ARCHIVED - From the Sugar Shack to the Biorefinery
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March 07, 2007— Ottawa, Ontario
Canada's maple industry may one day focus less on making maple syrup than on creating value-added "green products" derived from biopolymers. An NRC study has found that maple sap is an excellent food source for growing bacteria that produce natural polymers. This discovery could create jobs and raise incomes for maple producers, solve the problem of surplus syrup – and eventually reduce our dependence on fossil fuel-derived plastics and other polymers.
Today, Canada dominates the maple syrup market, producing about 85% of the global supply. Quebec alone accounts for more than 90% of our total production. Maple syrup is Canada's most important non-timber forest product, with exports valued at more than $140 million per year. Yet in Quebec, only about one-third of 110 million tapped maple trees are actually used to collect sap – and millions more trees likely go untapped.
"A few years ago, we read in La Presse about the problem of surplus sap, which exceeds 60 million pounds in Quebec alone – most of which is being stored in cellars," says Dr. Jalal Hawari, Group Leader of Environmental and Analytical Chemistry at the NRC Biotechnology Research Institute (NRC-BRI). "Maple sap is only being used to make maple syrup, so we decided to search for new applications for this renewable resource."
Since maple sap contains pure sugar, Dr. Hawari and his colleague, Dr. Abdessalem Yezza, tried feeding sap to Alcaligenes latus – bacteria that are known to transform sucrose into polyhydroxyalkanoates (PHAs), a family of naturally occurring polymers. The most common PHA is poly-3-hydroxybutyrate (PHB), a biodegradable substance with physical properties similar to polypropylene.
In Europe and the United States, PHBs are currently used in environmentally friendly packaging materials such as biodegradable film and food containers. Since they are compatible with and absorbable by biological tissue, PHBs also have potential in medical applications including tissue engineering, slow-release drug delivery systems, surgical sutures and wound dressings. And research is underway to integrate the biopolymer in nanocomposite fibres for automobile, aerospace and other industrial uses.
The NRC-BRI team found that Alcaligenes grows just as well on maple sap as on a pure sucrose-based medium. In fact, bacteria grown on sap produced even higher yields of biomass and PHBs than bacteria grown on sucrose. More importantly, maple sap requires virtually no preparation as a bacterial feedstock. "Maple sap is sterile and has the right sugar content, mineral composition and pH required for bacterial growth," explains Dr. Hawari. "You can take it directly from the tree to the bacteria – that's its main advantage."
|Scaling up production of PHB from 100 mL flasks to 20 L fermenters|
This means Canadian maple sap, which just drips from maple trees, is much more cost effective than conventional sources of sucrose, such as Brazilian sugarcane, European sugar beets and U.S. corn. All of these sources require extensive pretreatment prior to microbial fermentation. To extract sugar from corn, explains Dr. Hawari, "you have to shred it and separate the cellulose from the carbohydrate. You then break down the carbohydrates into sucrose, using other catalysts or enzymes." The cost of producing sucrose from sugarcane and corn can range from $150 to $450 per ton. But such costs do not apply to maple sap.
Having demonstrated the advantages of maple sap, the team now plans to scale up the process of growing bacteria on this medium, using NRC-BRI's pilot plant facility. "We also want to fully determine the composition of maple sap to explore its potential conversion into other value-added products," says Dr. Hawari.
|PHB granules: Accumulation of PHB in Alcaligenes latus.|
"We don't intend to focus just on turning sap into PHAs," adds Dr. Diane Fournier, an NRC-BRI microbiologist working with the team. "The important thing we've shown is that sap can be transformed by bacteria into new, environmentally friendly materials with food, medical or other applications. Its characteristics offer Canadian maple producers some excellent opportunities to access new markets."
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