In contrast, the fungal communities became more pronounced during the digestion process: the M1 and M3 samples taken in the beginning of the experiment from different reactors were more similar to each other than to M2 and M4 samples, suggesting that organic loading rate is a more important factor
in determining the fungal community structure than the process temperature. As the digester was a completely stirred tank reactor, the new feed material is constantly mixed with old material while the mixture is being washed out. The operating time span before sampling was over one HRT in samples M1 and M3 and slightly less one HRT in samples M2 and M4 (Table 1, Figure 1). Due to constant stirring, this difference is not likely to have a major effect on the reactor microbiota. The minimum HRT used in this study was 9–10 days Epigenetics inhibitor which is selleckchem approximately the same as the generation time of methanogens and other microbial groups and as such is sufficient for proper decomposition of organic material. The efficiency of the degradation was also illustrated by the fact that no accumulation of degradation intermediates, i.e. VFA, occurred. Saracatinib manufacturer bacterial diversity The mesophilc
(M1 and M2) and thermophilic (M3 and M4) samples contained in total 15 bacterial phyla. Most commonly found bacterial phyla included Bacteroidetes Firmicutes and Thermotogae, constituting 47%, 24% and 9% of all bacterial sequence reads, respectively. The phylum Bacteroidetes was more abundant in the mesophilic reactor, and the bacterial classes of Flavobacteria Sphingobacteria and Bacteroidia were found solely from the mesophilic reactor. Clostridia
and Bacilli, the two classes of Firmicutes, were detected in both reactors but were more prevalent in thermophilic conditions, and Thermotogae was detected exclusively in the thermophilic reactor. Different classes of Proteobacteria and Actinobacteria were found in thermophilic conditions in quite small numbers, but these groups were substantially more abundant in the mesophilic reactor. Spirochaetes Synergistes and Verrucomicrobia were present only in the mesophilic reactor. We also detected several bacterial phyla comprised merely of environmental clones including OP8, OP11, SR1 and TM7. Somewhat concordant results regarding the heterotrophic bacteria in anaerobic digestors have been published before [51–54]. Bacterial Teicoplanin phyla Bacteroidetes Firmicutes and Thermotogae are often found in both mesophilic and thermophilic AD processes which reflects their importance in degradation of complex organic compounds . Bacterial genera frequently encountered in AD include Spirochaeta sp., Clostridium sp., Propionibacterium sp., Thermotoga sp., Arthrobacter sp. and Bacillus sp. . In the present study, 7% of all bacterial sequence reads were classified to genus level. All in all, we identified a total of 19 bacterial genera. The most common bacterial genus was Clostridium, present in all samples but more abundant in the thermophilic reactor.