Evaluation of the influence of iron and nickel nanoparticles on the fermentative production of hydrogen in batch and continuous reactors

Author(s)

Alana Gandra Lima de Moura

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2021-08-16

Examining board members

Maria Bernadete Amancio Varesche Silva; Claudia Etchebehere Arenas; Tiago Palladino Delforno; Sávia Gavazza dos Santos Pessoa; Valeria Reginatto Spiller

• Advisor: Maria Bernadete Amancio Varesche Silva

Abstract

In this study, chemical properties of nanomaterials, including their large surface area and reaction activity, were used for metals supplementation in batch and continuous reactors (Anaerobic Fluidized Bed Reactors - AFBR operated in 3 h HRT). The comparison between reactors with iron and nickel nanoparticles (NPs) and control reactors without the addition of NPs was performed to evaluate their influence on three configuration of the fermentation process: (1) In batch reactors fed with RCM medium and inoculated with pure culture C .butyricum statistical design of experiments was applied (Plackett-Burman and Rotational Central Composite Design). Under such conditions, the addition of NPs of iron (30 mg Fe0 L-1) and nickel (20 mg Ni0 L-1) optimized the production of H2. However, the addition of nickel NPs above 50 mg L-1 reduced the production of H2. Furthermore, the production route of valeric acid (a high value-added acid in the market) was favored over acetic and butyric acid when NPs were added to the medium. In the batch reactor with NPs, a greater amount and lower expression of the hydrogenase enzyme was observed when compared to the control reactor; (2) In continuous reactors fed with glucose and inoculated with natural fermentation and C. butyricum bioaugmentation, the immobilization of metals in the support material (expanded clay) and its consequent greater availability favored the higher production of Volatile Fatty Acids (VFAs), when compared to the control reactor. Furthermore, the addition of NPs influenced the metabolic pathways, with a higher concentration of acetic and butyric acids in AFBR - NP and lactic acid in AFBR - Control. Higher relative abundance (48.8%) of Lactobacillus was observed in AFBRNP biofilm. (3) In continuous reactors fed with vinasse and inoculated with anaerobic sludge bioaugmented with C. butyricum, the composition of H2 in biogas was significantly higher in AFBR - NP when compared to AFBR - Control. The decrease in lactic acid concentration during vinasse fermentation process was observed in both reactors and in all operational stages. During stage II (4 gcarb L-1), metallic NPs favored genes related to the first stages of vinasse digestion, with higher percentages of betaglucosidase, glucokinase and pyruvate-ferredoxin oxidoreductase enzymes that were related to greater relative abundance of Bacteroides and Prevotella. However, when fed with vinasse (7 gcarb L-1, stage III), L- and D-lactate dehydrogenase, 3-hydroxybutyrylCoA dehydrogenase, acetate kinase, pyruvate kinase and flavoprotein fumarate reductase were the favored enzymes in the presence of NPs. These enzymes are related to the final stages of removal of organic compounds from vinasse and greater relative abundance of Lactobacillus (11.4%) and Secundilactobacillus (7.5%). (AU)

• FAPESP's process: 17/23008-8 - Assessment of Iron and Nickel nanoparticles influence on batch and continuous reactors fermentative hydrogen production
• Grantee: Alana Gandra Lima de Moura
• Support Opportunities: Scholarships in Brazil - Doctorate