Difference between revisions of "Team:UESTC-China/Model h2"

In order to find the best fermentation conditions of hydrogen, we designed the experiment and obtained the hydrogen production function by using the experimental data. The optimal fermentation conditions and maximum yield were obtained for the optimal solution of the function. Then we tried again under the best fermentation conditions. The result shows that the yield has obviously increased.

Hydrogen is the richest and lightest element in the universe and has great potential for development. Hydrogenases catalyze one of the simplest chemical reactions, \({\rm{2}}{{\rm{H}}^{\rm{ + }}}{\rm{ + 2}}{{\rm{e}}^{\rm{ - }}} \leftrightarrow {{\rm{H}}^{\rm{2}}}\), but their structures are very complex. We try to establish the kinetic model of the hydrogen production process and verify that the modified Escherichia coli has high hydrogen production ability.

Similar to the process of butanol fermentation, hydrogen fermentation is also affected by three factors: temperature, initial pH, initial OD. The kinetic equation of hydrogen synthesis was established and the factors affecting hydrogen fermentation were analyzed to optimize the process of hydrogen synthesis in order to increase the production of hydrogen.

Hydrogenase catalyzes one of the simplest chemical reactions,\({\rm{2}}{{\rm{H}}^{\rm{ + }}}{\rm{ + 2}}{{\rm{e}}^{\rm{ - }}} \leftrightarrow {{\rm{H}}^{\rm{2}}}\), but their structure is very complex[1]. So we consider simplifying the model. A molecular dynamics model was established to simulate the hydrogen production process. By comparing the theoretical hydrogen production with that in other literatures, it is proved that the hydrogen production of our constructed Escherichia coli is relatively high.

Because the hydrogenase catalytic reaction is very complex, we simplify the reaction to the enzymatic redox reaction shown below.

This reaction can be written as follows:

Using MATLAB 2014a to solve the above differential equations, the following parameters are used:

Parameter	Variable Name	Value	Reference
Michaelis Constant for HydA	\[k_m^{Hyda}\]	800mM	[2]
Catalysed rate of reaction for HydA	\[k_{cat}^{Hyda}\]	29000s^(-1)	[2]
Inhibition constant for \({{\rm{H}}_{\rm{2}}}\)	\[k_i^{{{\rm{H}}_{\rm{2}}}}\]	16 mM	[2]

The result is shown in Fig.9: the maximum hydrogen production is 1.63mmol/g（gulose）,Hydrogen production rate per unit conversion is 1.8 \(\mu {\rm{mol}}\)(mg protein) \(^{{\rm{ - 1}}}{{\rm{h}}^{{\rm{ - 1}}}}\).

By comparing the results with the butanol production in other literatures, it is found that the hydrogen production of the constructed bacteria is in a high position.

System	\({{\rm{H}}_{\rm{2}}}\) production rate (converted units)	Reference
Expression of the Ralstonia eutropha SH operon	0.3μmol\({{\rm{H}}_{\rm{2}}}\) (mg protein)\(^{ - 1}{{\rm{h}}^{{\rm{ - 1}}}}\)	[3]
Expression of [NiFe]-hydrogenase 2 from Citrobacter sp. SG	2.6μmol\({{\rm{H}}_{\rm{2}}}\) (mg protein)\(^{ - 1}{{\rm{h}}^{{\rm{ - 1}}}}\)	[3]
Expression of HxEFUYH hydrogenase and the maturation proteins HypABCDEF and HoxW from Synechocystis sp. PCC 6803	0.004μmol\({{\rm{H}}_{\rm{2}}}\) (mg protein)\(^{ - 1}{{\rm{h}}^{{\rm{ - 1}}}}\)	[3]

[1] Gönül Vardar‐Schara, Toshinari Maeda, and Thomas K. Wood. Metabolically engineered bacteria for producing hydrogen via fermentation. Microb Biotechnol. 2008 Mar; 1(2): 107–125.

[2] Pierre-Pol Liebgott, Fanny Leroux, Bénédicte Burlat, Sébastien Dementin, Carole Baffert, Thomas Lautier, Vincent Fourmond, Pierre Ceccaldi, Christine Cavazza, Isabelle Meynial-Salles, Philippe Soucaille, Juan Carlos Fontecilla-Camps, Bruno Guigliarelli, Patrick Bertrand, Marc Rousset & Christophe Léger. Relating diffusion along the substrate tunnel and oxygen sensitivity in hydrogenase. Nature chemical biology, 2009(6):63-70.

[3] Toshinari Maeda, Kien Trung Tran, Ryota Yamasaki3, Thomas K. Wood. Current state and perspectives in hydrogen production by Escherichia coli: roles of hydrogenases in glucose or glycerol metabolism. Applied Microbiology and Biotechnology, 2018（102）: 2041-2050.