Genetic and phenotypic diversity of naturally isolated wild strains of Aspergillus niger with hyper glucose oxidase production

• Main Authors: MAHMOUD EL-HARIRI, HEIDY ABO AL-YAZEED, AHMED SAMIR, RAFIK SOLIMAN, REHAB ELHELW
• Format: Article
• Language: English
• Published: Plovdiv University Press 2015-12-01
• Series: Journal of BioScience and Biotechnology
• Subjects: Aspergillus niger; glucose oxidase; hyper production; GOD gene
• Online Access: http://www.jbb.uni-plovdiv.bg/documents/27807/1014563/jbb_2015-4(3)-pages_245-253.pdf

Glucose oxidase (GOx) is the basic stone for many of biological industry worldwide. The improvement of GOx production basically depends on selection of hyper producer strain of Aspergillus niger. Selective isolation and screening for natural hyper producer strains of A. niger and sequence analysis of the GOD gene, which is responsible for production of the enzyme, are very effective approaches to investigate the naturally modified strains of A. niger with hyper productive capacity of GOx enzyme. The aims of the current study were selective isolation of naturally hyper GOx producing strains of A. niger and evaluation of their GOx activities under optimized parameters in the laboratory. Five wild Egyptian isolates of A. niger were screened for GOx and catalase activity using two types of modified basal liquid media. The GOx activity was evaluated by high throughout liquid phase system. The isolates showed a variable activity for GOx production ranged from 0 to 28.7 U.ml-1. One isolate coded Strain 7 was negative GOx producer on Vogel's broth medium in comparison to other isolates, while its GOx activity on Cazpek Dox was considered as positive (7.28 U.ml-1). It was concluded that GOx production is affected by three controllable factors – the basal media components, time of incubation, and the strain with its adaption to the media components‎. Also, the catalase activity was tested and it was produced with a different degree of variability, which may be reflected on GOx stability. GOD genes of these wild variant of A. niger were cloned and sequenced to determine intraspecies diversity of GOD between the wild variants. The comparison of isolated wild variants to other reference hyper GOx producer strains of A. niger was performed to determine if the GOD sequence analysis of these strains can be distinguished based on their GOx activity. This is the first report for isolation and detection of naturally A. niger hyper GOx-producer strains with variable activity, which opening a way to improve GOx-production biotechnology.