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With the development and utilization of offshore petroleum resources, petroleum leakage accidents had gradually become an urgent problem to be solved. Immobilization technology had been widely concerned for protecting microorganisms from direct contact with toxic pollutants and improving biological density. In order to enhance the remediation effect of immobilized petroleum-degrading bacteria beads on petroleum-polluted seawater, a mobile bioreactor using immobilized petroleum-degrading bacteria beads was designed. Immobilized petroleum-degrading bacteria beads with Enteromorpha biochar was selected in bioreactor in this study. However, salinity and pH in different sea areas could affect the practical application of bioreactor with immobilized petroleum-degrading bacteria beads. Therefore, the influence of environmental factors on the physical and chemical properties of immobilized petroleum-degrading bacteria beads in the bioreactor was further investigated by changing the salinity and pH of input water. Research result showed alginate lyase had more binding sites with calcium alginate at the pH of 8.0 and 30‰ salinity when penetration time of bioreactor was least. The research in this paper would contribute to the development of a more efficient and widely applicable bioreactor, and further provide theoretical support for the biological remediation of petroleum-polluted sea areas. [ABSTRACT FROM AUTHOR]

A formate dehydrogenase gene ( fdh) originated from Candida boidinii was co-expressed in E. coli BL21 (DE3) with the cyclohexanone monooxygenase gene ( chmo) cloned from Acinetobacter calcoaceticus NCIMB 9871. The co-expression system was then used as a whole-cell biocatalyst to synthesize chiral phenyl methyl sulfoxide (PMSO) from thioanisole (PMS) and the reaction conditions were investigated. When the initial concentration of PMS was 20 mM, the specific productivity of PMSO in this system was 2.07 μmol g cw min (cw: wet cell weight) and the ee value for the R-sulfoxide was 99 %. In contrast, when chmo was the only gene expressed in E. coli, the specific productivity of PMSO was 0.053 μmol g cw min with no exact enantioselectivity. Further determination of NADPH concentration in the whole-cell catalysts suggested that co-expression of fdh with chmo significantly improved NADPH supply. Thus, this whole-cell biocatalyst system is highly advantageous for the synthesis of optically pure R-sulfoxide. [ABSTRACT FROM AUTHOR]

A novel aldo-keto reductase gene, Tm1743, from Thermotoga maritima was overexpressed in Escherichia coli. The enzyme displayed the highest activity at 90 °C and at pH 9. It retained 63 % of its activity after 15 h at 85 °C. The enzyme also could tolerate (up to 10 % v/v) acetonitrile, ethanol and 2-propanol with slightly increased activities. Methanol, DMSO and acetone decreased activity slightly. Furthermore, Tm1743 exhibited broad substrate specificity towards various keto esters, ketones and aldehydes, with relative activities ranging from 2 to 460 % compared to the control. Its optimum substrate, 2,2,2-trifluoroacetophenone, was asymmetrically reduced in a coupled NADPH-regeneration system with an enantioselectivity of 99.8 % and a conversion of 98 %. [ABSTRACT FROM AUTHOR]

The gene encoding a novel short-chain alcohol dehydrogenase in the thermophilic bacterium, Carboxydothermus hydrogenoformans, was identified and overexpressed in Escherichia coli. The enzyme was thermally stable and displayed the highest activity at 70 °C and pH 6.0. It preferred NAD(H) over NADP(H) as a cofactor and exhibited broad substrate specificity towards aliphatic ketones, cycloalkanones, aromatic ketones, and ketoesters. Furthermore, ethyl benzoylformate was asymmetrically reduced by the purified enzyme, using an additional coupled NADH regeneration system, with 95 % conversion and in an enantiomeric excess of (99.9 %). The results of this study may lead to the discovery of a novel method for asymmetric reduction of alcohols, which is an important tool in organic synthesis. [ABSTRACT FROM AUTHOR]