African Journal of Biotechnology Vol. 3 (5), pp. 273-280, May 2004            

Full Length Research Paper

Optimization of industrial production of rifamycin B  by Amycolatopsis  mediterranei.  II. The role of gene amplification and physiological factors in productivity in shake flasks

El-Tayeb, O.M.¹*, Hussein, M. M. M.², Salama, A.A.² and El-Sedawy, H.F.¹

¹Microbial Biotechnology Center, Faculty of Pharmacy, Cairo University, Cairo, Egypt.

²Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, Egypt.

*Corresponding author. Tel: (202) 336 3222.  Fax: (202) 362 0122. E-mail: omtayeb@link.net

Accepted 25 March 2004

Amplification of gene expression of the most productive colony type of Amycolatopsis mediterranei strain N1 under stress of chloramphenicol, resulted in isolation of a variant NCH with productivity of 2.56 g/l compared to 1.15 g/l by the parent strain N1 (2.2 fold increase) . This amplified variant has a further advantage of reduced variation in colony morphology with predominance of the most productive colony type. Using variant NCH, modification of the fermentation medium F1 by the addition of 0.1%  yeast extract or the use of 1.8% KNO₃  resulted in 3.8 and 5.8-fold increase in productivity, respectively, compared to  strain N1. When the F1 medium was replaced by a new medium F2 containing soytone, instead of the particulate constituents (peanut meal and soybean meal) the yield by variant NCH reached 7.85 g/l (6.8-fold increase). Modification of the F2 medium by addition of glycerol or the replacement of glucose by glucose syrup decreased rifamycin B production. Changing the concentration of soytone increased the yield only slightly while replacing it with peptone or tryptone or the addition of 1 % corn steep liquor failed to increase the yield. On the other hand, the addition of 0.1 % yeast extract, or the replacement of 0.6% (NH₄)₂SO₄ by 1.2% KNO₃ or 0.4% NH₄NO_3,  to F2 medium led to 8.2, 10.2 and 10.4-fold increase in productivity, respectively, compared to productivity of strain N1 in F1 medium. The change in the concentrations of either MgSO₄ or CaCO₃, the use of different types of antifoams and the use of higher concentrations  of sodium diethyl barbiturate did not significantly influence the yield. These collective optimization attempts thus resulted in a 10.4-fold increase in productivity, from 1.15 to 11.99 g/l.

Key words: Rifamycin B, fermentation, biotechnology, Amycolatopsis mediterranei, optimization, gene amplification, physiological factors.