Abstract
BACKGROUND: Use of avermectin B1b as anthelmintic and insecticidal agent has increased to protect soil and for enhanced crop production. Enhanced production of avermectin B1b was obtained from mutant strain of Streptomyces avermitilis 41445. OBJECTIVES: Modeling of mutant strain S. avermitilis 41445 UV 45(m) 3 growth and avermectin B1b production is therefore required for optimization during fermentation process. Kinetics of intracellular avermectin B1b production was studies in shake flask culture during submerged fermentation. MATERIALS AND METHODS: Mathematical models based upon Logistic and Piret Equations have been used to investigate the kinetics of avermectin B1b production and substrate utilization from S. avermitilis 41445 UV 45(m)3. Effect of carbon sources (glucose, maltose, lactose, potato starch, soluble corn starch, and wheat starch), pH (6.0, 6.5, 7.0, and 7.5), agitation speed (150, 200, and 250 rpm) on microbial growth and product formation were evaluated. RESULTS: Maximum avermectin B1b production (420.02mg.L(-1) and cell biomass (31.74 g.L(-1)) were obtained in media having potato starch as carbon substrate at adjusted medium pH 7.5 and 250 rpm agitation speed. Maximum specific growth rate(µ(max)), growth associated avermectin B1b production coefficient (α) and non-growth associated avermectin B1b production coefficient (β) obtained were 0.16h(-1), 0.0 mg.g(-1) and 3.5 mg.g(-1).h(-1) respectively. CONCLUSION: From above results we can conclude that avermectin B1b production is non-growth associated process.