Aeration rate effect on the growth kinetics, phytase production and plasmid stability of recombinant Escherichia coli BL21 (DE3)

Abstract

Phytase production using Escherichia coli BL21 (DE3), a recombinant strainharboring a plasmid encoding thermostable Bacillus phytase, in semi-industrial scalewas studied in this work. Among the factors needed to be considered in order to achievehigh enzyme yield, aeration rate plays an important role. Suitable aeration is required tosupply cells with sufficient amount of air for cell and phytase production. The effect of different aeration rates, (1.0, 2.0 and 3.0 vv -1 min -1 ), on the kinetics of cell growth andphytase production by the recombinant E. coli BL21 (DE3) in 16-L pilot scale stirred tankbioreactor was investigated. The highest cell concentration of 3.81 gL -1 concomitant withthe maximal total phytase production of 15.63 UmL -1 were obtained in a bioreactor of aeration rate 3.0vv -1 min -1 . At this high aeration rate, a maximal specific growth rate (µ max )and the maximal specific phytase production of 0.33 h -1 and 4102Ug -1 , respectively, wereachieved