Aspergillus niger produces a wide variety of carbohydrate hydrolytic enzymes which have potential applications in the baking, starch, textile, food and feed industries. The goal of this thesis is... Show moreAspergillus niger produces a wide variety of carbohydrate hydrolytic enzymes which have potential applications in the baking, starch, textile, food and feed industries. The goal of this thesis is to unravel the molecular mechanisms of starch and inulin modifying network of A. niger, in order to improve the enzyme production and substrate utilization as well as to find novel enzyme activities. The research described in this thesis shows how we identify genes which encode enzymes involved in starch and inulin catabolism, how they are transcriptionally regulated, as well as how the expressed enzymes react to the carbon sources and what are their physiological roles in A. niger. Important findings are outlined as follows. We have identified inulin pathway activator InuR. The activation of InuR is thought to be triggered by the pathway inducer, sucrose or its derivative, but not previously known fructose. The activated InuR induces the expression of genes encoding inulin modifying enzymes and related sugar transporters in inulin metabolism. In addition, using the tightly regulated inuE promoter combined with racA(G12V) and GFP reporter genes, we set up a novel screening method for isolation of mutants involved in inulin signaling pathway. Show less
