利用Red同源重组技术,快速敲除肺炎克雷伯氏菌中的编码D-乳酸脱氢酶的两个基因——ldhA和dld,获得KG1-1和KG1-2两个突变株,并研究了敲除编码D-乳酸脱氢酶基因丧失合成D-乳酸的KG1-1菌株的1,3-PD产量和菌体生长变化,实验结果表明乳酸合成缺失对现有工艺1,3-丙二醇发酵无影响.

Chloroperoxidase(CPO) is a kind of chiral catalyst which has extensive catalytic activities for various substrates.It can be used for catalyzing the peroxidation of halogen ion,aromatic hydrocarbons,alcohols ect.In this paper,phenol was applied as study object to investigate the promotion effect of CPO on phenol biodegradation.The results show that the biodegradation of phenol was greatly improved with the existence of CPO.The optimal catalyzing conditions were CPO 10 U/mL,pH 6.5,H2O2 dosage of 10 mg/L and biodegrading for 8 h.When the initial concentration of phenol was 500,1 000 mg/L,biodegradation rate of phenol was 86.6% and 83.8% respectively under these optimal conditions.The conclusions indicated that CPO could quickly remove the phenol in environment and improve the phenol biodegradation efficiency significantly.

This paper systematically investigated the expression of S-adenosylmethionine synthetase gene from yeast by using the pET soluble expression system. It was indicated that pET-44a (Nus fusion tag ) as the carrier and Origami (trxB and gor double mutant) as the host were suitable for the soluble expression of the target protein. Furthermore, the same result was obtained when the soluble expression of S-adenosylmethionine synthetase gene from different sources (E. coli, Bacillus subtilis, Bacillus thuringiensiss) were tested. It was also found that the gene from yeast got the highest soluble expression, which the specific activity of SAM synthetase was up to 60.9 U/mg.

Two phenol-degrading bacterial strains named XTT-1,XTT-3 were isolated from active sludge using the way of acclimatization and could grow on a medium with phenol as the sole carbon and energy sources,the two strains were identified preliminarily as Pseudomonas sp.The optimum degradation condition of the two strains was explored.Strain XTT-3 could degrade phenol completely at a concentration as high as 500 mg·L-1 in 48 h,while strain XTT-1 did it in 64h..The two strains could resist to phenol up to 1000 mg·L-1.Salt content higher than 2.0% had different degrees of inhibition on phenol degradation.

The hydrophilic polymer PEG6000 was used to co-precipitate with chloroperoxidase(CPO)in the saturated ammonium sulfate solution.Then,a aqueous two-phase system of PEG/phosphate was formed based on the co-precipitation resolution to extracted higher composition CPO,and the purity CPO sample from Sephadex G-100 chromatographic system was obtained.Results showed that the CPO yield was 85.5% by co-precipitate with PEG in the presence of the phosphate solution.In the aqueous two-phase system,CPO was dissolved in the bottom phase,the partition coefficient k was lower than 0.341,the yield reached 69.1%,and the purification ratio increased 21.57 times.The purity of CPO was further improved to 24.79 times by column chromatography,the total yield of CPO was 37.75%.