Work

The main research objective of this proposal is obtain effective producers of lactic acid from renewable raw materials (lignocellulose) based on the yeast Ogataea polymorpha. Lactic acid has numerous industrial applications. These promising polymers can be obtained from cheap renewable raw materials - lignocellulosic residues of the agricultural and woodworking industries (Wee et al. 2006). However, today there are unknown microorganisms capable of efficient conversion of agro-industrial waste to lactic acid. Thus, the improvement and refinement of microbial lactic acid producers from non-food raw materials are important task to reduce the cost and energy consumption of the process. Recently, interest in yeast as an alternative producer for lactic acid has increased (Ishida et al., 2005; Ilmen et al., 2007; Liaud et al., 2015). In the processes of industrial production of lactate from lignocellulosic biomass, the yeast Saccharomyces cerevisiae is usually used, which is capable of efficient fermentation of hexoses. However, S. cerevisiae cannot ferment pentose sugars such as D-xylose and L-arabinose (Jeroen et al., 2016). Thermotolerant methylotrophic yeast O. polymorpha was selected as a model organism to study because, they have a natural ability to metabolize xylose, is one of the most thermotolerant yeast species, with a maximum growth temperature above 50 oC and resistance to low pH levels, which makes them convenient for industrial production. Lactate production will be carried out by constructing recombinant yeast strains of O. polymorpha expressing the gene encoding the enzyme lactate dehydrogenase from Rhizopus oryzae and testing the ability of these strains to produce lactic acid from the main components of lignocellulosic hydrolysates and their mixtures. Additionally, selection of strains resistant to high lactic acid content in the culture medium will be carried out, as well as optimization of cultivation conditions for maximum yield of the final product.