Mannanases and Xylanases from Alkaliphilic Bacillus firmus K-1 and Their Binding Properties on Insoluble Polysaccharides

Abstract

Alkaliphilic Bacillus firmus K-1 produces not only mannanase but also xylanase when grown inan alkaline galactomannan medium. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) and active-PAGE showed that the crude enzyme of B. firmus K-1 had 5 major proteinbands at the molecular weight of 45, 42, 37, 29 and 23 kDa and contained 3 active bands of xylanaseswith molecular masses of 66, 45 and 23 kDa and 3 active bands of mannanases with molecularmasses of 66, 42 and 23 kDa. The binding of crude enzyme from B. firmus K-1 on insolublepolysaccharides was conducted. It was found that crude enzyme could not bind on mannan andpartially bind on cellulose. However, the enzyme was found to bind readily on xylan. The xylan-bindingproteins were found to be 42 and 23 kDa. The 42 kDa protein was mannanase and the 23 kDa proteinshowed mannanase and xylanase activities, whereas the 66 kDa unbound protein had activities ofmannanase and xylanase.

Keywords : Alkaliphilic Bacillus firmus K-1 / Mannanase / Xylanase / Xylan-binding Mannanase /Xylan-binding Xylanase