Selection of a hyperproducing strain ofAspergillus niger for biosynthesis of citric acid on unusual carbon substrates

Abstract

Several tens of mutants were obtained by UV irradiation of a spore suspension of Aspergillus niger. Producers yielding large amounts of citric acid were selected on a modified Czapek agar containing methyl red as pH indicator. After a submerged cultivation in flasks with baffles, a mutant characterized by yellow pigmentation on wort agar and by yields of citric acid up to 74.6% in the medium containing glucose was chosen from 130 isolates tested.

Microbial production of citric acid

“…Fukuda et al, 1970 The most employed technique to improve citric acid producing strains has been by inducing mutations in parental strains using mutagens. Among physical mutagens, γ-radiation (Bonatelli and Azevedo, 1983 ;Gunde-Cimerman, 1986 ;Islam et al, 1986) and UV-radiation (Pelechova et al, 1990) have often used. To obtain hyperproducer strains, frequently UV treatment could be combined with some chemical mutagens, e.g.…”

Microbial citric acid: Production, properties, application, and future perspectives

“…Improvement of strain can be also achieved by modifying the metabolism of the microorganism by inducing mutations in them through physical or chemicals mutagens (Swain et al, 2012). Among physical mutagens, the most common mutagens used are gamma and ultraviolet (UV) radiations (Pelechova et al, 1990). Among chemical mutagens, diethyl sulfonate, N-methyl-N-nitroso-guanidine, ethidium bromide aziridine, N-nitroso-N-methyl urea, and ethyl methane-sulfonate are very common (Musilkova et al 1983).…”