Optimization of glucose oxidase production by Aspergillus niger using genetic- and process-engineering techniques

Area of Science:

• Biotechnology
• Microbial Engineering
• Enzyme Production

Background:

• Aspergillus niger is a key microorganism for industrial enzyme production.
• Optimizing glucose oxidase (god) yield is crucial for its applications.
• Genetic modification offers a pathway to enhance enzyme secretion.

Purpose of the Study:

• To engineer Aspergillus niger for increased extracellular glucose oxidase production.
• To evaluate the impact of gene expression elements and culture conditions on enzyme yield.

Main Methods:

• Transformation of wild-type Aspergillus niger NRRL-3 with multiple copies of the glucose oxidase (god) gene.
• Utilizing the gpdA promoter from A. nidulans for gene expression.
• Incorporating the alpha-amylase signal peptide from A. oryzae for enhanced secretion.
• Cultivation in shake-flasks and bioreactors with varying media compositions.

Main Results:

• The recombinant strain NRRL-3 (GOD3-18) exhibited up to fourfold higher extracellular glucose oxidase production compared to the wild type.
• Addition of yeast extract to the mineral salts medium boosted volumetric and specific activities by 130% and 50%, respectively.
• Bioreactor cultivation resulted in over tenfold increase in volumetric and specific extracellular glucose oxidase activities compared to shake-flask cultures.

Conclusions:

• Genetic engineering strategies, including promoter choice and signal peptide insertion, effectively enhance glucose oxidase production in Aspergillus niger.
• Optimized fermentation conditions, particularly in bioreactors, significantly amplify enzyme yields.
• The developed recombinant strain and methods hold potential for more efficient industrial glucose oxidase manufacturing.