Kinetics of phosphatase activity in organic wastes

Abstract The phosphatase activity of different urban wastes, both fresh and composted, were determined in order to establish any differences which might exist between them as regards several kinetic parameters; these parameters being correlated with the degree of evolution of the organic matter contained in the wastes. All the materials studied contained alkaline phosphatase with an optimal activity at pH 9. The sewage sludges also contained neutral phosphatase (optimum pH 6–7). The composts showed the lowest values of phosphatase activity, suggesting that this parameter can be considered a valid index of the evolution of the organic matter contained in the wastes. The values of K m estimated for different substrate concentrations from the four Michaelis-Menten derived lineal equations, revealed the difficulty of establishing relationships between the affinity of the enzyme for the substrate and the nature of the waste or the degree of stability of its organic matter. The values of maximum phosphatase velocity in the four equations used appeared to establish differences between the different types of waste and between the composted and uncomposted products. Values of V max correlated both with ATP content and with the different carbon fractions of the wastes.