Yeasts identified that could turn agricultural waste to biofuels

Scientists from the Norwich Research Park have found strains of yeast that look particularly useful for turning agricultural by-products, such as straw, sawdust and corncobs, into bioethanol.

S. cerevisiae yeast Image by Kathryn Cross and Carmen Nueno Palop

S. cerevisiae yeast Image by Kathryn Cross and Carmen Nueno Palop

It is estimated that more than 400 billion litres of bioethanol could be produced each year from crop wastage.

The research team say that their findings could help to create biofuel which is more environmentally friendly and ethically sound than other sources because it would make use of waste products.

Processes to generate bioethanol from straw and other by-products are currently complex and inefficient.

This is because high temperatures and acid conditions are necessary in the glucose-release process. But this treatment process causes the waste to breakdown into compounds which are toxic to yeast (furfural and hydroxymethylfurfural) – making fermentation difficult.

One way to avoid these problems is to use genetically modified yeasts, but this new research has found five strains of naturally occurring yeasts which could be used successfully in the fermentation process.

Dr Tom Clarke, from UEA’s School of Biological Sciences, said: “Dwindling oil reserves and the need to develop motor fuels with a smaller carbon footprint has led to the explosion of research into sustainable fuels.

“Breaking down agricultural waste has previously been difficult because many strains of yeast necessary for fermentation are inhibited by compounds in the straw. Their toxic effects lead to reduced ethanol production.”

The UEA researchers worked with the National Collection of Yeast Cultures, a BBSRC-supported National Capability at the Institute of Food Research, as well as the Biorefinery Centre, also based at IFR.

It’s great to see the resources and expertise of the NCYC yeast collection being applied to important societal problems. Complete genome sequences are available for all the yeasts in this study which should really help speed up their exploitation for environmental benefits – Dr Ian Roberts, Curator of NCYC

The research team investigated more than 70 strains of yeast to find the most tolerant. They found five strains which were resistant to the toxic compound furfural, and which produced the highest ethanol yield.

Of the five furfural tolerant strains S. cerevisiae NCYC 3451 displayed the greatest furfural resistance. The genomic lineage of this strain links it to yeast used in the production of the Japanese rice wine Sake.

“These strains represent good candidates for further research, development and use in bioethanol production,” added Dr Clarke.

The project was funded by BBSRC and Defra, through the HOOCH project, a collaborative programme led by IFR that aims to produce bioalcohols from waste materials produced in the agri-food chain. The HOOCH partners provide expertise covering the whole process of biorefining, from biomass treatment to fermentation through to the motor industry.

Reference

Identification of furfural resistant strains of Saccharomyces cerevisiae and Saccharomyces paradoxus from a collection of environmental and industrial isolates, Biotechnology for Biofuels, 8:33  doi: 10.1186/s13068-015-0217-z

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