Abstract: A ZLSY5 strain isolated from the digestive tract of Procecidochares utilis larvae was identified, and the basic fermentation medium and fermentation conditions were optimized. The strain was identified morphologically and by phylogenetic tree. The fermentation conditions were evaluated according to the OD value of the bacterial solution measured at 600 nm by a spectrophotometry. The round leaf method was used to compare the effects of the strains before and after optimization of fermentation conditions on the leaves of Eupatorium adenophorum. The strain ZLSY5 was identified as Bacillus tequilensis 10 b. At 72 h after inoculation to different mediums, the largest amount of bacteria and the fastest growth rate was observed in the NYBD medium. Among the five carbon sources, maltose was the most beneficial to the growth of ZLSY5. Among the six nitrogen sources, the yeast extract had the best effect, followed by peptone. The most suitable fermentation conditions are 28℃, pH 6, inoculation amount 2.0%, filling volume 40 mL/250 mL, rotating speed 240 r/min, fermentation time 36 h, and photoperiod of 20 h/d. The most suitable medium for ZLSY5 strain:peptone 10 g/L, yeast extract 5 g/L, maltose 10 g/L, and distilled water 1 L. After optimization, the medium showed only a little influence on the leaves while the cultured bacteria had a high infectious efficacy on the leaves, with an infection index close to 90% at the original concentration.

Key words: Eupatorium adenophorum, Procecidochares utilis, identification, Bacillus tequilensis, herbicidal activity, fermentation conditions, selection