Citric and gluconic acid production from fig by Aspergillus niger using solid-state fermentation

The production of citric and gluconic acids from fig by Aspergillus niger A TCC 10577 in solid-state fermentation was investigated. The maximal citric and gluconic acids concentration (64 and 490 g/kg dry figs, respectively), citric acid yield (8%), and gluconic acid yield (63%) were obtained at a mo isture level of 75%, initial pH 7.0, temperature 30 degreesC, and fermentat ion time in 15 days. However, the highest biomass dry weight (40 g/kg wet s ubstrate) and sugar utilization (90%) were obtained in cultures grown at 35 degreesC. The addition of 6% (w/w) methanol into substrate increased the c oncentration of citric and gluconic acid from 64 and 490 to 96 and 685 g/kg dry fig, respectively.