Abstract：To explore the species distribution and probiotics function of enzyme-producing bacteria in gut of the silkworm, protease-producing bacteria strains were isolated from the inclusion in 4th larval guts of the silkworm Bombyx mori by NA mediums and casein-NA mediums and 16 Sr DNA sequences were used to identify the species. Meanwhile, the enzyme producing activities of the three strains and optimum fermentation conditions of Haoyue NA1 strain were investigated. The results showed that three strains Haoyue NA1, 951 NA3 and 951 NA6 belonged to Acinetobacter were isolated and confirmed. The maximum protease activity with 29.5 U/mL was found in Haoyue NA1 and the optimum fermentation conditions were corn powder 10 000 mg/L, soybean powder 10 000 mg/L, MgSO4 400 mg/L, NaC1 15 000 mg/L and K2HPO4 1 000 mg/L with a liquid volume of 80 mL in 150 mL bottol and cultured at 35 ℃, pH 9.0 under 180 r/min for 48 h. In this condition, the maximum protease activity produced by Haoyue NA1 reached 50 U/mL. This research can play an important role on the research of distribution of microrganisms in gut of the silkworm and on the control of the gut probiotics function.
