Enriching ruminal polysaccharide-degrading consortia via co-inoculation with methanogenic sludge and microbial mechanisms of acidification across lignocellulose loading gradients

Abstract

Using lignocellulosic materials as substrates, ruminal microbiota were co-inoculated with anaerobic sludge at different loading rates (LR) to study the microbial community in the semi-continuous mode. The results indicated that the highest CH yield reached 0.22 L/g volatile solid at LR of 4 g/L/day, which obtained 56-58% of the theoretical value. In the steady stage with LR of 2-4 g/L/day and slurry recirculation, copies of total archaea increased. Especially the Methanobacteriales increased significantly (p < 0.05) to 3.30 × 10 copies/mL. The microbial communities were examined by MiSeq 16S rRNA sequencing. Enriched hydrolytic bacteria mainly belonged to Clostridiales, including Ruminococcus, Ruminiclostridium, and Ruminofilibacter settled in the rumen. High-active cellulase and xylanase were excreted in the co-inoculated system. Acid-producing bacteria by fermentation were affiliated with Lachnospiraceae and Bacteroidales. The acidogen members were mainly Spirochaetaceae and Clostridiales. Syntrophic oxidation bacteria mainly consisted of Synergistetes, propionate oxidizers (Syntrophobacter and Pelotomaculum), and butyrate oxidizers (Syntrophus and Syntrophomonas). There had no volatile fatty acid (VFA) accumulation and the pH values varied between 6.94 and 7.35. At LR of 6 g/L/day and a recirculation ratio of 1:1, the hardly degradable components and total VFA concentrations obviously increased. The total archaea and Methanobacteriales then deceased significantly to 8.56 × 10 copies/mL and 4.14 × 10 copies/mL respectively (p < 0.05), which resulted in the inhibition of methanogenic activities. Subsequently, microbial diversity dropped, and the hydrolytic bacteria and syntrophic oxidizers obviously decreased. In contrast, the abundances of Bacteroidales increased significantly (p < 0.05). Acetate, propionate, and butyrate concentrations reached 2.02, 6.54, and 0.53 g/L, respectively, which indicated "acidification" in the anaerobic reactor. Our study illustrated that co-inoculated anaerobic sludge enriched the ruminal function consortia and hydrogenotrophic methanogens played an important role in anaerobic digestion of lignocelluloses.

Interaction Between Conservation Tillage and Nitrogen Fertilization Shapes Prokaryotic and Fungal Diversity at Different Soil Depths: Evidence From a 23-Year Field Experiment in the Mediterranean Area

“…Interestingly, at 0–15 cm soil depth, the bacterial phylum Cloacimonetes and the class Spirochaetia were the taxa uniquely found in unfertilized conventional tillage (CTN0), whereas the newly recognized phylum Berkelbacteria (Wrighton et al, 2014) was uniquely found in conventional fertilized tillage (CTN200). Cloacimonetes is a mesophylic phylum able to degrade cellulose and produce methane, while the members of Spirochaetia degrade cellulose and chitin (Limam et al, 2014; Chojnacka et al, 2015; Dai et al, 2016; Deng et al, 2018) and anaerobically decompose organic matter (Baba et al, 2014). Moreover, the phylum Berkelbacteria is an ATP binding and a putative transcriptional regulator with helix-turn-helix (HTH)-like protein.…”

Enhanced Biogas Production by Ligninolytic Strain Enterobacter hormaechei KA3 for Anaerobic Digestion of Corn Straw

“…Therefore, they were widely present in CK and TG. Many studies have reported that Ruminofilibacter can effectively degrade lignin substrates [43][44][45]. Bacillus was confirmed as a good species that can utilize carbohydrates with high efficiency [44].…”

The masking effect of extracellular DNA and robustness of intracellular DNA in anaerobic digester NGS studies: A discriminatory study of the total DNA pool

“…The microbiome shared by all DNA types (fDNA, iDNA, totDNA; Figure S1a) represented typical orders for farm-scale reactors and included a classical community performing AD (Calusinska et al, 2018;Deng et al, 2018).…”