Effectiveness of Aeromonas hydrophila for the removal of oil and grease from cattle slaughterhouse effluent

Abstract

Little is known about the use of microbial lipases for the treatment of beef industry effluent. It is essential to develop techniques for the sustainable management of this waste, given its high polluting potential, especially due to the high concentrations of oils and greases (O&G) present. Therefore, this study investigates the pretreatment of slaughterhouse effluent using lipase-producing microorganisms isolated from the waste itself. Firstly, a physicochemical characterization of the effluent was performed, followed by isolation and identification of a lipase-producing bacterium, which was used in a pretreatment step. A central composite rotational design (CCRD) was applied, considering the independent variables pH, temperature, and inoculum concentration, resulting in 17 assays, with lipolytic activity, O&G, and free fatty acids (measured during 72 h) as the response variables. The slaughterhouse effluent presented high polluting potential, with an O&G concentration of 2553.3 mg L−1 and COD of 8914.4 mg L−1. The isolated bacterium was identified as Aeromonas hydrophila. After 72 h of the experiment, lipolytic activity of 1.40 U mL−1, 59% O&G removal (pH: 7.0, temperature: 30.0 °C and inoculum concentration: 10%), and production of 36.0 μmol mL−1 of free fatty acids were obtained. It could be concluded that cattle slaughterhouse effluent is an excellent source of lipase-producing microorganisms and that the use of enzymes for the treatment of this waste is a promising technology.