Deacetylation Followed by Fractionation of Yellow Poplar Sawdust for the Production of Toxicity-Reduced Hemicellulosic Sugar for Ethanol Fermentation

Seong Kim,Kyeong Oh,Tae Kim

doi:10.3390/en11020404

Seong Kim, Kyeong Oh + Show 1 more

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https://doi.org/10.3390/en11020404

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Abstract

In order to produce bioethanol from yellow poplar sawdust without detoxification, deacetylation (mild alkali treatment) was performed with aqueous ammonia solution. To select the optimal conditions, deacetylation was carried out under different conditions: NH4OH loading (2–10% (w/v)) and a solid-to-liquid ratio of 1:4–1:10 at 121 °C for 60 min. In order to assess the effectiveness of deacetylation, fractionation of deacetylated yellow poplar sawdust was performed using dilute acid (H2SO4, 0.5–2.0% (w/v)) at a reaction temperature of 130–150 °C for 10–80 min. The toxicity-reduced hemicellulosic hydrolyzates that were obtained through a two-step treatment at optimized conditions were fermented using Pichia stipitis for ethanol production, without any further detoxification. The maximum ethanol production was 4.84 g/L, corresponding to a theoretical ethanol yield of 82.52%, which is comparable to those of intentionally made hydrolyzates as controls.

Highlights

The increasing demand for alternative sources of fuel has increased public interest in the development of biofuel
The effectiveness of deacetylation was determined by the appearance of the formation of acetic acid in the liquid phase derived from yellow poplar sawdust (YPS)
De Assis Castro et al [7] obtained the maximum formation of acetic acid in rice straw hemicellulosic hydrolyzate, which resulted in the highest hemicellulose extraction, since acetyl groups are structurally linked to hemicellulose

Summary

Introduction

The increasing demand for alternative sources of fuel has increased public interest in the development of biofuel. Significant effort has been invested in the conversion of lignocellulosic biomass into platform chemicals as well as further upgrading to biofuels [1,2,3]. Lignocellulosic biomass, which is generally sourced from wood and agricultural wastes, is mainly composed of cellulose, hemicellulose, and lignin. Due to its recalcitrant characteristics, the biomass requires an appropriate fractionation process to produce fermentable sugars [4,5]. The fractionation methods for lignocellulosic biomass mainly contain physical, chemical, and biological methods, and their combinations [6], which have different impacts on the structure of the lignocellulosic material, and have a significant impact on the downstream processings of the biomass conversion process, which is relevant to sugar recovery, hydrolyzate detoxification, enzymatic hydrolysis and fermentation, and waste water treatment [7].

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