Unlocking Sugars in Agricultural Waste for Biofuel Production

The Austrian Centre of Industrial Biotechnology (ACIB) has found ways to make these renewable sugar resources available for industry and for the production of biofuels from agricultural and biowastes.

According to Professor Christian Kubicek of the Technical University of Vienna the process utilises enzymes called cellulases, which can cleave cellulose and hemicellulose - both components of wood (besides lignin) - into small sugar molecules.

Through ACIB's Center of Excellence Kubicek has been working with researchers in Graz and at an industrial partner's site on the ability to access new industrial sugars from renewable resources.

Professor Anton Glieder, scientific director of ACIB explained that the enzymes work like "choppers".

"The long cellulose chains are transported through the enzymes. Thereby, the enzyme cuts small sugar molecules off the comparatively huge cellulose chain, until the whole cellulose is digested into smaller sugars," he added.

According to ACIB the best enzymes for the process are produced using the fungus Trichoderma reesei, which normally grows on decaying wood residues.

A project at Graz University of Technology called 'MacroFun' worked on improving the fungal enzymes by using the yeast Pichia pastoris to make the 'molecular shredder' more robust, said Glieder.

Work in progress

Kubicek added that the general procedure is still extensive, with plant remains needing to first be 'unlocked' to separate the lignin and make the cellulose accessible. Then specially designed cellulases come into play and cleave the long cellulose chains into small sugars.

According to Kubicek, in a process similar to that of alcoholic fermentation to make wine, these sugars are finally converted by yeast into bioethanol, which can then be used for biofuels.

ACIB said that the great advantage of this method is that food production remains completely unaffected and the carbon footprint is improved.

The organisation pointed out that in Europe alone 400 million tonnes is produced each year, but that to ensure a sustainable use, 30% of it should remain on the field to regenerate the soil.

The remainder said the Center could be processed further, with the potential to produce around 1 litre of bioethanol from 5 kg of straw.

According to Glieder the goal of the project is to raise the yield by optimisation of the degrading enzymes and to make more yet unused sugar sources available for biofuel production, with second generation biofuels ready to use within 3 to 5 years, says.