Exploration of the relationship between biogas production and microbial community under high salinity conditions

High salinity frequently causes inhibition and even failure in anaerobic digestion. To explore the impact of increasing NaCl concentrations on biogas production, and reveal the microbial community variations in response to high salinity stress, the Illumina high-throughput sequencing technology was employed. The results showed that a NaCl concentration of 20 g/L (H group) exhibited a similar level of VFAs and specific CO₂ production rate with that in the blank group, thus indicating that the bacterial activity in acidogenesis might not be inhibited. However, the methanogenic activity in the H group was significantly affected compared with that in the blank group, causing a 42.2% decrease in CH₄ production, a 37.12% reduction in the specific CH₄ generation rate and a lower pH value. Illumina sequencing revealed that microbial communities between the blank and H groups were significantly different. Bacteroides, Clostridium and BA021 uncultured were the dominant species in the blank group while some halotolerant genera, such as Thermovirga, Soehngenia and Actinomyces, dominated and complemented the hydrolytic and acidogenetic abilities in the H group. Additionally, the most abundant archaeal species included Methanosaeta, Methanolinea, Methanospirillum and Methanoculleus in both groups, but hydrogenotrophic methanogens showed a lower resistance to high salinity than aceticlastic methanogens.