Submitted to: Biotechnology for Fuels and Chemicals Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/12/2004
Publication Date: 5/12/2004
Citation: Dien, B.S., Whitehead, T.R., Nichols, N.N., Cotta, M.A. 2004. Engineering klebsiella oxytoca for production of lactic acid from hexose and pentose [abstract]. Biotechnology for Fuels and Chemicals. Paper No. 2-08.
Technical Abstract: Lactic acid is used as a feedstock for production of PLA based plastics and for production of ethyl lactate. Currently, lactate is produced from starch either using lactic acid producing bacteria or the fungus Rhizopus oryzae. Conversion of lignocellulose to lactic acid requires strains capable of fermenting mixtures of hexose and pentose sugars. Previously, we have reported on Escherichia coli strains capable of converting glucose to L-lactic acid with yields up to 93% of theoretical. We have now developed Klebsiella oxytoca bacterium as a host for lactate production from lignocellulosic biomass. K. oxytoca is well suited for fermentation of lignocellulose hydrolysates because the bacteria naturally grows in paper sulfite streams and ferments a wide variety of hexoses and pentoses, as well as cellobiose and short xylan oligomers. We have transformed and expressed the ldh gene from Streptococcus bovis into K. oxytoca strain MA51. The transformed strain produced almost all L-lactic acid from glucose at maximum yields of 0.82 g/g. The strain also converted cellobiose and xylose to lactic acid; however, yields were much lower, only 0.66 g/g and 0.18 g/g, respectively. We are currently seeking to increase the lactic acid yield on xylose by eliminating production of other side-products.