Artrocarpus heterophyllus -: a potential substrate for citric acid biosynthesis using Aspergillus niger

The growing demand for citric acid and the need for alternative materials as substrates in the recent years has led to the choice of a novel and economically viable substrate namely, Artrocarpus heterophyllus for citric acid biosynthesis. A pilot scale study was done using this substrate and the conditions required for preparing a good substrate from jack fruit carpel fibre were optimized. Hydrolysis of jack fruit carpel fibre with 14.6 mol/l HCl, followed by fermentation with Aspergillus niger produced 73 g/l of citric acid in a period of 48 h. Enrichment of the medium was also tried by sugar supplementation and the efficiency of the fermentation medium thus prepared in producing citric acid was compared with the synthetic medium. The products of the microbial metabolism namely total titrable acidity, citric acid, intracellular proteins, extracellular proteins, amylase activity, lipid and biomass contents were determined periodically. Experimentally observed growth stages were used for mathematical modeling to estimate the kinetic parameters. The values calculated agree with the experimental ones. (C) 2004 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.