Suchergebnisse

Lipases are the most widely used enzymes in biocatalysis, and the most utilized method for enzyme immobilization is using hydrophobic supports at low ionic strength. This method allows the one step immobilization, purification, stabilization, and hyperactivation of lipases, and that is the main cause of their popularity. This review focuses on these lipase immobilization supports. First, the advantages of these supports for lipase immobilization will be presented and the likeliest immobilization mechanism (interfacial activation on the support surface) will be revised. Then, its main shortcoming will be discussed: enzyme desorption under certain conditions (such as high temperature, presence of cosolvents or detergent molecules). Methods to overcome this problem include physical or chemical crosslinking of the immobilized enzyme molecules or using heterofunctional supports. Thus, supports containing hydrophobic acyl chain plus epoxy, glutaraldehyde, ionic, vinylsulfone or glyoxyl groups have been designed. This prevents enzyme desorption and improved enzyme stability, but it may have some limitations, that will be discussed and some additional solutions will be proposed (e.g., chemical amination of the enzyme to have a full covalent enzyme-support reaction). These immobilized lipases may be subject to unfolding and refolding strategies to reactivate inactivated enzymes. Finally, these biocatalysts have been used in new strategies for enzyme coimmobilization, where the most stable enzyme could be reutilized after desorption of the least stable one after its inactivation. ; We gratefully recognize the financial support from MINECO-Spanish Government (project number CTQ2017-86170-R), Colciencias (Colombia, project number FP 44842-076-2016), Colciencias, Ministerio de Educación Nacional, Ministerio de Industria, Comercio y Turismo e ICETEX, Convocatoria Ecosistema Científico – Colombia Científica. Fondo Francisco José de Caldas, Contract RC-FP44842-212-2018, Generalitat Valenciana (PROMETEO/2018/076), FAPERGS (project number 17/2551-0000939-8), FUNCAP (project number BP3-0139-00005.01.00/18) and CONACYT (Mexico, project number CB-2016-01, 286992).

Papain is a cysteine protease from papaya, with many applications due to its broad specificity. This paper reviews for first time the immobilization of papain on different supports (organic, inorganic or hybrid supports) presenting some of the features of the utilized immobilization strategies (e.g., epoxide, glutaraldehyde, genipin, glyoxyl for covalent immobilization). Special focus is placed on the preparation of magnetic biocatalysts, which will permit the simple recovery of the biocatalyst even if the medium is a suspension. Problems specific to the immobilization of proteases (e.g., steric problems when hydrolyzing large proteins) are also defined. The benefits of a proper immobilization (enzyme stabilization, widening of the operation window) are discussed, together with some artifacts that may suggest an enzyme stabilization that may be unrelated to enzyme rigidification. ; We gratefully recognize the support from the Ministerio de Ciencia e Innovación from Spanish Government (project number CTQ2017-86170-R) and CSIC for the project AEP045. The FPU fellowship (Ministerio de Educacion) for Mr. Morellon–Sterling is gratefully recognized. Dr. Tacias-Pascacio thanks the financial support from "Programa para el Desarrollo Profesional Docente" (PRODEP) from Mexican Government. ABM would like to thank Ministerio de Ciencia Innovación y Universidades and FEDER (Project RTI2018-095291-B-I00) and the Generalitat Valenciana (PROMETEOII/2018/076) for financial support.

As society becomes increasingly aware of environmental problems and their consequences, and looks for "greener" options, the necessity of those same alternatives to become viable to be used in large scale increases. The consequences of uncontrolled use of non-renewable resources such as fossil fuels and the implementation of non-sustainable politics are starting to become more and more visible and worrying, painting an uncertain and hostile future for the next generations. Taking this current scenario into account, the search for alternatives such as organic-based fuels created from biomass with low emissions has become increasingly more appealing, as a clean and sustainable solution to the high global energy demand. However, these alternatives still have high costs associated to their fabrication process, making them less competitive against conventional fuels. One of the main goals of the work developed in this dissertation is to determine the viability of using chitosan magnetic microspheres, activated with a glutaraldehyde solution, as an active support to use with enzymes like Viscozyme, in the hope that their magnetic properties allow for easier handling. This is achieved by studying the factors that influence the sphere's properties, optimizing their creation process and then immobilizing Viscozyme on their surface. Afterwards, the spheres are used in several hydrolysis reactions one after the other, in order to analyze their efficiency and operating stability. Results show that magnetic microspheres are as viable as non-magnetic ones in terms of production and size manipulation when using a coaxial airflow bead generator system. Both types of microspheres also show similar results in terms of surface activation with glutaraldehyde and immobilization of Viscozyme. Results obtained from HPLC are inconclusive in terms of yield difference between free enzyme and immobilized enzyme, but also show no clear difference in terms of viability between both types of microspheres.

Chickens have become emblematic of the Anthropocene: They embody the age of acceleration, (post-) industrial value, and intensification in scientific and technological knowledge and practice. Contemporary chickens are the bearers of significant genetic and nutritional knowledge, experimented upon and 'tweaked' so much so that some have denied that contemporary commercial chickens are chickens at all. This article reconsiders chickens through a metabolic lens, and the notion of metabolism through chickens, arguing that attending to chickens opens up new conceptualizations of life and labour in the metabosphere. The article tells a metabolic history of chickens from ornament to enclosed monocrop, by way of the laboratory and nutritional experiments. Then, it looks at chicken metabolism in three conceptual modes: first, as a conduit for value, metabolizing and enhancing human life for the past century; second, through technological innovations extending the gut outside chickens' immobilized bodies; and third, through the planetary impacts of metabolic porosity in geological manifestations, toxic atmospheres, and viral overflow. Ultimately, this article shows how techno-scientific production of chickens has taken place in and created the metabosphere as a site of experimentation and exploitation.