Application of encapsulated Penicillium variabile P16 in solubilization of rock phosphate

Penicicllium variabile P16, encapsulated in agar or calcium alginate, produced gluconic acid in repeated batch shake-flask cultures. Agar-encapsulated mycelium produced 21% more gluconic acid than Ca-alginate-encapsulated fungus, and was utilized in experiments for rock phosphate solubilization. The latter was closely related to gluconic acid production, which was affected by the presence of rock phosphate. Maximum amounts of dissolved P (0.226 gl−1 batch−1) were found at 14.0 gl−1 rock phosphate, but the solubilization efficiency was higher at 3.5 gl−1 rock phosphate. Gluconic acid productivity pattern and the degree of phosphate solubilization were not influenced by decreasing the glucose concentration in the cultivation medium from 80 to 25 gl−1. Encapsulated fungal cells systems could substitute for chemical solubilization of rock phosphate and could be applied as soil microbial inoculants.