TCP Solubilization by Growth Promotory Endophytic Acinetobacter calcoaceticus TM8 from Tomato

The endophytic strain, TM8 isolated from tomato fruit, was identified as Acinetobacter calcoaceticus TM8 on the basis of morphobiochemical characteristics and 16S rRNA gene sequence analysis. The strain with IAA, siderophore, ACC deaminase and phosphate solubilizing activity presented a direct mechanism for plant growth promotion. The strain possessed a remarkably high phosphate solubilising activity. The intent of the study was in vitro optimization of phosphate solubilizing activity in vitro and to assess its ability to solubilise P_i in broad range of pH, temperature and incubation period. Central composite design (CCD) and response surface methodology (RSM) were adopted to optimize phosphate solubilization in vitro and to investigate the mutual interactions between pH, temperature and incubation period. The maximum phosphate solubilization of TCP was 273.50 g mL⁻¹ under the optimum conditions: pH 7.3, temperature 37.6°C and incubation period of 7 days. The strain has ability to solubilize TCP even at alkaline pH. The strain with multiple PGPR traits could be exploited for developing Acinetobacter based biofertilizer.