Toward the construction of a technology platform for chemicals production from methanol: D-lactic acid production from methanol by an engineered yeast Pichia pastoris.

With the reduction in oil reserves and steady increases in the price of oil, alternative carbon sources like methanol are promising, but an efficient conversion process to fuels and other chemicals is still desired. In this study, we demonstrated for the first time the production of lactic acid from methanol using a lactate dehydrogenase copy number amplifying strategy in Pichia pastoris. We engineered methylotrophic yeast (Pichia pastoris) producing D-lactic acid by D-lactate dehydrogenase gene (d-LDH) integration into the non-transcribed spacer of the ribosomal DNA (rDNA) locus and post-transformational amplification. The resultant engineered strains GS115/S8/Z3 and GS115/S16/Z3 produced 3.48 and 3.26 g/L of D-lactic acid from methanol, respectively, in a 96-h test tube fermentation. To our knowledge, this is the first report about D-lactic acid production from methanol by an engineered P. pastoris strain. The technique of gene integration into the rDNA locus and post-transformational gene amplification could be useful for metabolic engineering in P. pastoris, and the chemical production from methanol by engineered P. pastoris represents a promising industrial technology.