Controlling bacterial contamination during fuel ethanol fermentation using thermochemically depolymerized lignin bio-oils

Ryan M. Kalinoski, Wenqi Li, Justin K. Mobley, Xiaowen Chen, Sue E. Nokes, Bert C. Lynn, Jian Shi

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Lactic acid bacteria (LAB) contamination during fuel ethanol fermentation can lead to significant economic loses. To circumvent this, fuel ethanol plants add antibiotics prophylactically, but their overuse has resulted in the emergence of antibiotic-resistant LAB strains. Lignin is a sustainable biopolymer that can be found as a waste product from lignocellulosic biorefineries. Technical lignins and their smaller phenolic subunits have been shown to exhibit broad-spectrum antimicrobial properties, but there is a lack of demonstrations of lignin derivatives with highly selective properties in the literature. Here, corn stover lignin from a biorefinery was oxidatively depolymerized using an environmentally benign organic oxidant, peracetic acid, into a bio-oil that has selective antimicrobial properties against LAB and not yeasts. The resulting bio-oil demonstrated up to 90% inhibition of commercially sampled LAB (including antibiotic-resistant strains) at 4 mg ml-1 with no inhibition against an industrial yeast strain. These antimicrobial properties of the bio-oil are attributed to larger unidentified lignin oligomers, compared to monolignols, that have a membrane damaging mode of action. Using the bio-oil (4 mg ml-1) during simultaneous saccharification and fermentation (SSF) of raw corn starch showed no inhibition of enzymatic activity, and in LAB contaminated fermentations the bio-oil treatments showed an 8% increase in ethanol yields at higher bacterial contamination ratios (l:100 yeast to LAB, CFU per ml). This study illustrates the efficacy of using lignin bio-oil as an antibiotic replacement during fuel ethanol fermentation and demonstrates the highly selective antimicrobial properties of lignin oligomers, which creates a viable lignin valorization strategy for biorefineries.

Original languageEnglish
Pages (from-to)6477-6489
Number of pages13
JournalGreen Chemistry
Issue number17
StatePublished - Sep 7 2021

Bibliographical note

Funding Information:
The authors acknowledge the National Science Foundation under Cooperative Agreement No. 1355438 and 1632854. This work is also supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch-Multistate project under accession number 1018315. We would also like to acknowledge Dr Patrick Heist and Dr Chris Skory for supplying the microorganism and their useful comments.

Publisher Copyright:
© 2021 The Royal Society of Chemistry.

ASJC Scopus subject areas

  • Environmental Chemistry
  • Pollution


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