Improvement of citric acid production by Aspergillus niger with addition of phytate to beet molasses

Abstract

Phytate is an important plant constituent and can be found in the seeds of cereals and legumes. Phytic acid has 12 replaceable protons in the phytic molecule, giving it the ability to complex with multivalent cations. In this study, the phytate was used as an additive to enhance citric acid production by Aspergillus niger from an untreated beet molasses. The addition of phytate caused increase of reducing sugar utilization and enhanced citric acid accumulation; however, the mycelial growth was slightly inhibited. The effect of phytate addition was found to be dependent on concentration and the stage of fermentation at which phytate was added. When added at the beginning of incubation, the optimal concentration of phytate in the medium for citric acid production was 10 g/l, which resulted in about a 3.1-fold increase in citric acid accumulation. During the fermentation, addition of 16 g/l phytate to the medium, after 3 days incubation, gave the maximal citric acid production which was about 2.4-fold higher than the control experiment.