Cellulosic Butanol Biorefinery: Production of Biobutanol from High Solid Loadings of Sweet Sorghum Bagasse—Simultaneous Saccharification, Fermentation, and Product Recovery

Nasib Qureshi,Nancy Nichols,Badal Saha,Thaddeus Ezeji,Siqing Liu

doi:10.3390/fermentation7040310

Abstract

Butanol was produced commercially from cornstarch and sugarcane molasses (renewable resources) until 1983, when production of these plants was forced to cease because of unfavorable economics of production caused in part by escalating prices of these feedstocks. During recent years, the focus of research has been on the use of economically available agricultural biomass and residues and cutting-edge science and technology to make butanol production a commercially viable process again. In this study, we produced butanol from sweet sorghum bagasse (SSB) by employing high concentrations of SSB solids and integrated process technology through which simultaneous saccharification, fermentation, and recovery (SSFR) were conducted as one unit operation. The concentrated SSB (16–22% dry wt. basis or 160–220 gL−1) was used to reduce reactor size and potentially reduce fixed and operational costs. Indeed, ABE productivity and yield of 0.21 gL−1h−1 and 0.39 were obtained, respectively, when 160 gL−1 SSB (16%, dry wt.) was used in the SSFR process. In nonintegrated systems, use of >90 gL−1 solid loading is improbable and has not been done until this study.

Highlights

High oil prices, lack of energy security, and concerns about climate change have triggered immense interest in the production of energy from cellulosic biomass sources.Energy security is threatened by political instability in some oil-supplying regions, which results in high gasoline prices
Presaccharification prepared the sweet sorghum bagasse (SSB) for simultaneous saccharification and fermentation, and the medium was inoculated with 10 mL of actively growing C. beijerinckii P260 (~6%, v/v)
This study revealed that use of 160 gL−1 SSB in an integrated process in which SSB saccharification, fermentation and recovery were combined was possible

Summary

Introduction

Lack of energy security, and concerns about climate change have triggered immense interest in the production of energy from cellulosic biomass sources.Energy security is threatened by political instability in some oil-supplying regions, which results in high gasoline prices. One of the solutions to these problems is the use of zero or overall low-carbon-emission fuels that can be produced from renewable cellulosic biomass [1]. Another solution is to develop and market electric or hybrid transportation vehicles [2], which is seen as a partial solution, as these vehicles are not yet cost competitive with gasoline-powered transportation counterparts. Prior to interest in the development of cellulosic biomassderived fuels, starch and sugar producing crops such as corn and sugarcane molasses have been used [3]. In the United States, corn is used to produce renewable biofuel; use of corn for this

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