2-haloacid dehalogenases constitute a group of dehalogenases which are capable of dehalogenating the halogenated organic compounds. So far, the 2-haloacid dehalogenases have been found in many bacteria, but not in Par...2-haloacid dehalogenases constitute a group of dehalogenases which are capable of dehalogenating the halogenated organic compounds. So far, the 2-haloacid dehalogenases have been found in many bacteria, but not in Paracoccus genus. In the present study, one enzyme 2-haloacid dehalogenase(designated as Deh99), induced by DL-2-chloropropionate(DL-2-CPA), was purified from the marine bacterium Paracoccus sp. DEH99, isolated from marine sponge Hymeniacidon perlevis. The enzyme of Deh99 was purified to homogeneity by ammonium sulfate precipitation, ion exchange chromatography(Q-Sepharose HP), and Superdex 200 gel filtration chromatography. The molecular weight of Deh99 was estimated to be 25.0 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE), and 50.0 kDa natively by gel filtration chromatography. The enzyme of Deh99 stereospecifically dehalogenated L-2-CPA to produce D-lactate, with an apparent Michaelis-Menten constant(Km) value of 0.21 mmol L-1 for L-2-CPA. The optimal pH and temperature for Deh99 activity were 10.0 and 40℃, respectively. The enzyme of Deh99 acted on short-carbon-chain 2-haloacids, with the highest activity towards monochloroacetate. The activity of Deh99 was slightly affected by DTT and EDTA, but strongly inhibited by Cu2+ and Zn2+. The enzyme of Deh99 shows unique substrate specificity and inhibitor sensitivities compared to previously characterized 2-haloacid dehalogenases and is the reported one about purified 2-haloacid dehalogenase isolated from the bacteria of Paracoccus genus.展开更多
Methomyl, an extremely toxic pesticide, is widely used in agriculture. A strain named mdw-1 capable of degrading methomyl rapidly was successfully isolated from activated sludge in this study. It could utilize methomy...Methomyl, an extremely toxic pesticide, is widely used in agriculture. A strain named mdw-1 capable of degrading methomyl rapidly was successfully isolated from activated sludge in this study. It could utilize methomyl as the sole carbon or nitrogen source. The optimal temperature and medium pH for its growth and methomyl biodegradation were 30℃ and 7.0, respectively. It was identified as a Paracoccus sp. according to its morphological features, physiological and biochemical characteristics, and phylogenetic analysis based on the sequence of 16S rDNA. Gas chromatography-mass spectrometry （GC-MS） analysis showed that methomyl could be completely transformed to S-methyl-N-hydroxythioacetamidate in 10 h of incubation with the isolate mdw-1.展开更多
Bioaugmentation is an efficient and eco-friendly strategy for the bioremediation of polycyclic aromatic hydrocarbons(PAHs).Since the degrading abilities of soils can greatly alter the abilities of PAH-degrading bacter...Bioaugmentation is an efficient and eco-friendly strategy for the bioremediation of polycyclic aromatic hydrocarbons(PAHs).Since the degrading abilities of soils can greatly alter the abilities of PAH-degrading bacteria,illustrating the potential and mechanism of highly efficient degrading bacteria in different soil environments is of great importance for bioremediation.A PAH-degrading bacterium,Paracoccus aminovorans HPD-2,and two soil types,red and paddy soils,with distinct PAH-degrading abilities,were selected for this study.A soil microcosm experiment was performed by adding pyrene(PYR)and benzo[a]pyrene(B[a]P).Illumina sequencing was used to examine bacterial community structure.The results showed that inoculation with HPD-2 significantly elevated PYR and B[a]P degradation rates by 44.7%and 30.7%,respectively,in the red soil,while it only improved the degradation rates by 1.9%and 11%,respectively,in the paddy soil.To investigate the underlying mechanism,the fate of strain HPD-2 and the response of the indigenous bacterial communities were determined.Strain HPD-2 occupied certain niches in both soils,and the addition of the bacterium changed the native community structure more noticeably in the red soil than in the paddy soil.The addition of PAHs and strain HPD-2 significantly changed the abundances of 7 phyla among the 15 detected phyla in the red soil.In the paddy soil,5 of the 12 dominant phyla were significantly affected by PAHs and the inoculation of HPD-2,while 6new phyla were detected in the low-abundance phyla(<0.1%).The abundances of Massilia,Burkholderia,and Rhodococcus genera with PAH degradation efficiency were significantly increased by the inoculation of HPD-2 in the red soil during 42 d of incubation.Meanwhile,in the paddy soil,the most dominant effective genus,Massilia,was reduced by HPD-2 inoculation.This research revealed the remediation ability and inherent mechanism of the highly effective PAH-degrading strain HPD-2 in two different soil types,which would provide a theoretical basis for the application of degrading bacteria in different soils.展开更多
As it was rear to find out detailed description, a study on biology and control measures ofP. marginatus was carried out at National Plant Quarantine Service, Katunayake Sri Lanka. Average length and width of differen...As it was rear to find out detailed description, a study on biology and control measures ofP. marginatus was carried out at National Plant Quarantine Service, Katunayake Sri Lanka. Average length and width of different stages, number of eggs in an egg sac, hatchability rate and duration of life cycle were studied. Control measures were tested using herbal oils and it was arranged in Completely Randomized Design with six replicates. Experiments were carried out in laboratory conditions under 28 ±2℃ and 70% RH. Range of length and width of different life stages revealed that, egg 0.3-0.1 mm ×0.15-0.10 mm, 1st instar 0.4-0.2 mm × 0.20-0.10 mm, 2nd instar 0.6-0.5 mm × 0.29-0.20 mm, 3rd instar male 0.8-0.5 mm × 0.30-0.20 mm, 3rd instar female 0.7-0.5 mm × 0.29-0.20 mm, adult male 0.9-0.7 mm× 0.20-0.10 mm and adult female 2.8-1.9 mm × 1.40-0.80 mm. A range of 100-200 eggs were in an ovisac and hatchability rate was 76-80%. Twenty to twenty-four days were taken to complete their life cycle. Cinnamon and Neem oil in cooperated with Surfactant and Kerosene oil could be effectively used as potential chemical agents for control of P. marginatus.展开更多
Coenzyme Q10 (CoQ10), an important antioxidant molecule playing a major role in electron transport chain, has been commercially produced by fermentation process for the use in oral nutraceutical formulations. Construc...Coenzyme Q10 (CoQ10), an important antioxidant molecule playing a major role in electron transport chain, has been commercially produced by fermentation process for the use in oral nutraceutical formulations. Constructing the high-yielding CoQ10 producing strains is a pre-requisite for cost-effective production. A superior mutant strain P-87 generated from Paracoccus denitrificans ATCC 19367, which showed 1.25-fold improvement in specific CoQ10 content higher than the wild type strain at shake flask level, was selected to carry out the studies on CoQ10 yield improvement through fermenter process optimization. In the course of study, initially the cane-molasses-based medium and fed-batch fermentation strategy using pHBA in combination with sucrose were standardized in shake flask using wild type strain. This strategy was subsequently translated at 2 L laboratory fermenter while optimizing the fermentation process parameters using improved mutant strain P-87. Under optimized fermentation condition, mutant strain P-87 produced 49.85 mg/L of CoQ10 having specific content of 1.63 mg/g of DCW, which was 1.36 folds higher than the specific CoQ10 content of wild-type strain under similar optimized condition. The temperature and DO were found to be critical parameters for CoQ10 production by mutant strain P-87. The optimum temperature was found to be 32°C and the optimum DO concentration to be maintained throughout the fermentation cycle was found to be 30% of air saturation. Overall, a new cost-effective process has been established for the production of CoQ10 using the cheaper substrate “cane molasses” and higher CoQ10 producing mutant strain P-87.展开更多
Astaxanthin(AXT)from microalgae is widely recognized for its potent antioxidant properties,yet the biological potential of bacterial AXT remains poorly characterized.This study provides the first integrative evaluatio...Astaxanthin(AXT)from microalgae is widely recognized for its potent antioxidant properties,yet the biological potential of bacterial AXT remains poorly characterized.This study provides the first integrative evaluation of free and nanoencapsulated AXT obtained from bacteria Paracoccus carotinifaciens,combining sustainable extraction,advanced formulation,antimicrobial assays,and in silico target prediction.A green dimethyl carbonate(DMC)extraction process was optimized by assessing temperature,extraction time,and solid-liquid ratio,achieving high AXT recovery(>85%)with efficient solvent recyclability.The AXT-rich extracts were incorporated into poloxamer-407 nanoparticles producing stable colloidal systems with controlled size(≈230-340 nm),low polydispersity,and negative surface charge,supporting their suitability for biological applications.Antimicrobial assays revealed that neither free nor nanoencapsulated AXT exhibited antibacterial activity against Escherichia coli,Enterococcus faecalis,or Staphylococcus aureus.However,nanoencapsulation selectively enhanced antifungal activity,yielding weak but fungistatic effects against Trichophyton rubrum(MIC=125μg/mL),whereas Candida albicans remained unaffected.To clarify this specificity,in silico screening identified key T.rubrum targets,primarily enzymes related to tryptophan metabolism and acetylation pathways.The results demonstrate that although Paracoccus-derived AXT lacks antibacterial activity,it exhibits a formulationenhanced and highly selective fungistatic effect.Importantly,the absence of antibacterial action represents a safety advantage,as it reduces the risk of disrupting beneficial microbiota or selecting for antibiotic resistance,features that are critical for food applications.These findings suggest that Paracoccus-derived AXT may be more appropriate for microbiota-compatible applications,given its lack of antibacterial activity,rather than for use as a broad-spectrum antimicrobial compound.展开更多
Carotenoids are biomolecules naturally produced as secondary metabolites.The scientific interest in microbial carotenoids production is gaining more attraction because of their economic sustainability and cost-effecti...Carotenoids are biomolecules naturally produced as secondary metabolites.The scientific interest in microbial carotenoids production is gaining more attraction because of their economic sustainability and cost-effectiveness.This study aimed to define the Paracoccus sp.LL1 carotenoids and fatty acids quali-quantitative profiles under controlled fermentation processes carried out at two different temperatures.Moreover,the whole genome of the selected strain LL1 has been sequenced and analyzed,allowing us to identify the gene clusters involved in carotenoid biosynthesis.The fatty acid profile detected and the genome sequencing allowed to rename the strain investigated Paracoccus marcusii strain LL1.Stearic and vaccenic fatty acids have been detected in the highest percentage as the main cellular membrane fatty acids characteristic of the strain investigated.Whereas,twelve different carotenoids produced by the bacterium investigated have been identified.Among these the most produced wasβ-carotene,which reached up a final concentration of 0.35±0.01 mg g-1 of dry biomass.Furthermore,Paracoccus sp.LL1 biomass extract was investigated for antibacterial activity against selected strains.This study allowed pointing out the great potential of the wild type bacterium Paracoccus marcusii strain LL1 as a promisingβ-carotene producer,representing an interesting alternative for natural carotenoids production.展开更多
从实验室定向驯化的活性污泥中分离筛选出一株具有异养硝化-好氧反硝化功能的菌株TS-1.通过生理生化及16S r RNA基因序列鉴定其为脱氮副球菌,通过单因素和正交实验对其去除NH4+-N的最佳条件进行优化,并通过对比进一步探究其在不同氮源...从实验室定向驯化的活性污泥中分离筛选出一株具有异养硝化-好氧反硝化功能的菌株TS-1.通过生理生化及16S r RNA基因序列鉴定其为脱氮副球菌,通过单因素和正交实验对其去除NH4+-N的最佳条件进行优化,并通过对比进一步探究其在不同氮源条件下对各形态无机氮的去除规律.结果表明该菌株最适碳源为丁二酸钠,最佳C/N为15,最佳接种量为5%,最适温度为30℃、p H为8.0.以初始浓度约为100 mg/L的NH4+-N、NO3--N和NO2--N分别为单一氮源时,菌株TS-1对各形态氮的去除率为97.49%、100%和95.94%;维持各形态氮初始浓度不变,将其两两混合时发现混合氮源中若包含NO2--N会使菌株OD600值达到最大值所用时间延长,氮源中含有NH4+-N会降低菌株对其他形态氮源的去除率,以及NO3--N的添加会使菌株对NH4+-N的去除能力降低;3种形态氮源同时存在的条件下,该菌对各氮源去除能力由强至弱为NO2--N>NH4+-N>NO3--N.本研究从活性污泥中分离筛选出一株具有高效异养硝化-好氧反硝化功能的菌株TS-1,通过研究碳源、氮源、温度、p H得到了最佳降解条件,可为废水短程脱氮提供参考.(图9表4参37)展开更多
To investigate the characteristics and metabolic mechanism of short-cut denitrifying phospho- rus-removing bacteria （SDPB） that are capable of enhanced biological phosphorus removal （EBPR） using nitrite as an elec...To investigate the characteristics and metabolic mechanism of short-cut denitrifying phospho- rus-removing bacteria （SDPB） that are capable of enhanced biological phosphorus removal （EBPR） using nitrite as an electron acceptor, an aerobic/anoxic sequencing batch reactor was operated under three phases. An SDPB-strain YC was screened after the sludge enrichment and was identified by morphological, physiological, biochemical properties and 16S rDNA gene sequence analysis. Denitrifying phosphorus-removing experiments were conducted to study anaerobic and anoxic metabolic mechanisms by analyzing the changes of chemical oxygen demand （COD）, phosphate, nitrite, poly-fl-hydroxybutyrate （PHB）, and glycogen. The results show that strain YC is a non-fermentative SDPB similar to Paracoccus denitrificans. As a kind of non-fermentative bacteria, the energy of strain YC was mainly generated from phosphorus release （96.2%） under anaerobic conditions with 0.32 mg P per mg synthesized PHB. Under anoxic conditions, strain YC accumulated 0.45 mg P per mg degraded PHB, which produced most of energy for phosphate accumulation （91.3%） and a little for glycogen synthesis （8.7%）. This metabolic mechanism of strain YC is different from that of traditional phosphorus-accumulating organisms （PAOs）. It is also found that PHB, a kind of intracellular polymer, plays a very important role in denitrifying and accumulating phosphorus by supplying sufficient energy for phosphorous accumulation and carbon sources for denitrification. Therefore, monitoring AP/APHB and ANO2 -N/APHB is more necessary than monitoring AP/ACOD, ANO2 -N/ACOD, or AP / ANO2 -N.展开更多
The contamination of soils by polycyclic aromatic hydrocarbons （PAHs） is a widespread environmental problem and the remediation of PAHs from these areas has been a major concern. The effectiveness of many in situ bi...The contamination of soils by polycyclic aromatic hydrocarbons （PAHs） is a widespread environmental problem and the remediation of PAHs from these areas has been a major concern. The effectiveness of many in situ bioremediation systems may be constrained by low contaminant bioavailability due to limited aqueous solubility or a large magnitude of sorption. The objective of this research was to evaluate the effect of methyl-β-cyclodextrin （MCD） on bioaugmentation by Paracoccus sp. strain HPD-2 of an aged PAH-contaminated soil. When 10% （W/W） MCD amendment was combined with bioaugmentation by the PAH-degrading bacterium Paracoccus sp. strain HPD-2, the percentage degradation of total PAHs was significantly enhanced up to 34.8%. Higher counts of culturable PAH- degrading bacteria and higher soil dehydrogenase and soil polyphenol oxidase activities were observed in 10% （W/W） MCD-assisted bioaugmentation soil. This MCD-assisted bioaugmentation strategy showed significant increases （p 〈 0.05） in the average well color development （AWCD） obtained by the BIOLOG Eco plate assay, Shannon-Weaver index （H） and Simpson index （λ） compared with the controls, implying that this strategy at least partially restored the microbiological functioning of the PAH-contaminated soil. The results suggest that MCD-aided bioaugmentation by Paracoccus sp. strain HPD-2 may be a promising practical bioremediation strategy for aged PAH-contaminated soils.展开更多
基金supported by National Basic Research Program of China(973 program,Grant No.2009CB724700)the Hundred Talent Program of the Chinese Academy of Sciences(A1097)National Natural Science Foundation of China(No.31100092)
文摘2-haloacid dehalogenases constitute a group of dehalogenases which are capable of dehalogenating the halogenated organic compounds. So far, the 2-haloacid dehalogenases have been found in many bacteria, but not in Paracoccus genus. In the present study, one enzyme 2-haloacid dehalogenase(designated as Deh99), induced by DL-2-chloropropionate(DL-2-CPA), was purified from the marine bacterium Paracoccus sp. DEH99, isolated from marine sponge Hymeniacidon perlevis. The enzyme of Deh99 was purified to homogeneity by ammonium sulfate precipitation, ion exchange chromatography(Q-Sepharose HP), and Superdex 200 gel filtration chromatography. The molecular weight of Deh99 was estimated to be 25.0 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE), and 50.0 kDa natively by gel filtration chromatography. The enzyme of Deh99 stereospecifically dehalogenated L-2-CPA to produce D-lactate, with an apparent Michaelis-Menten constant(Km) value of 0.21 mmol L-1 for L-2-CPA. The optimal pH and temperature for Deh99 activity were 10.0 and 40℃, respectively. The enzyme of Deh99 acted on short-carbon-chain 2-haloacids, with the highest activity towards monochloroacetate. The activity of Deh99 was slightly affected by DTT and EDTA, but strongly inhibited by Cu2+ and Zn2+. The enzyme of Deh99 shows unique substrate specificity and inhibitor sensitivities compared to previously characterized 2-haloacid dehalogenases and is the reported one about purified 2-haloacid dehalogenase isolated from the bacteria of Paracoccus genus.
基金Project supported by the National Natural Science Foundation of China(No.30600016)the National High Technology Research and Development Program of China(863 Program)(No.2007AA10Z405)+2 种基金the National Program for Sci-Tech Basic Platform Construction of China(No.2005DKA21201-2)the Program for Science and Technology Development ofJiangsu Province,China(No.BE2008669)the Program for Integration of Production,Education,and Research of Guangdong Province and Ministry of Education,China(No.2006090204007)
文摘Methomyl, an extremely toxic pesticide, is widely used in agriculture. A strain named mdw-1 capable of degrading methomyl rapidly was successfully isolated from activated sludge in this study. It could utilize methomyl as the sole carbon or nitrogen source. The optimal temperature and medium pH for its growth and methomyl biodegradation were 30℃ and 7.0, respectively. It was identified as a Paracoccus sp. according to its morphological features, physiological and biochemical characteristics, and phylogenetic analysis based on the sequence of 16S rDNA. Gas chromatography-mass spectrometry （GC-MS） analysis showed that methomyl could be completely transformed to S-methyl-N-hydroxythioacetamidate in 10 h of incubation with the isolate mdw-1.
基金funded by the National Key R&D Program of China(2019YFC1803705)the Projects of the National Natural Science Foundation of China(41991335and 42130718)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(QYZDJ-SSWDQC035)。
文摘Bioaugmentation is an efficient and eco-friendly strategy for the bioremediation of polycyclic aromatic hydrocarbons(PAHs).Since the degrading abilities of soils can greatly alter the abilities of PAH-degrading bacteria,illustrating the potential and mechanism of highly efficient degrading bacteria in different soil environments is of great importance for bioremediation.A PAH-degrading bacterium,Paracoccus aminovorans HPD-2,and two soil types,red and paddy soils,with distinct PAH-degrading abilities,were selected for this study.A soil microcosm experiment was performed by adding pyrene(PYR)and benzo[a]pyrene(B[a]P).Illumina sequencing was used to examine bacterial community structure.The results showed that inoculation with HPD-2 significantly elevated PYR and B[a]P degradation rates by 44.7%and 30.7%,respectively,in the red soil,while it only improved the degradation rates by 1.9%and 11%,respectively,in the paddy soil.To investigate the underlying mechanism,the fate of strain HPD-2 and the response of the indigenous bacterial communities were determined.Strain HPD-2 occupied certain niches in both soils,and the addition of the bacterium changed the native community structure more noticeably in the red soil than in the paddy soil.The addition of PAHs and strain HPD-2 significantly changed the abundances of 7 phyla among the 15 detected phyla in the red soil.In the paddy soil,5 of the 12 dominant phyla were significantly affected by PAHs and the inoculation of HPD-2,while 6new phyla were detected in the low-abundance phyla(<0.1%).The abundances of Massilia,Burkholderia,and Rhodococcus genera with PAH degradation efficiency were significantly increased by the inoculation of HPD-2 in the red soil during 42 d of incubation.Meanwhile,in the paddy soil,the most dominant effective genus,Massilia,was reduced by HPD-2 inoculation.This research revealed the remediation ability and inherent mechanism of the highly effective PAH-degrading strain HPD-2 in two different soil types,which would provide a theoretical basis for the application of degrading bacteria in different soils.
文摘As it was rear to find out detailed description, a study on biology and control measures ofP. marginatus was carried out at National Plant Quarantine Service, Katunayake Sri Lanka. Average length and width of different stages, number of eggs in an egg sac, hatchability rate and duration of life cycle were studied. Control measures were tested using herbal oils and it was arranged in Completely Randomized Design with six replicates. Experiments were carried out in laboratory conditions under 28 ±2℃ and 70% RH. Range of length and width of different life stages revealed that, egg 0.3-0.1 mm ×0.15-0.10 mm, 1st instar 0.4-0.2 mm × 0.20-0.10 mm, 2nd instar 0.6-0.5 mm × 0.29-0.20 mm, 3rd instar male 0.8-0.5 mm × 0.30-0.20 mm, 3rd instar female 0.7-0.5 mm × 0.29-0.20 mm, adult male 0.9-0.7 mm× 0.20-0.10 mm and adult female 2.8-1.9 mm × 1.40-0.80 mm. A range of 100-200 eggs were in an ovisac and hatchability rate was 76-80%. Twenty to twenty-four days were taken to complete their life cycle. Cinnamon and Neem oil in cooperated with Surfactant and Kerosene oil could be effectively used as potential chemical agents for control of P. marginatus.
文摘Coenzyme Q10 (CoQ10), an important antioxidant molecule playing a major role in electron transport chain, has been commercially produced by fermentation process for the use in oral nutraceutical formulations. Constructing the high-yielding CoQ10 producing strains is a pre-requisite for cost-effective production. A superior mutant strain P-87 generated from Paracoccus denitrificans ATCC 19367, which showed 1.25-fold improvement in specific CoQ10 content higher than the wild type strain at shake flask level, was selected to carry out the studies on CoQ10 yield improvement through fermenter process optimization. In the course of study, initially the cane-molasses-based medium and fed-batch fermentation strategy using pHBA in combination with sucrose were standardized in shake flask using wild type strain. This strategy was subsequently translated at 2 L laboratory fermenter while optimizing the fermentation process parameters using improved mutant strain P-87. Under optimized fermentation condition, mutant strain P-87 produced 49.85 mg/L of CoQ10 having specific content of 1.63 mg/g of DCW, which was 1.36 folds higher than the specific CoQ10 content of wild-type strain under similar optimized condition. The temperature and DO were found to be critical parameters for CoQ10 production by mutant strain P-87. The optimum temperature was found to be 32°C and the optimum DO concentration to be maintained throughout the fermentation cycle was found to be 30% of air saturation. Overall, a new cost-effective process has been established for the production of CoQ10 using the cheaper substrate “cane molasses” and higher CoQ10 producing mutant strain P-87.
基金supported by grants from ANID/FONDECYT/1250170 and ANID/FOVI/250065.
文摘Astaxanthin(AXT)from microalgae is widely recognized for its potent antioxidant properties,yet the biological potential of bacterial AXT remains poorly characterized.This study provides the first integrative evaluation of free and nanoencapsulated AXT obtained from bacteria Paracoccus carotinifaciens,combining sustainable extraction,advanced formulation,antimicrobial assays,and in silico target prediction.A green dimethyl carbonate(DMC)extraction process was optimized by assessing temperature,extraction time,and solid-liquid ratio,achieving high AXT recovery(>85%)with efficient solvent recyclability.The AXT-rich extracts were incorporated into poloxamer-407 nanoparticles producing stable colloidal systems with controlled size(≈230-340 nm),low polydispersity,and negative surface charge,supporting their suitability for biological applications.Antimicrobial assays revealed that neither free nor nanoencapsulated AXT exhibited antibacterial activity against Escherichia coli,Enterococcus faecalis,or Staphylococcus aureus.However,nanoencapsulation selectively enhanced antifungal activity,yielding weak but fungistatic effects against Trichophyton rubrum(MIC=125μg/mL),whereas Candida albicans remained unaffected.To clarify this specificity,in silico screening identified key T.rubrum targets,primarily enzymes related to tryptophan metabolism and acetylation pathways.The results demonstrate that although Paracoccus-derived AXT lacks antibacterial activity,it exhibits a formulationenhanced and highly selective fungistatic effect.Importantly,the absence of antibacterial action represents a safety advantage,as it reduces the risk of disrupting beneficial microbiota or selecting for antibiotic resistance,features that are critical for food applications.These findings suggest that Paracoccus-derived AXT may be more appropriate for microbiota-compatible applications,given its lack of antibacterial activity,rather than for use as a broad-spectrum antimicrobial compound.
文摘Carotenoids are biomolecules naturally produced as secondary metabolites.The scientific interest in microbial carotenoids production is gaining more attraction because of their economic sustainability and cost-effectiveness.This study aimed to define the Paracoccus sp.LL1 carotenoids and fatty acids quali-quantitative profiles under controlled fermentation processes carried out at two different temperatures.Moreover,the whole genome of the selected strain LL1 has been sequenced and analyzed,allowing us to identify the gene clusters involved in carotenoid biosynthesis.The fatty acid profile detected and the genome sequencing allowed to rename the strain investigated Paracoccus marcusii strain LL1.Stearic and vaccenic fatty acids have been detected in the highest percentage as the main cellular membrane fatty acids characteristic of the strain investigated.Whereas,twelve different carotenoids produced by the bacterium investigated have been identified.Among these the most produced wasβ-carotene,which reached up a final concentration of 0.35±0.01 mg g-1 of dry biomass.Furthermore,Paracoccus sp.LL1 biomass extract was investigated for antibacterial activity against selected strains.This study allowed pointing out the great potential of the wild type bacterium Paracoccus marcusii strain LL1 as a promisingβ-carotene producer,representing an interesting alternative for natural carotenoids production.
基金Supported by the Nafional Natural Science Foundation of China （51078008）, the Natural Science Foundation of Guangdong Province （06022869, 07003251）, and the National Key Scientific and Technological Project Water Pollution Control and Treatment （2008ZX07211-003, 2009ZX07314-009-003）.
文摘To investigate the characteristics and metabolic mechanism of short-cut denitrifying phospho- rus-removing bacteria （SDPB） that are capable of enhanced biological phosphorus removal （EBPR） using nitrite as an electron acceptor, an aerobic/anoxic sequencing batch reactor was operated under three phases. An SDPB-strain YC was screened after the sludge enrichment and was identified by morphological, physiological, biochemical properties and 16S rDNA gene sequence analysis. Denitrifying phosphorus-removing experiments were conducted to study anaerobic and anoxic metabolic mechanisms by analyzing the changes of chemical oxygen demand （COD）, phosphate, nitrite, poly-fl-hydroxybutyrate （PHB）, and glycogen. The results show that strain YC is a non-fermentative SDPB similar to Paracoccus denitrificans. As a kind of non-fermentative bacteria, the energy of strain YC was mainly generated from phosphorus release （96.2%） under anaerobic conditions with 0.32 mg P per mg synthesized PHB. Under anoxic conditions, strain YC accumulated 0.45 mg P per mg degraded PHB, which produced most of energy for phosphate accumulation （91.3%） and a little for glycogen synthesis （8.7%）. This metabolic mechanism of strain YC is different from that of traditional phosphorus-accumulating organisms （PAOs）. It is also found that PHB, a kind of intracellular polymer, plays a very important role in denitrifying and accumulating phosphorus by supplying sufficient energy for phosphorous accumulation and carbon sources for denitrification. Therefore, monitoring AP/APHB and ANO2 -N/APHB is more necessary than monitoring AP/ACOD, ANO2 -N/ACOD, or AP / ANO2 -N.
基金supported by the Natural Science Foundation of Jiangsu Province (No. BK2009016)the Chinese National Environmental Protection Special Funds for Scientific Research on Public Causes (No. 2010467016)the National High Technology Research and Development Program (863) of China (No. 2007AA061101)
文摘The contamination of soils by polycyclic aromatic hydrocarbons （PAHs） is a widespread environmental problem and the remediation of PAHs from these areas has been a major concern. The effectiveness of many in situ bioremediation systems may be constrained by low contaminant bioavailability due to limited aqueous solubility or a large magnitude of sorption. The objective of this research was to evaluate the effect of methyl-β-cyclodextrin （MCD） on bioaugmentation by Paracoccus sp. strain HPD-2 of an aged PAH-contaminated soil. When 10% （W/W） MCD amendment was combined with bioaugmentation by the PAH-degrading bacterium Paracoccus sp. strain HPD-2, the percentage degradation of total PAHs was significantly enhanced up to 34.8%. Higher counts of culturable PAH- degrading bacteria and higher soil dehydrogenase and soil polyphenol oxidase activities were observed in 10% （W/W） MCD-assisted bioaugmentation soil. This MCD-assisted bioaugmentation strategy showed significant increases （p 〈 0.05） in the average well color development （AWCD） obtained by the BIOLOG Eco plate assay, Shannon-Weaver index （H） and Simpson index （λ） compared with the controls, implying that this strategy at least partially restored the microbiological functioning of the PAH-contaminated soil. The results suggest that MCD-aided bioaugmentation by Paracoccus sp. strain HPD-2 may be a promising practical bioremediation strategy for aged PAH-contaminated soils.
