Abstract: The microwave-assisted extraction of trehalose was optimized using one-factor-at-a-time and orthogonal array design methods. Intracellular trehalose in yeast cells was determined by 3,5-dinitrosalicylic acid (DNS) method after hydrolysis by trehalase. The optimum conditions for extracting trehalose from 1.5 g of active dry yeast were determined to be extraction at 55 ℃ for 150 min using 40 mL of 0.7 mol/L trichloracetic acid as the extraction solvent with microwave treatment duration of?40 s at 231 W power. Under these conditions, the yield of trehalose was 280.15 mg/g, 15.2% higher than that before optimization. Furthermore, one of the 10 baker’s yeast strains preserved in our laboratory was selected for high yield production of trehalose. In a 50 L self-priming fermenter, the selected strain was used to perform fed-batch fermentation. The maximum wet yeast biomass was 198.34 g/L by using feedback control of dissolved oxygen concentration through feeding molasses. By feeding a predetermined amount of molasses, urea and phosphoric acid as nutrient source, the maximum wet yeast biomass was increased to 264.82 g/L, which was increased by up to 33.52% compared with the original procedure and suggested high density culture of baker’s yeast. In the fermentation process, the alcohol content (V/V) was controlled between 0.7% and 1.0%, thereby effectively improving wet yeast biomass and simultaneously ensuring that the fermentation power is over 650 mL/h, and the modified process was confirmed to stable.

Key words: baker’s yeast, trehalose, weighing feeding, alcohol content