The goal of the research focused on isolation and screening of different local strains of Aspergillus niger for their ability to grow and produce citric acid; selection of the most potent isolates for citric acid production; optimization certain environmental and nutritional parameters affecting citric acid production by the most efficient fungal strains; utilization of certain available and cheap agricultural wastes as alternatives to citric acid chemical substrates and studying of the influence of mutagenic agents on the most potent A. niger strains.