A note on crossing experiments with Aspergillus niger for the production of calcium gluconate

Effects of metal ions on simultaneous production of glucose oxidase and catalase by Aspergillus niger

The effects of various metal ions on the simultaneous production of glucose oxidase and catalase by Aspergillus niger were investigated. Calcium carbonate induced synthesis of both enzymes. The induction of calcium carbonate was accompanied by a metabolic shift from the glycolytic pathway (EMP, Embden-Meyerhof-Parnas) to direct oxidation of glucose by glucose oxidase. The time course of the biosynthesis of both enzymes is reported. The logistic model was in good agreement with the experimental growth results. The production of both enzymes was growth-associated. Finally, a model of growth and product formation was also proposed.

A new glucose oxidase from Aspergillus niger: characterization and regulation studies of enzyme and gene

A new glucose oxidase from Aspergillus niger was isolated and characterized. The enzyme showed different kinetic and stability characteristics when compared to a commercially available batch of A. niger glucose oxidase. The gene encoding the new glucose oxidase was isolated and DNA sequence analysis of the coding region showed 80% identity to the sequence of a glucose oxidase gene previously published. However, the similarity of the non-coding sequences up- and downstream of the open reading frame was much less, showing only 66% and 50% identity respectively. Despite the low degree of similarity between the promotor region of the new gene and the previously published one, the new glucose oxidase was likewise induced by calcium carbonate. In addition, we showed that this induction occurred on the transcriptional level. Observations concerning the effect of gluconolactone and the levels of glucose-6 phosphate isomerase upon calcium carbonate induction suggested that the enhancement of glucose oxidase biosynthesis by calcium carbonate was accompanied by a metabolic shift from glycolysis to the pentose phosphate pathway.

Genetic localization of a series of genes affecting glucose oxidase levels in Aspergillus niger

A number of mutants of Aspergillus niger, affected in glucose oxidase (GOX) expression, are described. The overproducing mutants could be classified into seven complementation groups whereas two glucose oxidase-negative complementation groups were recognized. These nine gox loci were assigned to linkage groups using master strains with marked chromosomes. Three gox loci are in linkage group II, one is in III, two are in V and two are in linkage group VII. One weak glucose oxidase-overproducing mutant could not be assigned to one of the linkage groups. These genetically well characterized mutants will be used in a strain improvement program based on genetic recombination.

Genetic analysis and the construction of master strains for assignment of genes to six linkage groups in Aspergillus niger

A start has been made on establishing a collection of Aspergillus niger colour and auxotrophic mutants with an isogenic background for use as a source of genetic markers. All strains have short conidiophores (csp A1), which makes them easy to handle on test plates. Genetic markers were combined stepwise by somatic recombination. Somatic diploids were obtained at frequencies of 10(-6) -10(-5) with conidiospores collected from a heterokaryon. The haploidization of heterozygous diploids was induced by benomyl. For unlinked markers, the frequency of recombinants varied from 35%-65%. Low frequencies of recombinants were found between markers on a same chromosome, but this was sometimes disturbed by mitotic crossing-over during an early stage of the diploid. Master strains were constructed having markers for six linkage groups.