title: Semicontinuous and continuous production of citric acid with immobilized cells of Aspergillus niger.
abstract: The citric acid excretion of Ca-alginate-immobilized cells of Aspergillus niger in batch culture decreased with a half-time of approximately 19 days. Reactivation of the biocatalysts by regeneration in growth medium was possible, but it was followed by a submerged sporulation of the fungus, and medium was highly contaminated with free cells. Citric acid production could better be prolonged by semicontinuous cultivation with medium exchange every 7 or 14 days, respectively. After 32 days the remaining activity in semicontinuous culture was 1.4-fold higher than in comparable batch experiments. Similar improvements were obtained with a continuous process at a dilution rate of 0.125 v/v X d, whereby medium efflux kept completely free of detaching mycelia.
mesh_terms: D001234:Aspergillus niger / Q000254:growth & development* / Q000378:metabolism; D002951:Citrates / Q000096:biosynthesis*; D019343:Citric Acid; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D008722:Methods
chemical_list: D002951:Citrates; D019343:Citric Acid