Making biofuels from wine waste

Thanks to the biomass-degrading ability of fungi, wine waste has the potential to be converted into valuable compounds such as biofuels or medicines.

A technique, developed by researchers at Swinburne University of Technology in collaboration with CSIRO and The Australian Wine Research Institute, is showing success in converting winery waste from a hazardous waste into more useful products.

Australia is the world’s sixth-largest wine producer, with around 1.75 million tonnes of grapes crushed for wine every year. After the final pressing, more than half of the grapes crushed end up as biomass waste comprising skins, pulp, stalks and seeds.

Unlike other agricultural by-products, this waste has limited use as animal feed due to its poor nutrient value and digestibility. It is also not suitable as compost because it doesn’t degrade, which means most grape waste ends up as toxic landfill.

The problem is ubiquitous and, in recent years, winery wastes have been classified as pollutants by the European Union.

As part of his PhD research, Swinburne student Avinash Karpe has been investigating how to break down the main components of grape biomass waste - cellulose, pectins and lignins (including tannins) - into simpler compounds that can be used to create ethanol or other biofuels.

Fungi belonging to the division Ascomycota, such as Trichoderma spp., Aspergillus spp. and Penicillium spp., are known for their biomass degrading ability so Karpe began a series of experiments to develop the best procedure for degrading the winery waste.

“Various fungi are known to degrade this waste by generating an array of enzymes,” Karpe said. “These enzymes convert the waste to soluble sugars which can then be converted into other products.”

Karpe discovered that a 30-minute heat-activated pretreatment aided in the breakdown of the biomolecules.

Using a ‘cocktail’ of four fungi - Trichoderma harzianum, Aspergillus niger, Penicillium chrysogenum and Penicillium citrinum, in a one-litre bioreactor - Karpe succeeded in breaking down the biomass, with noticeable increases in enzyme activity and lignin degradation.

This fermentation process takes one to three weeks and produced alcohols, acids and simple sugars of industrial and medicinal interest.

“We have demonstrated this technique in the laboratory, but this process can be scaled up to an industrial scale,” chair of Swinburne’s Department of Chemistry and Biotechnology, Professor Enzo Palombo, said.

This research has been published in the Journal of Chemical Technology and Biotechnology.