Study of gamba grass as carbon source for cellulase production by Fusarium verticillioides and its application on sugarcane bagasse saccharification

Gamba grass (Andropogon gayanus), a forage biomass, was used as carbon source for cellulases production by Fusarium verticillioides. A Plackett Burman design was employed to evaluate the effects of different factors over enzymatic production and two different media composition, M1 and M2, were found. In M1 media, endoglucanase and cellobiase activities were 6.5 and 0.39 U/mL, respectively. By another hand, the activities of endoglucanase and cellobiase in M2 conditions were 2.6 and 6.8 U/mL, respectively. Blends of these two extracts were tested on a sugarcane bagasse saccharification and M1 presented the best performance, indicating that higher ratios endoglucanase/cellobiase (12:1) improved sugarcane bagasse hydrolysis. Different dosages of protein (10, 20 and 40 mg/g of dry biomass) were tested intending to improve the hydrolysis performance of M1 extract. Saccharification rates of 43.4 and 73.1% were observed for glucan and xylan fractions respectively when 40 mg/g was used. Some non-productive factors such as enzyme adsorption, sugar inhibition and thermostability were evaluated to get a better understanding about saccharification bottlenecks related to Fusarium verticillioides enzymatic extract. This paper showed, for the first time, that gamba grass can be an efficient inductor for cellulase production in the endophytic fungus Fusarium verticillioides. It was also showed that, in Fusarium verticillioides, the induction of enzymes specialized on plant biomass degradation is highly dependent on carbon source concentration. Endoglucanase was mostly induced in middle concentrations while cellobiase is induced in high concentrations.