Background: One of the critical challenges of cost effective bioethanol production from lignocellulosic biomass is the decreasing yield of reducing sugars caused by increasing substrate loading. Hence, it is crucial to determine the best substrate concentration for efficient saccharification of lignocellulosic wastes.
Objective: This paper reports saccharification of corn cob by two lignocellulolytic fungi (Fusarium oxysporum and Sporothrix carnis) and concurrent production of lignocelluloytic enzymes at varied substrate concentrations.
Methods: F. oxysporum and S. carnis were cultivated on corn cob based media at 30°C and 160 rpm for 144 h. Lignocellulosic composition of corn cob was determined. Saccharification of varied concentrations of substrate was determined by evaluating the release of reducing sugar while production of cellulase and xylanase was monitored.
Results: Cellulose, hemicellulose and lignin contents of corn cob were 37.8±1.56%, 42.2±1.68% and 12.7±1.23%, respectively. Yields of reducing sugar by F. oxysporum and S. carnis were 5.03 µmol/mL and 6.16 µmol/mL; and 6.26 µmol/mL and 6.58 µmol/mL at 10.0 and 25.0% substrate concentration, respectively. Production of cellulase and xylanase was exponential as corn cob concentration increased from 0.5% to 10.0% yielding 586.93 U/mL and 1559.18 U/mL from F. oxysporum, with 590.7 U/mL and 1573.95 U/mL from S. carnis, respectively.
Conclusion: The study shows that the most efficient saccharification of corn cob by F. oxysporum and S. carnis was at 10.0% substrate concentration. This suggests that two separate saccharification processes at this concentration will result in higher yields of enzyme and reducing sugars than from a single process involving higher concentration.