By using acetonitrile as the sole nitrogen source, a microbial strain with high nitrilase activity, named as Alcaligenes sp. ECU0401, was newly isolated from soil, which could enantioselectively transform racemic mand...By using acetonitrile as the sole nitrogen source, a microbial strain with high nitrilase activity, named as Alcaligenes sp. ECU0401, was newly isolated from soil, which could enantioselectively transform racemic mandelonitrile into (R)-(?)-mandelic acid, with an enantiomeric excess of >99.9%.展开更多
Alcaligenes faecalis C16 was found to have the ability to heterotrophically nitrify and aerobically denitrify. In order to further understand its nitrogen removal ability and mechanism, the growth and ammonium removal...Alcaligenes faecalis C16 was found to have the ability to heterotrophically nitrify and aerobically denitrify. In order to further understand its nitrogen removal ability and mechanism, the growth and ammonium removal response were investigated at different C/N ratios and ammonium concentrations in the medium with citrate and acetate as carbon source separately. Furthermore, experiments of nitrogen sources, production of nitrogen gas and enzyme assay were conducted. Results show that the bacterium converts NH+4-N and produces NH2 OH during the growing phase and nitrite accumulation is its distinct metabolic feature. A. faecalis C16 is able to tolerate not only high ammonium concentration but also high C/N ratio, and the ammonium tolerance is associated with carbon source and C/N ratio. The nitrogen balance under different conditions shows that approximately28%–45% of the initial ammonium is assimilated into the cells, 44%–60% is denitrified and several percent is converted to nitrification products. A. faecalis C16 cannot utilize hydroxylamine, nitrite or nitrate as the sole nitrogen source for growth. However, nitrate can be used when ammonium is simultaneously present in the medium. A possible pathway for nitrogen removal by C16 is suggested. The preliminary enzyme assay provides more evidence for this nitrogen removal pathway.展开更多
The structure-function relationship of a gellan family of polysaccharides, S-198 gum produced by Alcaligenes ATCC31853 was investigated in terms of rheological aspects. The flow curves of S-198 gum showed plastic beha...The structure-function relationship of a gellan family of polysaccharides, S-198 gum produced by Alcaligenes ATCC31853 was investigated in terms of rheological aspects. The flow curves of S-198 gum showed plastic behavior above 0.3%. Gelation did not occur in S-198 gum solution at low temperature (0℃), even at 0.8%. Both the viscosity and the elastic modulus remained constant with increasing temperature up to 80?C. The elastic modulus decreased a little with the addition of CaCl2 (6.8 mM), but then once again remained constant up to 80℃. The highest elastic modulus was observed for deacylated gellan gum with the addition of CaCl2 and increased slightly with increasing temperature up to 80℃, which was considered to be a transition temperature, after which it decreased rapidly. The elastic modulus of S-198 gum in the presence of urea (4.0 M) was lower than that in aqueous solution at low temperature (0℃), but remained constant with increasing temperature up to 80℃. The intramolecular associations, (hydrogen bonding and van der Waals forces of attraction), of S-198 gum molecules in aqueous solutions were proposed. The gellan family of polysaccharides, S-198, S-88, S-657, rhamsan, welan and gellan gum, provided a good opportunity to investigate the structure-function relationship for polysaccharides.展开更多
Poly(3-hydroxybutyrate) (PHB) is an intracellular carbon and energy storage material accumulated by many kinds of microorganism under unfavorable growth conditions. For the production of PHB, Alcaligenes eutrophus has...Poly(3-hydroxybutyrate) (PHB) is an intracellular carbon and energy storage material accumulated by many kinds of microorganism under unfavorable growth conditions. For the production of PHB, Alcaligenes eutrophus has been widely used because it is easy to grow, and its physiological and biochemical changes during the PHB synthesis is understood in details. A very high concentration and productivity of PHB could be obtained by fed-batch culture of Alcaligenes eutrophus with phosphate limitation in 50 L fermenter.展开更多
The rifampin resistant Alcaligenes faecalis strain A1501R survived at a high, initially stable and later slowly declining population size (10 8 to 10 6 CFU per g dry soil) for 60 days in microcosm experiments. Intr...The rifampin resistant Alcaligenes faecalis strain A1501R survived at a high, initially stable and later slowly declining population size (10 8 to 10 6 CFU per g dry soil) for 60 days in microcosm experiments. Introduction of strain A1501R did not cause great changes in the community profiles generated via microbial community level 16S rDNA based PCR followed by denaturing gradient gel electrophoresis (DGGE) and the Biolog substrate utilization system. The introduction of A1501R had no impact on the dominant bacterial populations in soil. Significant differences in the utilization of some substrates were observed between the control and inoculated soils using a combination of DGGE and Biolog analysis. Results of DGGE and BIOLOG analysis show that introduction of A1501R can affect the lactic acid utilizing bacterial community in case of selection by lactic acid. A specific probe based on the 16S rDNA variable region V6 was constructed via PCR amplification of 16S rDNA using the 971(f) and 1057(r) primers for the detection of A. faecalis strains introduced into soils. Dot blot hybridization of strains or soil DNA and aligment of sequences of the V6 region of 16S rDNA from different bacterial strains show that the V6 probe is very specific for A. faecalis A1501R.展开更多
Exploration of biodemulsifiers has become a new research aspect.Using waste frying oils（WFOs） as carbon source to synthesize biodemulsifiers has a potential prospect to decrease production cost and to improve the ap...Exploration of biodemulsifiers has become a new research aspect.Using waste frying oils（WFOs） as carbon source to synthesize biodemulsifiers has a potential prospect to decrease production cost and to improve the application of biodemulsifiers in the oilfield.In this study,a demulsifying strain,Alcaligenes sp.S-XJ-1,was investigated to synthesize a biodemulsifier using waste frying oils as carbon source.It was found that the increase of initial pH of culture medium could increase the biodemulsifier yield but decrease the demulsification ratio compared to that using paraffin as carbon source.In addition,a biodemulsifier produced by waste frying oils and paraffin as mixed carbon source had a lower demulsification capability compared with that produced by paraffin or waste frying oil as sole carbon source.Fed-batch fermentation of biodemulsifier using waste frying oils as supplementary carbon source was found to be a suitable method.Mechanism of waste frying oils utilization was studied by using tripalmitin,olein and tristearin as sole carbon sources to synthesize biodemulsifier.The results showed saturated long-chain fatty acid was diffcult for S-XJ-1 to utilize but could effectively enhance the demulsification ability of the produced biodemulsifier.Moreover,FT-IR result showed that the demulsification capability of biodemulsifiers was associated with the content of C=O group and nitrogen element.展开更多
A bacterial strain ZWS11 was isolated from sulfonylurea herbicide-contaminated farmland soil and identified as a potential nicosulfuron-degrading bacterium. Based on morphological and physicochemical characterization ...A bacterial strain ZWS11 was isolated from sulfonylurea herbicide-contaminated farmland soil and identified as a potential nicosulfuron-degrading bacterium. Based on morphological and physicochemical characterization of the bacterium and phylogenetic analysis of the 16 S r RNA sequence, strain ZWS11 was identified as Alcaligenes faecalis. The effects of the initial concentration of nicosulfuron, inoculation volume, and medium p H on degradation of nicosulfuron were investigated. Strain ZWS11 could degrade 80.56% of the initial nicosulfuron supplemented at 500.0 mg/L under the conditions of p H 7.0, 180 r/min and30°C after incubation for 6 days. Strain ZWS11 was also capable of degrading rimsulfuron,tribenuron-methyl and thifensulfuron-methyl. Four metabolites from biodegradation of nicosulfuron were identified, which were 2-aminosulfonyl-N, N-dimethylnicotinamide（M1）, 4, 6-dihydroxypyrimidine（M2）, 2-amino-4, 6-dimethoxypyrimidine（M3） and2-（1-（4,6-dimethoxy-pyrimidin-2-yl）-ureido）-N,N-dimethyl-nicotinamide（M4）. Among the metabolites detected, M2 was reported for the first time. Possible biodegradation pathways of nicosulfuron by strain ZWS11 were proposed. The degradation proceeded mainly via cleavage of the sulfonylurea bridge, O-dealkylation, and contraction of the sulfonylurea bridge by elimination of a sulfur dioxide group. The results provide valuable information for degradation of nicosulfuron in contaminated environments.展开更多
To study the effect of ntrC gene product on the expression and regulation of other important nitrogen-fixing genes in Alcaligenes faecalis, partially nfrC-deleted mutants of A. faecalis have been generated. To start w...To study the effect of ntrC gene product on the expression and regulation of other important nitrogen-fixing genes in Alcaligenes faecalis, partially nfrC-deleted mutants of A. faecalis have been generated. To start with, the ntrC gene of A. faecalis was cloned into a suicide plasmid pSUP202 to create a recombinant plasmid pSUML The nfrCgene in pSUM1 was then replaced by a /acZ-Kmr fragment resulted in the generation of a plasmid pSUM2. The lacZfragment in pSUM2 was further removed and a plasmid pSUMS produced. As a second step, the plasmid pSUM2 or pSUM3 was introduced into the wild type of A. faecalis A1501 by conjugation and two partially nfrC-deleted mutants A15CM1 (ntrC:: lacZ) and A15CM2 (ntrC-) were obtained. To understand the regulatory effect of the NtrC on the expression of nifH and nifA, a nifH-lacZ gene or a nifA-lacZ gene was introduced into the ntrC- mutant by conjugation. The results indicated that: (i) although the ntrC - mutant was nif +, its nitrogen fixation activity was only 20%展开更多
Total DNA of Alcaligenes faecalis was probed with both the nifH and nifHD sequences from K. pneumoniae. One positive band of about 4.6 kb was discovered. This nifH homologous fragment was cloned into the vector pBlues...Total DNA of Alcaligenes faecalis was probed with both the nifH and nifHD sequences from K. pneumoniae. One positive band of about 4.6 kb was discovered. This nifH homologous fragment was cloned into the vector pBluescript SK to construct the recombinant plasmid pBZl. The inserted fragment in pBZl was analyzed by physical mapping and was further subcloned for sequencing. It was found that this A. faecalis nifHDK homology pos-sessed a typical σ54-dependent promoter region with upstream activator sequence (UAS) and A-T rich region. The nifH and nifD ORFs were 888 and 1 476 bp long respectively. The GC contents of these two genes were about 61. 6% and 60.0% . The intergenic regions of nifH-nifD and nifD-nifK were 101 and 105 bp respectively. There were sepa-rate SD sequences upstream of all the three genes. The deduced amino acid sequences of the nifH gene product (the Fe-protein ) and the nifD gene product (the Mo-Fc-protein) were also highly homologous to other nitrogen-fixing bacteria, especially in those conserved motif. The A. faecal is sequence has the highest similarity to that of A. vinelandii展开更多
The phosphorus concentration in the culture medium affects the production of poly (3 hydroxybutyrate) (PHB) by Alcaligenes Eutrophus. This investigation shows that the phosphorus concentration in the initial culture m...The phosphorus concentration in the culture medium affects the production of poly (3 hydroxybutyrate) (PHB) by Alcaligenes Eutrophus. This investigation shows that the phosphorus concentration in the initial culture medium influences both the residual cell mass and the PHB production. A kinetic model is proposed for the production of PHB in a fedbatch culture of Alcaligenes Eutrophus. The kinetic model is compared with the experimental results and appears to provide an excellent description of the overall fermentation process. A phosphate mass concentration of 45 g/L produced the highest level of dry cell mass concentration (266 g/L), PHB mass concentration (214 g/L), PHB mass content (804%) and PHB productivity (351 g/L·h) so far obtained.展开更多
文摘By using acetonitrile as the sole nitrogen source, a microbial strain with high nitrilase activity, named as Alcaligenes sp. ECU0401, was newly isolated from soil, which could enantioselectively transform racemic mandelonitrile into (R)-(?)-mandelic acid, with an enantiomeric excess of >99.9%.
基金National Natural Science Foundation of China(51078252)the Science and Technology Program of Taiyuan(120233)the Natural Science Foundation of Shanxi Province(2010011016–1)
文摘Alcaligenes faecalis C16 was found to have the ability to heterotrophically nitrify and aerobically denitrify. In order to further understand its nitrogen removal ability and mechanism, the growth and ammonium removal response were investigated at different C/N ratios and ammonium concentrations in the medium with citrate and acetate as carbon source separately. Furthermore, experiments of nitrogen sources, production of nitrogen gas and enzyme assay were conducted. Results show that the bacterium converts NH+4-N and produces NH2 OH during the growing phase and nitrite accumulation is its distinct metabolic feature. A. faecalis C16 is able to tolerate not only high ammonium concentration but also high C/N ratio, and the ammonium tolerance is associated with carbon source and C/N ratio. The nitrogen balance under different conditions shows that approximately28%–45% of the initial ammonium is assimilated into the cells, 44%–60% is denitrified and several percent is converted to nitrification products. A. faecalis C16 cannot utilize hydroxylamine, nitrite or nitrate as the sole nitrogen source for growth. However, nitrate can be used when ammonium is simultaneously present in the medium. A possible pathway for nitrogen removal by C16 is suggested. The preliminary enzyme assay provides more evidence for this nitrogen removal pathway.
文摘The structure-function relationship of a gellan family of polysaccharides, S-198 gum produced by Alcaligenes ATCC31853 was investigated in terms of rheological aspects. The flow curves of S-198 gum showed plastic behavior above 0.3%. Gelation did not occur in S-198 gum solution at low temperature (0℃), even at 0.8%. Both the viscosity and the elastic modulus remained constant with increasing temperature up to 80?C. The elastic modulus decreased a little with the addition of CaCl2 (6.8 mM), but then once again remained constant up to 80℃. The highest elastic modulus was observed for deacylated gellan gum with the addition of CaCl2 and increased slightly with increasing temperature up to 80℃, which was considered to be a transition temperature, after which it decreased rapidly. The elastic modulus of S-198 gum in the presence of urea (4.0 M) was lower than that in aqueous solution at low temperature (0℃), but remained constant with increasing temperature up to 80℃. The intramolecular associations, (hydrogen bonding and van der Waals forces of attraction), of S-198 gum molecules in aqueous solutions were proposed. The gellan family of polysaccharides, S-198, S-88, S-657, rhamsan, welan and gellan gum, provided a good opportunity to investigate the structure-function relationship for polysaccharides.
文摘Poly(3-hydroxybutyrate) (PHB) is an intracellular carbon and energy storage material accumulated by many kinds of microorganism under unfavorable growth conditions. For the production of PHB, Alcaligenes eutrophus has been widely used because it is easy to grow, and its physiological and biochemical changes during the PHB synthesis is understood in details. A very high concentration and productivity of PHB could be obtained by fed-batch culture of Alcaligenes eutrophus with phosphate limitation in 50 L fermenter.
文摘The rifampin resistant Alcaligenes faecalis strain A1501R survived at a high, initially stable and later slowly declining population size (10 8 to 10 6 CFU per g dry soil) for 60 days in microcosm experiments. Introduction of strain A1501R did not cause great changes in the community profiles generated via microbial community level 16S rDNA based PCR followed by denaturing gradient gel electrophoresis (DGGE) and the Biolog substrate utilization system. The introduction of A1501R had no impact on the dominant bacterial populations in soil. Significant differences in the utilization of some substrates were observed between the control and inoculated soils using a combination of DGGE and Biolog analysis. Results of DGGE and BIOLOG analysis show that introduction of A1501R can affect the lactic acid utilizing bacterial community in case of selection by lactic acid. A specific probe based on the 16S rDNA variable region V6 was constructed via PCR amplification of 16S rDNA using the 971(f) and 1057(r) primers for the detection of A. faecalis strains introduced into soils. Dot blot hybridization of strains or soil DNA and aligment of sequences of the V6 region of 16S rDNA from different bacterial strains show that the V6 probe is very specific for A. faecalis A1501R.
基金supported by the National Natural Science Foundation of China(No.50908166)the China Postdoctoral Science Foundation(No.20100480621)+2 种基金the Program for New Century Excellent Talents in University of ChinaProgram for Young Excellent Talents in Tongji University(No.2010KJ060)the International S&T Cooperation Program of China(No.2009DFA92140)
文摘Exploration of biodemulsifiers has become a new research aspect.Using waste frying oils（WFOs） as carbon source to synthesize biodemulsifiers has a potential prospect to decrease production cost and to improve the application of biodemulsifiers in the oilfield.In this study,a demulsifying strain,Alcaligenes sp.S-XJ-1,was investigated to synthesize a biodemulsifier using waste frying oils as carbon source.It was found that the increase of initial pH of culture medium could increase the biodemulsifier yield but decrease the demulsification ratio compared to that using paraffin as carbon source.In addition,a biodemulsifier produced by waste frying oils and paraffin as mixed carbon source had a lower demulsification capability compared with that produced by paraffin or waste frying oil as sole carbon source.Fed-batch fermentation of biodemulsifier using waste frying oils as supplementary carbon source was found to be a suitable method.Mechanism of waste frying oils utilization was studied by using tripalmitin,olein and tristearin as sole carbon sources to synthesize biodemulsifier.The results showed saturated long-chain fatty acid was diffcult for S-XJ-1 to utilize but could effectively enhance the demulsification ability of the produced biodemulsifier.Moreover,FT-IR result showed that the demulsification capability of biodemulsifiers was associated with the content of C=O group and nitrogen element.
基金supported by the National Basic Research Programme of China (No. 2010CB126104)
文摘A bacterial strain ZWS11 was isolated from sulfonylurea herbicide-contaminated farmland soil and identified as a potential nicosulfuron-degrading bacterium. Based on morphological and physicochemical characterization of the bacterium and phylogenetic analysis of the 16 S r RNA sequence, strain ZWS11 was identified as Alcaligenes faecalis. The effects of the initial concentration of nicosulfuron, inoculation volume, and medium p H on degradation of nicosulfuron were investigated. Strain ZWS11 could degrade 80.56% of the initial nicosulfuron supplemented at 500.0 mg/L under the conditions of p H 7.0, 180 r/min and30°C after incubation for 6 days. Strain ZWS11 was also capable of degrading rimsulfuron,tribenuron-methyl and thifensulfuron-methyl. Four metabolites from biodegradation of nicosulfuron were identified, which were 2-aminosulfonyl-N, N-dimethylnicotinamide（M1）, 4, 6-dihydroxypyrimidine（M2）, 2-amino-4, 6-dimethoxypyrimidine（M3） and2-（1-（4,6-dimethoxy-pyrimidin-2-yl）-ureido）-N,N-dimethyl-nicotinamide（M4）. Among the metabolites detected, M2 was reported for the first time. Possible biodegradation pathways of nicosulfuron by strain ZWS11 were proposed. The degradation proceeded mainly via cleavage of the sulfonylurea bridge, O-dealkylation, and contraction of the sulfonylurea bridge by elimination of a sulfur dioxide group. The results provide valuable information for degradation of nicosulfuron in contaminated environments.
文摘To study the effect of ntrC gene product on the expression and regulation of other important nitrogen-fixing genes in Alcaligenes faecalis, partially nfrC-deleted mutants of A. faecalis have been generated. To start with, the ntrC gene of A. faecalis was cloned into a suicide plasmid pSUP202 to create a recombinant plasmid pSUML The nfrCgene in pSUM1 was then replaced by a /acZ-Kmr fragment resulted in the generation of a plasmid pSUM2. The lacZfragment in pSUM2 was further removed and a plasmid pSUMS produced. As a second step, the plasmid pSUM2 or pSUM3 was introduced into the wild type of A. faecalis A1501 by conjugation and two partially nfrC-deleted mutants A15CM1 (ntrC:: lacZ) and A15CM2 (ntrC-) were obtained. To understand the regulatory effect of the NtrC on the expression of nifH and nifA, a nifH-lacZ gene or a nifA-lacZ gene was introduced into the ntrC- mutant by conjugation. The results indicated that: (i) although the ntrC - mutant was nif +, its nitrogen fixation activity was only 20%
基金Project supported by the 863 High-technology Program.
文摘Total DNA of Alcaligenes faecalis was probed with both the nifH and nifHD sequences from K. pneumoniae. One positive band of about 4.6 kb was discovered. This nifH homologous fragment was cloned into the vector pBluescript SK to construct the recombinant plasmid pBZl. The inserted fragment in pBZl was analyzed by physical mapping and was further subcloned for sequencing. It was found that this A. faecalis nifHDK homology pos-sessed a typical σ54-dependent promoter region with upstream activator sequence (UAS) and A-T rich region. The nifH and nifD ORFs were 888 and 1 476 bp long respectively. The GC contents of these two genes were about 61. 6% and 60.0% . The intergenic regions of nifH-nifD and nifD-nifK were 101 and 105 bp respectively. There were sepa-rate SD sequences upstream of all the three genes. The deduced amino acid sequences of the nifH gene product (the Fe-protein ) and the nifD gene product (the Mo-Fc-protein) were also highly homologous to other nitrogen-fixing bacteria, especially in those conserved motif. The A. faecal is sequence has the highest similarity to that of A. vinelandii
文摘The phosphorus concentration in the culture medium affects the production of poly (3 hydroxybutyrate) (PHB) by Alcaligenes Eutrophus. This investigation shows that the phosphorus concentration in the initial culture medium influences both the residual cell mass and the PHB production. A kinetic model is proposed for the production of PHB in a fedbatch culture of Alcaligenes Eutrophus. The kinetic model is compared with the experimental results and appears to provide an excellent description of the overall fermentation process. A phosphate mass concentration of 45 g/L produced the highest level of dry cell mass concentration (266 g/L), PHB mass concentration (214 g/L), PHB mass content (804%) and PHB productivity (351 g/L·h) so far obtained.
