Abstract: An endophytic strain R\|2\|1， Lysobacter enzymogenes， was firstly isolated from traditional Chinese medicine Artemisia annua Linn. Bioassay indicated that the ethyl acetate extract of fermentation broth of this strain had a broad spectrum of antimicrobial activities. The present work focused on optimization of its fermentation conditions using orthogonal experiment and response surface analysis （RSA）. The former was used to optimize the LB liquid medium. The best medium included the following components: corn flour 20 g·L-1， peanut meal 20 g·L-1， bean pulp 20 g·L-1， yeast extract 2 g·L-1， tryptone 4 g·L-1， （NH4）2SO4 6 g·L-1，K2HPO4 6 g·L-1， MgSO4·7H2O 4.8 g·L-1， MnSO4·H2O 0.02 g·L-1， FeSO4·7H2O 0.01 g·L-1， CaCl2·2H2O 0.12 g·L-1， NaCl 2.4 g·L-1， riboflavin 3.0 g·L-1， thiamine 1.2 g·L-1， vitamin B6 0.01 g·L-1， biotin 0.1 g·L-1， and the number of living microbe of strain R\|2\|1 reached 694×108 cfu·mL-1 under the optimal condition after 24 h. The fermentation condition of L. enzymogenes was optimized by RSA with statistical software Design Expert 7.00. Under the optimum conditions （fermentation time 87.2 h， initial pH 7.55， fermentation volume 204 mL， inoculation volume 7.90 mL）， the yield reached （0.518±0.050） g·200 mL-1. The yield could be raised to （0.523±0.023） g·200 mL-1 at 210 r·min-1 and 30℃ conditions. These results could provide references to scale up production of biobactericide of L. enzymogenes R\|2\|1.

Key words: endophytic bacterium, Lysobacter enzymogenes, fermentation condition, orthogonal experiment, response surface analysis