Enzymatic saccharification of biologically pretreated Pinus densiflora using enzymes from brown rot fungi

Abstract

Enzymatic saccharification of lignocellulosic biomass was performed using culture filtrates of brown rot fungi including Gloeophyllum sepiarium, Fomitopsis pinicola, and Laetiporus sulphureus. Biological treatment with white rot fungi was used as pretreatment prior to enzymatic saccharification. Endoglucanase, beta-glucosidase, xylanase and cellobiohydrolase activities were determined from concentrated culture filtrates of the brown rot fungi. L. sulphureus has the highest endoglucanase, beta-glucosidase, and xylanase activities, and F. pinicola has the highest cellobiohydrolase activity. When enzymes from L. sulphureus were used along with the lignocellulosic biomass pretreated with Stereum hirsutum as the carbon source, the total sugar yield was 11.36 mg/0.25 g of dry weight biomass, with the highest activities of cellulase and hemicellulase. In order to increase the sugar yield, the enzymes from L. sulphureus were mixed with those from F. pinicola, which showed high cellobiohydrolase activity. This caused an increase in the sugar yield from 11.36 mg to 15.22 mg. When temperature was increased to 50 degrees C, the total sugar yield increased to 17.74 mg for the same reaction time. The crystallinity of lignocellulosic biomass decreased from 68.4% to 60.2%, when lignocellulosic biomass pretreated with S. hirsutum was hydrolyzed using enzymes from L. sulphureus.