Effective production of a thermostable alpha-glucosidase from Sulfolobus solfataricus in Escherichia coli exploiting a microfiltration bioreactor

A microfiltration (MF) membrane bioreactor was developed for an efficient p roduction of a recombinant thermostable alpha -glucosidase (rSsGA) from Sul folobus solfataricus MT-4. The aim of the membrane bioreactor was to improv e the control of the concentration of key components in the growth of genet ic engineered microorganisms, such as Escherichia coli. The influence of me dium composition was studied in relation to cell growth and alpha -glucosid ase production. The addition of components such as yeast extract and trypto ne resulted in a higher enzyme production. High cell density cultivation of E. coil BL21(DE3) on semidefined medium, exploiting a microfiltration bior eactor, was studied in order to optimize rSsGA production. In addition to m edium composition, the inducer employed (either isopropyl beta -D-thiogalac topyranoside or lactose), the induction duration, and the cultivation mode influenced both the final biomass and the enzyme yield. The MF bioreactor a llowed a cell concentration of 50 g/L dry weight and a corresponding alpha -glucosidase production of 11,500 U/L. The improvement obtained in the enzy me production combining genetic engineering and the microfiltration strateg y was estimated to be 2,000-fold the wild-type strain. (C) 2000 John Wiley & Sons, Inc.