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
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
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展开更多
以渤海和黄海分离出400多株在低温条件下生长良好的菌株为出发菌株,利用常规筛选方法选出2株低温蛋白酶产生菌(Pseudom onas alcaligenes)。经UV、DES、NTG、EMS、L iC l单独及复合诱变,选育出一株(Pa040523)蛋白酶高产突变株。通过单...以渤海和黄海分离出400多株在低温条件下生长良好的菌株为出发菌株,利用常规筛选方法选出2株低温蛋白酶产生菌(Pseudom onas alcaligenes)。经UV、DES、NTG、EMS、L iC l单独及复合诱变,选育出一株(Pa040523)蛋白酶高产突变株。通过单因素实验,确定了Pa040523菌株蛋白酶发酵培养基为:玉米淀粉糖1.8%,尿素0.6%,磷酸氢二钾0.6%,磷酸二氢钾0.3%。该突变株低温蛋白酶产量为940.8 U/mg。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%.
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
