Journal of Pure and Applied MicrobiologyVol. 8 No. 4

Aeration Rate Effect on the Growth Kinetics, Phytase Production and Plasmid Stability of Recombinant Escherichia coli BL21 (DE3)

Nor Zalina Othman1, Elsayed A. Elsayed2,3, Roslinda Abd Malek1, Solleh Ramli1, Helmy J. Masri1 , Mohamed R. Sarmidi1, Ramlan Aziz1, Mohamad A. Wadaan2 and Hesham A. El Enshasy1,4*

1Institute of Bioproduct Development (IBD), Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia. 2Bioproducts Research Chair, Zoology Department, Faculty of Science, King Saud University, Riyadh, Saudi Arabia. 3Natural and Microbial Product Department, National Research Centre, Dokki, Cairo, Egypt. 4Genetic Engineering and Biotechnology Research Institute, City for Scientific Research and Technology Applications (CSAT), New Burg Al Arab, Alexandria, Egypt.

Received on 21 January 2014 and accepted on 10 March 2014

ABSTRACT

Phytase production using Escherichia coli BL21 (DE3), a recombinant strain harboring a plasmid encoding thermostable Bacillus phytase, in semi-industrial scale was studied in this work. Among the factors needed to be considered in order to achieve high enzyme yield, aeration rate plays an important role. Suitable aeration is required to supply 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-1min-1), on the kinetics of cell growth and phytase production by the recombinant E. coli BL21(DE3) in 16-L pilot scale stirred tank bioreactor was investigated. The highest cell concentration of 3.81 gL-1 concomitant with the maximal total phytase production of 15.63 UmL-1 were obtained in a bioreactor of aeration rate 3.0vv-1min-1. At this high aeration rate, a maximal specific growth rate (?max) and the maximal specific phytase production of 0.33 h-1 and 4102Ug-1, respectively, were achieved.

Keywords : Phytase production, Escherichia coli, aeration rate, Plasmid stability, bioreactor cultivation.