Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
2,3-Butanediol (2,3-BDO) is a four-carbon chemical intermediate with industrial potentials for synthetic rubber, plastic and antifreezing agent. Traditional and chemical synthesis of 2,3-BDO has faced the drawback of the petroleum deficiency and environmental pollution that allows the development of microbial production of 2,3-BDO from renewable biomass. A gram negative bacteria, Klebsiella oxytoca has been known to be a potential microorganism for 2,3-BDO production. In fermentation process, K. oxytoca generally produces 2,3-BDO as the main product as well as several organic acids as byproduct from renewable biomass substrates. To minimize the organic acid production and hence increase 2,3-BDO production from glucose, in this study, chemical mutation and evolutionary engineering were chosen for selection of K. oxytoca mutant with low-acid producing ability. Through a method using sodium bromide and sodium bromate, K. oxytoca NBR2-4 was selected. Batch fermentation of K. oxytoca NBR2-4 in a defined medium with 20 g/L glucose resulted in 4.45 g/L 2,3-BDO concentration, 0.26 g/g its yield and 1.69 g/L total organic acid concentration, which were 26% and 44% higher, and 3% lower than those of the wild strain (K. oxytoca ATCC43863).