Production of phytase enzyme by Frateuria sp. UMK-PPS3, a phosphate-solubilising bacterium isolated from paddy rhizosphere

Frateuria sp. are known for their plant growth-promoting abilities, particularly in phosphate solubilisation and nutrient cycling within the rhizosphere. Phosphate-solubilising bacteria (PSB) can solubilise organic phosphorus compounds into a form available for plant uptake by producing the phytase enzyme, whose activity is influenced by carbon and nitrogen sources. This study was conducted to identify a previously isolated PSB strain from the paddy rhizosphere and to determine the optimal nutrient condition for phytase production. The PSB strain, labelled as UMK-PPS3, was molecularly identified by 16S rRNA gene analysis. Phytase production was assessed by measuring the amount of inorganic phosphate released from sodium phytate using the molybdate-blue method under different nutrient conditions. To determine the optimal enzyme production, the Pikovskaya medium was prepared with varying carbon sources, including glucose, fructose, and sucrose, while maintaining ammonium sulphate as the nitrogen source. Additionally, the production of phytase enzyme under different nitrogen sources, namely ammonium sulphate, potassium nitrate, and sodium nitrate, while maintaining glucose as a carbon source, was also tested. Molecular identification revealed that isolate UMK-PPS3 shared 99% similarity with Frateuria aurantia based on 16S rRNA gene analysis. The results for phytase production showed that the isolate produced the highest phytase activity in the presence of glucose and ammonium sulphate, with 37.620 ± 0.185 U/mL and 33.542 ± 0.731 U/mL, respectively. These findings highlight that determining optimal nutrient conditions can enhance phytase production and provide essential information for designing biofertilizer formulations that sustain the enzyme activity and phosphorus-solubilising efficiency of Frateuria sp. UMK-PPS3 under soil conditions.