Molecular advances in microbial α-galactosidases: challenges and prospects

alpha-Galactosidase (alpha-D-galactosidase galactohydrolase; EC 3.2.1.22), is an industrially important enzyme that hydrolyzes the galactose residues in galactooligosaccharides and polysaccharides. The industrial production of alpha-galactosidase is currently insufficient owing to the high production cost, low production efficiency and low enzyme activity. Recent years have witnessed an increase in the worldwide research on molecular techniques to improve the production efficiency of microbial alpha-galactosidases. Cloning and overexpression of the gene sequences coding for alpha-galactosidases can not only increase the enzyme yield but can confer industrially beneficial characteristics to the enzyme protein. This review focuses on the molecular advances in the overexpression of alpha-galactosidases in bacterial and yeast/fungal expression systems. Recombinant alpha-galactosidases have improved biochemical and hydrolytic properties compared to their native counterparts. Metabolic engineering of microorganisms to produce high yields of alpha-galactosidase can also assist in the production of value-added products. Developing new variants of alpha-galactosidases through directed evolution can yield enzymes with increased catalytic activity and altered regioselectivity. The bottlenecks in the recombinant production of alpha-galactosidases are also discussed. The knowledge about the hurdles in the overexpression of recombinant proteins illuminates the emerging possibilities of developing a successful microbial cell factory and widens the opportunities for the production of industrially beneficial alpha-galactosidases. [GRAPHICS] .