A model-based
nonlinear optimum experimental design technique has
been implemented to estimate the kinetic parameters of the lignocellulose
enzymatic hydrolysis process, mainly focused on the calculation of
reaction rate constants and activation energy parameters. Analysis
of the reaction was based on the mechanism of simultaneous consecutive
enzymatic reactions of cellulose and hemicellulose to produce sugar-rich
syrups. A mathematical model was developed as a set of ordinary differential
equations (ODEs). To enhance the parameter estimation process, a control
variable that directly affects the response of the system (temperature)
was included to predict the state variable profiles over a broad experimental
range. To determine the optimal profiles for the temperature gradient,
optimal control problems were set up and solved numerically. A comparison
between model prediction profiles and experimental data was performed
to adjust kinetic parameter estimation to real process features. The
results show that nonlinear optimum experiments enhance the quality
of the estimates because of the optimality criterion included in the
objective function and because the embedded nonlinear behavior is
explicitly addressed.
Poly-R-hydroxyalkanoates (PHAs) are polymers produced by a vast number of bacterial species under stress conditions. PHAs exhibit different thermal and mechanical properties that depend on their molecular structure. In this work, PHAs were produced using avocado oil as the carbon source. Cupriavidus necator H16 was cultured in three-stage fermentation using fructose during the cell growth stages and avocado oil during the PHA synthesis stage. Different concentrations of avocado oil were used during the third stage to test the incorporation of various monomeric units into the PHAs. Biomass and PHA production were measured during the fermentation. DSC, FTIR, and gas chromatography analysis aided the PHA characterization. Different proportions of 3-hydroxyvalerate were present in the 3-hydroxybutyrate main chain depending on the concentration of avocado oil. The results suggest that avocado oil is a viable new substrate for PHA production.
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