Abstract: To study factors affecting the protoplast formation of Phaffia rhodozyma with PEG. Culture time,culture temperature, generation times, medium volume, enzyme concentration, property of osmotic stabilizer, pH, temperature and time of enzyme action,all of which affect the formation of protoplast greatly. The optimum conditions of protoplast formation are as follows; 0 ~2 generations cultivating at 15 or 25℃ for 12 ~ 16 h, medium volume 100 mL, osmotic stabilizer 0. 8 mol/L KCl, enzyme concentration 1% ; temperature ,time and pH for enzyme action are 22℃,16 h and 8.0 respectively.

Key words: Phaffia rhodozyma, protoplast formation, affecting factor