Methodological test of efficiency of heterotrophic potential

Abstract

This study aimed at describing the kinetic aspects of glucose aerobic mineralization by different types of microorganisms selected by filtration membranes of different pore sizes: 0.22, 0.45, 2.2 and 7.4 μm, and also in glass wool. Water samples were collected from Óleo Lagoon (21º36´ S and 47º49´ W). About 30 mg of glucose was added into filtered water, and the samples were incubated in the dark at 21ºC under aerobic conditions. The dissolved oxygen consumption was determined periodically during 59 days (polarographic method; DOmeter YSI model 58). The data were fitted into a first-order kinetic model. The maximum values of consumed oxygen varied from 2.10 mg L^-1 (pore size 0.22 μm treatment) to 32.83 mg L^-1 (pore size 0.45 μm treatment). The glucose mineralization on the 0.22 μm treatment showed the lowest oxygen consumption coefficient k_d = 0.03 day^-1 and half time (t_1/2) = 23 days) and the highest value was observed on the 0.45 μm treatment and 2.2 μm treatment (k_d = 0.08 day^-1 and t_1/2 = 9 days). Oxygen consumption was higher in the sample filtered into 0.45 μm, suggesting that bacterivory occurred in treatments with glass wool, 2.2 and 7.4 μm. The filtration into 0.22 μm pore size membranes favored chemical oxidation.