Surfaces and Interfaces in Biocatalysis

Biocatalysis is related to the application of all naturally occurring living biological systems (e.g., biomolecules, whole cells, microorganisms, and especially enzyme-specific proteins) or their parts to catalyze reactions for the synthesis of new materials [1]. Biomolecules, biological materials, or organic polymers are terms used for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development, performing a wide array of functions [2]. Biomolecules exist in a wide range of sizes and structures, from large macromolecules (or poly-anions) such as proteins, carbohydrates, lipids and nucleic acids, to small molecules such as primary metabolites, secondary metabolites and natural products, with biomolecule basic units such as amino acids containing carbon, hydrogen, oxygen, nitrogen, sulfur, amine (–NH₂) and carboxyl (–COOH) functional groups along a side chain (R group) specific for each amino acid [3]. Natural enzyme-specific proteins of high efficiency play an important role in living organisms. They are complex, large, well-defined, chiral organic molecules, which often carry metal ions and water molecules for maintaining their enzymatic structure and activities in chemical reactions such as hydrolysis, redox, condensation, substitution, isomerization, and cyclization.

Biocatalysis is, nowadays, an established technology for the production of chemicals. Examples of biocatalytic reactions already used for hundreds of years are the synthesis of alcohol via fermentation, cheese via enzymatic breakdown of milk proteins, brewery processes, etc. The biocatalyst acts via different mechanisms, such as the destabilization of bonds, conformational changes, the presence of acidic or basic groups affecting bond polarization and reaction speed, electrostatic attractions stabilizing the activated complex, and covalent bonding or cofactors. The challenging possibilities of biocatalysis are not accessible by conventional chemical synthesis. The most significant advantages of biocatalysis are its enantioselectivity, stereoselectivity, diastereoselectivity, regioselectivity and chemoselectivity. It also has mild and green chemistry operational conditions, as well as good biocompatibility and minimized energy and waste, resulting in high efficiency and selectivity due to reducing protected groups, minimized side reactions, easy separation, limited operating regions, substrate and product inhibition, and reactions in aqueous solutions [1,3].

Bio-nanotechnology is a fast-growing field in numerous areas of development in science and technology. It involves a combination of biomolecules with different kinds of nanomaterials or other synthetic biomaterials, providing biocompatibility and/or unique and tunable properties different from properties of both components, and can be utilized in a wide range of applications involving biocatalytic processes. Such hybrid new biomaterials can be applied in materials science, electronics, the food and cosmetics industries, environmental waste management, and especially in medicine for tissue engineering, regeneration, diagnosis (bio-imaging, sensing), and therapy (drug carriers, cell targeting) [1,4,5,6,7,8].

The interactions at the biointerface, which is the region of contact between biomolecule, cell, biological tissue, or a living organism, interacting with another biomaterial or inorganic/organic nanomaterial and biomolecule/water nanomaterial, is of great importance for designing new hybrid nanomaterials of desired properties. Understanding the biointerface requires a description of physicochemical interactions, their kinetics and thermodynamics, and exchanges between nanomaterial surface and the surface of biological components ruled by long-range (physisorption) and short-range (chemisorption) interactions. Such studies have been already performed extensively using a variety of MD and DDF calculations [9,10,11,12], and experimental techniques such as NEXAFS, XPS, STM, AFM, FTIR, SFG, DLS, etc. [13,14,15,16,17]. Surface chemistry and catalysis may still benefit from the development of “in-situ” surface techniques such as STM, AFM, SFG, etc., and ambient pressure XPS. Despite an increasing number of applications for biomaterials, the potential for cognition of the interactions and mechanisms has not yet been fully realized.

This Special Issue is dedicated to a broad spectrum of topics, from methods of synthesis of novel biomaterials, methods of different nanomaterials’ surface biofunctionalization/biomodification, and methods of attachment of biomaterials with molecular precision, to the chemical and physical characterization of biomaterials at the surface and interface. It is also dedicated to novel experimental methods for describing the interactions of biomaterials at the interface, and an explanation of biocatalytic mechanisms and processes taking place due to biofunctionalization, as well as new approaches of theoretical calculations for revealing the processes and their mechanisms at the surface and interface.

It is expected that the collection of publications will represent the progresses and latest trends in the constantly evolving areas related to biocatalytic processes. The authors of all the valuable contributions published in this Special Issue will provide wide-spread knowledge and inspiration to many scholars working in this field.