Sunday, April 29, 2007

The effects of wheat bran composition on the production of biomass-hydrolyzing enzymes by Penicillium decumbens

Xianyun Sun, Ziyong Liu, Yinbo Qu Sr., and Xuezhi Li. State Key Laboratory of Microbial Technology, Shandong University, 27 Shandanan road, Jinan, 250100, China

The roles of the starch, protein and soluble saccharide contents of wheat bran on the extracellular cellulase, β-glucosidase, xylanase, amylase and protease activities released by Penicillium decumbens mycelia grown in batch fermentations have been investigated.  The results shown that the starch content of wheat bran is an important, potentially negative factor, as high starch contents stimulate amylase production, but do not support high levels of mycelial growth, cellulase or xylanase production.  Similarly, although high amounts of protein in wheat bran did not inhibit growth, it did result in a reduction in the levels of cellulase, xylanase and protease released to the medium. Differences observed in the extracellular levels of cellulase and xylanase activities in P. decumbens cultures grown with wheat bran with different granule sizes, have been correlated primarily with different starch contents.  The soluble mono- and oligosaccharides present in wheat bran and in cellulose powder were identified by high-pressure liquid chromatography, and the soluble cello-oligosaccharides composition of wheat bran has been considered as the most significant factor in enhancing cellulase production.

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