Kinetics of gluconic acid production and cell growth in a batch bioreactor by Aspergillus niger using breadfruit hydrolysate

Abstract

AbstractThe kinetics of gluconic acid production by Aspergillus niger (A. niger) using breadfruit hydrolysate was studied in a batch bioreactor. A simple model of Luedeking–Piret, logistic, and Luedeking–Piret‐like equations were proposed for gluconic acid production, cell growth, and breadfruit hydrolysate consumption respectively. The maximum gluconic acid concentration (Pt) of 109.95 g/L with 0.967 g/g process yield (88.70%) was obtained for the medium containing 120 g/l breadfruit hydrolysate at 2 vvm aeration rate. For the same conditions, the biomass concentration and maximum specific growth were obtained as 24.3 g/L and 0.018 hr−1 respectively. The models proposed for the gluconic acid production was sufficiently satisfactory, since the theoretical values of Pt (100.94 g/L) and biomass concentration (23.43 g/L) obtained from the models were almost the same with the experimental values. The model for the breadfruit hydrolysate utilization gave R2 and Adj. R2 of above 0.840 and 0.660 respectively; an indication that the model is suitable for the production of gluconic acid. Therefore, the concentration of initial breadfruit hydrolysate as substrate and aeration rate have shown significant effect on gluconic acid production and A. niger accumulation. The evaluation of the models showed that the gluconic acid production was growth‐associated.Practical applicationsBreadfruits, a perishable fruit has been abundantly found in Ile‐Ife, Nigeria where 50% of it perishes due to its short shelf‐life. This study therefore provides alternative use for breadfruit, in order to reduce its wastage. Furthermore, the growing demand of gluconic acid can be met through the use of this cheap and available breadfruit. The findings in this study can be employed to develop a bioreactor for fermentation of breadfruit hydrolysate to produce gluconic acid.