Biocatalyst improvement for the production of short-chain hydroxamic acids

Abstract

The wide spectrum amidase gene ( amiE) derived from Rhodococcus sp. R312 was overexpressed in a recombinant Escherichia coli strain. Amidase was extracted during the stationary phase by cell grinding. After partial purification with Q-Sepharose chromatography, the enzyme was immobilized on Duolite A-378 resin. A higher immobilization yield ( R i = 87%) was achieved with NaH 2 PO 4 Na 2 HPO 4 phosphate buffer (100 m m) at pH 7. Study of the immobilized amidase demonstrated that the physicochemical properties were similar to those of the free enzyme with respect to pH and activation energy. On the other hand, the optimal working temperature was higher for the immobilized amidase and thermostability was slightly improved. Ten g of insoluble biocatalyst produced 1 l of acetohydroxamic acid (at least 4.1 g l −1) solution after 90 min reaction time. The acetamide bioconversion rate was 55–60% (mol mol −1). After lyophilization, a 10 g powder containing 40% (wt wt −1) acetohydroxamic acid was recovered.