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A chitosanase and a protease were purified from the culture supernatant of Serratia marcescens subsp. sakuensis TKU019 with shrimp shell as the sole carbon/nitrogen source. The culture condition suitable for production of chitosanase was found to be shaken at 37 °C for 3 days in 100 mL of medium containing 0.5 % shrimp shell powder, 0.1 % K2HPO4 and 0.05 % MgSO4•7 H2O at pH 7. The TKU019 chitosanase was suppressed by the simultaneously existing protease, which also showed the maximum activity at the third day of incubation. The molecular masses of the chitosanase and protease determined by SDS‐PAGE were approximately 36 kDa and 58 kDa, respectively. Cu2+, Mn2+ and Zn2+ inhibited the chitosanase activity, and all of tested divalent metals inhibited in the protease activity. The optimum pH, optimum temperature, pH stability, and thermal stability of the chitosanase was pH 7, 60 °C, pH 4–7, and < 60 °C, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of the protease was pH 10, 50 °C, pH 5–10, and <50 °C, respectively. Tween 40 (2 %, v/v) had stimulatory effect on TKU019 protease activity.