| dc.description.abstract | The first step of the present work was characterizing a dairy effluent in terms microbiological and physical-chemical used to obtain a microbial consortium for its biodegradation. Microbiological characterization was performed by total heterotrophic bacteria, filamentous fungi and yeasts count according to the official methodologies. Physical-chemical characterization was accomplished by content of protein, ash, lipids, carbohydrates, pH and chemical oxygen demand (COD). Microbial consortium was obtained in batch using a bioreactor containing 1,5L of dairy effluent, at 200 rpm, 1vvm, at 28 - 30oC. Cultivations were performed in duplicate for eleven days, being applied a pulse of 10% (v/v) of effluent on the seventh day of the experiment. Cellular growth kinetics, chemical oxygen demand concentration and lipolytic activity were determined. Initial concentrations of bacteria and fungi and yeasts were equal to 3x109CFU/mL and 8x104CFU/mL, respectively. Effluent presented a COD of 64.000mgO2/L, pH 5,0 and concentrations of 5g/100mL of carbohydrates, 0,8g/100mL of protein and 0,6g/100mL of lipids. Cultivations showed an increase on the bacteria concentration, reaching 1x1013CFU/mL after eight days, while filamentous fungi and yeast concentrations were inhibited. An reduction of COD concentration in the range of 47 to 63,5% was observed after eleven days of cultivation, demonstrating the potentiality of use of microbial consortium for effluent treatment. Qualitative assays showed the presence of the enzymes lipase, amylase, protease and cellulase in the metabolic extract of the microbial consortium. However, low values of lipolytic activity were obtained as compared to the commercial enzyme, being observed that activity decreases along time. In the second step of this study, was evaluated the enzymatic hydrolysis of floated material, obtained from the column flotation of a dairy industry, using the technique of experimental design. Initially, performance was evaluated by a commercial lipase (lipolase®), being investigated the effects of agitation and enzyme concentration on hydrolysis. A statistical analysis was performed considering the significance of effects to a confidence level of 95%. Higher enzyme concentrations in the range investigated (1 to 7%) maximize the hydrolysis of oils and fats in the floated material, and to agitation levels between 100 and 150rpm. In all experiments, fatty acids were released in rates near to 100% only after 4 hours of reaction. Moreover, rates of released fatty acids were greater than 92% in all the concentration range tested. An agitation of 150rpm was used in a second experimental design, evaluating the concentration of commercial enzyme associated with a microbial consortium. The kinetic monitoring of the process showed that the addition of the consortium did not influence in a positive manner the increase the content of free fatty acids. | eng |
