Kyung-Hwan Han, Won-Chan Kim, Kenneth Keegstra, Ida Barbara Reca
Global civilization is heavily reliant on petroleum for necessary fuels and specialty polymers. Although new fossil fuels are continually being formed through natural processes, the conversion of organic material to oil takes millions of years. At the current rate of global consumption, oil reserves are being depleted much faster than new ones are being made, therefore oil reserves will soon run dry if consumption does not change. In addition to being a limited resource, the use of fossil fuels raises several environmental concerns. Harvesting and burning of fossil fuels releases a large amount of pollution into the environment. To address the limitations and pitfalls of fossil fuels, a global movement to create and use cleaner, renewable energy sources continues to grow. One source of renewable energy is biofuels, fuels that are derived from plants or waste products of other living organisms. Plant biomass could offer a large renewable source of fermentable sugar for the production of biodiesel. Plant biomass primarily consists of cell wall polymers, such as cellulose and hemicellulose. These polymers must be broken down into smaller oligosaccharide constituents in order to make biodiesel. Cellulose is the most abundant polymer in the cell wall, but is extremely difficult to break down due to its structure and ability to create densely packed bundles that are resistant to many solvents. Industrial digestion of cellulose requires a large energy input and expensive enzymes to release oligosaccharides. Hemicellulose is less abundant, but easier to break down because it contains easily digested glucomannans. Conversion of biomass to biodiesel could be simplified by manipulating the cell wall composition to include higher amounts of glucomannan.
Michigan State University has developed compositions and a method for increasing glucomannan content in plant biomass. Plants are genetically engineered to express transcription factors that increase expression of CSLA9, a glucomannan synthase gene. Increased expression of CSLA9 increases the glucomannan content in plant biomass providing a feedstock with lower processing requirements for biodiesel production. Other plant polymers, such as cellulose and lignin, are not altered, so plants grow normally and have good structural integrity.
Lower energy cost: requires less energy to break down biomass into sugars
Less expensive: lower enzyme requirements
Growing market: output and demand volumes have increased almost sevenfold for biofuels since 2005
Government incentives: many countries around the world have renewable fuel policies with production and use goals that must be met
Non-food feedstock: cellulosic biomass is generally not used for food, but is rather an agricultural by-product or waste