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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Renewable Product Technology Research » Research » Publications at this Location » Publication #311272
Title: Lactic acid production from xylose by engineered Saccharomyces cerevisiae without PDC or ADH deletion

Author
item TURNER, TIMOTHY - University Of Illinois
item ZHANG, GUOCHANG - University Of Illinois
item SUBRAMANIAM, VIJAY - University Of Illinois
item STEFFEN, DAVID - University Of Illinois
item Skory, Christopher - Chris
item JIN, YONG-SU - University Of Illinois

Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2015
Publication Date: 6/6/2015
Citation: Turner, T.L., Zhang, G., Kim, S.R., Subramaniam, V., Steffen, D., Skory, C.D., Jang, J.Y., Yu, B.J., Jin, Y. 2015. Lactic acid production from xylose by engineered Saccharomyces cerevisiae without PDC or ADH deletion. Applied Microbiology and Biotechnology. 99(19):8023-8033. doi: 10.1007/s00253-015-6701-3.

Interpretive Summary: Production of lactic acid from renewable sugars has received growing attention as lactic acid can be used for making renewable and bio-based plastics. Lactic acid is typically made by microorganisms that are able to ferment sugars obtained from agricultural or energy crops into this important product. Most prior studies have focused on production of lactic acid from glucose despite an abundance of the sugar xylose in plant biomass. Microbial strains capable of fermenting both glucose and xylose into lactic acid are needed for sustainable and economic lactic acid production. In this study, we introduced a lactic acid-producing pathway into an engineered Saccharomyces cerevisiae capable of fermenting xylose. The resulting strain produced lactic acid from glucose or xylose in high yields. This work is expected to be a significant contribution towards the development of improved technologies for producing lactic acid.

Technical Abstract: Production of lactic acid from renewable sugars has received growing attention as lactic acid can be used for making renewable and bio-based plastics. However, most prior studies have focused on production of lactic acid from glucose despite cellulosic hydrolysates contain xylose as well as glucose. Microbial strains capable of fermenting both glucose and xylose into lactic acid are needed for sustainable and economic lactic acid production. In this study, we introduced a lactic acid-producing pathway into an engineered Saccharomyces cerevisiae capable of fermenting xylose. Specifically, ldhA from the fungi Rhizopus oryzae was overexpressed under the control of the PGK promoter through integration of the expression cassette in the chromosome. The resulting strain exhibited a high lactic acid dehydrogenase activity and produced lactic acid from glucose or xylose. Interestingly, we observed that the engineered strain exhibited substrate-dependent product formation. When the engineered yeast was cultured on glucose, the major fermentation product was ethanol while lactic acid was a minor byproduct. In contrast, the engineered yeast produced lactic acid almost exclusively when cultured on xylose. The yields of ethanol and lactic acid from glucose were 0.31 g ethanol/g glucose and 0.22 g lactic acid/g glucose, receptively. On xylose, the yields of ethanol and lactic acid were <0.01 g ethanol/g xylose and 0.69 g lactic acid/g xylose, respectively. These results demonstrate that lactic acid can be produced from xylose with a high yield by S. cerevisiae without deleting pyruvate decarboxylase, and the formation patterns of fermentations can be altered by substrates.