with the stop codon of vector origin open reading frame. Then, the recombinant plasmids were transformed into Escherichia coli DH5α and Lactococcus lactis subsp, lactis MG1363 and confirmed by determining β-galactosidase activities. Results The non-fusion expression plasmids showed a significantly higher β-galactosidase activity in transformed strains than the fusion expression plasmids. The highest enzyme activity was observed in Lactococcus lactis transformed with the non-fusion expression plasmids which were inserted into the β-galactosidase gene from Lactobacillus bulgaricus wch9901. The β-galactosidase activity was 2.75 times as high as that of the native counterpart. In addition, β-galactosidase expressed by recombinant plasmids in Lactococcus lactis could be secreted into the culture medium. The highest secretion rate （27.1%） was observed when the culture medium contained 20 g/L of lactose. Conclusion Different properties of the native bacteria may have some effects on the protein expression of recombinant plasmids. Non-fusion expression shows a higher enzyme activity in host bacteria. There may be a host-related weak secretion signal peptide gene within the structure gene of Lb. bulgaricus β-galactosidase, and its translation product may introduce the enzyme secretion out of cells in special hosts.
基金supported by the National Science Foundation of China (NO. 30800910)
文摘Objective This study is to examine the secretion effects of β-galactosidase in Lactococcus lactis.Methods The usp45 and β-galactosidase genes were cloned and inserted into plasmid pMG36e to obtain the recombinant plasmid pMG36e-usp-lacZ.This recombinant plasmid was transformed into both Escherichia coli DH5α and L.lactis MG1363.The enzyme activity,gene sequencing,SDS-PAGE and hereditary stability were assessed and studied.Results The lacZ gene inserted into plasmids pMG36e-usp-lacZ was 99.37% similar to the GenBank sequence,and SDS-PAGE revealed an evident idio-strap at 116 KDa between L.lactis MG1363/pMG36eusp-lacZ in both supernatant and cell samples.β-Galactosidase activity measured 0.225 U/mL in L.lactis pMG36e-usp-lacZ transformants,and its secretion rate was 10%.The plasmid pMG36e-usp-lacZ appeared more stable in MG1363.Conclusion The authors concluded that these new recombinant bacteria well expressed and secreted β-galactosidase,indicating that the β-galactosidase expression system was successfully constructed,and this might provide a new solution for management of lactose intolerance specifically and promote the use of gene-modified organisms as part of the food-grade plasmid in general.
基金Supported by the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), No.980198
文摘AIM： To construct the recombinant Lactococcus/actis as oral delivery vaccination against malaria. METHODS： The C-terminal 19-ku fragments of MSP1 （MSP-119） of Plasmodium yoelii265-BY was expressed in L. lactis and the recombinant L. lact/s was administered orally to BALB/c and C57BL/6 mice. After seven interval vaccinations within 4 wk, the mice were challenged with P. yoelii 265-BY parasites of erythroo/tic stage. The protective efficacy of recombinant L. lactiswas evaluated. RESULTS： The peak parasitemias in average for the experiment groups of BALB/c and C57BL/6 mice were 0.8± 0.4% and 20.8±26.5%, respectively, and those of their control groups were 12.0±0.8% and 60.8±9.6%, respectively. None of the BALB/c mice in both experimental group and control group died during the experiment. However, all the C57BL/6 mice in the control group died within 23 d and all the vaccinated mice survived well. CONCLUSION： The results imply the potential of recombinant L. lactis as oral delivery vaccination against malaria.
基金Supported by Priority Academic Talent Team Cultivation Program of Shandong Colleges and Universities and Agricultural Industry Research System of Shandong Province(SDAIT-06-022-08)People’s Livelihood Science and Technology Program of Qingdao City(16-6-2-42-nsh)
文摘To evaluate the specific immune responses induced by recombinant Lactococcus lactis（L.lactis） which expresses porcine epidemic diarrhea virus（PEDV） S1 protein through oral administration,the spike gene fragment of PEDV was amplified from PEDV SDLY strain to construct p MG36 e-S1 recombinant plasmid.The recombinant plasmid was then electro-transferred into competent cells of L.lactis MG1363,to prepare the recombinant L.lactis expressing S1 protein of PEDV.The expression of target protein was identified by SDS-PAGE and Western-blot.New Zealand white rabbits were orally administered with the recombinant strain;the antibody titer in intestinal mucosa and serum was detected by neutralizing test;and the specific Ig G in serum was evaluated by indirect ELISA.The results showed that the recombinant L.lactis could effectively induce high level of Ig G in serum and high level of mucosal immune antibody.The recombinant L.lactis is qualified to be a potential oral vaccine because it could successfully stimulate both humoral and mucosal immune responses against PEDV.
基金supported by the funds of Ministry of Higher Education,Malaysia and Universiti Putra Malaysia through Fundamental Research Grant Scheme (FRGS/1/2017/SKK11/UPM/01/1) and Putra Grant (GP/2017/9571800)
文摘Objective:To determine the inhibition mechanisms of secretome protein extracted from Paenibacillus polymyxa Kp10(Kp10)and Lactococcus lactis Gh1(Gh1)against methicillin-resistant Staphylococcus aureus(MRSA)and vancomycin-resistant Enterococcus(VRE).Methods:The sensitivity and viability of MRSA and VRE treated with secretome proteins of Kp10 and Gh1 were determined using minimal inhibitory concentration,minimum bactericidal concentration,and time-to-kill assays.The morphological changes were observed using scanning electron microscopy and transmission electron microscopy.To elucidate the antimicrobial mechanism of secretome protein of Kp10 and Gh1 against MRSA and VRE,2D gel proteomic analysis using liquid chromatography-mass spectrometry was run by comparing upregulated and downregulated proteins,and the proton motive force study including the efflux of ATP,pH gradient,and the membrane potential study were conducted.Results:MRSA and VRE were sensitive to Kp10 and Gh1 secretome protein extracts and displayed apparent morphological and internal composition changes.Several proteins associated with cellular component functions were either downregulated or upregulated in treated MRSA and VRE by changing the membrane potential gradient.Conclusions:Kp10 and Gh1 secretome proteins reduce the growth of VRE and MRSA by damaging the cell membrane.Cell division,cell wall biosynthesis,and protein synthesis are involved in the inhibition mechanism.
基金Supported by Forestry Science and Technology Innovation and Promotion Project of Jiangsu Province(LYKJ[201N]46)Cultivation Project of Jiangsu Vocational College of Agriculture and Forestry(2018KJ27)Innovation and Entrepreneurs hi p Training Program for College Students"Assessment of Food Palatability of Pet Dogs and Cats"(20193103003Y).
文摘[Objective]The paper was to study the improvement of poplar bark extract on intestinal Lactococcus lactis of white feather broilers.[Method]Totally 450 Ross 308 white-feather broilers were randomly divided into five groups:control group,low dose group,medium dose group,high dose group,and antibiotic group(oxytetracycline hydrochloride).The feeding duration was 45 d.The probiotics were screened and isolated through homology,and the physiological and biochemical characteristics of chicken intestinal bacteria in different groups were compared to determine the properties of bacterial strain.The drug resistance,antibacterial ability,proliferation ability,acid resistance and bile salt resistance of isolated strain were tested,and a strain of L.lactis was obtained.[Result]The isolated L.lactis was sensitive to other drugs except natural tetracyclines,and there was no significant difference among the four groups except oxytetracycline group;as the concentration of extract increased,the inhibition of L.lactis against Salmonella sp.increased;the medium dose extract had the largest increase in the ability to tolerate the proliferation of L.lactis.[Conclusion]Feeding poplar bark extract will produce positive effects on the physiological characters of intestinal L.lactis in broiler chicken,which will provide potential probiotic strain for chicken production.
文摘Oxidative stress has been strongly related with Alzheimer disease pathogenesis. We determined the effects of watermelon powder (WMP) and Lactococcus lactis subsp lactis (LAL) supplementation on the generated Aβ42-induced phenotypes in a Drosophila melanogaster model of AD. Enhanced Aβ42 expression in D. melanogaster neurons can diminish lifespan and flight ability. We have observed longevity methods to assay the effects of WMP and LAL on D. melanogaster survival. Furthermore, flies expressing Aβ42 in their body fed WMP and LAL had up to 90 days, or 35% longer median lifespan than those fed a control diet. In addition, synergistic effect of WMP and LAL improved Aβ42-induced flight impairments in the Drosophila wing tissues. Our microscope experiments revealed that individuals fed synergistic effect of WMP and LAL had ameliorated Aβ42 expression as well as increment of flight ability than Aβ42-induced flies. We propose that WMP is typically rich in L-citrulline and LAL, rich in naturally occurring probiotics and antioxidants, and that it promotes the survival of neurons in brain and wing muscle tissues with increased levels of Aβ42 via a protective cell survival mechanism.
基金supported by the National Research Foundation of Korea(NRF)[NRF-2022M3A9I3082364]Korea Institute of Planning and Evaluation for Technology in Food,Agriculture and Forestry(IPET)through the High Valueadded Food Technology Development Program funded by the Ministry of Agriculture,Food and Rural Affairs(MAFRA)[RS-2022-IP322014].
文摘This study evaluated the probiotic potential of Lactococcus lactis strain DMLL15,previously selected as a starter candidate based on safety and enzymatic activity.Antifungal efficacy was further investigated.Strain DML15 exhibited 98.44%bile tolerance and 89.70%acid tolerance under conditions of 0.3%(w/v)oxgall and pH 2.5,respectively,and showed 86.46%mucin-binding ability.These results were significantly superior to those of the reference strain L.lactis KACC 13877^(ᵀ),which showed 88.93%,87.59%,and 80.83%,respectively.In addition,antifungal activity was observed against Cladosporium herbarum KACC 47604,Clonostachys rosea KACC 40320,and Epicoccum nigrum KACC 47166,with inhibition zones of 4.58±0.15 mm,3.55±0.55 mm,and 6.38±0.35 mm,respectively.These activities were higher than those of the reference strain L.lactis KACC 13877^(ᵀ).Whole-genome analysis identified genes associated with safety,enzymatic activity,health benefits,and antimicrobial activity.Notably,strain DMLL15 uniquely harbors an exopolysaccharide biosynthesis operon(AAE362_RS00370-AAE362_RS00440)that may enhance survival under acidic or bile-rich conditions,as well as genes encoding endothelin-converting enzyme,RecA proteins,neutral endopeptidases,and the oligopeptide-binding protein OppA.In addition,the strain possesses the nisin operon,contributing to its antimicrobial po-tential.These genomic insights,together with functional assessments,support the use of strain DMLL15 as a starter culture and probiotic candidate for food applications.
基金supported by the National Natural Science Foundation of China(No.31770102)the Shanxi Province Science Foundation for Youths(No.202203021222007).
文摘The ability of Lactococcus lactis to grow under moderate oxygen conditions enables its expansion from the food industry to microbial cell factories.While leveraging known antioxidative regulatory mechanisms represents a promising strategy for engineering robust strains under high oxygen conditions,the complete genetic basis of oxygen tolerance in L.lactis remains incompletely understood.Here,we identified and characterized a novel antioxidative system and its corresponding regulatory mechanism in L.lactis N8.Genetic analyses demonstrated that RmaH,a MarR-family transcriptional regulator,is essential for mediating the oxidative stress response.Transcriptomic and qPCR analysis further revealed that RmaH acts as a transcriptional repressor of dps,which encodes a DNA-binding protein from starved cells(Dps).In vitro and in vivo protein-DNA binding assays confirmed that RmaH specifically binds to the coding sequence(CDS)of dps,with DNase I footprinting precisely identifying the binding motif(TGTAAG-12nt-CTTTCA).Finally,functional investigations revealed that under oxygen conditions,RmaH expression was suppressed,leading to upregulated dps expression.Dps thereby confers cellular protection via two distinct mechanisms:physically shielding DNA from hydroxyl radicals and inhibiting the Fenton reaction through its ferroxidase activity.Collectively,our findings elucidated a previously uncharacterized RmaH-Dps regulatory pathway that enhances oxygen tolerance in L.lactis,providing both mechanistic insight and a potential target for engineering industrially robust strains.
文摘Lactococcus lactis is used as a starter for fermented milk,particularly in traditional cheese products.In this study,the anti-Listeria monocytogenes(Lm)activity of 32 coast-isolated Lc.lactis strains was compared to that of the typical nisin A-producing strain NBRC 12007 using the overlay plate assay,to identify a novel Lc.lactis starter with beneficial properties.The 10 isolates exhibited anti-Lm activity greater than that of NBRC 12007.Among them,the isolate Nagasaki-SU6 was selected based on its anti-Lm and cow-and soymilk fermentation activity.Cow-and soymilk were inoculated with 7 log CFU/mL Lm,with or without fermentation using NBRC 12007 and Nagasaki-SU6 at 37◦C for 48 h.The fermentation and anti-Lm activities of Nagasaki-SU6 were significantly greater than those of NBRC 12007.In the case of soymilk fermented with Nagasaki-SU6,the Lm viable count decreased by 2.8 log CFU/mL The fermented samples were inoculated with Lm and stored at 10◦C for 14 d.In Nagasaki-SU6 fermented samples,Lm growth was suppressed both in fermented cow milk and reduced in soymilk.Whole genome sequencing revealed the presence of nisin Z and sucrose PTS pathway genes in Nagasaki-SU6.However,the type and number of drug resistance and virulence genes in Nagasaki-SU6 did not differ from those in the type strain and NBRC 12007.These results suggest that Nagasaki-SU6 can be used as a desirable starter not only in cow milk but also in plant-based milk alternatives.
基金supported by the National Key Research and Development Program(2018YFA0900100)the Key Projects of the National Natural Science Foundation of China(41831287)the National Natural Science Foundation of China(31770102).
文摘Nisin is a ribosomally synthesized and post-translationally modified peptide(RiPP)bacteriocin produced by Lactococcus lactis that holds significant value in food preservation and medicine.Although extensive research has centred on optimizing its native biosynthetic machinery,the possibility of metabolic competition between nisin biosynthesis and other secondary metabolic processes,such as those encoded by nonribosomal synthesis pathways,has been overlooked.In this study,we reveal that a nonribosomal peptide synthetase-polyketide synthase(NRPS-PKS)gene cluster in L.lactis acts as a potent negative regulator of nisin biosynthesis.Comparative transcriptomics revealed a striking inverse correlation in the expression of the two gene clusters.Genetic disruption of the NRPS-PKS cluster or its specific regulatory genes(npkK and npkR)dramatically increased nisin production by 8.1%,an effect that was reversible upon genetic complementation.Moreover,high-producing NRPS-PKS knockout mutants exhibited altered sensitivity to a broad spectrum of stressors.We further identi-fied the global carbon catabolite regulator CcpA as a key mediator of this interaction.Integrated transcriptomic and proteomic analyses suggested that the NRPS-PKS pathway exerts its suppressive effect primarily by competing for essential cellular resources-precursor amino acids,ATP,and the lipid carrier undecaprenyl-phosphate-thereby starving the nisin biosynthetic machinery.Our work uncovers a competitive dynamic between ribosomal and non-ribosomal biosynthetic systems and provides a novel metabolic engineering strategy for enhancing industrial nisin production by targeting the NRPS-PKS cluster for inactivation.
基金supported by a project funded by the National Natural Science Foundation of China(31972094,31700079)the Natural Science Foundation of Jiangsu Province(BK20170496)+1 种基金the Scientific and Technological Innovation Platform Cobuilt by Yangzhou City-Yangzhou University(YZ2020265)the Postgraduate Research and Practice Innovation Program of Jiangsu Province(Yangzhou University,SJCX24_2364).
文摘A novel strain of Lactococcus lactis grx602,exhibiting both intracellular and extracellular lipase activity,was isolated from raw milk using a selective medium with butter as the sole carbon source.Both intracellular and extracellular lipase activity shared identical optimal reaction conditions including substrate,pH,temperature and NaCl concentration.Fermentation with L.lactis grx602 modified the fatty acids profile and raised the acid value by 0.48 mg/mL.L.lactis grx602 also demonstrated promising probiotic traits,including acid tolerance,bile salt resistance,and cholesterol-lowering ability.When applied to prepare Lg-sour cream,L.lactis grx602 significantly enhanced the key quality attributes,including physicochemical properties,structural integrity,flavor profile,and nutritional value.The comprehensive performance of L.lactis grx602 indicated its substantial potential as a multifunctional starter culture for developing functional dairy products.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research[grant numbers 2020B0301030005].
文摘Sufu,a traditional fermented soybean curd,is prone to contamination by Bacillus cereus.In this study,133 lactic acid bacteria(LAB)strains were initially screened from spring and winter Mao-tofu samples for their ability to inhibit the growth of B.cereus ATCC 14579T.Among these strains,five Lactococcus lactis strains exhibited a good safety profile and were capable of growing in pH 4-9 and salt concentrations of 6%-8%.Antimicrobial experiments conducted on the B.cereus group from sufu factories showed that L.lactis LJL7m20 strain had the strongest inhibitory effect.Whole-genome sequencing revealed the presence of three genes associated with high osmotic stress response and eight distinct two-component systems that may contribute to the strain’s tolerance,enhancing its survival in high-salt environments.The strain was further identified as L.lactis subsp.lactis through a combination of phenotypic and genotypic analysis.Additionally,bacteriocins nisin Z and nisin A/Q were identified using the BAGEL4 and antiSMASH databases.ELISA further confirmed the strain’s ability to produce nisin.A fermentation validation study demonstrated that inoculation with the strain contributed to reduce the number of B.cereus group in sufu pehtzes.This study provides a theoretical foundation for the use of new biocontrol bacteria to improve the safety of traditional fermented soybean foods.
