Identification and characterization of fermentation inhibitors formed during hydrothermal treatment and following SSF of wheat straw

Mette Hedegaard Thomsen, Anders Thygesen, Anne Belinda Thomsen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    A pilot plant for hydrothermal treatment of wheat straw was compared in reactor systems of two steps (first, 80A degrees C; second, 190-205A degrees C) and of three steps (first, 80A degrees C; second, 170-180A degrees C; third, 195A degrees C). Fermentation (SSF) with Sacharomyces cerevisiae of the pretreated fibers and hydrolysate from the two-step system gave higher ethanol yield (64-75%) than that obtained from the three-step system (61-65%), due to higher enzymatic cellulose convertibility. At the optimal conditions (two steps, 195A degrees C for 6 min), 69% of available C6-sugar could be fermented into ethanol with a high hemicellulose recovery (65%). The concentration of furfural obtained during the pretreatment process increased versus temperature from 50 mg/l at 190A degrees C to 1,200 mg/l at 205A degrees C as a result of xylose degradation. S. cerevisiae detoxified the hydrolysates by degradation of several toxic compounds such as 90-99% furfural and 80-100% phenolic aldehydes, which extended the lag phase to 5 h. Acetic acid concentration increased by 0.2-1 g/l during enzymatic hydrolysis and 0-3.4 g/l during fermentation due to hydrolysis of acetyl groups and minor xylose degradation. Formic acid concentration increased by 0.5-1.5 g/l probably due to degradation of furfural. Phenolic aldehydes were oxidized to the corresponding acids during fermentation reducing the inhibition level.
    Original languageEnglish
    JournalApplied Microbiology and Biotechnology
    Volume83
    Issue number3
    Pages (from-to)447-455
    ISSN0175-7598
    DOIs
    Publication statusPublished - 2009

    Keywords

    • Bio energy
    • Bioenergy and biomass

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