DETERMINATION OF YIELD AND MAINTENANCE COEFFICIENTS IN CITRIC-ACID PRODUCTION BY ASPERGILLUS-NIGER

One method for economic planning and management of production processe s is a balance of substrate mass and energy it contains. Theoretical a ssumptions and practical applications of mass and energy balances in t he process of citric acid production by Aspergillus niger are discusse d in the study. In the calculation of biomass and product yields as we ll as the maintenance coefficients mechanistic values such as true bio mass and citric theoretical acid yields Y-ATP,Y-X(P)(max) on ATP and s pecific ATP consumption m(ATP) due to maintenance processes were used. A set of limitations imposed on theoretical and true yield coefficien ts in the linear growth equation is also presented. The experimental m easurements were performed in an air-lift bioreactor of 220 dm(3) oper ating capacity, with external circulation loop. The sole carbon source for the cultivation of A. niger was sucrose at an initial concentrati on of 100 g l(-1). The experimentally obtained yield coefficients rela tive to cell growth and citric acid production have reached 96% and 83 % respectively of real maximum theoretical values. Calculated true bio mass and citric acid yield coefficients were closely correlated with t he values from the balance analysis of stoichiometric equations. Calcu lated value of specific maintenance requirements m(ATP) was 0.015 mol ATP [mol C(dry mass)](-1) h(-1).