Biological production of citric acid in submerged culture of Aspergillus niger using cassava pulp wastes

Abstract

Utilization of cassava pulp wastes for citric acid production was investigated using Aspergillus niger in a submerged culture. A series of experiments were designed on various fermentation parameters to establish the optimal conditions for citric acid production from cassava pulp. This study revealed that production parameters such as cassava pulp concentration, initial pH, incubation temperature, agitation, and nitrogen source and fermentation period had effect on the amount of citric acid produced from cassava pulp. Citric acid concentration increased as the concentration of cassava pulp increases up to 20% with maximum citric acid concentration of 14.9 ± 0.413 g/l after 120 hours of fermentation. pH 5.5 was the optimum with maximum citric acid concentration of 16.8 ± 0.23 g/l after 120 hours of fermentation. Incubation temperature at 300 C was the optimum, with citric acid concentration of 19.15 ± 0.43 g/l. Increased in agitation speed from 100 to 225 rpm gave the maximum citric acid concentration of 25.2 ± 0.32 g/l after 120 hours of fermentation. Soybean meal supplementation was the best maximum citric acid concentration of 28.2 ± 0.51 g/l. Evaluating the effect of different concentration of soybean meal shows that 0.3 % supplementation was the optimum with maximum concentration of 31.2 ±0.35g/l from cassava pulp after 120 hours of fermentation. The result suggested that citric acid can be accumulated using cassava pulp by Aspergillus niger in submerged culture during fermentation. Cassava pulp if well harnessed can be used for large scale citric acid production.