Chitinases have the potential to control many pathogen species, such as fungi containing chitin on their cell walls. In the present study, chitinase from novel isolate Serratia marcescens MO-1, isolated from Poecilimon tauricola (Orthoptera: Tettigoniidae) in Turkey, was investigated. The optimum pH and temperature for the chitinase activity were found to be pH 7.0 (36.6 U/mL) and 50 degrees C (37.1 U/mL), respectively. Moreover, the activity was still high in acidic (23.0 U/mL at pH 3.0) and basic (17.3 U/mL at pH 11.0) conditions as well as at lower (29.5 U/mL at 20 degrees C) and higher (28.7 U/mL at 80 degrees C) temperatures. The enzyme was highly thermotolerant, keeping 63.7% (23.5 U/mL) of its activity after incubation at 90 degrees C for 15 min. Antifungal activity of the chitinase against Alternaria citri, Fusarium oxysporum, Trichoderma harzianum, Aspergillus niger, and Rhizopus oryzae was determined. In addition, chitinase production by immobilized S. marcescens MO-1 cells was monitored over 10 days; the enzyme activity was found to be 36-41 U/mL during this period. Our results showed that the chitinase from S. marcescens MO-1 seems to be valuable in terms of its biotechnological applications; it can be produced using immobilized cells and can be used against fungal pathogens as an alternative to chemical pesticides.