Regulatory aspects of carbohydrate metabolism in relation to citric acid accumulation by aspergillus niger

Abstract

Fermentative production by the fungus Aspergillus niger is the world'sexclusive source ofcitric acid to be used for the food, pharmaceutical and detergents' industry. The extraordinary high yields and the delicate nutrient requirements of this process have attracted numerous investigations on its mechanism. This review highlights recent results on the regulation of its biosynthesis, emphazising especially a) the role of pH, b) the role of type and concentration of the carbon source, and c) the role of anaplerotic carbon dioxide fixation in the accumulation of citric acid.

Metabolism of citric acid production byAspergillus niger: Model definition, steady-state analysis and constrained optimization of citric acid production rate

“…Other metabolic steps whose catalytic activity should be increased are the glycolytic steps, namely the reactions catalyzed by hexokinase (X 21 ), phosphofructokinase I (X 26 ), and pyruvate kinase (X 28 ). These results are also in agreement with the available experimental data, which point to the important role of the glycolytic pathway in citric acid synthesis Schreferl-Kunar et al, 1989;Steinbock et al, 1991;Torres, 1994b). However, the enzymes involved in the substrate cycle, leading to the synthesis and degradation of phosphofructokinase effector fructose-2,6-biphosphate, phosphofructokinase II (X 25 ), and fructose biphosphatase (X 24 ), contribute more strongly to the increase of citric acid production rate by reducing its activity to approximately 10% of the basal value.…”

Citric Acid Production from Waste Substrate by Using Some Fungi

“…One of the most important fungi used in industrialmicrobiologyAspergillusniger, has been employed for manyyears for the commercial production of citric acid [18,19,20].However,the worldwide demand for citric acid is increasing fasterthan its production and more economical processes arerequired. Aspergillusnigeris most commonly used for citric acidproduction.…”

Polyploid Formation Between Aspergillus niger and Trichoderma viride For Enhanced Citric Acid Production From Cellulose

“…Citric acid is one of the heavily utilized commodities, which mainly produced from molasses or starch hydrolysates by a fermentation process with the filamentous fungus, Aspergillus niger [1,2]. Although, there is a high demand of citric acid used each year, it is provided at a low price as a commodity chemical.…”