Improving ethanol yields with deacetylated and two-stage pretreated corn stover and sugarcane bagasse by blending commercial xylose-fermenting and wild type Saccharomyces yeast

Authors: WANG, ZHAOQIN - University Of Illinois; Dien, Bruce; RAUSCH, KENT - University Of Illinois; TUMBLESON, MIKE - University Of Illinois; SINGH, VIJAY - University Of Illinois

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2019
Publication Date: 3/1/2019
Citation: Wang, Z., Dien, B.S., Rausch, K.D., Tumbleson, M.E., Singh, V. 2019. Improving ethanol yields with deacetylated and two-stage pretreated corn stover and sugarcane bagasse by blending commercial xylose-fermenting and wild type Saccharomyces yeast. Bioresource Technology. 282:103-109. https://doi.org/10.1016/j.biortech.2019.02.123.
DOI: https://doi.org/10.1016/j.biortech.2019.02.123

Interpretive Summary: Corn stover and sugarcane bagasse are abundant agricultural residues. Corn stover includes the stalks, leaves, and corn cobs, presently left in the field during grain harvest. The sugarcane bagasse consists of the fiber portion left behind following extraction of the sweet juice. Both are expected to be potential resources for producing advanced biofuels. In this study, both feedstocks were studied for conversion to ethanol at laboratory scale using novel process technologies. The biomass is pretreated to open the plant cell wall, the fibers are next converted to sugars using commercial cellulases, and the sugars fermented to ethanol using a binary mixture of yeast. The final ethanol titer was over 30 g/l and the pathway used is expected to be commercially scalable. Important conclusions are that combining treatment of biomass with hot-water followed by milling results in higher sugar yields than treating with hot-water alone and that mixing a commercial glucose/xylose GMO Saccharomyces with a widely available non-GMO Saccharomyces yeast gives better results than using either alone for fermentation. The paper should be of interest to corn ethanol producers and agriculture processors in general

Technical Abstract: Corn stover and sugarcane bagasse are the most widely available agriculture processing biomass and could serve as feedstocks for production of biofuel. In this study, three different technologies are combined to develop a more efficient conversion process for each of these feedstocks. The three technologies are diluted alkaline deacetylation process, combined thermochemical and mechanical shear pretreatment, and fermentation using a combined inoculum of two commercial Saccharomyces yeast strains. The two yeast strains used were a non-GMO and GMO strain engineered for xylose fermentation. The final ethanol concentrations obtained were 35.7 g/L from deacetylated corn stover and 32.9 g/L from sugarcane bagasse. Blending the two yeast reduced residual xylose content from 1.24 g/L to 0.48g/L and increased ethanol production by 6.5% compared to solely using the C5/C6 yeast. The optimized yeast blend also lowered the amount of C5/C6 yeast required for inoculation by 80%.