Abstract: Effect of initial pH on the mycelial growth and intracellular nucleoside production of Paecilomyces tenuipes was studied in a 30 L fermentor during submerged fermentation. The results showed that the optimal initial pH was 6.5. The maximal biomass reached up to 28.7 g/L and the maximal nucleoside production was up to 5.94 mg/g. The maximal biomasses corresponding to different initial pH values such as 7, 6, 5.5, 5 and 4.5 were 26.4, 27.3, 23.6, 21.2 mg/g and 18.5 mg/g, respectively, which were achieved on the 9th, 10th, 11th, 11th days and 13th days of fermentation and the corresponding maximal nucleoside production was 5.27, 5.51, 4.89, 4.29 mg/g and 4.05 mg/g, respectively, which was observed on the 11th, 11th, 11th, 13th days and 13th days. Therefore, the best mycelial growth intracellular nucleoside production could be achieved by initial pH adjustment.

Key words: Paecilomyces tenuipes (Peck) Samson, intracellular metabolites, biomass, nucleoside