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Abstract.

Distillers‘ dried grains with solubles (DDGS) are by-products of dry-mill bioethanol production from corn and wheat. The DDGS is leftover by the yeast after converting the starch into ethanol and it has a high nutritional profile including undigested fiber and protein fractions. The DDGS can be used as cheap microbial feedstock for the production of cellulase and xylanases, which are produced from expensive industrial feedstocks. In this study, screening of several bacterial and fungal strains was done using DDGS as the feedstock for the hydrolytic enzyme production. Among all these strains, Aspergillus niger (NRRL 1956) produced the maximum cellulase of 0.592 IU/ml. On the other hand, stable high production of xylanase of 34.8 IU/ml was obtained by Aspergillus niger (NRRL 567) on day twelfth. Bacterial enzyme production by Bacillus subtilis (NRRL NSR352, DSM 17766, and NF1) was relatively lower (0-0.261 IU/ml for cellulase and 1.2-5.2 IU/ml for xylanase) than the fungal enzyme production. In conclusion, this study demonstrated that the hydrolyzed DDGS can be an alternative economical substrate for A. niger strains to produce cellulase and xylanase, respectively. The next phases of the study should further optimize the production of cellulase and xylanase in terms of growth parameters and medium components by using benchtop bioreactors.