The full-scale unit used in this study was typical in this sense. The pilot-scale DMXAA unit thus represented an optimized situation, but running with parameters that realistically could be implemented in full-scale units. The amount of matrix material was sufficient to Epigenetics inhibitor guarantee good exchange

of gas, and the feeding schedule was designed to obtain efficient composting, instead of trying to treat maximal amounts of waste. Since the conditions observed in the studied full-scale unit are very common among composting plants in at least the Nordic countries (M. Romantschuk, unpublished), the results presented here have more relevance for people doing commercial composting at full scale rather than composting in ideal conditions with no pressure of maximal usage of the capacity. On the other hand, the comparison EPZ004777 in vivo made here may help in finding the key parameters for transforming a suboptimally functioning unit towards improved performance. Furthermore, in both the

case of the suboptimally working, and the optimized unit, the bacterial community analysis presented is the broadest and most accurate ever performed in the area of composting. Bacterial diversity in full-scale samples The bacteria found in the feed were as expected mesophilic bacteria, such as members of the Lactobacillus, Leuconostoc and Pseudomonas genera, typical for organic household waste [40, 41]. Interestingly, the feed also contained sequences related to the thermophilic Thermus genus. The waste was processed at waste treatment stations, which means that material from old waste and mature compost may inoculate the incoming waste. Bacteria may be present throughout the composting process as active or dormant cells, or as spores. Only their numbers and level of activity change during the composting process [42]. The diversity and the numbers of bacteria divided into different OTUS was more Amrubicin evident in the feed than at later stages, which is likely

to reflect the fact that the composting process and competition for nutrients had not yet started [1]. Since the temperatures rose rather slowly from ambient (0°C – 25°C) to the mesophilic range (25°C – 45°C), it is not surprising that sequences of mesophilic bacteria were still found in the feeding end of the drum in the full-scale composting unit. The low pH in the feeding end of the drum is apparently a result of the high occurrence of lactic acid bacteria in combination with ample fermentable sugars which are broken down to form lactic acid and other organic acids, plus carbon dioxide and ethanol in oxygen limited conditions [6, 43]. It is known that many lactic acid bacteria possess an ability to produce antibiotic compounds [44], which could partly explain the low levels of other bacterial genera in some samples. In addition, many Lactobacillus species are known to live in close interaction with yeasts. Several yeast species are known to posses the ability to stimulate certain Lactobacillus species to produce lactic acid [45].