Study On Fermentation Of Pristinamycin By Streptomyces Pristinaespiralis

Pristinamycin, produced by Streptomyces pristinaespiralis, is a kind of streptogramin. It includes PI, a kind of cyclic hexadepsipeptides, and PII, a kind of polyunsaturated macrolactone. RP5900, obtained from pristinamycin by chemical modification, is very active to inhibit the growth of most Gram-positive bacteria and some Gram-negative bacteria.The major objective of this article is to study the optimum conditions of pristinamycin fermentation to improve the yield.(1) The condition of pristinamycin fermentation was studied. Firstly, inoculum time, inoculum size and temperature were optimized by 'one-variable-at-a-time' approach (OVAT), and the optimum condition in shake flash was inoculum time, 36h; inoculum size, 6%; temperature, 28℃. Secondly, the influence of the initial glucose concentration on pristinamycin fermentation was studied, and the optimum initial glucose concentration was 10g/L. At last, the influence of metal ion on pristinamycin fermentation was studied. The result was: by adding 50mg/L Cu²⁺ into fermentation medium, the yield of pristinamycin was improved by 11%; by adding 50mg/L Mo⁶⁺ into the fermentation medium the yield of pristinamycin was improved by 14%; by adding 25mg/L Fe²⁺ into the fermentation medium, the yield of pristinamycin was improved by 43%..(2) Addition of 1,2 or 3 glass beads into fermentation medium had little effect on the yield of pristinamycin. The yield of pristinamycin was 224.7mg/L in 2.5L fermentor, which was 71.4% higher than that in shake flask. Fitted by Origin 7.0, we can get the equations as follows:S=8.92687-0.2774t+0.02983t² -0.00128t³ +2.05146* 10^-6t⁴ -1.10708* 10^-7t⁵ P=3302.62424-378.33094t +16.20499t² -0.31622t³ +0.0029t⁴ -1.01974*10^-5t⁵(t∈[30, 72])(3) Adding 0.15% n-propanol into the medium after 36h of fermentation in shake flask, the yield was as high as 197.8mg/L, which was 50.8% higher than the control. Adding 0.15% n-propanol after 24h of fermentation, the yield in 2.5L fermentor was as high as 318.8mg/L, which was 41.9% higher than the control. It was found that the pH of the fermentative broth with addition of n-propanol was lower than the control, and that the consumption of sugar and nitrogen with addition of n-propanol was much faster than the control.(4) By adding the various nitrogen sources (soybean powder 2%, fish flour 0.8%, (NH₄)₂SO₄ 0.2%, NaNO₃ 0.12%) twice at 24h and 30h of fermentation and keeping the glucose concentration at 6g/L after 40h of fermentation, the yield in the shake flask was improved effectively, and the same in the 2.5L fermentor. Because of addition of precurosor, glucose and various nitrogen sources, the variation of pH was slower than that of batch fermentation; the maximum dry weight reached 68.5g/L, which was 63.5% higher than that of batch fermentation; the maximum yield of pristinamycin reached 508.4mg/L, which was 126.3% higher than that of batch fermentation.