CITRIC ACID PRODUCTION FROM SUGARCANE MOLASSES BY ASPERGILLUS NIGER UNDER DIFFERENT FERMENTATION CONDITIONS AND SUBSTRATE LEVELS

Aspergillus niger, one of the most important fungi used in industrial microbiology, has been employed for many years for the commercial production of citric acid. However, citric production and recovery may vary greatly depending upon type of substrate as well as the fermentation conditions like temperature, fermentation time and the type of culture/strain. The present study was aimed to investigate the potential of Aspergillus niger to convert sugarcane molasses into citric acid through fermentation carried out for 8 days at three different temperatures 20°C, 24°C and 28°C and five substrate levels 0, 6%, 12%, 18% and 24%. The optimum citric acid production was achieved after 6 days of fermentation from 24% substrate level at 28°C. The maximum citric acid yield was 6.87±0.12 g 100 mL -1 (68.7 g L -1 ) with a mean recovery of 51.62% with respect to initial total sugar contents of the media. However, the optimum recovery of citric acid (59.64%) with respect to initial total sugar contents was achieved from 18% substrate level after the completion of fermentation period of 6 days. The study suggested that the 6 days of fermentation period with 18% substrate level and temperature 28 o C were the optimum conditions for citric acid recovery from sugarcane molasses through Aspergillus niger.