A Comparison between Hot Liquid Water and Steam Fractionation of Corn Fiber

Abstract

Dried, milled corn fiber (0.2-0.5 kg) was fractionated by treatment with either hot liquid water (3-4 kg) at low solids loadings (5-10%) or steam (0.1-0.4 kg) at high solids loadings (>50%) at 210-220 °C for 2 min, using the same novel process equipment. Pentosan recovery and inhibition of yeast fermentation were evaluated and compared. In addition, the reactivity of pretreated fiber with respect to enzymatic hydrolysis was evaluated using a simultaneous saccharification and fermentation (SSF) system consisting of β-glucosidase-supplemented Trichoderma reesei cellulase together with fermentation by Saccharomyces cerevisiae. Greater solubilization was achieved at 215 °C with hot liquid water at 5% solids loading than with steam at 70% solids loading (54% solubilization vs 37%). The lignocellulosic residue from this hot liquid water fractionation was enriched in glucan. Conversely, the steam fractionation caused no significant change in the fraction of glucan in the residue, relative to the feed material. In both cases, the pentosan fraction of the lignocellulosic residue was reduced, with the steam fractionation resulting in a larger reduction of these carbohydrates. Steam fractionation (70% solids loading) resulted in much lower pentosan recovery (as monosaccharides after posthydrolysis) than fractionation with hot liquid water at 5% solids loading (40% vs 82%). In both cases, the majority of the solubilized pentosans existed as oligomers (>80%). These recoveries indicate that the monosaccharides are protected while in the form of oligomers because recoveries of largely oligomeric carbohydrates are higher than recoveries of monomeric xylose pretreated under similar conditions. The lignocellulosic residues from fractionation at 215 °C with hot liquid water at 5% solids loading and with steam at 70% solids loading were both reactive to enzymatic hydrolysis, exhibiting 86 and 90% conversion of glucan to ethanol respectively vs 64% conversion with untreated corn fiber, obtained by SSF at an enzymatic loading of 15 FPU cellulase/g of cellulose.The liquid product (extract) from the hot liquid water fractionation did not inhibit the final yield of glucose fermentation by S. cerivisiae, while the liquid product from the steam fractionation did.

Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysts, and Engineering

“…Hemicellulose hydrolysis even occurs in hot water (∼210°C), where the water is thought to break down hemicellulose and release acetic acid, which continues to catalyze the reaction. 257 Water-soluble oligomers form in high yields with hot water treatments. Dilute acid treatments of lignocellulose at 160°C, 10 min reaction time, and 0.7 wt % acid, yields 85-90% of the hemicellulose sugars.…”

Comparison of hot-water extraction and steam treatment for production of high purity-grade dissolving pulp from green bamboo

“…Also, a kinetic study of pentosan solubility during ST (Luo et al 2013b) and comparisons of HWE and ST for sugar recovery and ethanol production (Allen et al 2001;Kemppainen et al 2012;Laser et al 2002 andPerez-Cantu et al 2013) have also been conducted. However, at severe prehydrolysis intensity, the relationship between hemicellulose removal and lignin condensation extent during HWE and ST, and their antagonistic effects on subsequent kraft pulping were rarely investigated in the research fields of bio-ethanol production and dissolving pulp production.…”

Efficacy of Hydrothermal Treatment for Production of Solid Fuel from Oil Palm Wastes

“…Many studies using hydrothermal treatment have been conducted, but most of these used the method as a biomass pretreatment step in bio-ethanol production [11][12][13][14]. Few studies have considered benefits of the resulting solid.…”