Abstract
As a consequence of intensive feeding, the bulk deposition of livestock manure causes severe environmental problems. Composting is a promising method for waste disposal, and the fermentation process is driven by microbial communities. However, chicken manure contains diverse gut microbes, mainly species derived from Proteobacteria, which may include pathogens that threaten human health. To evaluate composting as a harmless treatment of livestock manure, the dynamics of the microbiota in two chicken manure composts were studied, and the influences of adding maize straw on the compost microbiota were compared. The results revealed that microbes from Firmicutes including Bacillus and Lentibacillus are the most dominant degraders with a strong amino acid metabolism, and they secrete a diverse array of proteases as revealed in metaproteomics data. The addition of maize straw to the chicken manure compost accelerated species succession at the initial stage, and stimulated carbohydrate metabolism in the dominant microbiota. Besides, under the resulting high temperature (>70°C) conditions, the relative abundance of Proteobacteria was reduced by 78% in composts containing maize straw by day 4, which was faster than in compost without added maize straw, in which the abundance was reduced by 66%. Adding maize straw to chicken manure composts can therefore increase the fermentation temperature and inhibit the growth of Proteobacteria. In general, these findings provide increased insight into the dynamic changes among the dominant functional microbiota in chicken manure composts, and may contribute to the optimization of livestock manure composting on an industrial scale.
Highlights
The animal breeding industry has expanded rapidly in recent years across the globe due to the increasing demand for animal products, and this has resulted in an increase in livestock-derived manure
Based on measurement of the compost temperature, both piles of compost entered the thermophilic phase from day 4, with the temperature of the chicken manure compost (CM) reaching 63◦C ± 2.5, while the temperature of the chicken manure compost supplemented with maize straw (CS) reached 71◦C ± 2.5 (Figure 1A), indicating a relatively higher activity of the microbiota in the CS
With time the moisture contents of these two composts declined, but the moisture content of CS dropped by a mere 2% compared with a 46% drop in the moisture content of CM (Figure 1B), suggesting a water conservation effect of maize straw
Summary
The animal breeding industry has expanded rapidly in recent years across the globe due to the increasing demand for animal products, and this has resulted in an increase in livestock-derived manure. It is crucial to find an effective biosafety method for processing livestock manure. Microbial communities play an important role in the degradation of organic materials. To better understand the composting process and increase the efficiency of composting, the dominant functional microbial communities and their dynamics need to be investigated. To date, most studies have focused on the composition of the microbial communities in composts, while their functions and dynamics have remained largely unexplored (Bernal et al, 2009; Hui et al, 2012; Gannes et al, 2013; Wei et al, 2014). By combining high-throughput sequencing and metaproteomics approaches, the composition and functions of microbial communities can be linked, and dominant functional members that make the most important contributions to the composting process can be identified
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