Lactic acid production from cellobiose and xylose by engineered Saccharomyces cerevisiae

Abstract

Efficient and rapid production of value-added chemicals from lignocellulosic biomass is an important step toward a sustainable society. Lactic acid, used for synthesizing the bioplastic polylactide, has been produced by microbial fermentation using primarily glucose. Lignocellulosic hydrolysates contain high concentrations of cellobiose and xylose. Here, we constructed a recombinant Saccharomyces cerevisiae strain capable of fermenting cellobiose and xylose into lactic acid. Specifically, genes (cdt-1, gh1-1, XYL1, XYL2, XYL3, and ldhA) coding for cellobiose transporter, β-glucosidase, xylose reductase, xylitol dehydrogenase, xylulokinase, and lactate dehydrogenase were integrated into the S. cerevisiae chromosomes. The resulting strain produced lactic acid from cellobiose or xylose with high yields. When fermenting a cellulosic sugar mixture containing 10 g/L glucose, 40 g/L xylose, and 80 g/L cellobiose, the engineered strain produced 83 g/L of lactic acid with a yield of 0.66 g lactic acid/g sugar (66% theoretical maximum). This study demonstrates initial steps toward the feasibility of sustainable production of lactic acid from lignocellulosic sugars by engineered yeast.

Toward “homolactic” fermentation of glucose and xylose by engineered Saccharomyces cerevisiae harboring a kinetically efficient l‐lactate dehydrogenase within pdc1‐pdc5 deletion background

“…Despite the comparably low CaCO 3 concentration of 11 g/L used in our experiments (cf. Ishida et al, 2006b;Koivuranta et al, 2014;Turner et al, 2015Turner et al, , 2016, which made the pH drop to a value as low as 3.6 during the reactions, IBB14LA1_5 could still convert 80% of the offered glucose into LA (Fig. S1).…”

“…Lactic acid production on xylose has been further reported for an engineered strain of S. cerevisiae . It was enabled to xylose utilization through the integration of the oxidoreductive pathway, in which xylose reductase (XR) and xylitol dehydrogenase (XDH) catalyze a two‐step isomerization of xylose into xylulose via xylitol (Turner et al, , ). Remarkably, despite having a fully intact pyruvate‐to‐ethanol pathway, the presented S. cerevisiae strain showed lactic acid yields of up to 0.7 g/g in xylose conversions under aerobic conditions.…”

“…Remarkably, despite having a fully intact pyruvate‐to‐ethanol pathway, the presented S. cerevisiae strain showed lactic acid yields of up to 0.7 g/g in xylose conversions under aerobic conditions. Under anaerobic conditions or when glucose was utilized, however, mixed ethanol and lactic acid fermentation was obtained (Turner et al, , ). In fermentation processes at large scale, generally, the continuous supply of oxygen is undesirable because it significantly adds to process complexity and costs.…”

Cascade Production of Lactic Acid from Universal Types of Sugars Catalyzed by Lanthanum Triflate

“…[1] The market for lactic acidi si ncreasingr apidly, owing to the expanding use of lactic acid to produce renewable and biodegradable platform solvents and plastics, such as methyl lactate and polylactide. [6][7][8][9][10] However,the sugar sources suitable for fermentationa re typically monomeric sugars, which necessitate an additional hydrolysis step to break down cellulose and hemicellulose into monomeric sugars like glucosea nd xylose. [6][7][8][9][10] However,the sugar sources suitable for fermentationa re typically monomeric sugars, which necessitate an additional hydrolysis step to break down cellulose and hemicellulose into monomeric sugars like glucosea nd xylose.…”

Short communication: Conversion of lactose and whey into lactic acid by engineered yeast

“…The ldhA was integrated into the S. cerevisiae chromosome using the pITy3-ldhA-G418 plasmid to integrate at Ty δ loci (Parekh et al, 1996) and selected using G418 (geneticin) as an antibiotic selection pressure. For all experiments, 2 engineered S. cerevisiae yeast strains were used, both expressing the cdt-1 and gh1-1 lactosefermenting pathway: EJ4 (no ldhA; Wei et al, 2015) and EJ4L (expressing ldhA; Turner et al, 2016). The EJ4 strain served as the control, which in all fermentations was unable to produce lactic acid.…”