Variations in Enzyme Concentrations During High-Temperature Composting of Livestock and Poultry Manure and Study on Enzymatic Reaction Mechanisms

Abstract

Cow, pig, and chicken manure were collected from farms located in the proximity of Lanzhou University, Lanzhou City, Gansu Province, and were used as raw materials. Before composting, straws at a concentration of 10% were used as bulking agent. Different parameters were monitored during the composting process. Specifically, we analyzed changes in catalase, invertase, urease, and cellulase concentrations. In addition, the mechanisms of enzymatic reactions at high-temperatures were determined. The results showed that: (1) at the first stages of composting, the initial contents of catalase were 48.21±1.11, 45.04±0.85, and 44.29±0.65/0.002 mol·L−1·g−1, for cow, pig, and chicken manure, respectively. As composting proceeded, the content of catalase gradually increased. On the 6th day, catalase contents reached their maximum values, with numbers of 55.21±0.58, 57.28±0.14, and 62.18±0.45 mol·L−1·g−1, correspondingly. In addition, when composting ended, catalase content followed the order (chicken manure > cow manure > pig manure, with values of 34.33±0.58, 29.31±0.79, and 28.42±0.89/0.002 mol·L−1·g−1), in the same order; (2) According to the Michaelis-Menten expression, temperature greatly affects enzymatic reactions. Our data indicated that content of catalase, urease, sucrose, and cellulose, as well as number of microorganisms and compost temperature were positively correlated.