Metagenomic Diversity During Start Up Stage of Anaerobic Digesters

LEONARDO ERIJMAN; M. C. LORENZO; LEANDRO GUERRERO; R. PONTIGGIA; IGNACIO VARDÉ; EVA FIGUEROLA; M.ALTINA; CAROL DAVIES SALA

San Miguel de Tucumn

Congreso; XII Congreso Argentino de Microbiología General (SAMIGE); 2017

Asociación Civil de Microbiología General (SAMIGE)

Anaerobic digestion constitutes a sustainable process widely used for organic waste management that has the advantage of generating biogas in addition to the stabilization of organic matter. The process of anaerobic digestion depends on the assembly of a complex microbial community, in which methanogenic archaea and syntrophic bacteria are the leading actors. It has been observed that for certain substrates, a suitable inoculum source may be critical for efficient biogas production. However, the availability of adequate inocula is severely limited at the local level, due to the very low degree of adoption of technologies based on anaerobic digestion. This work aims at understanding the adaptation of inocula arising from different sources to food waste. Four lab- scale anaerobic reactors (5 L) were operated during 91 days and fed daily with increasing concentrations of food waste. Reactor operational parameters, including biogas production, volatile solids (VS), alkalinity and volatile fatty acids concentration (VFA) were measured on regular basis. Metagenomic DNA was obtained from sludge samples taken weekly. Methanogenic archaea abundance was estimated using qPCR assays, whereas total microbial community analysis was conducted using amplicon sequencing with primers for the V3-V4 rRNA16S region. Specific biogas production (Biogas/VS) and volatile fatty acids (VFA) varied depending on the inoculum´s source and feeding rate. Using USEARCH, OTUs were defined at 97%, obtaining 2690 OTUs that then were classified with rdp database. Under our experimental set up, adaptation to food waste was associated to the presence of acetoclastic methanogenic archaea from Methanosaeta genus, which were mapped with high abundance when biogas production was higher and identified as key taxa associated to process stability. This results underlies the critical role of the inoculum source for reactor start up. We are currently analyzing methanogenic archaea applying amplicon sequencing of the mcrA gene, which encodes methyl coenzyme-M reductase.