Valorisation of sawdust through the combined microwave-assisted hydrothermal pre-treatment and fermentation using an oleaginous yeast

Luca Longanesi, Florent P. Bouxin, Jiajun Fan, Hadiza Auta, Richard Gammons, Vitaily L. Budarin, Aikaterini Vriza, James H. Clark, Christopher J. Chuck

Research output: Contribution to journalArticlepeer-review

Abstract

Oleaginous yeast, cultured on second-generation lignocellulosic resources, has the potential to be a key part of the future energy sector. However, the multiple unit operations necessary to produce concentrated hydrolysates, with a minimum of fermentation inhibitors, limit the applicability to date. In this study, a simple microwave-assisted hydrothermal pre-treatment step of oak or beech sawdust was deployed to produce an oligosaccharide-rich hydrolysate. This was then catabolised by the oleaginous yeast, Metschnikowia pulcherrima, avoiding the need for costly enzymatic or further chemical steps in the processing. Up to 85% of the sawdust’s hemicelluloses could be solubilised under these conditions, and 8 g/L DCW yeast with a 42% lipid content produced. While a number of studies have demonstrated that oleaginous yeasts possess high inhibitor tolerance, using this real lignocellulosic hydrolysate, we demonstrate that lipid production is actually very sensitive to inhibitor and carbon availability, and the optimal system is not the one that gives the highest hydrolysate or cell biomass. Indeed, the yeast was shown to detoxify the inhibitors in the process, but at high inhibitor loading, this leads to very poor lipid production, especially at high furfural levels. These findings clearly highlight the importance of considering multiple variables when real, complex lignocellulosic media are involved, tuning process conditions based on the desired fermentation outcomes.

Original languageEnglish
JournalBiomass Conversion and Biorefinery
Early online date18 May 2020
DOIs
Publication statusE-pub ahead of print - 18 May 2020

Keywords

  • Fermentation
  • Metschnikowia pulcherrima
  • Microbial lipids
  • Microwave-assisted pretreatment
  • Sawdust

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment

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