maki Posted June 10, 2013 Share Posted June 10, 2013 Hi Using GWB software, I’m trying to reproduce the in-situ transition of functional microbial communities with thermodynamic ladder. According to the existing advices in this forum, I have started trial under the simplified condition. I attached the React file for the trial. The main concept of the trial is to reproduce the decrease of Eh with consumption of O2(aq) by aerobes in closed chamber. Next is that carbonate and hydrogen are used as resources for hydrogenotrophic methanogenesis. Analysis time was basically for 5 days (besides, 1 day, 5 month, and so on). Thermo.com.V8.R6+.dat was used with the decoupling of Lactic_acid(aq)/HCO3-, H2(aq)/H+, and Methane(aq)/HCO3-.. Lactic_acid(aq) was swapped to Lactate. Results were as below: - The decrease of Eh was not observed in the result of the above simulation although O2(aq) concentration and Lactic_acid(aq) concentration decreased until zero with the increase of Aerobe biomass. Rather, the Eh acutely increased. - Though HCO3- and H+ were provided to the system, they seemed to be used by methanogen. I have several questions. Concerning the decrease of Eh in the system and the consistency between change of Eh and methanogenesis. -Q1. I think that the ‘Eh’ in the Gtplot seems to reflect ‘Eh(O2(aq)/H2O)’ only, without reflecting other redox couplings, for example ‘Eh(H+/H2(aq)’, ‘Eh(Lactic_acid(aq)/Methane(aq)’, and so on. I hope to express the anaerobic condition (around -250 mV) for methanogenesis after O2(aq) is completely consumed. How should I revise the React setting? In addition, what does the ‘Eh’ in the Gtplot represent? Mixed potential or Eh(O2(aq)/H2O) only? -Q2. I expect that the methanogenesis which needs extremely low Eh (around -250 mV) starts after all of O2 is consumed. However, methanogen didn’t start after O2 consumption in the simulation. On the other hand, when I input larger value of H2(aq) (ex. 1e-5), methanogenesis have started in spite of the fact that there remained O2(aq) in the system and Eh value was so high (around +700 mV). Could anyone give me advices regarding the decrease of Eh in the system and the consistency between change of Eh and methanogenesis? -Q3. In this case, can the helper function in rate law option on the Kinetic microbe-Aerobe be available for solving this problem? If so, could you give me any example of rate raw available for this case? Concerning the consumption of H2(aq) or H+. -Q4. Hydrogenotrophic methanogenesis is shown by the equation as below. HCO3- + 4*H2(aq) + H+ -> Methane(aq) + 3*H2O However, hydrogen released from Aerobic respiration seems not to be used in methanogenesis in the simulation. Because H+ in fluid didn’t decrease and H2(aq) concentration was constant for any analysis time. Of course, biomass of methanogen decreased according to only decay constant. Even if I set hydrogen of equation by unifying in either H2(aq) or H+ in the all kinetics for microbes, it results in charge imbalance. How should I handle Basis and Reactants to describe hydrogenotrophic methanogenesis? Thank you for your consideration. Best regards, Maki O_Me1_simplified.rea Quote Link to comment Share on other sites More sharing options...
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