In this study hyper-production of citric acid Aspergillus niger was carried out using agro-industrial residues as carrier substrates in solid state fermentation (SSF) of sucrose molasses medium. It was concluded from this study that banana stalk was a good carrier substrate among the six substrates (Corncobs, corn stover, wheat straw, wheat bran and sugarcane bagasse) used for citric acid production in SSF of molasses medium and SSF gave higher citric acid production as compared to liquid state fermentation (LSF). Mutants of Aspergillus niger were produced through UV irradiations, Ethyle...