Purification and Characterization of an Extracellular Acidic Protease of Pediococcus pentosaceus Isolated from Fermented Fish

Protease from lactic acid bacteria is of great importance to flavor and texture quality of fermented foods. An acidic protease from Pediococcus pentosaceus 220 was purified to homogeneity with a 11.5-fold increase in specific activity and 13.4% of recovery by precipitation with ammonium sulfate (20 – 60%, w/v), DEAE-Sepharose CL-6B ionic exchange chromatography, and Sephadex G-75 gel filtration chromatography. The molecular weight of the purified protease was estimated to be 37 kDa by Sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The optimum pH and temperature for protease activities were around pH4.0 and 35°C, respectively. The enzyme was stable at 20 – 40°C and showed pH stability between 4.0 and 7.0. The protease was activated by Ca2+, but inhibited by Zn2+, Mg2+ and Fe3+. The enzyme activity was also strongly inhibited by Sodium dodecyl sulfate and EDTA. It could be deduced that the purified enzyme was an acidic metalloprotease.