Efficient Production of l -Lactic Acid from Xylose by Pichia stipitis

Abstract

Microbial conversion of renewable raw materials to useful products is an important objective in industrial biotechnology. Pichia stipitis, a yeast that naturally ferments xylose, was genetically engineered for L-(؉)-lactate production. We constructed a P. stipitis strain that expressed the L-lactate dehydrogenase (LDH) from Lactobacillus helveticus under the control of the P. stipitis fermentative ADH1 promoter. Xylose, glucose, or a mixture of the two sugars was used as the carbon source for lactate production. The constructed P. stipitis strain produced a higher level of lactate and a higher yield on xylose than on glucose. Lactate accumulated as the main product in xylose-containing medium, with 58 g/liter lactate produced from 100 g/liter xylose. Relatively efficient lactate production also occurred on glucose medium, with 41 g/liter lactate produced from 94 g/liter glucose. In the presence of both sugars, xylose and glucose were consumed simultaneously and converted predominantly to lactate. Lactate was produced at the expense of ethanol, whose production decreased to ϳ15 to 30% of the wild-type level on xylose-containing medium and to 70 to 80% of the wild-type level on glucose-containing medium. Thus, LDH competed efficiently with the ethanol pathway for pyruvate, even though the pathway from pyruvate to ethanol was intact. Our results show, for the first time, that lactate production from xylose by a yeast species is feasible and efficient. This is encouraging for further development of yeast-based bioprocesses to produce lactate from lignocellulosic raw material.

Production of Lactic Acid from Whey by Lactobacillus sp. Isolated from Local Dairy Products

“…Furthermore, the fermentation process could produce optically pure isomers of lactic acid by selecting an appropriate strain (Ilmen, 2007). Pure isomers, L or D lactic acid, are more valuable than the racemic DL form because each isomer has its own applications in the cosmetics and pharmaceuticals industries.…”

Bioethanol a Microbial Biofuel Metabolite; New Insights of Yeasts Metabolic Engineering

“…Additionally, P. stipitis has many other bioconversion related traits: forming various esters and aroma components [97], reducing acyclic enones to the corresponding alcohols [98], modifying low-molecular-weight lignin moieties [99], and can be engineered to produce xylitol [100] or lactic acid [101] in high yields. Also, P. stipitis strains are resistant to hydroxyl-methyl furfural and furfural [102].…”

Second Generation Ethanol from Residual Biomass: Research and Perspectives in Ecuador

“…Xylose to ethanol conversion in nature is been done by a few organisms such as yeasts like Scheffersomyces stipitis, an ascomycetous yeast that has been extensively investigated for the fermentation of xylose to ethanol, L-lactic acid for its further polymerization into PLA (Poliy Lactic Acid) and other products from hemicellulose, the second abundant component of cellulosic biomass [5,6,7]. Laboratory strains of Schef.…”