The presence of Acetobacter-like phylotypes in the feeding end of the drum is explained by the fact that those bacteria use substances produced by lactic acid bacteria and by yeasts as growth substrates [46, 47]. The oxygen-limited find more conditions

appear to persist in the unloading end of the drum, apparently as a result of a high moisture content and poor aeration. This is in agreement with the fact that a large fraction of the sequences clustered with the Clostridium-group and the closely related Megasphaera. High numbers of yeast-like sequences from genera Pichia, Candida and Issatchenkia were also detected in the unloading end of the drum phase [22]. This location appears to represent a transition Cell Cycle inhibitor phase since some species

of Bacillus were becoming abundant. These typically aerobic species and the anaerobic Clostridium are known to metabolize relatively recalcitrant materials such as cellulose and lignin. In addition, species of Bacillus are known to secrete catabolic enzymes, such as proteases, which through proteolysis may raise the pH, as earlier suggested in the case of composting [48] and soy product fermentation [49]. Truly thermophilic composting conditions were only reached in the tunnel of the full-scale composting unit. In samples FS4 and FS8 a high concentration of phylotypes clustered with Bacillus and Thermoactinomyces. Only one sequence clustering with Lactobacillus was detected in sample FS4. The high number of Clostridium sequences in the tunnel sample FS11 suggests that the oxygen supply may be restricted

even in the tunnel phase. In the samples FS9 and FS10 taken on the same day from different stages of the process, the sequences clustering with the Lactobacillus-group were particularly abundant – the percentages of these sequences were 63% and 50% respectively. Although the full-scale facility did not represent an optimal composting process, it does represent a typical situation at many full-scale composting plants. Bacteria in the pilot-scale composting unit Also in the pilot-scale unit the high concentration of Lactobacillus spp. as well as numerous Acetobacter spp. sequences 3-oxoacyl-(acyl-carrier-protein) reductase is symptomatic of low pH and mesophilic temperatures in the beginning of the composting process. However, a relatively high concentration of Bacillus spp. sequences in samples from the feeding end of the drum suggests that decomposition of proteins and amino acids had started. Also, higher numbers of Actinobacteria, compared to compost of equal age from the full-scale feeding end, BI 10773 research buy indicates the beginning of the decomposition of slowly degradable material like lignin and cellulose. The high temperature and high pH environment in the unloading end of the pilot-scale drum represents an active stage of composting where Actinobacteria and Bacillus spp.