Abstract:
Phosphorus (P) is often found inaccessible to plants, as it forms precipitates with cations and can be converted to
accessible forms by using Phosphate solubilizing bacteria (PSB). In the present study, isolation and character ization of PSB from rhizospheric soil of coffee plants were performed. The influence of four independent variables
(incubation temperature, incubation time, pH, and inoculum size) was investigated and optimized using an
artificial neural network and response surface methodology on the solubility of phosphate and indole acetic acid
production. The bacterium that can dissolve phosphate were isolated in Pikovskaya's agar containing insoluble
tricalcium phosphate. Total, six Phosphate Solubilizing Bacteria were isolated and three of them (PSB1, PSB3, and
PSB4) were found to be effectively solubilizing phosphate. Based on phosphate solubilizing index results Pseu domonas bacteria (PSB1) was selected for modeling. The results showed that both models performed reasonably
well, but properly trained artificial neural networks have the more powerful modeling capability compared to the
response surface method. The optimum conditions were found to be incubation temperature of 37.5 C, incu bation time of 9 days, pH of 7.2, and inoculum size of 1.89 OD. Under these conditions, the model predicted
solubility of phosphate of 260.69 μg/ml and production of IAA of 80.00 μg/ml with a desirability value of 0.947.
In general, the isolated Pseudomonas is expected to have phosphorus-degrading ability that promotes plant
growth, and further field experimental work is required to use this bacterial strain as biofertilizer, as an alter native to synthetic fertilizer.
