Removal of amino and nitro-substituted stilbenesulfonic acids from aqueous environment: biosorption and biodegradation by isolated Aspergillus awamori ( Nakazawa)

Abstract

Asperillus awamori ( Nakazawa) an effective fungal strain for removal of substituted aromatic sulfonic acids was isolated from the aerobic sludge of an industrial effluent treatment plant in Hyderabad, India. It was tested for the removal of 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNSDA), 4-amino-4′-nitrostilbene-2,2′-disulfonic acid (ANSDA) and 4,4′-diaminostilbene-2,2′-disulfonic acid (DASDA) from industrial waste waters and the experimental parameters were optimized. The effects of amino and nitro substituents on biosorption and biodegradation of aromatic sulfonic acids were investigated. Soluble starch was found to be an effective and economical source of carbon. The initial pH of the media was in between 4.0 and 7.0 for growth of the fungi and removal of the test compounds. Two different mechanisms viz., biosorption and biodegradation were responsible for the removal of the test compounds by Asperillus awamori. The extent of removal by both the mechanisms was found to be dependent upon the functional groups present on the aromatic rings. Within 5 days, 99% of 50 mg/L of DNSDA was removed by biosorption while 72% of ANSDA and 53% of DASDA were adsorbed as well as converted into corresponding products. Biosorption was found to be pH-dependent and dominant when it reached around 2.5. The isolated Asperillus awamori ( Nakazawa) was found to be quite effective for removal of the test compounds in complex environmental matrices.