Abstract
Back ground: For enzyme production, the costs of solid state fermentation (SSF) techniques were lower and the production higher than submerged cultures. A large number of fungal species was known to grow well on moist substrates, whereas many bacteria were unable to grow under this condition. Therefore, the aim of this study was to isolate a highly efficient strain of Bacillus sp utilizing wheat bran in SSF and optimizing the enzyme production and soluble carbohydrates.
Results: A local strain Bacillus megatherium was isolated from dung sheep. The maximum production of pectinase, xylanase and a-amylase, and saccharification content (total soluble carbohydrates and reducing sugars) were obtained by application of the B. megatherium in SSF using wheat bran as compared to grasses, palm leaves and date seeds. All enzymes and saccharification content exhibited their maximum production during 12-24 h, at the range of 40-80% moisture content of wheat bran, temperature 37-45 degrees C and pH 5-8. An ascending repression of pectinase production was observed by carbon supplements of lactose, glucose, maltose, sucrose and starch, respectively. All carbon supplements improved the production of xylanase and a-amylase, except of lactose decreased a-amylase production. A little increase in the yield of total reducing sugars was detected for all carbon supplements. Among the nitrogen sources, yeast extract induced a significant repression to all enzyme productivity. Sodium nitrate, urea and ammonium chloride enhanced the production of xylanase, a-amylase and pectinase, respectively. Yeast extract, urea, ammonium sulphate and ammonium chloride enhanced the productivity of reducing sugars.
Conclusions: The optimization of enzyme production and sccharification content by B. megatherium in SSF required only adjustment of incubation period and temperature, moisture content and initial pH. Wheat bran supplied enough nutrients without any need for addition of supplements of carbon and nitrogen sources.