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
Lactic acid bacteria(LAB)are often exposed to ionizing radiation(IR)in the process of mutagenesis and food processing,and high doses of IR can cause damage and death to LAB.LlrG,a response regulator(RR)in twocomponent...Lactic acid bacteria(LAB)are often exposed to ionizing radiation(IR)in the process of mutagenesis and food processing,and high doses of IR can cause damage and death to LAB.LlrG,a response regulator(RR)in twocomponent system(TCS),holds a significant role in enabling LAB to adapt to the environment.In our previous study,the expression of LlrG protein in Lactococcus lactis subsp.lactis IL1403(L.lactis IL1403)was significantly increased after induction by IR.To explore the IR adaptation mechanism of L.lactis IL1403 regulated by LlrG,the gene llrG in L.lactis IL1403 was overexpressed(L.lactis IL1403-llrG)and the transcriptomics and proteomics were studied.Results showed that L.lactis IL1403-llrG had significantly higher survival rate and stronger antioxidant capacity under IR conditions compared with L.lactis IL1403-p(L.lactis IL1403 contained pMG36e).Meanwhile,the transcriptomics and proteomics analyses indicated that the overexpression of llrG resulted in the enhancement of oxidation-reduction process,response to stimulus and carbohydrate metabolism and the downregulation of amino acid biosynthesis.This research provided a new perspective on understanding the adaptive mechanism of L.lactis IL1403 response to IR based on LlrG.Furthermore,L.lactis strain with IRstress tolerance characteristic could act as a reference for the application in IR sterilization of probiotic fermented dairy products.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
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
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
Lactococcus lactis subsp.lactis is a common starter culture in the dairy industry.In this study,the key pathway of five strains of Lactococcus lactis subsp.Lactis regarding their fermentation characteristics in milk s...Lactococcus lactis subsp.lactis is a common starter culture in the dairy industry.In this study,the key pathway of five strains of Lactococcus lactis subsp.Lactis regarding their fermentation characteristics in milk systems were studied by metabolomic approach,fermentation characterization and sensory evaluation.Strains DSCAB11M15 and DYNDL21-2,which express the cell wall proteinase PrtM/P,exhibited rapid proliferation and acidification,with significant differences in volatile and non-volatile metabolites including upregulation of flavor compounds such as ethyl butyrate and 2,3-butanedione.Additionally,DYNDL21-2,which carries theα-ketoacid decarboxylase gene,significantly increased the content of 3-methyl-butyric aldehyde,a compound that imparts a caramel-like flavor,in fermented milk.This study offers guidance for the comprehensive investigation of starter cultures with multiple approaches.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
Clostridium sporogenes and Clostridium tepidium strains were detected in traditional Kashar cheese samples with late blowing characteristics.To control Clostridium spp.,in Kashar cheese,dairy originated Lactic Acid Ba...Clostridium sporogenes and Clostridium tepidium strains were detected in traditional Kashar cheese samples with late blowing characteristics.To control Clostridium spp.,in Kashar cheese,dairy originated Lactic Acid Bacteria(LAB)strains were tested under in vitro conditions and during Kashar production.Two strains,Lactiplantibacillus plantarum and Lactococcus lactis subsp.lactis demonstrated anticlostridial activity in vitro and the co-inoculum of these two strains(107 cfu g^(-1))were tested during the challenge test on Kashar cheese production in which a contamination ratio of 10^(4) cfu g^(-1) with spores of Cl.sporogenes were applied.Kashar samples were stored at 4℃ and 25℃ during 40 days of storage period and microbiological and physicochemical properties of Kashar samples were determined during this period.A decrement of nearly 1 log cfu g^(-1) in Cl.sporogenes numbers was observed in Kashar samples produced with co-inoculum of Lb.plantarum and L.lactis subsp.lactis stored at 4℃ but this was not the case for the Kashar samples stored at 25℃.This study revealed the potential of distinct LAB strains to control Cl.sporogenes spores in semi-hard cheese samples as biocontrol agents at 4℃ storage.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
【目的】寻找精氨酸代谢途径中与酸胁迫相关的关键作用因素。【方法】通过在Lactococcus lactis NZ9000中分别过量表达来源于Lactobacillus casei Zhang的精氨酰琥珀酸合成酶(ASS)和精氨酰琥珀酸裂解酶(ASL)改变精氨酸代谢提高酸胁迫抗...【目的】寻找精氨酸代谢途径中与酸胁迫相关的关键作用因素。【方法】通过在Lactococcus lactis NZ9000中分别过量表达来源于Lactobacillus casei Zhang的精氨酰琥珀酸合成酶(ASS)和精氨酰琥珀酸裂解酶(ASL)改变精氨酸代谢提高酸胁迫抗性。【结果】与对照菌株对比,重组菌株在环境胁迫下表现了较高的生长性能、存活率和发酵性能。生理学分析发现,酸胁迫环境下,重组菌株细胞有较高的胞内NH4+、ATP含量和H+-ATPase活性,并显著提高了精氨酸脱亚胺酶(ADI)途径中的氨基酸浓度。进一步的转录分析发现,天冬氨酸合成、精氨酸代谢相关的基因转录水平上调。【结论】在L.lactis NZ9000中过量表达ASS或ASL可以引发精氨酸代谢流量的上调,进而提高了细胞的多种胁迫抗性。精氨酸合成途径广泛存在于多种微生物中,为微生物,尤其是工业微生物提高胁迫抗性提供了新思路。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
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.
基金supported by the Zhongyuan Sci-Tech Innovation Leading Talents(254000510040)the National Natural Science Foun-dation of China(32172211)+2 种基金the Key Science Research Projects of Higher Education Institutions in Henan Province(21A530006)the Henan Provincial Natural Science Foundation General Program(252300421403)the Key Research and Development and Promo-tion Projects of Henan Province(232102310293).
文摘Lactic acid bacteria(LAB)are often exposed to ionizing radiation(IR)in the process of mutagenesis and food processing,and high doses of IR can cause damage and death to LAB.LlrG,a response regulator(RR)in twocomponent system(TCS),holds a significant role in enabling LAB to adapt to the environment.In our previous study,the expression of LlrG protein in Lactococcus lactis subsp.lactis IL1403(L.lactis IL1403)was significantly increased after induction by IR.To explore the IR adaptation mechanism of L.lactis IL1403 regulated by LlrG,the gene llrG in L.lactis IL1403 was overexpressed(L.lactis IL1403-llrG)and the transcriptomics and proteomics were studied.Results showed that L.lactis IL1403-llrG had significantly higher survival rate and stronger antioxidant capacity under IR conditions compared with L.lactis IL1403-p(L.lactis IL1403 contained pMG36e).Meanwhile,the transcriptomics and proteomics analyses indicated that the overexpression of llrG resulted in the enhancement of oxidation-reduction process,response to stimulus and carbohydrate metabolism and the downregulation of amino acid biosynthesis.This research provided a new perspective on understanding the adaptive mechanism of L.lactis IL1403 response to IR based on LlrG.Furthermore,L.lactis strain with IRstress tolerance characteristic could act as a reference for the application in IR sterilization of probiotic fermented dairy products.
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 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 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(No.31871829,31820103010,and 32021005)the Collaborative Innovation Centre of Food Safety and Quality Control in Jiangsu Province(Jiangsu,China).
文摘Lactococcus lactis subsp.lactis is a common starter culture in the dairy industry.In this study,the key pathway of five strains of Lactococcus lactis subsp.Lactis regarding their fermentation characteristics in milk systems were studied by metabolomic approach,fermentation characterization and sensory evaluation.Strains DSCAB11M15 and DYNDL21-2,which express the cell wall proteinase PrtM/P,exhibited rapid proliferation and acidification,with significant differences in volatile and non-volatile metabolites including upregulation of flavor compounds such as ethyl butyrate and 2,3-butanedione.Additionally,DYNDL21-2,which carries theα-ketoacid decarboxylase gene,significantly increased the content of 3-methyl-butyric aldehyde,a compound that imparts a caramel-like flavor,in fermented milk.This study offers guidance for the comprehensive investigation of starter cultures with multiple approaches.
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.
基金Fatmanur Demirbas¸was supported by Turkish Council of Higher Education with 100/2000 PhD programme and by TUB˙ITAK with 2211-C programme.
文摘Clostridium sporogenes and Clostridium tepidium strains were detected in traditional Kashar cheese samples with late blowing characteristics.To control Clostridium spp.,in Kashar cheese,dairy originated Lactic Acid Bacteria(LAB)strains were tested under in vitro conditions and during Kashar production.Two strains,Lactiplantibacillus plantarum and Lactococcus lactis subsp.lactis demonstrated anticlostridial activity in vitro and the co-inoculum of these two strains(107 cfu g^(-1))were tested during the challenge test on Kashar cheese production in which a contamination ratio of 10^(4) cfu g^(-1) with spores of Cl.sporogenes were applied.Kashar samples were stored at 4℃ and 25℃ during 40 days of storage period and microbiological and physicochemical properties of Kashar samples were determined during this period.A decrement of nearly 1 log cfu g^(-1) in Cl.sporogenes numbers was observed in Kashar samples produced with co-inoculum of Lb.plantarum and L.lactis subsp.lactis stored at 4℃ but this was not the case for the Kashar samples stored at 25℃.This study revealed the potential of distinct LAB strains to control Cl.sporogenes spores in semi-hard cheese samples as biocontrol agents at 4℃ storage.
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.
