Effect of alcohol compounds found in hemicellulose hydrolysate on the growth and fermentation of ethanologenicEscherichia 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. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 68: 524–530, 2000.

Screening of lactic acid bacteria for their potential as microbial cell factories for bioconversion of lignocellulosic feedstocks

“…In the case of furfuryl alcohol, no literature data has been reported regarding the concentrations found in the lignocellulosic biomass and therefore a minimal inhibitory concentration of Escherichia coli strain LY01 [[11]] was used for the screening (20 g/L). 40.5% of the screened lactic acid bacteria strain collection was found to be resistant to that concentration of furfuryl alcohol.…”

“…No literature data was available on methylcatechol concentrations in lignocellulose, and therefore the minimal inhibitory concentration of E. coli LY01 [[11]] was tested (1.5 g/L). However, since none of the tested strains showed any growth on that concentration, it was decreased to 0.15 g/L.…”

RETRACTED ARTICLE: Bacterial conversion of depolymerized Kraft lignin

“…4-HBA, which belongs to the p -coumaryl branch of the upper funneling pathway, has been reported to be converted by a number of microbes, including Acinetobacter baylyi, Cupriavidus necator, P. aeruginosa , and is apparently not very toxic [29, 57–59]. In contrast, vanillin and guaiacol (belonging to the coniferyl branch of the funneling pathway) have been reported to be quite toxic to many organisms [60–65]. Microbial detoxification mechanisms of vanillin are related to conversion of its aldehyde group either by oxidation to vanillic acid or by reduction to vanillyl alcohol [66].…”

Engineering membrane and cell-wall programs for tolerance to toxic chemicals: Beyond solo genes

“…In addition to these ‘gatekeeper’ functions, the ability of the membrane to maintain a chemical potential is crucial for energy generation and other cellular functions. Damage to the cell membrane has long been implicated in the toxicity of various chemicals, with the degree of toxicity correlating to the hydrophobicity[12,13]. Short alcohols and hydrophobic compounds, such as ethanol or butanol, can partition into lipid bilayer membranes[14,15].…”