Bolívar Bolívar, Juan Manuel

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First Name
Juan Manuel
Last Name
Bolívar Bolívar
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Ingeniería Química y de Materiales
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Now showing 1 - 4 of 4
  • Publication
    Intensification of oxygen-dependent biotransformations catalyzed by immobilized enzymes
    (Elsevier, 2021-12) Lorente Arévalo, Alvaro; Ladero Galán, Miguel; Bolívar Bolívar, Juan Manuel
    Oxidative biotransformations find a prominent role in the fine chemical industry and the valorization of renewable feedstocks. Implementation of oxygen-dependent reactions faces some challenges across scales and at different levels of development. First, the fruitful development of enzyme candidates and identification of reaction possibilities is not in consonance with the implementation in process engineering. Second, reaction engineering faces a complex interplay of reaction kinetic, oxygen transfer and process stability. Third, given the advances in synergic fields such as molecular biology, chemistry, material sciences, and (micro)process engineering, an interdisciplinary assembly from a consistent discipline around heterogeneous biocatalyst engineering would be of strategic value. We show advances in design of active and robust immobilized enzyme catalysts to be applied in (continuous) intensified processes. A framework based on the joint design of a catalyst and reactor will be discussed for the design and optimization of the catalysts and biotransformations involved.
  • Publication
    The Microenvironment in Immobilized Enzymes: Methods of Characterization and Its Role in Determining Enzyme Performance
    (MDPI, 2019-09-24) Bolívar Bolívar, Juan Manuel; Nidetzky, Bernd
    The liquid milieu in which enzymes operate when they are immobilized in solid materials can be quite different from the milieu in bulk solution. Important differences are in the substrate and product concentration but also in pH and ionic strength. The internal milieu for immobilized enzymes is affected by the chemical properties of the solid material and by the interplay of reaction and diffusion. Enzyme performance is influenced by the internal milieu in terms of catalytic rate (“activity”) and stability. Elucidation, through direct measurement of differences in the internal as compared to the bulk milieu is, therefore, fundamentally important in the mechanistic characterization of immobilized enzymes. The deepened understanding thus acquired is critical for the rational development of immobilized enzyme preparations with optimized properties. Herein we review approaches by opto-chemical sensing to determine the internal milieu of enzymes immobilized in porous particles. We describe analytical principles applied to immobilized enzymes and focus on the determination of pH and the O2 concentration. We show measurements of pH and [O2] with spatiotemporal resolution, using in operando analysis for immobilized preparations of industrially important enzymes. The effect of concentration gradients between solid particle and liquid bulk on enzyme performance is made evident and quantified. Besides its use in enzyme characterization, the method can be applied to the development of process control strategies.
  • Publication
    Extraction of Antioxidants from Grape and Apple Pomace: Solvent Selection and Process Kinetics
    (MDPI, 2022) Garcia Montalvo, Jorge; García Martín, Alberto; Ibañez Bujan, Jon; Santos Mazorra, Victoria Eugenia; Yustos Cuesta, Pedro; Bolívar Bolívar, Juan Manuel; Ladero Galán, Miguel
    Polyphenols have become a research target due to their antioxidant, anti-inflammatory and antimicrobial activity. Obtention via extraction from natural sources includes the revalorization of food wastes such as grape pomace (GP) or apple pomace (AP). In this work, GP and AP were submitted to a liquid–solid extraction using different solvents of industrial interest. Process kinetics were studied measuring the total phenolic content (TPC) and antioxidant capacity (AC), while the extraction liquor composition was analyzed employing chromatographic methods. Extraction processes using water-solvent mixtures stood out as the better options, with a particular preference for water 30%–ethanol 70% (v/v) at 90 °C, a mixture that quickly extracts up to 68.46 mg GAE/gds (Gallic Acid Equivalent per gram dry solid) and 122.67 TEAC/gds (TROLOX equivalent antioxidant capacity per gram dry solid) in case of GP, while ethylene water 10%–ethylene glycol 90% (v/v) at 70 °C allows to reach 27.19 mg GAE/gds and 27.45 TEAC/gds, in the case of AP. These extraction processes can be well-described by a second-order kinetic model that includes a solubility-related parameter for the first and fast-washing and two parameters for the slow mass transfer controlled second extraction phase. AP liquors were found to be rich in quercetin with different sugar moieties and GP extracts highlighted flavonols, cinnamic acids, and anthocyanins. Therefore, using identical extraction conditions for AP and GP and a comparative kinetic analysis of TPC and AC results for the first time, we concluded that ethanol/water mixtures are adequate solvents for polyphenols extraction due to their high efficiency and environmentally benign nature.
  • Publication
    Immobilization-Stabilization of β-Glucosidase for Implementation of Intensified Hydrolysis of Cellobiose in Continuous Flow Reactors
    (MDPI, 2022) Alvarez-Gonzalez, Celia; Santos Mazorra, Victoria Eugenia; Ladero Galán, Miguel; Bolívar Bolívar, Juan Manuel
    Cellulose saccharification to glucose is an operation of paramount importance in the bioenergy sector and the chemical and food industries, while glucose is a critical platform chemical in the integrated biorefinery. Among the cellulose degrading enzymes, β-glucosidases are responsible for cellobiose hydrolysis, the final step in cellulose saccharification, which is usually the critical bottleneck for the whole cellulose saccharification process. The design of very active and stable β-glucosidase-based biocatalysts is a key strategy to implement an efficient saccharification process. Enzyme immobilization and reaction engineering are two fundamental tools for its understanding and implementation. Here, we have designed an immobilized-stabilized solid-supported β-glucosidase based on the glyoxyl immobilization chemistry applied in porous solid particles. The biocatalyst was stable at operational temperature and highly active, which allowed us to implement 25 °C as working temperature with a catalyst productivity of 109 mmol/min/gsupport. Cellobiose degradation was implemented in discontinuous stirred tank reactors, following which a simplified kinetic model was applied to assess the process limitations due to substrate and product inhibition. Finally, the reactive process was driven in a continuous flow fixed-bed reactor, achieving reaction intensification under mild operation conditions, reaching full cellobiose conversion of 34 g/L in a reaction time span of 20 min.