Biodiversity and secretion of enzymes with potential utility in wastewater treatment

Abstract

The main organic contaminants in municipal wastewater are proteins, polysaccharides, and lipids, which must be hydrolyzed to smaller units. A high concentration of oil and grease in wastewater affects biological wastewater treat- ment processes by forming a layer on the water surface, which decreased the oxygen transfer rate into the aerobic process. Microbial prote- ases, lipases, amylases, and celullases should play essential roles in the biological wastewater treatment process. The present study aimed to isolate lipase- and other hydrolytic enzyme-pro- ducing microorganisms and assess their deg- radation capabilities of fat and oil wastewater in the laboratory. We also evaluated microbial in- teractions as an approach to enhance lipolytic activity. We place emphasis on lipase activity because oil and grease are not only environ- mental pollutants, but also form an undesirable tough crust on pipes of sewage treatment plants. Thirty-five lipolytic microorganisms from sew- age were identified and assessed for hydrolytic enzyme profiles. Lipases were characterized in detail by quantification, chain length affinity, and optimal conditions for activity. The good stabil- ity of isolated lipases in the presence of chemi- cal agents, thermal stability, wide range of pH activity and tolerance, and affinity for different lengths of ester chains indicates that some of these enzymes may be good candidates for the hydrolysis of organic compounds present in wastewater. A combination of enzymes and fer- menting bacteria may facilitate the complete hydrolysis of triglycerides, proteins, and ligno- cellulose that normally occur in the wastes of industrial processes. This study identifies en- zymes and microbial mixtures capable of digest- ing natural polymeric materials for facilitating the sewage cleaning process.