pH adjustment increases biofuel production from inhibitory switchgrass hydrolysates

Barten, Lillian M.; Crandall, Johnathan G.; Xie, Dan; Serate, Jose; Handowski, Evan; Jen, Annie; Overmyer, Katherine A.; Coon, Joshua J.; Hittinger, Chris Todd; Landick, Robert; Zhang, Yaoping; Sato, Trey K.

doi:10.1016/j.biortech.2025.132651

pH adjustment increases biofuel production from inhibitory switchgrass hydrolysates

Journal Article · Fri May 09 04:00:00 EDT 2025 · Bioresource Technology

DOI:https://doi.org/10.1016/j.biortech.2025.132651· OSTI ID:2566848

^[1]; ^[2]; Xie, Dan ^[2]; Serate, Jose ^[2]; Handowski, Evan ^[2]; ^[2]; ^[3]; Coon, Joshua J. ^[3]; ^[2]; Landick, Robert ^[2]; Zhang, Yaoping ^[2]; ^[2]

University of Wisconsin-Madison, WI (United States); University of Wisconsin Wisconsin Energy Institute
University of Wisconsin-Madison, WI (United States)
University of Wisconsin-Madison, WI (United States); Morgridge Institute for Research, Madison, WI (United States)

Biofuels derived from renewable and sustainable lignocellulosic biomass, such as switchgrass, offer a promising means to limit greenhouse gas emissions. However, switchgrass grown under drought conditions contains high levels of chemical compounds that inhibit microbial conversion to biofuels. Fermentation of drought switchgrass hydrolysates by engineered Saccharomyces cerevisiae and Zymomonas mobilis results in lower ethanol production than does fermentation of hydrolyzed switchgrass from a typical rainfall year. Here, it is demonstrated that this inhibitory effect can be alleviated by altering the pH of drought switchgrass hydrolysates produced by two different pretreatment methods: Ammonia Fiber Expansion (AFEX) and Soaking in Aqueous Ammonia (SAA). Fermentation rates and biofuel production by Saccharomyces cerevisiae and Zymomonas mobilis were higher at pH 5.8 than at pH 5.0 from all feedstock years and following both pretreatment methods. SAA pretreatment of drought switchgrass furthermore enabled increased fermentation rates and biofuel titers compared to AFEX pretreatment. A synthetic mimic of switchgrass hydrolysate was developed and identified relief from pH-dependent inhibition by lignocellulose-derived inhibitors as the cause of increased biofuel production above a pH of 5.0. These results demonstrate that SAA pretreatment and pH adjustment can significantly improve fermentation and biofuel production from inhibitory feedstocks by industrial microorganisms.

View Accepted Manuscript (DOE)

Research Organization:: Great Lakes Bioenergy Research Center (GLBRC), Madison, WI (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF); National Institutes of Health (NIH)

Grant/Contract Number:: SC0018409

OSTI ID:: 2566848

Journal Information:: Bioresource Technology, Journal Name: Bioresource Technology Vol. 432; ISSN 0960-8524

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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