Investigating microbial activities during a starch-amended co-composting process at mesophilic and thermophilic temperatures

The aim of this study was to assess the use of functional microbial ecological techniques in detailing processes during composting. Using starch as an amendment for a co-composting process, small-scale individual mesocosms were investigated at two temperatures, 30 degrees C and 60 degrees C, over a five-week period. In order to determine the more exact processes occurring during degradation, extracellular enzyme analysis (EEA) and community-level physiological profiling (CLPP) were used. The EEA demonstrated that, although assay temperature effects were present, no significant difference between the two in situ composting temperatures was observed for the two enzyme substrates, alpha-and beta-glucosidase, used. The CLPP profiling was only performed on the 30 degrees C compost samples. These analyses indicated a dynamic, but broadly predictable, environment, suggesting that the use of this approach may be further applicable to these types of study. By investigating both total dry and organic weights, no difference in organic matter degradation between the two temperatures was observed. These results showed that either starch degradation acted independently of temperature or compensatory effects occurred. The former hypothesis was supported by a second experiment investigating starch degradation at both temperatures with appropriate negative controls. Trying to reconcile the EEA results with the changes in total matter was difficult without making speculative assumptions. The study highlights the need to further develop and evaluate these microbial ecological techniques to address such problems.