Effect of alcohol compounds found in hemicellulose hydrolysate on the growth and fermentation of ethanologenic Escherichia coli

Abstract

Lignocellulose can be readily hydrolyzed into a mixture of sugars using dilute mineral acids. During hydrolysis, a variety of inhibitors are also produced which include aromatic alcohols from lignin and furfuryl alcohol from pentose destruction. Seven compounds were investigated individually and in binary combinations (catechol, coniferyl alcohol, furfuryl alcohol, guaiacol, hydroquinone, methylcatechol, and vanillyl alcohol). Aromatic alcohols and furfuryl alcohol inhibited ethanol production from xylose in batch fermentations primarily by inhibiting the growth of Escherichia coli LY01, the biocatalyst. The toxicities of these compounds were directly related to their hydrophobicity. Methylcatechol was the most toxic compound tested (MIC = 1.5 g/L). In binary combination, the extent of growth inhibition was roughly additive for most compounds tested. However, combinations with furfuryl alcohol and furfural (furaldehyde) appear synergistic in toxicity. When compared individually, alcohol components which are formed during hemicellulose hydrolysis are less toxic for growth than the aldehydes and organic acids either on a weight basis or a molar basis.

Effect of Lignocellulose-Derived Inhibitors on Growth of and Ethanol Production by Growth-Arrested Corynebacterium glutamicum R

“…Although the pretreatment of lignocellulosic biomasses is a necessity for efficient saccharification and ethanol production (10,15), ethanol production by microorganisms is inhibited in the presence of small concentrations of some of these byproducts of pretreatment (20,(27)(28)(29). In order to avoid such inhibition, various treatments for the detoxification of fermentation inhibitors have been investigated (10).…”

Functional Characterization of a Novel Xylanase from a Corn Strain of Erwinia chrysanthemi

“…The application of acid hydrolysis for the release of fermentable xylose has resulted in limited yields as well as the production of inhibitors of fermentation (36,37,38), and several groups are looking at enzymatic means for depolymerizing xylan. A number of endoxylanases have been purified from xylanolytic microorganisms (21).…”

Identification of Genes Conferring Tolerance to Lignocellulose-Derived Inhibitors by Functional Selections in Soil Metagenomes

“…However, lignocellulose requires harsh thermochemical pretreatment methods to liberate fermentable monosaccharides (7)(8)(9), producing an additional compendium of compounds inhibitory to microbial growth that ultimately reduce production efficiencies (10)(11)(12). These small-molecule inhibitors derived from lignocellulose pretreatment (here called lignocellulosic inhibitors) are typically aldehydes, organic acids, furans, or phenolics and can originate from the cellulosic, hemicellulosic, and lignified fractions of the feedstock (11)(12)(13)(14)(15).…”

“…Given the sequence divergence of the cloned soil metagenome from known functions (Fig. 2), vague or unassignable annotations are not surprising and may be particularly common with selections using furfuryl alcohol given the compound's poorly characterized modes of toxicity (14).…”