Logging residue, branch clippings and even prawn shells may serve as raw materials for cheaper biofuels -- thanks to a new enzyme that breaks down biomass more quickly. What's more, this could help to curtail the current practice of using valuable food plants for fuel production
Norwegian scientists reported the promising findings recently in the journal Science.
Simple in theory, but...
Ethanol and methane are alternative energy sources that can be produced through the decomposition of carbohydrate-rich biomass of both marine and terrestrial origins. Potential sources include shellfish, which are full of the carbohydrate chitin, and wood and waste wood, since they contain cellulose.
Finding a quick, efficient means of converting biomass that is rich in chitin or cellulose into biofuel, however, has been difficult. This means that much of today's biofuel is derived from food plants such as sugar cane, corn and rapeseed -- crops that could be used to feed people.
"In theory it's easy to convert the carbohydrates in cellulose, for instance, to small sugar molecules that nourish microorganisms which in turn produce methane and ethanol. But in practice, it has proven to be quite challenging," explains Dr Gustav Vaaje-Kolstad, Researcher at the Norwegian University of Life Sciences (UMB). He is among the seven co-authors of the article in the journal Science.
Breaks down strong glucose chains
The hard part, so to speak, is that the respective carbohydrate polymers of both chitin and cellulose form extremely dense, resilient bonds. Indeed, the biological function of chitin and cellulose is precisely to make the organism physically hard and durable -- slowing the breakdown rate for enzymes whose function is to decompose these kinds of material.
The Science article describes how the "new" enzymes (the authors have designated them oxidohydrolases) help to biodegrade the seemingly insoluble carbohydrate polymers in cellulose and chitin.
Enzyme design is the key to the solution. To do their job, the enzymes must first be designed to attach securely to the crystalline glucose chains they are intended to break down. This allows them to split the sugars repeatedly without falling off.
Simpler, cheaper, more sustainable
Oxidohydrolases could make it both less costly and easier to produce biofuel.
They could also serve to scale back the controversial practice of using edible plants to produce that biofuel. Sustainable large-scale biofuel production will require materials that are more readily available -- so scientists, politicians and environmentalists have long sought an efficient method for utilising less-valuable biological resources as the raw materials.
The Norwegian researchers' findings may well represent the long-awaited breakthrough. The UMB researchers have applied for a patent on their method and are discussing further collaboration with the international enzyme producer Novozymes.
Broad-based funding from the Research Council
The Research Council of Norway has funded this research through several sources, including the open competitive arena for independent, researcher-initiated basic research projects (FRIPRO) and the research programmes on Basic Industry-oriented Biotechnology (GNBIO -- terminated), Clean Energy for the Future (RENERGI), and Nature-based Industry (NATUROGNAERING).
"Funding for independent projects from the Research Council has enabled us to carry out basic research," project manager Gustav Vaaje-Kolstad told the Norwegian News Agency (NTB). "Independent basic research allows one to think freely, to be creative and follow one's scientific intuition, without being limited by the demands of an industrial project."
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