Chay B. Pham, Raquel B. Marquez, and Jocelyn T. De Guzman
National Institute of Molecular Biology and Biotechnology (BIOTECH)
University of the Philippines Los Baños
doi.org/10.57043/transnastphl.1997.5938
Abstract
The demand for citric acid requirement in the country is met by importation. It is used in food, pharmaceutical, feed and medical industries. This study was carried out to optimize the effect of initial ammonium (1.0, 2.0 and 3.0 g/l) and glucose (50, 100 and 150 g/l) concentrations and pH (3.0, 4.0 and 5.0) using the multiple regression equation, and to model the kinetics of submerged batch fermentation of citric acid production by Aspergillus niger. Initial ammonium concentration effects on glucose, biomass and citric acid concentrations are shown by ANOVA (P>F=0.0001). The highest citric acid concentration, 84.11 g/l was obtained from 1.0 g/l initial ammonium concentration at 30°C, 3.5 pH, 0.8 vvm aeration and 400 rpm agitation rate. The fermentation kinetics related to growth model, product formation, substrate uptake were used to determine the kinetic parameters (m,qm,k,C,D) using Leudeking-Piret equations. At the optimum fermentation conditions, the specific growth rate, m for 1 g/l initial ammonium concentration was 0.071 h−1. The non-growth related parameter, qm (0.0095 g.product/g.biomass.h) was obtained at 1.0 g/l initial ammonium concentration indicating that product formation is growth related. Substrate consumption was also growth related since higher value of growth related parameter C (1.6558 g. substrate/g.biomass) was obtained compared to the non-growth related parameter D (0.0458 g.substrate/g.biomass.h). Computed parameters were used to predict biomass, glucose and citric acid concentration using the model. The model satisfactorily represented the glucose concentration at 1 g/l initial ammonium concentration.