Bacterial diversity at different stages of the composting process

Abstract

BackgroundComposting is an aerobic microbiological process that is facilitated by bacteria and fungi. Composting is also a method to produce fertilizer or soil conditioner. Tightened EU legislation now requires treatment of the continuously growing quantities of organic municipal waste before final disposal. However, some full-scale composting plants experience difficulties with the efficiency of biowaste degradation and with the emission of noxious odours. In this study we examine the bacterial species richness and community structure of an optimally working pilot-scale compost plant, as well as a full-scale composting plant experiencing typical problems. Bacterial species composition was determined by isolating total DNA followed by amplifying and sequencing the gene encoding the 16S ribosomal RNA.ResultsOver 1500 almost full-length 16S rRNA gene sequences were analysed and of these, over 500 were present only as singletons. Most of the sequences observed in either one or both of the composting processes studied here were similar to the bacterial species reported earlier in composts, including bacteria from the phyla Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria and Deinococcus-Thermus. In addition, a number of previously undetected bacterial phylotypes were observed. Statistical calculations estimated a total bacterial diversity of over 2000 different phylotypes in the studied composts.ConclusionsInterestingly, locally enriched or evolved bacterial variants of familiar compost species were observed in both composts. A detailed comparison of the bacterial diversity revealed a large difference in composts at the species and strain level from the different composting plants. However, at the genus level, the difference was much smaller and illustrated a delay of the composting process in the full-scale, sub-optimally performing plants.

Use of the co-composting time extract agar to evaluate the microbial community changes during the co-composting of activated sludge and date palm waste

“…However, some actinobacteria isolates in this study were thermotolerant (results not shown). Partanen et al (2010) and Sundberg et al (2011) showed a correlation between a rising pH with an increase in actinobacteria. However, Goodfellow and Williams (1983) reported that various actinobacteria are involved in all compost stages which demonstrates a wide temperature range for their growth, often with an optimum between 25 and 30°C for mesophiles and 45-55°C for thermophiles.…”

“…3a, b). Partanen et al (2010); Kurola et al (2011) demonstrated that high proportions of actinobacteria indicate good composting conditions. The results of the (PCA) run between the all identified mesophilic and thermophic microflora profile and physicochemical parameters, during co-composting, show that the actinobacteria (domain I) are inversely correlated with temperature and highly correlated with pH (case of mixture B) (Fig.…”

The Geobacillus paradox: why is a thermophilic bacterial genus so prevalent on a mesophilic planet?

“…Whether in controlled laboratory settings or in waste recycling centres, Geobacillus species can become the dominant culturable bacterial taxon in composts at 60-69 u C (Blanc et al, 1997;Ronimus et al, 2003;Strom, 1985;Takaku et al, 2006). When culture-independent methods are employed, however, a richer and much more nuanced picture emerges in which Geobacillus and other thermophilic members of class Bacilli still play a part, although a numerically minor one (Martins et al, 2013;Michel et al, 2002;Partanen et al, 2010;Peters et al, 2000). Yet the prevalence of geobacilli in active, hot composts gives us a place to start in assessing the likely role of Geobacillus in the natural environment.…”

Application of Potent Actinomycete Strains for Bio-Degradation of Domestic Agro-Waste by Composting and Treatment of Pulp-Paper Mill Effluent

“…Thermo-tolerant and thermophilic population dominates the middle phase, producing enzymes responsible for degradation of complex organic material and temperature rises further. Concluding stage of the composting is characterized by the growth of actinomycetes and fungi that degrade the most complex organic matters under high temperature and high pH environment [11] [12]. Raw material used for composting is ligno-cellulosic biomass.…”