Industrial strain of Aspergillus niger has been used to produce citric acid for almost a century and is currently the primary source of commercial citric acid production. In this study, several enzymes involving the protein N-glycosylation and one of the global gene regulators were examined for the potential effects on fungal morphology and citric acid production via gene deletion or overexpression in A. niger.

Researchers from PNNL have demonstrated that the deletion of Dolichyl-P-Man:Man(5)GlcNAc(2)-PP-dolichyl mannosyltransferase gene (alg3) or overexpression of laeA gene alters fungal morphology and significantly enhances citric acid production in A. niger .