Feasibility test of utilizing Saccharophagus degradans 2-40^T as the source of crude enzyme for the saccharification of lignocellulose

Abstract

In the conversion of lignocellulose into high-value products, including fuels and chemicals, the production of cellulase and the enzymatic hydrolysis for producing fermentable sugar are the largest contributors to the cost of production of the final products. The marine bacterium Saccharophagus degradans 2-40^T can degrade more than ten different complex polysaccharides found in the ocean, including cellulose and xylan. Accordingly, S. degradans has been actively considered as a practical source of crude enzymes needed for the saccharification of lignocellulose to produce ethanol by others including a leading commercial company. However, the overall enzyme system of S. degradans for hydrolyzing cellulose and hemicellulose has not been quantitatively evaluated yet in comparison with commercial enzymes. In this study, the inductions and activities of cellulase and xylanase of cell-free lysate of S. degradans were investigated. The growth of S. degradans cells and the activities of cellulase and xylanase were promoted by adding 2 % of cellulose and xylan mixture (cellulose:xylan = 4:3 in mass ratio) to the aquarium salt medium supplemented with 0.2 % glucose. The specific cellulase activity of the cell-free lysate of S. degradans, as determined by the filter paper activity assay, was approximately 70 times lower than those of commercial cellulases, including Celluclast 1.5 L and Accellerase 1000. These results imply that significant improvement in the cellulase activity of S. degradans is needed for the industrial uses of S. degradans as the enzyme source.