Monday, August 13, 2012
Columbia Hall, Terrace Level (Washington Hilton)
While many feedstocks can be used in microbial conversions to form biofuels and chemicals, there has been less attention to use of the galactose rich carbohydrates from soybean and cotton seed. Carbohydrate is the 2nd most predominant component in soybean, cotton seeds and some additional oilseeds. Soluble sugars of these oilseeds consist of sucrose, raffinose, stachyose, glucose, fructose, and trace amounts of arabinose, rhamnose, fucose, ribose, xylose, and mannose. In the current study we used soluble sugars including nondigestible oligosaccharides of soy bean and cotton seed to demonstrate succinate and ethanol production by recombinant E. coli strains harboring a raffinose metabolizing plasmid and a plasmid overexpressing the pepc or fdh genes. Strain HL27659(pKK313)(pRU600) consumed 306 mM and 380 mM hexose present in soy solubles hydrolysate and produced 250 mM and 312 mM succinate aerobically in 24 h and 48 h, respectively. The molar succinate yield at 24 h and 48 h was 0.81 and 0.82 mol/mol hexose, respectively. Similarly, the strain showed efficient production of succinate using cotton seed hydrolysate. Ethanol production under anaerobic conditions was demonstrated using GJT001 and MG1655 strains. When soy solubles hydrolysate was used, GJT001(pRU600) produced 84 mM ethanol from 64 mM hexose in 72 h. Whereas in the case of cotton seed hydrolysate, MG1655(pRU600)(pSBF2) produced 64 mM ethanol from 37 mM hexose in 48 h. This study showed remarkable potential for large-scale succinate and ethanol production using inexpensive and abundantly available sugar rich soybean and cotton seed feedstocks.