使用野生型和重组耐汞细菌对汞进行微生物解毒的重复补料分批操作。

Repeated fed-batch operations for microbial detoxification of mercury using wild-type and recombinant mercury-resistant bacteria.

作者信息

Chang J S, Chao Y P, Law W S

机构信息

Department of Chemical Engineering, Feng Chia University, Taichung, Taiwan, ROC.

出版信息

J Biotechnol. 1998 Oct 8;64(2-3):219-30. doi: 10.1016/s0168-1656(98)00112-6.

DOI:10.1016/s0168-1656(98)00112-6

PMID:9821677

Abstract

A wild-type mercury-resistant strain Pseudomonas aeruginosa PU21 (Rip64), and an Escherichia coli PWS1 strain genetically engineered to harbor mercury resistance were examined for their capacity to detoxify soluble mercuric ions with repeated fed-batch operations. The specific mercury detoxification activity for the two strains at different initial mercury concentrations was determined by resting-cell experiments. The fed-batch operations were conducted with different initial culture volumes (Vo), inoculum sizes (Xo), and different mercury feeding rates (FHg) to investigate the effects of those operation parameters on the performance of mercury detoxification. The results showed that the wild-type and the recombinant strains had an optimal specific activity of 5 x 10(-7) and 8 x 10(-8) micrograms cell-1 h-1, respectively. In fed-batch operation for P. aeruginosa PU21, under the conditions of Vo = 400 ml and Xo = 4.5-4.8 x 10(9) cells ml-1 the overall mercury detoxification efficiency (eta) for FHg = 16.9 mg Hg h-1 was 5.26 mg Hg l-1 h-1, nearly 35% higher than that for a lower FHg (11.7 mg Hg h-1). Among the three initial culture volumes examined in this study, the highest eta (5.60 mg Hg l-1 h-1) was obtained when Vo = 1200 ml and FHg = 16.9 mg Hg h-1. It was also found that an inoculum size higher than 4.0 x 10(9) cells ml-1 enabled a stable fed-batch operation, while as the inoculum was reduced to around 1.6 x 10(9) cells ml-1, the mercury feeding caused severe cell death, leading to an unsuccessful fed-batch operation. In the fed-batch operation for E. coli PWS1 strain with Vo = 1200 ml and FHg = 16.9 mg Hg h-1, the mercury detoxification efficiency was 3.07 mg Hg l-1 h-1, only 54% of that for the wild-type P. aeruginosa PU21 strain under the same operating conditions. It was also noticed that the operation with E. coli PWS1 became less efficient at the second fed-batch cycle due to plasmid instability of the recombinant strain.

摘要

对野生型耐汞铜绿假单胞菌菌株PU21（Rip64）以及经过基因工程改造以具有耐汞性的大肠杆菌PWS1菌株进行了研究，考察它们在重复补料分批操作下对可溶性汞离子的解毒能力。通过静息细胞实验测定了这两种菌株在不同初始汞浓度下的比汞解毒活性。进行了不同初始培养体积（Vo）、接种量（Xo）以及不同汞进料速率（FHg）的补料分批操作，以研究这些操作参数对汞解毒性能的影响。结果表明，野生型菌株和重组菌株的最佳比活性分别为5×10⁻⁷和8×10⁻⁸微克细胞⁻¹小时⁻¹。对于铜绿假单胞菌PU21的补料分批操作，在Vo = 400 ml和Xo = 4.5 - 4.8×10⁹个细胞毫升⁻¹的条件下，FHg = 16.9毫克汞小时⁻¹时的总汞解毒效率（η）为5.26毫克汞升⁻¹小时⁻¹，比FHg较低（11.7毫克汞小时⁻¹）时高出近35%。在本研究考察的三个初始培养体积中，当Vo = 1200 ml且FHg = 16.9毫克汞小时⁻¹时，获得了最高的η（5.60毫克汞升⁻¹小时⁻¹）。还发现接种量高于4.0×10⁹个细胞毫升⁻¹能够实现稳定的补料分批操作，而当接种量降至约1.6×10⁹个细胞毫升⁻¹时，汞进料导致严重的细胞死亡，导致补料分批操作失败。对于Vo = 1200 ml且FHg = 16.9毫克汞小时⁻¹的大肠杆菌PWS1菌株的补料分批操作，汞解毒效率为3.07毫克汞升⁻¹小时⁻¹，仅为相同操作条件下野生型铜绿假单胞菌PU21菌株的54%。还注意到，由于重组菌株的质粒不稳定，大肠杆菌PWS1在第二个补料分批循环时操作效率降低。