Acetic acid fermentability with Clostridium thermoaceticum and Clostridium thermocellum of standard compounds found in beech wood as produced in hot-compressed water

Abstract

Acetic acid fermentability of various compounds from beech wood as produced in a two-step hot-compressed water treatment was evaluated by fermentation tests using standard compounds with Clostridium thermoaceticum and Clostridium thermocellum. For cellulose- and hemicellulose-derived products, the former microorganism was found to ferment compounds with low molecular weights such as monosaccharides, decomposed products, and organic acids to acetic acid, while the latter was found to ferment compounds with high molecular weights such as polysaccharides and oligosaccharides to acetic acid. Lignin-derived products were, on the other hand, fermented by both microorganisms to acetic acid. Based on these lines of evidence, co-culture with C. thermoaceticum and C. thermocellum was evaluated and proven to increase acetic acid fermentability. Consequently, almost all compounds produced from beech wood in hot-compressed water were found to be converted to acetic acid when using these microorganisms in combination. Thus, hot-compressed water treatment coupled with acetic acid fermentation would likely be a powerful method to produce acetic acid from lignocellulosics.