Sulfate- and pH-driven metabolic flexibility in sugarcane vinasse dark fermentation stimulates biohydrogen evolution, sulfidogenesis or homoacetogenesis

Author(s)

Piffer, Michael Antonio ; Oliveira, Cristiane Arruda ; Bovio-Winkler, Patricia ; Eng, Felipe ; Etchebehere, Claudia ; Zaiat, Marcelo ; do Nascimento, Claudio Augusto Oller ; Fuess, Lucas Tadeu

• Document type: Journal article
• Source: INTERNATIONAL JOURNAL OF HYDROGEN ENERGY; v. 47, n. 73, p. 21-pg., 2022-08-26.

Abstract

Dark fermentation of sugarcane vinasse can be used as a "cleaning" step to remove sulfate prior to methanogenesis because sulfidogenic conditions can be successfully established in parallel with biohydrogen production. Using a 2(2) central composite rotational design (CCRD) and response surface methodology (RSM), this study assessed the impacts of bicarbonate and sulfate availability on the establishment of sulfidogenesis in the thermophilic (55 degrees C) fermentation of vinasse in batch reactors, equally assessing the impacts on biohydrogen evolution. CCRD-RSM results indicated the favoring of biohydrogen production at the lowest sulfate and bicarbonate concentrations, whilst the opposite was observed for sulfidogenesis. Glycerol, lactate, and hydrogen were the preferential electron donors utilized by sulfate-reducing bacteria (SRB), whilst ethanol was markedly consumed only at high sulfate concentrations. SRB were inhibited by sodium when dosing excess NaHCO3 and Na2SO4. Complementary tests revealed maximum biohydrogen production (2.40 mmol) out of the CCRD, at pH exceeding 7.5 with no interference of sulfidogenesis. Non-efficient biohydrogen production was observed at low pH (<5.0; similar to 1.90 mmol) because the uptake of lactate was inhibited. Meanwhile, homoacetogenesis was established under intermediate pH range (5.5-6.5), as revealed by the accumulation of acetate (up to 2.5 g L-1). 16S rRNA gene amplicon sequencing further revealed the genera Thermoanaer- obacterium/Pseudoclostridium, Desulfotomaculum/Desulfohalotomaculum and Sporomusaceae/Moorella as the main biohydrogen-producing, sulfate-removing and biohydrogen-consuming (homoacetogens) microbial groups, respectively. Hence, using a single inoculum source, vinasse may provide a butyrate-rich (along with biohydrogen-rich biogas) or a sulfate-free and acetate-rich fermented effluent, depending mainly on proper pH control. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. (AU)

• 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: 15/06246-7 - 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: 20/03429-1 - Investigation of the impacts of sulfate reduction in Hydrogenogenic activity during the thermophilic fermentation of sugarcane vinasse
• Grantee: Michael Antonio Piffer
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 15/50684-9 - Sustainable gas pathways for Brazil: from microcosm to macrocosm
• Grantee: Reinaldo Giudici
• Support Opportunities: Research Projects - Thematic Grants
• 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