Mérida-Figueróa, Fernando J.

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    Kinetics and modeling of batch bioethanol production using suspended co-cultures of Saccharomyces cerevisiae and Pichia stipitis in glucose-xylose media
    (2010) Mérida-Figueróa, Fernando J.; Saliceti-Piazza, Lorenzo; College of Engineering; Colucci, José; Nadathur, Govind; Carlos Sáez, Juan; Department of Chemical Engineering; Pando, Miguel A.
    A mathematical structured model was developed to predict the behavior of glucosexylose mixtures using the suspended co-culture of the wild-type yeast strains Saccharomyces cerevisiae Montrachet and Pichia stipitis NRRL Y-11545 for ethanol production. Kinetic characterization was estimated in single substrate and single strain batch fermentations in order to construct the model for the mixture systems. The simple Monod model was used to describe the behavior of single substrate fermentations with a high degree of accuracy (R2 > 0.96) and residual standard deviations, (RSD < 7.5%). The agreement between the simulated and experimental data was superior for the fermentation system glucose – S. cerevisiae, and the system xylose – P. stipitis promoted the best balance between cell growth and ethanol production with a yield coefficient of 0.35 g of ethanol/g xylose. A non-linear ordinary differential equation system comprising of nine equations was constructed under the cybernetic framework to model the behavior of glucose-xylose mixtures with the specified yeast co-culture. The results obtained from the simulations suggest that the proposed model fits accurately the experimental data. The sensitivity of the model was slightly higher for the mixture having the same proportion of glucose and xylose (50% glucose – 50% xylose), with average values of R2 = 0.99 and RSD = 2.21%. The accurate prediction of the experimental concentrations confirms that the model utilized provides reliable kinetic information. Small deviations were observed but they are commonly found in one simulation system which has not been object of further error minimizations. In the future, the model can be utilized for other process configurations such as fed-batch and continuous culture, either with the same co-culture scheme or using immobilization techniques to evaluate both fermentation efficiency and model accuracy.
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    Development of optimized therapeutic platforms for magnetic fluid hyperthermia in adjuvant cancer therapies
    (2018-05) Mérida-Figueróa, Fernando J.; Torres-Lugo, Madeline; College of Engineering; Domenech, Maribella; Juan, Eduardo; Almodóvar, Jorge; Acevedo, Aldo; Department of Chemical Engineering; Pagán, Solangie
    Magnetic Fluid Hyperthermia (MFH) has a great potential as an adjuvant in cancer therapy, enhancing the effects of antineoplastic agents, sensitizing resistant cancers and reducing undesired side effects. When compared to other local hyperthermia approaches, non-specific heating is reduced with MFH since the heat is produced only when alternating magnetic fields are turned on. The clinical translation of MFH faces several challenges including nanoparticle low heat dissipation rates, limited cellular uptake of drugs and/or nanoparticles, and poor nanoparticle accumulation in tumors after intravenous injection. To tackle these challenges, the following hypotheses were proposed: (i) optimization of synthesis and peptization of magnetic nanoparticles will lead to increased heat dissipation rates; (ii) the use of low-intensity ultrasound will improve the cellular uptake of drugs and nanoparticles, potentiating the effects of MFH/drug combination therapies, and (iii) the intraperitoneal administration of nanoparticles will induce their uptake by mouse peritoneal macrophages and tumors. To test these hypotheses, systematic experimental designs were proposed to evaluate nanoparticle properties and their performance in vitro and in vivo. The coprecipitation synthesis and peptization of iron oxide nanoparticles were optimized, obtaining nanoparticles with remarkably high heat dissipation rates in liquid and solid matrices. Using an in vitro ovarian cancer model, increased cytotoxic profile of the drug 2-phenylethynesulfonamide was observed when lowintensity ultrasound was coupled to MFH/drug combination therapies. In vivo intraperitoneal administration of nanoparticles did not improve nanoparticle accumulation in subcutaneous breast cancer tumors, but significantly induced uptake by peritoneal macrophages which promoted accumulation in omental tissues. These results demonstrated that optimization of experimental methodologies was key to enhance nanoparticle properties, potentiating novel chemotherapeutic agents and fostering opportunities for improved nanoparticle delivery in vivo.