Valorização da fibra de coco verde para produção de lignosulfonato aplicado à produção de etanol de segunda geração

Abstract

In order to reduce the environmental impacts generated by the inappropriate disposal of agroindustrial waste, their reuse promotes a more attentive look at second-generation ethanol, in addition to the use of lignin for the production of value-added products. The present study evaluated ethanol and lignosulfonate (LS) productions, from green coconut fiber. The sugar production in enzymatic hydrolysis was studied by varying the biomass concentration (5, 10 and 15%) and the enzymatic load (10, 15 and 20 FPU/g), after pre-treatments with sodium hydroxide (test HS) and combined (steam explosion followed by treatment with sodium hydroxide) (test EVHS). Then, the ethanolic production was evaluated for both tests, varying the solids load and in simultaneous (SSF) and semi-simultaneous (SSSF) saccharification and fermentation strategies. The lignosulfonate produced from a lignin sulfomethylation was added in the biomass enzymatic hydrolysis, in order to evaluate its effect on the sugars yield. In the enzymatic hydrolysis, the increase in the solid load showed a significant increase in the glucose concentration obtained for both tests. However, the variation in the enzymatic load was not statistically significant. Only for test EVHS, at 15% solids, with 15 FPU/g (>34 g/L) and 20 FPU/g (>31 g/L). Furthermore, lignosulfonate is efficient in reducing the nonproductive adsorption of lignin on the enzyme when added in the hydrolysis process. In fermentation, the change in fermentation strategy and the variation in enzymatic load did not indicate a significant variation in ethanol production for test HS. In turn, for test EVHS, the significant increase in enzymatic load increased the ethanol produced concentration. In addition, changing the strategy from SSF (at 20 FPU/g) to SSSF (at 15 FPU/g) showed an increase equivalent to 40% in the ethanol obtained concentration, while reducing about 25% of used enzyme. Regarding lignosulfonates, FTIR analyzes corroborate the efficiency of sulfomethylation process for sulfonation of the aromatic groups of lignin. As for its addition in enzymatic hydrolysis, for a concentration of 0.5 g/L (1% m/m of biomass), it showed a 30% increase in cellulosic conversion. Therefore, the results indicate that increasing the amount of solids in enzymatic hydrolysis increases cellulosic conversion, but increasing the enzymatic load is not always necessary. In addition, it was verified that the change in the fermentation strategy, in some cases, allows the reduction of the amount of cormaceous enzyme used, even increasing the production of ethanol in the process.