A sustainable replacement option for petroleum derived plastics are poly-lactic acid (PLA) plastics which are able to be derived from renewable resources. Mixtures of L- and D-poly-lactic acid have higher melting points than poly-L-lactic acid alone. This higher melting point characteristic of stereocomplex PLA will allow for broader applications of PLA. There have been many studies on the production of L-lactic acid but few on the biosynthesis of D-lactic acid. In our study, corn stover was hydrolyzed using CTec2 and HTec2 to provide sugars for the biosynthesis of D-lactic acid. L. plantarum NCIMB 8826 ∆ldhL mutant with the ldhL gene knocked out and a recombinant L. plantarum NCIMB 8826 ∆ldhL carrying pCU-xylAB plasmid were used in our study to produce lactic acid from different carbon sources. L. plantarum NCIMB 8826 ∆ldhL produced D-lactic acid with an optical purity of 99.1% and a yield of 0.94 g. The recombinant strain with pCU-xylAB was able to use xylose and produced D-lactic acid with a yield of 0.51 g. The high optical purity, yield and productivity of the mutant strain shows an efficient production of D-lactic acid from corn stover which may be used to create innovative PLAs in the polymer industry and the results with the recombinant strain showed evidence that the recombinant strain of L. plantarum may be able to produce higher concentrations of lactic acid by utilizing all of the sugars present in biomasses.

D-Lactic acid biosynthesis from corn stover using engineered Lactobacillus plantarum

249th National Meeting (2015)

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