The microbial community structure in industrial biogas plants influences the degradation rate of straw and cellulose in batch tests

Abstract

BackgroundMaterials rich in lignocellulose, such as straw, are abundant, cheap and highly interesting for biogas production. However, the complex structure of lignocellulose is difficult for microbial cellulolytic enzymes to access, limiting degradation. The rate of degradation depends on the activity of members of the microbial community, but the knowledge of this community in the biogas process is rather limited. This study, therefore, investigated the degradation rate of cellulose and straw in batch cultivation test initiated with inoculums from four co-digestion biogas plants (CD) and six wastewater treatment plants (WWTP). The results were correlated to the bacterial community by 454-pyrosequencing targeting 16S rRNA gene and by T-RFLP analysis targeting genes of glycoside hydrolase families 5 (cel5) and 48 (cel48), combined with construction of clone librariesResultsUniFrac principal coordinate analysis of 16S rRNA gene amplicons revealed a clustering of WWTPs, while the CDs were more separated from each other. Bacteroidetes and Firmicutes dominated the community with a comparably higher abundance of the latter in the processes operating at high ammonia levels. Sequences obtained from the cel5 and cel 48 clone libraries were also mainly related to the phyla Firmicutes and Bacteroidetes and here ammonia was a parameter with a strong impact on the cel5 community. The results from the batch cultivation showed similar degradation pattern for eight of the biogas plants, while two characterised by high ammonia level and low bacterial diversity, showed a clear lower degradation rate. Interestingly, two T-RFs from the cel5 community were positively correlated to high degradation rates of both straw and cellulose. One of the respective partial cel5 sequences shared 100 % identity to Clostridium cellulolyticum.ConclusionThe degradation rate of cellulose and straw varied in the batch tests dependent on the origin of the inoculum and was negatively correlated with the ammonia level. The cellulose-degrading community, targeted by analysis of the glycoside hydrolase families 5 (cel5) and 48 (cel48), showed a dominance of bacteria belonging the Firmicutes and Bacteriodetes, and a positive correlation was found between the cellulose degradation rate of wheat straw with the level of C. cellulolyticum.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0543-9) contains supplementary material, which is available to authorized users.

Phylogenetic Analysis of Anaerobic Co-Digestion of Animal Manure and Corn Stover Reveals Linkages between Bacterial Communities and Digestion Performance

“…Like class Clostridia, Bacteroidetes populations were also commonly reported as cellulose/hemicellulose degraders [27]- [29] and observed in anaerobic digestion at low abundance (average 17%) [30]- [34]. There were 21% -40% of Bacteroidetes populations in our pilot bioreactors and we observed a shift from the dominance of identifiable Bacteroidetes to unclassified Bacteroidetes, which correlated with the overall improved system performance reported in the companion study [20].…”

Resuscitation of viable but non‐culturable bacteria to enhance the cellulose‐degrading capability of bacterial community in composting

“…Previous studies have demonstrated that Proteobacteria and Actinobacteria were key players in the compost sample, and they were also the effective phyla for organic pollutants degradation (Awasthi et al ., ; Xie et al ., ). Moreover, some studies also revealed similar bacterial diversity in waste composting samples by the high‐throughput sequencing (Lv et al ., ; Sun et al ., ). However, the abundance of Firmicutes obtained in our study was lower than that reported by Partanen et al .…”

Novel Syntrophic Populations Dominate an Ammonia-Tolerant Methanogenic Microbiome

“…Previous SSU rRNA gene analysis of a sample (Link_ADIa) collected from the high-ammonia/SAO CD01 reactor in Sweden revealed a unique microbiome with several dominant species and an uneven distribution that has seldom been observed in other mesophilic biogas reactors to date (5, 12, 13). Annotation of population genomes that were reconstructed from the Link_ADIa metagenome showed that the second most abundant phylotype (unFirm_1) encoded a carbon monoxide dehydrogenase/acetyl coenzyme A (acetyl-CoA) synthase (Acs) operon, which is characteristic of homoacetogens, including the majority of known SAOB (Fig.…”

“…Samples were obtained from a commercial biogas reactor (CD01, located in Sweden) that has endured high ammonia levels for extended periods and has been the focus of other research-and-development activities that have comprehensively described its operational history (5, 11, 12, 28). For the two CD01 samples used in this study, the operating data and substrates used are shown in Table 1.…”

“…We have carried out analysis of a commercial biogas reactor in Sweden (here referred to as CD01) that has a long history of productive stable operation under high free-ammonia levels of >0.2 g/liter and up to 0.4 g/liter (5, 11, 12). Initial studies carried out in our labs indicated that the CD01 microbiome produces methane predominantly via syntrophic acetate oxidation (SAO) (5).…”