Enzymatic hydrolysis and simultaneous saccharification and fermentation of green coconut fiber under high concentrations of ethylene oxide-based polymers

Abstract

The present study focuses on elucidating the effects of ethylene oxide-based polymers on cellulosic ethanol production from green coconut fiber (GCF). Data on ethanol production, cell viability, adsorption of cellulases, and enzymatic digestibility were collected from experiments with high concentrations of PEG 4000 and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) 5800 (EOPO 5800). PEG 4000 and EOPO 5800 favored cell viability and ethanol production in simulated experiments with S. cerevisiae CAT-1 and Kluyveromyces marxianus. Enzymatic hydrolysis under 175 g L−1 PEG 4000 increased the sugar release using untreated GCF (702.0%), hydrothermally-pretreated GCF (63.2%), and acid-pretreated GCF (40.1%). However, there were no benefits to using SigmaCell cellulose as the substrate. EOPO 5800 at 100 g L−1 had positive effects on cellulolytic activity preservation and on the sugar release during enzymatic hydrolysis. Both polymers provided higher ethanol titers for simultaneous saccharification and fermentation (SSF) of pretreated GCF compared to polymer-free experiments. A high ethanol yield (89.8%) was reached by the SSF of untreated GCF using 175 g L−1 PEG 4000. This result implies that high polymer concentrations may enable the cellulosic ethanol scheme without the need for pretreatment.