Metabolic Engineering of Yarrowia Lipolytica for Value-Added Products Synthesis from Glycerol

Growing world population requires progressively more energy sources, therefore the production of biodiesel increased. Glycerol is an important renewable feedstock as it is the main side-product of the biodiesel production process, which is nowadays applied on a large commercial scale. Moreover, glycerol is produced by several others industries, such as fat saponification and alcoholic beverage production units. Despite the high contamination, crude glycerol might be easily utilized by yeast Yarrowia lipolytica. Oleaginous yeast Y. lipolytica is an interesting host for converting a diverse range of feedstocks, such as waste glycerol, into value-added products such as erythritol (sweetener) or citric acid. Glycerol in Y. lipolytica cells is assimilated by phosphorylation pathway, the substrate first is phosphorylated to 3-P-glycerol by a glycerol kinase (GK) and subsequently is dehydrogenated to dihydroxyacetone phosphate by glycerol-3-P dehydrogenase (GDH). To enhance glycerol assimilation we over-expressed the GUT1 gene coding GK and GUT2 gene encoding GDH. The modified strains have been tested for glycerol consumption rate and erythritol and citric acid synthesis. Erythritol is a natural sweetener, a four-carbon sugar alcohol, occurring in fruits, such as grapes or melons. Because of its low energy value and non- insulin stimulant properties, erythritol is used as a non-caloric sweetener and pharmaceutical excipient. Citric acid is mainly produced by the mycelial fungus Aspergillus niger, but in the past few years much consideration has been focused on the potential use of the yeast Yarrowia lipolytica.The engineered strains might be used as a starting platform for further modification for broad-range value-added products biosynthesis.

This work was financed by the polish National Centre for Research and Development under project LIDER/010/207/L-5/13/NCBR/2014