Identification of Bio-oil Compound Utilizing Yeasts Through Phenotypic Microarray Screening

Emily T Kostas,Mick Cooper,Benjamin J Shepherd,John P Robinson

doi:10.1007/s12649-019-00636-7

Emily T Kostas, Mick Cooper + Show 2 more

Open Access

https://doi.org/10.1007/s12649-019-00636-7

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Abstract

Biomass pyrolysis bio-oil contains a plethora of carbon sources with the potential to be utilized by microorganisms and converted into high value products. However, the majority of these compounds are either highly toxic to microorganisms or are not directly utilizable. Hence research is required to develop methods of separating microbe friendly compounds from inhibitory ones, and to also identify novel microorganisms that can utilise the principal carbon sources in pyrolysis bio-oil. This study employed a phenotypic microarray (PM) technique that measured yeast metabolic output to screen for and shortlist yeast strains able to metabolize various bio-oil carbon sources, with a focus on the anhydrosugar levoglucosan. Four strains of yeast (two Pichia spp. and two Kluyveromyces spp.) were shortlisted due to their high metabolic output (between 79.7 and 113.7 redox signal intensity) on levoglucosan from the PM assay. Under anaerobic fermentation conditions the strains were able to uptake levoglucosan (between 79 and 100% uptake efficiency) but not produce bioethanol; yet trace amounts of acetic acid were generated. This study demonstrated the application of applying the PM technique to screen for novel yeast strains with abilities to metabolize compounds present in pyrolysis bio-oil that could lead to the identification of novel levoglucosan utilization pathways.Graphical

Highlights

In order for a future bio-based economy to be viable, efficient methods of converting renewable feedstocks into high value bio-based products need to be established and optimised
Glucose has been included to serve as a positive control and as a benchmark to compare to the redox signal intensities (RSI) values of the bio-oil compounds
There were measureable metabolic outputs for all yeast strains on glucose (Fig. 1a) after 96 h of incubation at 30 °C; between 34 and 100 RSI

Summary

Introduction

In order for a future bio-based economy to be viable, efficient methods of converting renewable feedstocks into high value bio-based products need to be established and optimised. Its rich chemical composition makes it a viable source for the thermo-chemical-based bio-refinery which enables the production of platform chemicals and conventional biofuels [4], and as a direct fermentation substrate. This concept of combining thermal biomass deconstruction followed by subsequent biological processing has been termed ‘hybrid processing’ [5,6,7]. Polysaccharide derived substrates such as the anhydrosugar ‘levoglucosan’ is the most abundant sugar in bio-oil; making it a direct target for microbial processing. Aromatic compounds (e.g. phenol, guaiacol, syringol) and heterocyclic compounds (e.g. furfural) present in the complex medium makes bio-oil inhibitory to microorganisms and most lack the ability to directly metabolize levoglucosan [8]

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