Abstract
Cattle manure is frequently used as an inoculum for the start-up of agricultural biogas plants or as a co-substrate in the anaerobic digestion of lignocellulosic feedstock. Ruminal microbiota are considered to be effective plant fiber degraders, but the microbes contained in manure do not necessarily reflect the rumen microbiome. The aim of this study was to compare the microbial community composition of cow rumen and manure with respect to plant fiber-digesting microbes. Bacterial and methanogenic communities of rumen and manure samples were examined by 454 amplicon sequencing of bacterial 16S rRNA genes and mcrA genes, respectively. Rumen fluid samples were dominated by Prevotellaceae (29%), whereas Ruminococcaceae was the most abundant family in the manure samples (31%). Fibrobacteraceae (12%) and Bacteroidaceae (13%) were the second most abundant families in rumen fluid and manure, respectively. The high abundances of fiber-degrading bacteria belonging to Prevotellaceae and Fibrobacteraceae might explain the better performance of anaerobic digesters inoculated with rumen fluid. Members of the genus Methanobrevibacter were the predominant methanogens in the rumen fluid, whereas methanogenic communities of the manure samples were dominated by the candidate genus Methanoplasma. Our results suggest that inoculation or bioaugmentation with fiber-digesting rumen microbiota can enhance the anaerobic digestion of lignocellulosic biomass.
Highlights
During the last decade, demand for livestock products, in developing countries, has massively grown as a result of population growth, urbanization, and rising income [1]
Plant polymers such as cellulose, hemicellulose, and lignin components are degraded by hydrolytic exoenzymes released or exposed by microbes and subsequently converted by acidogenic fermentation into short chain fatty acids, which are consumed as nutrient by the ruminant
The results of our study revealed substantial differences in the bacterial communities of rumen and manure microbiomes with regard to the hydrolytic bacteria known to be involved in plant fiber degradation
Summary
Demand for livestock products, in developing countries, has massively grown as a result of population growth, urbanization, and rising income [1]. Cattle manure is commonly considered as an inoculum well-suited for the start-up of anaerobic digesters, since it contains a diverse microbial community that can adapt to changing operational conditions [11,12]. The microbial diversity and especially possible differences between the structures of microbial communities in the rumen and the manure of the same animal has not yet received much attention. This knowledge, is required to identify the key microorganisms of use for efficient lignocellulose degradation.
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