Title: Mechanism of imidazolium ionic liquids toxicity in Saccharomyces cerevisiae and rational engineering of a tolerant, xylose-fermenting strain

Abstract

In this study, imidazolium ionic liquids (IILs) underpin promising technologies that generate fermentable sugars from lignocellulose for future biorefineries. However, residual IILs are toxic to fermentative microbes such as Saccharomyces cerevisiae, making IIL-tolerance a key property for strain engineering. To enable rational engineering, we used chemical genomic profiling to understand the effects of IILs on S. cerevisiae. As a result, we found that IILs likely target mitochondria as their chemical genomic profiles closely resembled that of the mitochondrial membrane disrupting agent valinomycin. Further, several deletions of genes encoding mitochondrial proteins exhibited increased sensitivity to IIL. High-throughput chemical proteomics confirmed effects of IILs on mitochondrial protein levels. IILs induced abnormal mitochondrial morphology, as well as altered polarization of mitochondrial membrane potential similar to valinomycin. Deletion of the putative serine/threonine kinase PTK2 thought to activate the plasma-membrane proton efflux pump Pma1p conferred a significant IIL-fitness advantage. Conversely, overexpression of PMA1 conferred sensitivity to IILs, suggesting that hydrogen ion efflux may be coupled to influx of the toxic imidazolium cation. PTK2 deletion conferred resistance to multiple IILs, including [EMIM]Cl, [BMIM]Cl, and [EMIM]Ac. An engineered, xylose-converting ptk2Δ S. cerevisiae (Y133-IIL) strain consumed glucose and xylose faster and produced more ethanol in the presence ofmore » 1 % [BMIM]Cl than the wild-type PTK2 strain. We propose a model of IIL toxicity and resistance. In conclusion, this work demonstrates the utility of chemical genomics-guided biodesign for development of superior microbial biocatalysts for the ever-changing landscape of fermentation inhibitors.« less

Authors:

Dickinson, Quinn; Bottoms, Scott; Hinchman, Li; McIlwain, Sean; Li, Sheena; Myers, Chad L.; Boone, Charles; Coon, Joshua J.; Hebert, Alexander; Sato, Trey K.; Landick, Robert; Piotrowski, Jeff S.

Publication Date:

Wed Jan 20 00:00:00 EST 2016

Research Org.:

Wisconsin Alumni Research Foundation, Madison, WI (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1618801

Alternate Identifier(s):

OSTI ID: 1242892

Grant/Contract Number:  

FC02-07ER64494

Resource Type:

Published Article

Journal Name:

Microbial Cell Factories

Additional Journal Information:

Journal Name: Microbial Cell Factories Journal Volume: 15 Journal Issue: 1; Journal ID: ISSN 1475-2859

Publisher:

Springer Science + Business Media

Country of Publication:

United Kingdom

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; chemical genomics; ionic liquids; Lignocellulosic; biofuel; biocatalysts