Engineering thermotolerant Yarrowia lipolytica for sustainable biosynthesis of mannitol and fructooligosaccharides

Yarrowia lipolytica is an important industrial microbe and a commonly used synthetic chassis in synthetic biology. In recent years, it has become increasingly popular in the field of industrial biotechnology to synthesize lipophilic molecules, such as lycopene, beta-carotene, docosahexaenoic acid (DHA) and arachidonic acid. It is also a novel chassis for synthesizing erythritol and D-mannitol. Chemical synthesis is currently the most common method for producing mannitol, which has disadvantages, including multi-steps and great risks (under high pressure and high temperature). Based on the unique properties of Y. lipolytica to synthesize erythritol and mannitol simultaneously, this study overexpressed its heat shock protein Hsp90 gene to enhance its heat tolerance and ferment glucose at a higher temperature (34-35 degrees C) to realize the shift from mainly synthesizing erythritol to mannitol. The relative expression level of genes in the mannitol and erythritol synthesis pathway was detected by qPCR. The shift was achieved, according to preliminary findings, by raising the expression level of genes in the mannitol synthesis route and decreasing the expression level of genes in the erythritol synthesis pathway. To diversify the sugar alcohol profile, fructosyltransferase was displayed on the cell surface. The yeast cells, after mannitol synthesis, can also be used as a whole cell catalyst to catalyze the synthesis of fructooligosaccharides (FOS) from sucrose.