Microbial population dynamic involved in thermophilic-dry anaerobic digestion of municipal solid waste (Spanish text)

The main objective of this work is to estimate the concentration of principal groups of microorganisms involved in anaerobic depuration during start-up and stabilization of a thermophilic-dry anaerobic reactor.; Therefore, four experimental stages were carried out: (1) Optimization of fluorescent in situ hybridization (FISH); (2) Selection of pre-treatment for samples with high content in solids; (3) Protocol of FISH for samples with high content in solids and (4) Application of different microbiological techniques for monitoring and control of process during starting-up and stabilization in laboratory reactor. Two laboratory-scale continuously stirred tank reactors, without recycling solids were used in this study. Reactors temperature was maintained at 55°C and the feed was added in a semi-continuous mode: one per day. One reactor was fed to vinasses and another to organic fraction of municipal solid waste. Quantification of total microbial population was performed by epifluorescence microscopy, using DAPI as the staining agent. The autofluorescent methanogens in the reactors were counted by autofluorescence microscopy. Main specific groups of microorganisms were quantified by Fluorescent in situ Hybridization (FISH), employing different oligonucleotides probes. The most appropriate pre-treatment for application of microbiological techniques in samples with high content in solids were the addition of Tween 80 together the shaking for 60 seconds.; The application of 88% inoculum from thermophilic SEBAC with 23% of methanogens (63% H2-utilising methanogens: 37% acetate-utilising methanogens) has been successful to reach rapid start-up of reactor. In the stable conditions the percentages of Eubacteria:Archaea and H2-utilising methanogens:acetate-utilising methanogens were 60:40 and 17:83, respectively. These percentages are in accordance to the obtained results with organic removal efficiency, methane yield coefficient, biogas production rate and percentage of CO2 and CH4. These results show the importance of H2-utilising methanogens during starting-up, consuming H2 generated in the hydrolysis and acidogenesis of waste and removing inhibitory effect about acetoclastic methanogens.; The most abundant microbial populations (Eubacteria, Archaea and acetate-utilising methanogens) in the digester during the stabilization were correlated to organic loading rate degraded and total solid removal. The evolution of total methanogenic population (Archaea), and specifically acetate-utilising methanogens, was correlated with the volume of methane generated in the digester.