Effect of a novel method for in-house cellulase production on 2G ethanol yields

- The method used for enzyme production affects the yields of 2G ethanol production.
- Composition and activity of enzymatic cocktails are affected by the cultivation method.
- The sequential fermentation method improves sugarcane bagasse hydrolysis by 11%.
- Low loadings of in-house produced enzyme increased sugarcane hydrolysis up to 19%.

Significant enzyme loadings are needed in the production of second-generation (2G) ethanol from biomass, and the cost of these enzymes remains a critical challenge for implementation of industrial plants at commercial scale. Aiming to contribute to 2G ethanol viability, its production yield was investigated in terms of the fermentability of sugarcane bagasse hydrolysates obtained using enzymatic cocktails produced in-house. For that, two different cultivation methods (sequential solid-state and submerged fermentation and conventional submerged fermentation) were compared. Sequential and submerged fermentation methods resulted in enzymatic cocktails with different compositions in terms of endoglucanase, xylanase, and β-glucosidase activities. At the same protein loading, use of the sequential fermentation cocktail resulted in 11% hydrolysis increase, relative to that achieved with the submerged fermentation cocktail. Sugarcane bagasse hydrolysis was increased by 8-19% with the addition of low loadings of in-house produced cocktails to a commercial enzyme. Furthermore, the yield of 2G ethanol production (78%) from the hydrolysate obtained using the sequential fermentation cocktail was higher than the yields achieved using the conventional submerged fermentation cocktail hydrolysate (71%) and the commercial enzyme hydrolysate (74%). The sequential fermentation method was superior to conventional submerged fermentation, resulting in a cocktail with higher enzyme activities and better performance in sugarcane bagasse hydrolysis. Moreover, this work shows the improvement on 2G ethanol production by the sequential fermentation process developed for in-house enzyme production. These findings contribute to existing knowledge of 2G ethanol production by demonstrating the effect of the enzymatic cocktails composition on the fermentability of sugarcane bagasse hydrolysates.

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