Methanogenic consortia from thermophilic molasses-fed structured-bed reactors: microbial characterization and responses to varying food-to-microorganism ratios

Author(s)

Fuess, Lucas Tadeu ; Eng, Felipe ; Bovio-Winkler, Patricia ; Etchebehere, Claudia ; Zaiat, Marcelo ; Nascimento, Claudio Augusto Oller do

• Document type: Journal article
• Source: Brazilian Journal of Chemical Engineering; v. N/A, p. 21-pg., 2022-12-15.

Abstract

The heterogeneous character of fixed-film reactors may create highly specialized zones with a stratified distribution of microbial groups and varying capabilities to withstand high organic loads in anaerobic digestion (AD) systems. The microbial distribution and methane-producing potential of biomass from different regions (feeding zone and structured bed) of two second-stage thermophilic (55 oC) fixed-film reactors were assessed. Three levels of food-to-microorganism (F/M) ratio (0.4, 1.0 and 3.0 g-COD g(-1)VS) using fermented (two-stage AD) and fresh (single-stage AD) sugarcane molasses were tested in batch reactors, simulating low to high organic loads. Specific methane production rates increased as the F/M increased when using fermented molasses, maintaining efficient methanogenesis at substrate availability levels threefold higher than single-stage schemes (3.0 vs. 1.0 g-COD g(-1)VS). Success in methane production derived from the homogenous establishment (similar in both feeding zone and bed) of syntrophic associations between acetogens (Pelotomaculum, Syntrophothermus, Syntrophomonas and Thermodesulfovibrio), acetate oxidizers (Thermoacetogenium, Mesotoga and Pseudothermotoga) and hydrogenotrophic methogens (Methanothermobacter and Methanoculleus) replacing acetoclastic methanogens (Methanosaeta). Phase separation under thermophilic conditions was demonstrated to boost methane production from sugar-rich substrates, because the process depends on microbial groups (hydrogenotrophs) that grow faster and are less susceptible to low pH values compared to acetotrophs. (AU)

• FAPESP's process: 17/00080-5 - Enhancement of energy production from sugarcane in first generation biorefineries: biodigestion as the core conversion step
• Grantee: Lucas Tadeu Fuess
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 15/06246-7 - Biorefinery concept applied to biological wastewater treatment plants: environmental pollution control coupled with material and energy recovery
• Grantee: Marcelo Zaiat
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 14/50279-4 - Brasil Research Centre for Gas Innovation
• Grantee: Julio Romano Meneghini
• Support Opportunities: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 15/50684-9 - Sustainable gas pathways for Brazil: from microcosm to macrocosm
• Grantee: Reinaldo Giudici
• Support Opportunities: Research Projects - Thematic Grants