Abstract: Optimization of four parameters, including initial total sugar concentration, carbon source, nitrogen source and carbonnitrogen ratio (C/N), was surveyed by using single factor experiment for the optimal production of sporulation of biocontrol strain Col-68 and the increasing activity of fermentation filtrate against Digitaria Sanguinalis root growth. The optimal fermentation medium was as follows：the optimal carbon source was surcose, the optimal nitrogen source was nitrate nitrogen, carbonnitrogen ratio was 2.5∶1.0, and an initial total sugar concentration between of 30～50 g·L-1. The suitable fermentation conditions were as follows:initial pH 7.0, temperature 28℃, medium volume 120 mL·300 mL-1, inoculum volume 5% (v/v), for 10 day. In such optimal nutrition and environmental conditions, the maximum sporulation and herbicidal activity of fermentation filtrate of were obtained. The results also showed that the inhibition of fermentation filtrate of the strain Col-68 to Digitaria Sanguinalis root growth was significantly higher than the sprout．

Key words: biocontrol fungus, Col-68, Digitaria sanguinalis, fermentation