ARCHIVED - Natural fibres help build green economy
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October 07, 2009— Ottawa, Ontario
They say you can't turn a sow's ear into a silk purse. But what about turning waste from a farmer's field into materials for planes, trains and automobiles? NRC is paving the way to do just that - with innovative, green processing technologies.
Researchers from several NRC institutes are contributing to a national effort to develop eco-friendly biocomposites from biomass - especially from hemp and flax stems. They are part of the Agriculture and Agri-Food Canada-Natural Resources Canada-NRC National Bioproducts Program as well as Canada's Agricultural Bioproducts Innovation Program: Natural Fibres for the Green Economy Network (NAFGEN).
NRC researchers are working on "green" bioprocessing technologies to convert low-value biomass from farmers' fields into high-quality, eco-friendly materials for Canadian industry.
Their research will accelerate progress toward the commercialization of bioproducts and bioprocesses while helping Canadian farmers harness a higher value market from low-value agricultural residue.
The quest for clean solutions
The first challenge is to develop a reliable, cost-efficient and eco-friendly way to recover natural fibres from straw - a process called "retting."
Field and water retting have long been used to break down the woody stems of hemp and flax so that the fibre inside could be recovered. Field retting involves leaving straw in its natural habitat to be broken down over time by microorganisms. Water retting involves the submersion of bundles of stalks in water for 30-40 days to make the stalks swell and burst. These traditional processes are slow, uncontrolled and cause environmental concerns.
Drs Peter Lau and Denis Rho of the -NRC Biotechnology Research Institute (NRC-BRI) in Montréal are working together to develop energy-efficient and environmentally acceptable ways to transform hemp and flax into high-quality fibres. Dr. Lau is working on upstream enzymatic processes, while Dr. Rho is working on downstream bioprocessing. Their goal is to produce high-quality biofibres of varying characteristics that could replace the glass fibres, for example, in today's fibre-reinforced plastics.
"The majority of today's fibre-reinforced plastics are made with fibreglass, carbon or synthetic fibres, while the polymer is an epoxy or polyester plastic," says Dr. Lau. "The fabrication of these materials requires large quantities of energy, water and chemicals. Plus, these materials don't biodegrade easily, or at all. Using flax or hemp in industrial materials would offer distinct environmental advantages."
Genetically modified enzymes
"Enzymes occur naturally, work at ambient temperatures and are biodegradable, which makes them environmentally friendly catalysts," he says. Dr. Lau aims to develop an enzyme "cocktail" to ret the flax or hemp in a bioprocess that would yield high-quality natural fibres in easily controlled conditions.
Different enzymes act in different ways, which is why Dr. Lau and his team have been characterizing various enzymes to find an optimal combination. As part of this work, they have modified the encoding genes, substituting certain amino acids in enzymes of interest such as pectinases. Pectinases are used in the fruit, paper, detergent and textile industries, and are key components in the retting of natural fibres.
Cross section of flax stem.
Using pectate lyase, Dr. Lau has found that certain amino acid substitutions can substantially affect either the thermostability or the catalytic activity of the enzyme. In fact, he found that a single amino acid substitution resulted in a 6◦ C increase in the melting temperature of this enzyme - a rare protein engineering feat. Enzymes that remain stable at higher temperatures have a longer shelf life, which - in the retting business - adds up to higher productivity at lower cost.
"We have a 23-fold increase in the half-life of this enzyme by changing one amino acid, without compromising the enzyme's catalytic effect," explains Dr. Lau. "Because the enzyme lasts longer, you can use less of it."
Dr. Lau is now working on another enzyme that will improve the surface properties of the fibres, making them more compatible for use in biocomposites. "If we can develop an enzyme that will do a better job of removing the plant cuticle (skin) without digesting the fibre inside, we can not only increase the penetration of the other enzyme to help us derive high-quality fibres, but also produce fibres with improved surface characteristics."
NRC has already filed for a patent on its genetically modified pectate lyase and will seek to patent other enzymes in the future. The ultimate goal is to license these enzymes to Canadian entrepreneurs to help bring bioprocessing into the mainstream for fibre production.
[Next month, read about Dr. Rho's discoveries on the bioprocessing of flax and hemp.]
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