Isolasi Bakteri Proteolitik Dari Pencernaaan Ikan Nila Galur Gift (Oreochromis Niloticus (Linnaeus) Trewavas) Dan Karakterisasi Protease Ekstraselulernya

Abstract

At least 31 isolates of proteolytic bacteria were isolated from digestive tract of Tilapias strain GIFT (Genetic Improvement of Farm Tilapias), but only 2 isolates that can be used for the protease characterization. The result showed that both of them are Aeromonas sp. strain NU8 and Enterobacter sp. strain NU5. They were compared by the pathogenic Aeromonas hydrophila. Protease of Aeromonas sp. strain NU8 was metaloprotease, the optimum temperature and pH were 70ºC and 7, the protease activity increases by adding 5 mM K+, and decrease by adding 5 mM EDTA. The protease activity of Aeromonas sp. strain NU8 was unstable when incubated for 120 minutes at the optimum temperature, but stable at all ranges pH after incubated for 1 hour at 4ºC. Protease of Enterobacter sp. strain NU5 was metaloprotease, the optimum temperature and pH were 50ºC and 7, the protease activity increases by adding 5 mM Co2+, and decrease by adding 5 mM EDTA. The protease activity of Enterobacter sp. strain NU5 was unstable after incubating for 120 minutes at the optimum temperature, but it is stable at all ranges pH after incubated for 1 hour at 4ºC. Protease of A. hydrophla was metaloprotease, the optimum temperature and pH were 70ºC and 8, the protease activity increases by adding 5 mM Cu2+, and there was no effect by adding 5 mM EDTA. The protease activity of A. hydrophila was stable approximately when incubated for 120 minutes at the optimum temperature and it was stable at all ranges pH after incubated for 1 hour at 4ºC. The spesific protease activity of Aeromonas sp. strain NU8 was higher than A. hydrophila and Enterobacter sp. strain NU5.