Recombinant microbial systems for improved β-galactosidase production and biotechnological applications

beta-Galactosidases (EC 3.2.1.23) constitute a large family of proteins that are known to catalyze both hydrolytic and transgalactosylation reactions. The hydrolytic activity has been applied in the food industry for decades for reducing the lactose content in milk, while the transgalactosylation activity has been used to synthesize galacto-oligosaccharides and galactose containing chemicals in recent years. The main focus of this review is on the expression and production of Aspergillus niger, Kluyveromyces lactis and bacterial beta-galactosidases in different microbial hosts. Furthermore, emphasis is given on the reported applications of the recombinant enzymes. Current developments on novel beta-galactosidases, derived from newly identified microbial sources or by protein engineering means, together with the use of efficient recombinant microbial production systems are converting this enzyme into a relevant synthetic tool. Thermostable beta-galactosidases (cold-adapted or thermophilic) in addition to the growing market for functional foods will likely redouble its industrial interest. (C) 2011 Elsevier Inc. All rights reserved.