Screening Of Osmophilic Strain For Erythritol Production And The Optimization Of Fermentation Condition

Erythritol is a new polyol food sweetener, widely present in the seaweed, mushrooms, melons, grapes, and fermented foods. Due to low calorific value, non-induced dental caries and applicability in diabetic food, erythritol has broad application prospects in the new condiment, high-grade food, baby food, healthy food, pharmaceutical sugar coating and flavoring agents, chemicals, cosmetics and other industries.Firstly, several hypertonic environment samples in nature were collected, a high erythritol production strain was screened in selective agar plates containing bromocresol green, chlorinated triphenyl tetrazolium, xylitol, and iodoacetic acid. Then this strain was subjected to mutagenesis by ultraviolet light combined mutagenesis of lithium chloride and diethyl sulfate (DES). As a result, a strain named JunA-27 was obtained with the high erythritol yield of 67.5 g/L , 4.2 times higher than the original strain(16.0g/L), The mutant strain was observed by colony morphology, microscopic morphology and scanning electron microscopy. Through 18S rDNA homology comparison with blast, the strain was similar with Yarrowia lipolytica, and it was named Yarrowia lipolytica WX 506.To improve the production of erythritol with Yarrowia lipolytica WX 506, the fermentation medium and culture conditions were opitimized through the single factor optimization and response surface optimization. The optimize process conditions were as follows: the cell growth temperature 32°C, pH 6.0, glucose 50g/L, yeast extract 2.5g/L, urea 0.25 g/L, KH2PO4 2g/L, MgSO4 1g/L;The condition for erythritol fermentation: 30°C , pH 3.0, glucose 200g/L, yeast extract 10g/L, urea 1g/L, K2HPO4 4g/L, CaCl2 7.32g/L, CuSO4 0.21g/L, Tween-40 6.48g/L, shaking speed 200r/min, liquid volume 30mL/250mL, the inoculum 10%. Erythritol production under this condition is 83.7g / L.Batch fermenter was performed in a 7-L fermenter to produce erythritol. In batch fermentation, erythritol production reached to 98.9 g/L, the production rate is 0.59 g/L·h, and the conversion rate is 51.9%. The cell growth of Yarrowia lipolytica WX 506 and erythritol production are non-coupled type. In fed-batch fermentation experiments with the initial glucose concentration of 100g/L and addition of 200g/L at 48h, erythritol production reached 126.4g/L, with the production rate of 0.66g/L·h and conversion rate of 52.6%. The erythritol yield and productivity are higher than before.