Screening for conditions of enhanced production of a recombinant β-glucanase secreted into the medium by Escherichia coli
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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.
Keywordsβ-Glucanase Extracellular enzyme Fermentation E. coli Complex and synthetic media
U Beshay is grateful to the Alexander von Humboldt-Foundation for the financial support in the form of a fellowship.
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