MICROBIAL REMOVAL OF CHROMATE BY PSEUDOMONAS PUTIDA

• Main Authors: Ting-yen Chou, 周廷彥
• Other Authors: Ming-tse Lin
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/04374617734319822474

碩士 === 大同大學 === 生物工程學系(所) === 92 === Chromium is common industrial pollution element. Cr is used in chemical industrial processes, mainly leather tanning, pigments and electroplating. The most stable and common forms are the trivalent Cr(Ⅲ) and hexavalent Cr(IV) species. Cr(Ⅵ), considered the most toxic form of Cr, is usually associated with oxygen as chromate (CrO42-) or dichromate (Cr2O72-) ions. In contrast, Cr(Ⅲ) in the form of oxides, hydroxides or sulfates, is much less mobile and exists mostly bound to organic matter in soil and aquatic environments. About the waste chromium, it usually reduce Cr(Ⅵ) to Cr(Ⅲ) is a common policy to detoxify Cr pollution. Pseudomonas species can survive or grow in chromium-related oxides. After biochemical analysis, the Pseudomonas putida BCRC 10459 have the best chromate resistance. P. putida BCRC 10459 treated Cr(Ⅵ) with 5 hours can reduce 1000�嵱 Cr(Ⅵ) to 777�嵱. P. putida BCRC10459 treated with 50�嵱 Cr(Ⅵ) for 2hours, it reached highest specific activity: 106.7 (units per mg of crude extract). Consequently, the chromate reductase was cloned from Pseudomonas putida CCRC10459. An expression plasmid, pQE30, was ligated with it and then transferred to host E. coli DH5α. The chromium resistance of transgenic E. coli was also promoted. The highest specific activity was 39 units per mg of crude extract obtained from LB cultures for 3 hours after induction with 1mM IPTG. According this induction condition, the recombinant E. coli treated with 1000�嵱 Cr(Ⅵ) for 3 hours could remove or reduce 152mM chromate. After Ni-NTA method purification, the specific activity of purified chromate reductase was improved to 1.6 times of crude extract.