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

Abstract

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 representative strains were selected and grown in submerged cultures for evaluating their cell-bound and extracellular hydrolytic activity independently on various naphthyl and aliphatic esters. The best lipolytic strain was lyophilized and used as dry mycelium for catalysing the synthesis of various aliphatic esters in heptane, with molar conversions ranging from 28 to 78% after 3 days.

Conclusions: Carboxylesterase activities can easily be found among the Streptomyces, often being cell-bound and also employable for catalysing esterification 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.