Phytase production from rice bran extract using Bacillus spp. isolated from sediments of the Caspian Sea

Phytic acid is the main phosphorus storage form that is not digestible for monogastric animals such as poultry, fish and even humans. The aim of this study was to produce phytase from rice bran extract as a rich and inexpensive source of phytic acid using Bacillus isolated from sediments of the Caspian Sea. Using thermal treatment of the sediment samples, phytase producing Bacillus isolates were screened on PSM agar. In addition, after a quantitative assay of phytase production using the ammonium molybdate method, phytase production of the isolates was investigated in the MGE broth containing rice bran extract. Screening results of 40 isolates demonstrated that the four isolates MGH2, MGH3, MGH4 and MGH7 showed high levels of phytase production with a clear halo zone forming around the colony. Morphological and physiological characteristics indicated that all of the selected isolates belong to Bacillus. Maintaining a clear halo zone after staining with ammonium molybdate confirmed the production of phytase in all selected isolates. In addition, the results of the quantitative assay of phytase production in the isolates showed that maximum and minimum phytase production relate to MGH4 with 10.58 U ml-1 and MGH3 with 9.34 U ml-1, respectively. The results showed an increase of 55-60 percent of phytase production in MGE broth compared to PSM broth. The results of present study indicated that rice bran extract can be considered as a suitable and affordable substrate with high levels of phytase production.