Temperature Effect on the Activity of Soil Microbes Measured from Heat Evolution during the Degradation of Several Carbon Sources

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Heat evolution during the microbial degradation of different carbon sources in soil was calorimetrically studied with a multiplex heat-conduction calorimeter over the incubation temperature range of 295.2 to 320.9 K. Different thermograms were obtained with the degradation of D-glucose, D-fructose, D-galactose, D-mannose, sucrose or lactose as a limited energysource.While the shapes of the thermograms changed with changing of the incubation temperature, the total amount of heat evolved during the degradation of carbon sources in soil was unchanged in the temperature range of 303.6 to 320.9 K. This observation was commonfor all the experiments with the different sugars. The total amount of heat evolved observed in this temperature range was in the range of 14 to 15 kJ (g of sugar)-1. From the earlier phase of the thermogram where the heat evolution rate increased exponentially, the degradation rate constant was determined. Applying the Arrhenius equation to the system, apparent activation energies were obtained. The values obtained with the six different carbon sources were in the range of 64 to 92 kJ mol-1. The apparent Gibbs energy of activation was determined to interpret themicrobial activity for the degradation of each sugar and the degradation activity for the sugars in soil was found to be in the following order at 298.15 K; D-glucose>sucrose>lactose>dfructose > D-galactose > D-mannose.
社団法人日本農芸化学会の論文