Development of bio-refineries has recently attracted increasing attention as a means to provide sustainable alternative solutions to deplete environmental pollution and energy crisis. As more and more Jatropha seeds are used to extract crude oil for biodiesel, a large amount of hulls is generated. How to make full use of these hulls is important for Jatropha biodiesel industry. As Jatrophahulls are rich in carbohydrate (cellulose: 43%; hemicellulose: 15%), further studies are necessary to utilize these polysaccharides to produce sugars for value-added products, such as ethanol, acetic acid, 2,3-butanediol. 2,3-Butanediol is one of the important bio-based chemicals and liquid fuels that exhibits a wide range of potential utilizations in the manufacture of printing inks, perfumes, fumigants, moistening, plasticizers, foods and pharmaceuticals.
The Biomass Group of Xishuangbanna Tropical Botanical Garden (XTBG) successfully for the first time used Jatropha hulls as raw material for the production of 2,3-butanediol via dilute acid hydrolysis followed by fermentation with Klebsiella oxytoca. Some chemicals in the hulls after hydrolysis had significant unfavorable influence on the 2,3-butanediol metabolic pathway and biological activities. So, the Jatropha hull powders were washed with neutral detergent to remove extractives (e.g., proteins, lipids, pectins and nonfibrous carbohydrates).
Two-step hydrolysis was used to effectively hydrolyze both hemicellulose and cellulose to fermentable sugars after pretreatment.In the first-step, less severe conditions (0.5 h, 150 °C, 1.5%) was used to hydrolyze amorphous hemicellulose to avoid secondary decomposition. The second-step at severe conditions (1 h, 150 °C, 4%) was needed for the hydrolysis of the remained cellulose in the solid residue. After the two-step hydrolysis, total hydrolysis yield was 64%, which was much higher than that (37%) from the first-step hydrolysis only.Maximum yield of 2,3-butanediol and acetoin in flasks from the hydrolysates of the first- and second-step hydrolysis were equivalent to 70 and 80% of the theoretical values, respectively. In bioreactor, similar yields were obtained but with higher productivity. The study could not only promote the development of biodiesel, but also cut down the production cost of 2,3-butanediol.
The study entitled “ Production of 2,3-Butanediol from Acid Hydrolysates of Jatropha Hulls with Klebsiella Oxytoca)” has been published online in Bioresource Technology , http://dx.doi.org/10.1016/j.biortech.2011.12.083
Production of 2,3-butanediol by Klebsiella oxytoca fermentation in bioreactor. (Image by Jiang Liqun)