Carob pod: A new substrate for citric acid production by Aspergillus niger

The production of citric acid from carob pod extract by A. niger in surface fermentation was investigated. A maximum citric acid concentration (85.5 g /L), citric acid productivity (4.07 g/L/d), specific citric acid production rate (0.18 g/g/d), and specific sugar uptake rate (0.358 g/g/d) was achiev ed at an initial sugar concentration of 200 g/L, pH of 6.5, and a temperatu re of 30 degrees C. Other kinetic parameters, namely, citric acid yield, bi omass yield, specific biomass production rate, and fermentation efficiency were maximum at pH 6.5, temperature 30 degrees C, and initial sugar concent ration 100 g/L. The external addition of methanol into the carob pod extrac t at a concentration up to 4% (v/v) improved the production of citric acid.