N. Barros et al., Interpretation of the metabolic enthalpy change, Delta H-met, calculated for microbial growth reactions in soils, J THERM ANA, 63(2), 2000, pp. 577-588
The microcalorimetric method was used to calculate the metabolic enthalpy c
hange per mol of glucose degraded by soil microorganisms, DeltaH(met). This
parameter has been calculated by microcalorimetry for many organic, inorga
nic and biochemical reactions, but there is only some information about its
quantification for microbial growth reactions in soils. Values of DeltaH(m
et) were calculated for different soil samples collected in Galicia (Spain)
and Campinas (Sao Paolo, Brazil). Exponential microbial growth was stimula
ted in all soil samples by the addition of glucose and power-time curves we
re recorded. Results showed changes in the values of DeltaH(met) calculated
for all the soil samples, suggesting a dependence of this value with the m
icrobial growth rate constant, with the percentage of growth, with the init
ial number of microorganisms of soil samples, with the quantity of glucose
added and with the strain of bacteria growing in soil.
The interpretation of variations of DeltaH(met) provides important qualitat
ive and quantitative information. It reports data that allow to interpret f
rom a qualitative point of view, the increase in biomass as a consequence o
f the degradation of the organic matter in soil, to understand changes in t
he percentages of soil organic matter and to know if the microbial populati
on growing in differential soil samples is homogeneous. Therefore, to repor
t that value would be very important in ecological studies, but beforehand,
it is necessary to solve some problems that can appear in the experiments
done to make the quantification.