Biofuel waste could be turned into building blocks for industrial chemicals, thanks to an enzyme-based process developed by European scientists.

Tijs Lammens, at Wageningen University, the Netherlands, and colleagues studied the conversion of glutamic acid to -aminobutyric acid (GABA) using a decarboxylase enzyme. Glutamic acid is a major component of the waste formed when grains, such as maize, are converted into bioethanol. Because glutamic acid contains nitrogen, it could be used to make nitrogen-containing industrial chemicals more cheaply than the energy intensive, fossil fuel- and ammonia-based routes usually used.

The waste from bioethanol production can be used to make nitrogen-containing chemicals

GABA is a useful intermediate in the pathway from glutamic acid to industrial chemicals because it can be turned into many useful products, explains Lammens. Although the enzymatic conversion of glutamic acid to GABA is known, Lammens showed that the process could be scaled up for industrial production by immobilising the enzyme in a batch reactor.

'There is a scientific basis for making bulk chemicals from agricultural waste,' says Lammens. '[This study] shows industry that this process can be economically feasible using an enzyme.'

'Apart from being scalable, this process could also contribute to improving the green credentials and the economics of biofuel production,' comments Rafael Luque, a biofuel expert at the University of Cordoba, Spain. 'But the suitability of directly using an actual waste effluent containing glutamic acid requires further evaluation.'

Lammens acknowledges that the process would be too expensive if only glutamic acid produced by fermentation could be used. He says the next step is to 'investigate further if we can isolate amino acids, such as glutamic acid, from agricultural waste streams in a cost effective way.'

Carl Saxton

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