Yeast Derived LysA2 Can Control Bacterial Contamination in Ethanol Fermentation.

Jun-Seob Kim,Michael Miller,Yong-Su Jin,M Daum

doi:10.3390/v10060281

Jun-Seob Kim, Michael Miller + Show 2 more

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https://doi.org/10.3390/v10060281

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Journal: Viruses	Publication Date: May 24, 2018
Citations: 13	License type: CC BY 4.0

Affiliation: University of Illinois Urbana-Champaign, Goodwin College

Abstract

Contamination of fuel-ethanol fermentations continues to be a significant problem for the corn and sugarcane-based ethanol industries. In particular, members of the Lactobacillaceae family are the primary bacteria of concern. Currently, antibiotics and acid washing are two major means of controlling contaminants. However, antibiotic use could lead to increased antibiotic resistance, and the acid wash step stresses the fermenting yeast and has limited effectiveness. Bacteriophage endolysins such as LysA2 are lytic enzymes with the potential to contribute as antimicrobials to the fuel ethanol industries. Our goal was to evaluate the potential of yeast-derived LysA2 as a means of controlling Lactobacillaceae contamination. LysA2 intracellularly produced by Pichia pastoris showed activity comparable to Escherichia coli produced LysA2. Lactic Acid Bacteria (LAB) with the A4α peptidoglycan chemotype (L-Lys-D-Asp crosslinkage) were the most sensitive to LysA2, though a few from that chemotype were insensitive. Pichia-expressed LysA2, both secreted and intracellularly produced, successfully improved ethanol productivity and yields in glucose (YPD60) and sucrose-based (sugarcane juice) ethanol fermentations in the presence of a LysA2 susceptible LAB contaminant. LysA2 secreting Sacharomyces cerevisiae did not notably improve production in sugarcane juice, but it did control bacterial contamination during fermentation in YPD60. Secretion of LysA2 by the fermenting yeast, or adding it in purified form, are promising alternative tools to control LAB contamination during ethanol fermentation. Endolysins with much broader lytic spectrums than LysA2 could supplement or replace the currently used antibiotics or the acidic wash.

Highlights

In the search for renewable sources to replace petroleum-based fuel, ethanol from carbohydrate-rich plant sources continues to outstrip the alternatives in terms of production and efficiency at the desired scales
This study further explores the spectrum and activity of LysA2 produced by the yeasts Pichia pastoris GS115 and Saccharomyces cerevisiae D452-2
To compare the activity of LysA2 produced by yeast with the activity of LysA2 from the Escherichia coli BL21 (DE3) expression system used by Ribelles et al [25], Pichia pastoris GS115 was employed

Summary

Introduction

In the search for renewable sources to replace petroleum-based fuel, ethanol from carbohydrate-rich plant sources continues to outstrip the alternatives in terms of production and efficiency at the desired scales. Among the various outstanding issues, bacterial contamination of fuel ethanol fermentation continues to be a challenge to producers [2,3,4,5], and can make the difference between running at a profit or a loss [6]. One analysis determined that a 100 MMgy fuel ethanol plant with a moderate level of contamination can expect an annual revenue loss of $4.5 million at 2016 ethanol prices [7]. Both wild yeasts and bacteria that thrive under the ethanol fermentation conditions preferred by industrial Saccharomyces cerevisiae strains have been identified as sources of contamination.

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