Alg3 Inactivation and LaeA Overexpression in Aspergillus niger

The patent applies parameter changes by genetically modifying the Aspergillus niger strain through inactivation of the Alg3 gene and overexpression of the LaeA gene. These genetic parameter changes alter the post-translation modification parameters (N-glycosylation patterns) of cellular proteins, which in turn optimizes metabolic flux toward citric acid production. The modified strain achieves enhanced citric acid production efficiency by changing the biochemical parameters of protein glycosylation without requiring complex external control systems.

The patent applies inversion by reversing the conventional approach to protein glycosylation. Instead of enhancing glycosylation to improve cellular formation (which would consume more carbohydrates and reduce citric acid production), the patent inactivates the Alg3 gene to reduce N-glycosylation. This inverse approach decreases carbohydrate consumption for glycosylation, thereby redirecting metabolic flux toward citric acid production while maintaining sufficient metabolic regulation through the LaeA overexpression.

The patent uses LaeA as an intermediary to compensate for the potential negative effects of Alg3 inactivation. The LaeA gene overexpression acts as a mediator that maintains protein secretion and stability functions even when N-glycosylation is reduced due to Alg3 deficiency. This intermediary approach allows the system to achieve enhanced carbohydrate flux to citric acid while preserving essential protein functions through the compensatory action of LaeA.