Psychrotrophic Streptomyces spp. cells immobilisation in alginate microspheres produced by emulsification-internal gelation

The objective of the investigations was the optimisation of the parameters for cold-adapted Streptomyces MIUG 4 Alga strain cells immobilisation using emulsification-internal gelation technique in calcium alginate microspheres and testing their ability to produce cold-active beta-amylase. By Box-Behnken design and response surface methodology, the effects of independent variables were established, which included sodium alginate concentration (A), sodium alginate: living cell ratio (B) and the Span 80 concentration (C) upon microspheres formation and their functionality. Mean diameter of formed microspheres with immobilised biomass and cold-active b-amylase production were chosen as dependent variables in order to increase the yield of starch hydrolysis. Diameters of microspheres <25.5 mu m provided large yield of cold-active b-amylase comparing with microspheres with bigger diameter. A 1.5-fold increase in the substrate hydrolysis yield was achieved using the immobilised biocatalyst compared with the crude enzyme extract, after 96 h of substrate bioconversion.