Pressurized pretreatment and simultaneous saccharification and fermentation with in situ detoxification to increase bioethanol production from green coconut fibers

Abstract

In this study, we investigated four conventional pretreatments under pressurized conditions, as well as in situ detoxification using polyethylene glycol (PEG 400), for the simultaneous saccharification and fermentation (SSF) of green coconut fibers. The highest fermentable sugar production (22.05% g/g untreated fiber) was reached with pressurized dilute alkaline pretreatment. In the SSF, the addition of PEG favored ethanol production compared to that in experiments without the polymer, reaching a maximum value of 7.87 g/L at a liquor content of 50% v/v for the pressurized water pretreatment. After lignin recovery by acid precipitation, the liquors had interesting antioxidant properties, similar to those of fruit extracts. The proposed pressurized water pretreatment could be an advantageous choice because it can be performed at mild temperatures (70 °C) and high solid loadings (26.67% w/v) and achieves a high mass yield (72.84% w/w) without the addition of a chemical agent. Furthermore, the liquor can be used in the SSF, reducing the water consumption and number of steps in the cellulosic ethanol process.