Xylanase Production by Bacillus circulans D1Using Maltose as Carbon Source

摘要

Bacillus circulans D1 is a good producer of extracellular thermostable xylanase.Xylanase production in different carbon sources was evaluated and the enzyme synthesiswas induced by various carbon sources. It was found that D-maltose is the best inducer ofthe enzyme synthesis (7.05 U/mg dry biomass at 48 h), while D-glucose and D-arabinoselead to the production of basal levels of xylanase. The crude enzyme solution is free ofcellulases, even when the microorganism was cultivated in a medium with D-cellobiose.When oat spelt xylan was supplemented with D-glucose, the repressive effect of this sugaron xylanase production was observed at 24 h, only when used at 5.0 g/L, leading to areduction of 60% on the enzyme production. On the other hand, when the xylan mediumwas supplemented with D-xylose (3.0 or 5.0 g/L), this effect was more evident (80 and 90%of reduction on the enzyme production, respectively). Unlike that observed in the xylanmedium, glucose repressed xylanase production in the maltose medium, leading to areduction of 55% on the enzyme production at 24 h of cultivation. Xylose, at 1.0 g/L,induced xylanase production on the maltose medium. On this medium, the repressive effectof xylose, at 3.0 or 5.0 g/L, was less expressive when compared to its effect on the xylanmedium.