The humble soybean could become an inexpensive new source of a widely used chemical for plastics, textiles, drugs, solvents and as a food additive according to scientists, offering an export window to Kenyan farmers at a time when local efforts to promote its growth are paying off in increased production and yields.
Succinic acid, traditionally drawn from petroleum, is one focus of research by chemists George Bennett and Ka-Yiu San from Rice University in Texas USA. In 2004, the Department of Energy named succinic acid one of 12 "platform" chemicals that could be produced from sugars by biological means and turned into high-value materials.
The potential demand that would come with this discovery offers an opportunity to farmers and researchers in Kenya who have focused attention to the once neglected but highly valued bean. Agricultural organisations have flagging the bean as a crop with huge growth potential, alongside projects now delivering sharply higher soybean yields and drawing smallholders into soybean processing, in a double drive that is upping earnings by up to 15-fold.
Concentrated around a soybean project in Mumias, Western Kenya, the new soybean models have already tripled the incomes of more than 3000 farmers in the region, and could equally be applied to the more than 30,000 smallholders now growing the crop across Kenya, say agricultural experts.
Several years ago, Rice patented a process by Bennett and San for the bio-based production of succinic acid that employed genetically modified E. coli bacteria to convert glucose into succinic acid in a way that would compete with petroleum-based production.
The new succinate process developed by Bennett, San and Chandresh Thakker and reported recently in Bioresource Technology promises to make even better use of a cheap and plentiful feedstock, primarily the indigestible parts of the soybean.
"We are trying to find a cheaper, renewable raw material to start with so the end product will be more profitable," said Thakker, a research scientist in the Bennett lab at Rice's BioScience Research Collaborative and lead author of the study. "The challenge has been to make this biomass process cost-competitive with the petrochemical methods people have been using for many years."
Bennett feels they have done that with soybean-derived feedstock as an inexpensive source of the carbon that organisms digest to produce the desired chemical through fermentation. "A lot of people use plant oils for cooking -- corn or soybean or canola -- instead of lard, as they did in the old days," he said. "The oils are among the main products of these seeds. Another product is protein, which is used as a high-quality food.
"What's left over is indigestible fiber and small carbohydrates," said Bennett, Rice's E. Dell Butcher Professor of Biochemistry and Cell Biology. "It's used in small amounts in certain animal feeds, but overall it's a very low-value material." The Rice researchers are changing that with the help of E. coli bacteria engineered to process soy meal that generally gets discarded.
Expanding on their success in producing succinic acid from glucose, the new cells are engineered to metabolize a variety of sugars found in soybean meal. The theoretical ideal is a 1:1 ratio of feedstock which is the extracted sugars, to product, which they feel is achievable by industry. In the lab, under less controlled conditions, they still found the process highly efficient. "We're demonstrating a very high yield," Thakker said. "We're achieving in a flask a non-optimized formation of succinate that is close to the theoretical goal."
Bennett said his lab has been looking at soybeans for nearly three years. "We're always interested in low-cost feedstock," he said. "We were able to get a connection with a soybean group that is very interested in technologies to make better and more profitable use of their crop.
"There's a fair amount of oilseed residuals available, including cottonseed carbohydrates, that are not used for any high-value product, and we're in the space of microbial engineering to enable these sorts of materials to be used in a good way," he said.