Isolation and Characterization of Salt-Loving Protease Producing Bacteria form Fish Sauce Samples

Abstract

Fermented fish samples from fish sauce factories in the eastern part of Thailand were used as sources for the isolation of salt-loving protease-producing bacteria. The conditions for optimal growth and salt-loving protease production were established for the extremely halophilic bacteria. Two hundred and eighty five strains of halophilic bacteria were isolated. Among these isolated strains, a totally ten strains of extremely halophilic bacteria exhibited the highest salt-loving proteases producing ability. Maximal growth and salt-loving proteases of these strain occurred in mM73 agar medium at 4M (24 %, w/v) NaCl. On the other hand, bacterial growth and salt-loving protease activity did not occur when NaCl concentration in mM73 agar medium was lowered to 2M (12 %, w/v). All of these strains were further secondary screened in liquid medium. These selected strains were cultured on a rotary shaker at 200 rpm at 37 ^oC in M73 liquid medium with 4M (24 %, w/v) NaCl at pH 7. The bacteria strain PB407 exhibited
the highest salt-loving protease activity. In addition, the strain PB407 was identified and characterized. It was a Gram-negative, rod. The colonies were circle with red pigmentation. Growth occurred in a medium containing 17.5-25 % NaCl. Based on the data obtained in this study, it was concluded that the extremely halophilic bacteria strain PB407 belonged to the genus Halobacterium.