Screening Of Yarrowia Lipolytica Strains And Optimization Of Culture Conditions For High Erythritol Production

Erythritol(1,2,3,4-butantetraol),a natural polyol,has many advantages including low moisture absorption,good thermostability,and anticarious property.Despite being quickly absorbed from the small intestine,erythritol is not metabolized by the body and is rapidly excreted in urine.It is calorie-free and has no effect on glycaemia.Erythritol has therefore been widely used as a bio-sweetener in the food and pharmaceutical industries.Yarrowia lipolytica is highly tolerant to osmotic pressure and has the potential to efficiently convert raw glycerol into erythritol.In this study,Y.lipolytica strain CICC1853 was used as the starting strain.After cultivated in an optimized medium YPG150 for 9 days,the erythritol production of strain CICC1853 reached 75 g/L,an increase of 36%compared to that obtained in the initial medium.Through uniform experiments,it was found that the most important factor affecting erythritol synthesis was osmotic pressure.Three groups of CICC1853 cells fermented under different osmotic pressures were selected for transcriptome sequencing to obtain Clean Data 46.68 Gb.A total of 7315 expressed genes were detected,including 6408 known genes and 907 new genes.Analysis of significantly different genes speculates that the two genes YALI0A15906g and YALI0B21780g are potential erythrose reductase genes(ER).The overexpression of the genes GUT1,GUT2,and TKL1 could promote the production of erythritol,but the improvement was limited.At the same time,under the conditions of high glycerol concentration and low salt ion concentration,overexpression of genes YALI0D11638g,YALI0A11 627g,YALI0A15906g was conducive to the production of erythritol.Visualized triphenyltetrazolium chloride(TCC)hypertonic plates were used for screening of wild-type Y.lipolytica strains with high erythritol production and finally 6 strains were obtained from honeycomb,honey,grape and other sources.The strain 508-1 was fermented in YPG150 medium for 9 days with erythritol production of 90 g/L,productivity of 0.41 g/L·h,and the conversion yield on glycerol of 61%.In summary,this study has provided a number of potential Y.lipolytica strains for erythritol production.Further genetic and fermentation engineering improvements are therefore required in order to obtain industrial applications.