Produção, purificação e concentração de queratinases via fermentação submersa e aplicação ambiental na redução da concentração de cromo em efluente sintético

Abstract

The extensive production of keratinous waste in Brazil, due to the high productivity of poultry and pigs, annually generates a significant load of materials of difficult natural degradation that require attention in the environmental context. In this sense, the production of keratinases, proteolytic enzymes with specificity for the degradation of keratin contained in structures such as hairs, feathers, beaks, hair and hooves, via low-cost fermentation processes using microorganisms with affinity for their production, is of paramount importance in the environmental and economic context, aiming at reducing the load discarded and valorization of by-products from the agro-industrial sector. Therefore, this work evaluated the production of keratinases via biotechnology in batch bioreactor and concentration processes of the enzymes produced through a Biphasic Aqueous System (BAS), containing polyethylene glycol and different salts and solvents. The extract was characterized against different pH and temperatures showing better results when exposed to higher values for both analyzed characteristics. In addition, the potential of the substrate to reduce the concentration of chromium in synthetic effluent of potassium dichromate with initial concentration of 20 mg/L of chromium was evaluated with readings in spectrophotometer according to the methodology described in Standard Methods, with the presence of 1% w/v substrate, maintained on orbital shaker at 150 rpm and 28°C. The extract resulting from the fermentative process showed promising purification results for the salt/solvent precipitation, using acetone and sodium chloride in 5 different conditions evaluated, with purification factor ranging between 1.16 and 1.92. With the use of ammonium sulfate salt, it was possible to obtain 1.37 of purification factor, and 1.58 when the system was prepared in a proportion of 50% for the enzyme/solvent ratio and 0.5 mol/L of salt. As for the analyses performed with the remaining substrate after the end of the fermentation, it showed a decrease of 44.91% of its initial mass due to its degradation during the process. Still using the dried substrate at the end of fermentation, there was a 93.45% reduction in the concentration of hexavalent chromium after 9 hours in an orbital shaker. Thus, the study proved to be relevant for the production of keratinases, with subsequent environmental applicability and the possibility of concentrating the extract via low-cost processes.