Cell-bound and extracellular carboxylesterases from Streptomyces: hydrolytic and synthetic activities

Aim: The distribution of cell-bound and extracellular carboxylesterases was investigated among the genus Streptomyces using 420 strains. Methods and Results: Primary screening was carried out on solid media using tributyrin, triolein and Tween 60 as current substrates. Eleven representa tive strains were selected and grown in submerged cultures for evaluating t heir cell-bound and extracellular hydrolytic activity independently on vari ous naphthyl and aliphatic esters. The best lipolytic strain was lyophilize d and used as dry mycelium for catalysing the synthesis of various aliphati c esters in heptane, with molar conversions ranging from 28 to 78% after 3 days. Conclusions: Carboxylesterase activities can easily be found among the Stre ptomyces, often being cell-bound and also employable for catalysing esterif ication in organic solvent. Significance and Impact of the Study: A wide screening among Streptomyces, a genus poorly studied for the production of carboxylesterases, has allowed the selection of several strains with interesting enzymatic activities to be used in commercially valuable biotransformation.