Screening Of Dihydroxyacetone-Producing Strains And Studies On The Fermentation Process

Nowadays, oil and other fossil energy content decrease, biodiesel as one of biological energy to get a fast development. In the production processes of biodiesel obtained a lot of glycerol as by-product. Because of the glycerol market is small, glycerol is in low price. Looking for new ways of development and utilization of glycerol, not only can improve the added value of glycerol use, also can reduce the cost of biodiesel production. With glycerol can get lots of derivative products, with cheap glycerol as raw materials can produce the dihydroxyacetone. Dihydroxyacetone is applications and the current market demand is big. Dihydroxyacetone products cost high prices and its products have a high economic performance. In this research, a yielding dihydroxyacetone strain was breeding, and their culture was optimized, key findings are as follows:(1) A new rapid and accurate method to determine dihydroxyacetone in fermentation broth was developed by capillary electrophoresis with a fused-quartz capillary (50pm×60cm,45cm effective length) at detection wavelength of200nm and separation voltage of24kV. The buffer solution was30mmol/L borax at pH9.5.The calibration curve was linear in the range from100μg/mL to1000μg/mL (R2=0.9995) for DHA with3.220g/L DHA in the fermentation broth was detected by HPLC. The average recovery was97.79%with RSD of1.81%. The method was applicable for DHA determination in the fermentation process.(2) There were more than20strains capable of producing dihydrox-yacetone from glycerol were isolated from soil samples collected from orchard and garden in the campus. Among these strains there was strain of WT-15which had a higher converting capability. Under a better culture and conversion condition, the highest convert yield of strain WT-15from glycerol to DHA was7.6g/L. It was identified as a strain of Acetobacter by observing the culture characteristics and cell morphology of strain WT-15.(3) The UV-Hydroxylamine Hydrochloride mutagenesis conditions of Acetobacter WT-15were investigated. As UV irradiation time was30s and Hydroxylamine Hydrochloride dosage was0.6%, the positive mutation rate could reach up to9.8%. Then a genetically-stable yield dihydroxyacetone strain of VH-23was obtained successfully with its dihydroxyacetone yield as9.44g/L (increasing by30.6%than that of the starting strain).(4) Based on the experimental results of single factor Study of single factor, response surface methodology was used to determine the optimal fermentation medium composition and fermentation process conditions. The optimum fermentation conditions were:sorbierite33.6g/L yeast15.1g/L, ammonium sulfate2g/L, monopotassium phosphate1.5g/L manganese sulfate3.2g/L, calcium carbonate addition20g/L, initial pH6.0and mediumvolume100mL/500mL, the yield of dihydroxyacetone was9.24g/L by mutant VH-23, which was31.9%higher than that before optimization.