Influence of Ammonium Salt and Fermentation pH on Acarbose Yield from Streptomyces M37

Purpose: To investigate the effect of ammonium salts and fermentation pH on the biosynthesis of acarbose by Streptomyces M37. Methods: Different ammonium salts were added to the fermentation broth of Streptomyces M37 to explore their effects on acarbose production. The concentration and addition time of ammonium salts, and the fermentation pH on acarbose biosynthesis were investigated. To study the effect of pH on acarbose yield, the activities of glutamate dehydrogenase (GDH) and glucose-6-phosphate dehydrogenase (G6PDH) were also studied. Results: The optimal supplemental concentration and addition time of NH4Cl were 0.1 M and 72 h, respectively. Regulation of pH at 8.5 until the stationary phase was reached favoured acarbose production. Furthermore, GDH and G6PDH exhibited higher activity at pH 8.5 than at other pHs. Increase in acarbose yield was 53.4 % (compared with control) by NH4Cl, and was approximately 5460 mg/L. Conclusion: The results suggest that the addition of NH4Cl and maintenance of fermentation pH at 8.5 for 72 h after inoculation was an effective strategy for enhancing acarbose biosynthesis.