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"This study reports a fermentative hydrogen production by Escherichia coli using cheese whey as substrate. To improve the biohydrogen production, an E. coli ΔhycA ΔlacI strain (WDHL) was constructed. The absence of hycA and lacI genes had a positive effect on the biohydrogen production. The strain produced 22% more biohydrogen in a shorter time than the wild-type (WT) strain. A Box-Behnken experimental design was used to optimize pH, temperature and substrate concentration. The optimal initial conditions for biohydrogen production by WDHL strain were pH 7.5, 37 °C and 20 g/L of cheese whey. The specific production rate was improved from 3.29 mL H2/optical density at 600 nm (OD600nm) unit-h produced by WDHL under non-optimal conditions to 5.88 mL H2/OD600nm unit-h under optimal conditions. Using optimal initial conditions, galactose can be metabolized by WDHL strain. The maximum yield obtained was 2.74 mol H2/mol lactose consumed, which is comparable with the yield reached in other hydrogen production processes with Clostridium sp. or mixed cultures."
Generally, energy is defined as the capacity to do work, and it is basic to understand life. Life is a state of activity controlled genetically and driven by energy to maintain and reproduce its cellular organization (Mendoza and Mendoza 2011). What is surprising is that all known living organisms share the same energy and cell synthesis processes.
The following can be credited to Gibbs and Helmholtz: the internal energy of a system is made up by reactants, where H is the energy contained by the number of chemical bonds in a given volume; G is the available energy to do work (movement, growth, maintenance, reproduction); S is entropy (energy loss); and T is temperature of a reaction (Gaudy and Gaudy, 1980). When a biochemical reaction takes place.