Screening for conditions of enhanced production of a recombinant β-glucanase secreted into the medium by Escherichia coli

Abstract

The extracellular production of a hybrid bacterial β-glucanase using Escherichia coli was studied by using combinations of promoters of varying strength for both a β-glucanase as the target protein and the Kil protein as the releasing factor. Four strains with different combinations of promoter strengths were cultivated in shake-flasks on four different media to assess the cross-influence of promoter and medium in a general manner. Promoters were taken from natural as well as synthetic sequences known to exhibit either weak or strong promoter strength. By far the highest extracellular glucanase activity (>200 U ml-1) was achieved when a strain harbouring the kil gene under control of a strong synthetic stationary-phase promoter and the glucanase gene under control of a strong synthetic constitutive promoter was cultivated on a complex medium mainly composed of casein peptone, yeast extract, and glycerol. © 2009 Springer Science+Business Media B.V.