Stimulation of avermectin B1a biosynthesis in Streptomyces avermilitis by feeding glucose and propionate

The biosynthetic ability of avermectin B1a in Streptomyces avermilitis was improved with propionate addition and glucose feeding. The results showed t hat B1a production was increased by 12.8-13.8% through supplement of 0.8% p ropionate at 24 h of cultivation. A stronger stimulation on B1a biosynthesi s in S. avermilitis was observed by 3.0% glucose feeding at 5 d of cultivat ion. The B1a biosynthesis could be further enhanced by repeated glucose fed -batch process in a 10-1 bench-top fermenter. A maximal B1a concentration o f 780.0 mg/l was obtained by repeated 1.0% glucose addition on 4 d, 5 d and 6 d, which was 2.1-fold higher than that in a control fermentation. Corres ponding with this, an additional 6.8% increase of B1a proportion was observ ed in comparison with the control process. This stimulation on avermectin B 1a production was obvious even in a 2000-1 fermenter under suitable control of aeration.