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Abstract: The gene encoding a putative protein from Candida parapsilosis CDC317 (CPE) was cloned and overexpressed in Escherichia coli. The protein was amenable to overexpression in E. coli and constituted 35% of the total cell protein content. The optimal activity was determined at pH 5.5 and 40°C with the substrate 4-chloro-3-oxobutanoate ethyl ester (COBE). The optical purity of the product was over 99% enantiomeric excess for the (S)-isomer, and the molar conversion yield of the product was 91.1%. The apparent k m value for COBE was 0.19±0.01mM, which is an order of magnitude lower than that of other enzymes in the literature. [Copyright &y& Elsevier]

Abstract: To establish a stable and efficient immobilization technique under microwave irradiation, a focused microwave reaction system was used, where the temperature was set appropriately in the microwave system and cooling module to produce consecutive microwave irradiation. 2-Deoxy-D-ribose-5-phosphate aldolase (DERA) was rapidly and efficiently immobilized in mesocellular siliceous foams (MCFs) under microwave irradiation. When the output power in the microwave system was set to 30W, after 3min, 88.4% of the enzyme protein was coupled to the wall of the support pores and the specific activity of the immobilized enzyme was 2.24Umg−1, 149.2% higher than that of the free enzyme and 157.0% higher than that of the non-microwave-assisted immobilized enzyme. In catalysis, microwave-assisted immobilized DERA tolerated a wider range of both pH and temperature than other DERA preparations. The thermal and storage stabilities were also significantly improved. This focused; microwave-assisted immobilization technique has proven to be simple, stable and highly efficient. This technique could also be applied to other enzyme immobilizations. [ABSTRACT FROM AUTHOR]

Abstract: In this study, an esterase, designated EstC23, was isolated from a soil metagenomic library. The protein was amenable to overexpression in Escherichia coli under control of the T7 promoter, resulting in expression of the active, soluble protein that constituted 30% of the total cell protein content. This enzyme showed optimal activity at 40°C and retained about 50% maximal activity at 5–10°C. EstC23 showed remarkable stability in up to 50% (v/v) benzene and alkanes (high log P solvents). When incubated for 7days in the presence of 50% benzene or alkanes, the enzyme maintained its 2–3 fold elevated activity. The purified enzyme also cleaved sterically hindered esters of tertiary alcohols. These results indicate that EstC23 has potential for use in industrial processes. [Copyright &y& Elsevier]

Abstract: Sodium chloride salting-in and microwave irradiation were combined to drive thermolysin molecules into mesoporous support to obtain efficiently immobilized enzyme. When the concentration of sodium chloride was 3M and microwave power was 40W, 93.2% of the enzyme was coupled to the support by 3min, and the maximum specific activity of the immobilized enzyme was 17,925.1Umg−1. This was a 4.5-fold increase in activity versus enzyme immobilized using conventional techniques, and a 1.6-fold increase versus free enzyme. Additionally, the thermal stability of the immobilized thermolysin was significantly improved. When incubated at 70°C, there was no reduction in activity by 3.5h, whereas free thermolysin lost most of its activity by 3h. Immobilization also protected the thermolysin against organic solvent denaturation. The microwave-assisted immobilization technique, combined with sodium chloride salting-in, could be applied to other sparsely soluble enzymes immobilization because of its simplicity and high efficiency. [Copyright &y& Elsevier]