Comparison of common carbon sources with unhydrolyzed, dilute acid and steam hydrolyzed distillers’ dried grains with solubles for lignocellulolytic enzyme productions by fungal strains

Abstract

Distillers’ dried grains with solubles (DDGS) are the byproduct of first-generation bioethanol production. DDGS has a high fiber content, which can be used for hydrolytic enzyme production after pretreatment by physical or chemical methods such as dilute acid or semi-continuous steam explosion. This study compares the treated DDGS samples to common carbon sources such as glucose, Avicel (crystalline cellulose), and untreated DDGS along with other cellulosic materials during the production of cellulases and xylanases by selected four fungal strains. Acid treated DDGS without filtration produced up to 0.72 IU/ml of cellulases and 36.44 IU/ml of xylanases. The results showed that acid hydrolysis was a better treatment than untreated, and steam treated DDGS for both cellulase and xylanase productions (p < 0.05). The comparison of enzyme productions with acid hydrolyzed DDGS to common carbon sources also showed that acid hydrolyzed DDGS was a significantly better carbon source than others. Among four fungal strains, two Aspergillus niger strains (NRRL 567 and NRRL 330) were better than the others in enzyme activity levels. The results confirm the significant positive effect of dilute acid treatment in making DDGS a feasible feedstock for hydrolytic enzyme production.