title: Citric acid production by a novel Aspergillus niger isolate: I. Mutagenesis and cost reduction studies.
abstract: Ultraviolet-irradiation (UV), ethyl methane sulfonate (EMS) and acridine orange (AO) were used to induce citric acid overproduction mutations in Aspergillus niger UMIP 2564. Among 15, eight of the mutant derivatives, were improved with respect to citric acid production from sucrose in batch cultures. Maximum product yield (60.25%) was recorded by W5, a stable UV mutant, with approximately 3.2-fold increase when compared to the parental wild type strain. In terms of the kinetic parameters for batch fermentation processes, the mutation doubled the specific substrate uptake rate and achieved 4.5- and 7.5-fold improvements in citric acid productivity and specific productivity, respectively. For reduction of the fermentation medium cost, corn steep liquor and calcium phosphate pre-treated beet molasses were successfully used as substituents of nitrogen and carbon sources in the growth medium, respectively. These medium substitutions resulted in a W5 citric acid fermentation culture with a product yield of 74.56%.
authors.affiliation: Department of Botany, Faculty of Science, University of Alexandria, Alexandria 21526, Egypt.
authors.forename: Walid A
authors.initials: WA
authors.lastname: Lotfy
authors.forename: Khaled M
authors.initials: KM
authors.lastname: Ghanem
authors.forename: Ehab R
authors.initials: ER
authors.lastname: El-Helow
mesh_terms: D000165:Acridine Orange / Q000494:pharmacology; D001234:Aspergillus niger / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D001709:Biotechnology / Q000191:economics*; D019343:Citric Acid / Q000378:metabolism*; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D005285:Fermentation; D016296:Mutagenesis; D014466:Ultraviolet Rays
chemical_list: D019343:Citric Acid; D005020:Ethyl Methanesulfonate; D000165:Acridine Orange