Production of Ethanol from Green Coconut Fiber by Integrating Cloud Point Extraction and Simultaneous Saccharification and Fermentation

Abstract

The fermentation of whole slurry favors the increase in ethanol titers and minimizes water consumption. However, inhibitors accumulate in the liquid fraction pretreatment, reducing fermentation performance. In order to find a way out, the present study proposed an integration between cloud point extraction (CPE) and ethanol production using fiber of green coconut (GCF) as substrate. Triton X-114 was used to detoxify the liquid fraction from acid pretreatment, and optimal operating conditions were obtained by mathematical modeling. The effects of the residual surfactant from the dilute phase of CPE were analyzed in cellulase adsorption tests, enzymatic hydrolysis, and fermentation of acid-pretreated GCF. CPE promoted high removal of furans (86.23–100%) and phenolic compounds (22.79–75.15%), while the sugars migrated to the dilute phase. A neural network model coupled with a genetic algorithm obtained an optimal condition of 2.38% Triton X-114, temperature of 42 °C, pH of 4.3, and 0.55% sodium chloride. The incubation with the CPE dilute phase increased the residual activity from 25.1 to 50.1% and increased the cellulosic conversion from 32.28 to 41.15%. CPE-saccharification and simultaneous fermentation integration boosted the ethanol production to 12.40 g/L, while the untreated whole slurry reached only 6.29 g/L. Because of these results, the CPE emerges as a promising alternative to favor the full use of sugars from lignocellulosic biomass.