IMPROVEMENT IN THE PRODUCTION OF CITRIC-A CID BY MEANS OF IMMOBILIZEDASPERGILLUS-NIGER

The influence of the initial substrate concentration on citric acid an d polyols production by means of free and immobilized A. niger was stu died in this work. The immobilization increases yield and concentratio n of citric acid. With both free and immobilized cultures, citric acid concentration increases with substrate, pass a maximum value and decl ines at high substrate concentration, although the obtained profiles a re different for the several cultures. Polyols are only detected at re latively high substrate concentrations; when these latter are small, p olyols are consumed by the microorganisms, disappearing continously of the medium. More abundant polyol is glicerol, which reaches its maxim um value for free A. niger experiment, with a 30% sacarose. Erythritol and arabitol are always with low concentration values.