Production of l-lactic acid by the yeast Candida sonorensis expressing heterologous bacterial and fungal lactate dehydrogenases

Microbial Cell Factories

Research

Pirkko Suominen¹  Vineet Rajgarhia²  Merja Penttilä³  Kari Koivuranta³  Laura Ruohonen³  Marja Ilmén³ 

[1] Cargill Biotechnology Research and Development, Minnesota, USA;Cargill Biotechnology Research and Development, Minnesota, USA;Total Gas and Power Biotech USA, Emeryville, California, USA;VTT Technical Research Centre of Finland, Espoo, Finland;

关键词: Lactic Acid;    Ethanol Production;    Lactate Concentration;    Lactate Production;    Lactic Acid Production;   

DOI  :  10.1186/1475-2859-12-53

 received in 2013-02-19, accepted in 2013-05-19,  发布年份 2013

来源: Springer

【 摘 要 】

BackgroundPolylactic acid is a renewable raw material that is increasingly used in the manufacture of bioplastics, which offers a more sustainable alternative to materials derived from fossil resources. Both lactic acid bacteria and genetically engineered yeast have been implemented in commercial scale in biotechnological production of lactic acid. In the present work, genes encoding l- lactate dehydrogenase (LDH) of Lactobacillus helveticus, Bacillus megaterium and Rhizopus oryzae were expressed in a new host organism, the non-conventional yeast Candida sonorensis, with or without the competing ethanol fermentation pathway.ResultsEach LDH strain produced substantial amounts of lactate, but the properties of the heterologous LDH affected the distribution of carbon between lactate and by-products significantly, which was reflected in extra-and intracellular metabolite concentrations. Under neutralizing conditions C. sonorensis expressing L. helveticus LDH accumulated lactate up to 92 g/l at a yield of 0.94 g/g glucose, free of ethanol, in minimal medium containing 5 g/l dry cell weight. In rich medium with a final pH of 3.8, 49 g/l lactate was produced. The fermentation pathway was modified in some of the strains studied by deleting either one or both of the pyruvate decarboxylase encoding genes, PDC1 and PDC2. The deletion of both PDC genes together abolished ethanol production and did not result in significantly reduced growth characteristic to Saccharomyces cerevisiae deleted of PDC1 and PDC5.ConclusionsWe developed an organism without previous record of genetic engineering to produce L-lactic acid to a high concentration, introducing a novel host for the production of an industrially important metabolite, and opening the way for exploiting C. sonorensis in additional biotechnological applications. Comparison of metabolite production, growth, and enzyme activities in a representative set of transformed strains expressing different LDH genes in the presence and absence of a functional ethanol pathway, at neutral and low pH, generated a comprehensive picture of lactic acid production in this yeast. The findings are applicable in generation other lactic acid producing yeast, thus providing a significant contribution to the field of biotechnical production of lactic acid.

【 授权许可】

CC BY   
© Ilmén et al.; licensee BioMed Central Ltd. 2013