TY - JOUR
T1 - Microbiological hydrogen (H2) thresholds in anaerobic continuous-flow systems
T2 - Effects of system characteristics
AU - Karadagli, Fatih
AU - Marcus, Andrew
AU - Rittmann, Bruce E.
N1 - Funding Information: We thank Drs. César Torres and Yen‐jung Lai for their invaluable suggestions and discussions of this work. This work was supported by the Scientific and Technological Council of Turkey (TUBITAK) 2219—International Post‐doctoral Fellowship Programme; and the Swette Trust, Phoenix, Arizona, USA. We are grateful for funding from TUBITAK ‐ National Academic Network and Information Center (ULAKBIM) for “open access” publication of this article. Funding Information: We thank Drs. César Torres and Yen-jung Lai for their invaluable suggestions and discussions of this work. This work was supported by the Scientific and Technological Council of Turkey (TUBITAK) 2219—International Post-doctoral Fellowship Programme; and the Swette Trust, Phoenix, Arizona, USA. We are grateful for funding from TUBITAK - National Academic Network and Information Center (ULAKBIM) for “open access” publication of this article. Publisher Copyright: © 2023 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals LLC.
PY - 2023/7
Y1 - 2023/7
N2 - Hydrogen (H2) concentrations that were associated with microbiological respiratory processes (RPs) such as sulfate reduction and methanogenesis were quantified in continuous-flow systems (CFSs) (e.g., bioreactors, sediments). Gibbs free energy yield (ΔǴ ~ 0) of the relevant RP has been proposed to control the observed H2 concentrations, but most of the reported values do not align with the proposed energetic trends. Alternatively, we postulate that system characteristics of each experimental design influence all system components including H2 concentrations. To analyze this proposal, a Monod-based mathematical model was developed and used to design a gas–liquid bioreactor for hydrogenotrophic methanogenesis with Methanobacterium bryantii M.o.H. Gas-to-liquid H2 mass transfer, microbiological H2 consumption, biomass growth, methane formation, and Gibbs free energy yields were evaluated systematically. Combining model predictions and experimental results revealed that an initially large biomass concentration created transients during which biomass consumed [H2]L rapidly to the thermodynamic H2-threshold (≤1 nM) that triggerred the microorganisms to stop H2 oxidation. With no H2 oxidation, continuous gas-to-liquid H2 transfer increased [H2]L to a level that signaled the methanogens to resume H2 oxidation. Thus, an oscillatory H2-concentration profile developed between the thermodynamic H2-threshold (≤1 nM) and a low [H2]L (~10 nM) that relied on the rate of gas-to-liquid H2-transfer. The transient [H2]L values were too low to support biomass synthesis that could balance biomass losses through endogenous oxidation and advection; thus, biomass declined continuously and disappeared. A stable [H2]L (1807 nM) emerged as a result of abiotic H2-balance between gas-to-liquid H2 transfer and H2 removal via advection of liquid-phase.
AB - Hydrogen (H2) concentrations that were associated with microbiological respiratory processes (RPs) such as sulfate reduction and methanogenesis were quantified in continuous-flow systems (CFSs) (e.g., bioreactors, sediments). Gibbs free energy yield (ΔǴ ~ 0) of the relevant RP has been proposed to control the observed H2 concentrations, but most of the reported values do not align with the proposed energetic trends. Alternatively, we postulate that system characteristics of each experimental design influence all system components including H2 concentrations. To analyze this proposal, a Monod-based mathematical model was developed and used to design a gas–liquid bioreactor for hydrogenotrophic methanogenesis with Methanobacterium bryantii M.o.H. Gas-to-liquid H2 mass transfer, microbiological H2 consumption, biomass growth, methane formation, and Gibbs free energy yields were evaluated systematically. Combining model predictions and experimental results revealed that an initially large biomass concentration created transients during which biomass consumed [H2]L rapidly to the thermodynamic H2-threshold (≤1 nM) that triggerred the microorganisms to stop H2 oxidation. With no H2 oxidation, continuous gas-to-liquid H2 transfer increased [H2]L to a level that signaled the methanogens to resume H2 oxidation. Thus, an oscillatory H2-concentration profile developed between the thermodynamic H2-threshold (≤1 nM) and a low [H2]L (~10 nM) that relied on the rate of gas-to-liquid H2-transfer. The transient [H2]L values were too low to support biomass synthesis that could balance biomass losses through endogenous oxidation and advection; thus, biomass declined continuously and disappeared. A stable [H2]L (1807 nM) emerged as a result of abiotic H2-balance between gas-to-liquid H2 transfer and H2 removal via advection of liquid-phase.
KW - continuous-flow systems
KW - hydrogen (H) thresholds
KW - methanogens
KW - steady-state
KW - transient
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U2 - 10.1002/bit.28415
DO - 10.1002/bit.28415
M3 - Article
C2 - 37148477
SN - 0006-3592
VL - 120
SP - 1844
EP - 1856
JO - Biotechnology and bioengineering
JF - Biotechnology and bioengineering
IS - 7
ER -