Optimization of enzymatic hydrolysis for bioethanol production by semi-simultaneous saccharification and fermentation using mature coconut fibre

Abstract

Alternative substrates to produce useful chemicals such as biofuel have been attractive, in particular, for cellulosic ethanol production. In this context, the objective of this work was optimized the synergistic mixture of enzymes and bioethanol production. The enzymes of Trichoderma reesei and crude enzyme extract from Lichtheimia ramosa were used in the hydrolysis of mature coconut fibre pretreated by sequential process of alkaline hydrogen peroxide (Alk-H2O2)-sodium hydroxide (NaOH). Furthermore, these enzymes and pretreated vegetable biomass were applied in the bioethanol production by Saccharomyces cerevisiae in semi-simultaneous saccharification and fermentation strategy (SSSF). Resulting in the yields and conversions of delignified mature coconut fibre into reducing sugars between 12.7-82.14% and 0.09-0.64 g reducing sugars/g dry biomass, respectively, with an initial hydrolysis rate at 12 h between 0.10-0.89 g/(L.h). Yields and conversions of delignified mature coconut fibre into glucose between 10.16-83.78% and 0.06-0.43 g glucose/g dry biomass, in that order, with an initial hydrolysis rate at 12 h between 0.03-0.35 g/(L.h). Bioethanol production by S. cerevisiae using delignified mature coconut fibre, enzymes from T. reesei and crude enzyme extract from L. ramosa resulted in the production of 4.62 g/L, yield of 0.41 g ethanol/g glucose and volumetric productivity of ethanol of 0.13 g/(L.h), respectively. The results showed synergistic effects between enzymes from T. reesei and crude enzyme extract from L. ramosa, without promoting inhibition in the alcoholic fermentation. Therefore, allowing to formulate an optimized enzymatic preparation aiming cellulosic ethanol production.