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Quantifying second generation ethanol inhibition: Design of Experiments approach and kinetic model development

Schneiderman, Steven J., Johnson, Roger W., Menkhaus, Todd J., Gilcrease, Patrick C.
Bioresource technology 2015 v.179 pp. 219-226
Saccharomyces cerevisiae, acetic acid, ethanol, ethanol production, experimental design, feedstocks, fermentation, hydrolysates, hydroxymethylfurfural, kinetics, models, softwood
While softwoods represent a potential feedstock for second generation ethanol production, compounds present in their hydrolysates can inhibit fermentation. In this study, a novel Design of Experiments (DoE) approach was used to identify significant inhibitory effects on Saccharomyces cerevisiae D5A for the purpose of guiding kinetic model development. Although acetic acid, furfural and 5-hydroxymethyl furfural (HMF) were present at potentially inhibitory levels, initial factorial experiments only identified ethanol as a significant rate inhibitor. It was hypothesized that high ethanol levels masked the effects of other inhibitors, and a subsequent factorial design without ethanol found significant effects for all other compounds. When these non-ethanol effects were accounted for in the kinetic model, R¯2 was significantly improved over an ethanol-inhibition only model (R¯2=0.80 vs. 0.76). In conclusion, when ethanol masking effects are removed, DoE is a valuable tool to identify significant non-ethanol inhibitors and guide kinetic model development.