Penicicllium variabile P16, encapsulated in agar or calcium alginate, produ
ced gluconic acid in repeated batch shake-flask cultures. Agar-encapsulated
mycelium produced 21% more gluconic acid than Ca-alginate-encapsulated fun
gus, 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 g
l(-1) batch(-1)) were found at 14.0 gl(-1) rock phosphate, but the solubili
zation efficiency was higher at 3.5 gl(-1) rock phosphate. Gluconic acid pr
oductivity pattern and the degree of,phosphate solubilization were not infl
uenced by decreasing the glucose concentration in the cultivation medium fr
om 80 to 25 gl(-1). Encapsulated fungal cells systems could substitute for
chemical solubilization of rock phosphate and could be applied as soil micr
obial inoculants. (C) 2000 Elsevier Science Ltd. All rights reserved.