Immobilization of enzymes on monofunctional and heterofunctional epoxy-activated supports

Disulfiram Inhibits Opsonin-Independent Phagocytosis and Migration of Human Long-Lived In Vitro Cultured Phagocytes from Multiple Inflammatory Diseases

Disulfiram (DSF), an anti-alcoholism medicine, exerts treatment effects in patients suffering from persistent Borreliosis and also exhibits anti-cancer effects through its copper chelating derivatives and induction of oxidative stress in mitochondria. Since chronic/persistent borreliosis is characterized by increased amounts of pro-inflammatory macrophages, this study investigated opsonin-independent phagocytosis, migration, and surface marker expression of in vivo activated and in vitro cultured human monocyte-derived phagocytes (macrophages and dendritic cells) with and without DSF treatment. Phagocytosis of non-opsonized Dynabeads® M-450 and migration of macrophages and dendritic cells were monitored using live cell analyzer Juli™ Br for 24 h, imaging every 3.5 min. To simultaneously monitor phagocyte function, results were analyzed by a newly developed software based on the differential phase contrast images of cells before and after ingestion of Dynabeads. DSF decreased the phagocytic capacities exhibited by in vitro enriched and long-lived phagocytes. Although no chemotactic gradient was applied to the test system, vigorous spontaneous migration was observed. We therefore set up an algorithm to monitor and quantify both phagocytosis and migration simultaneously. DSF not only reduced phagocytosis in a majority of these long-lived phagocytes but also impaired their migration. Despite these selective effects by DSF, we found that DSF reduced the expression densities of surface antigens CD45 and CD14 in all of our long-lived phagocytes. In cells with a high metabolic activity and high mitochondrial contents, DSF led to cell death corresponding to mitochondrial oxidative stress, whereas metabolically inactive phagocytes survived our DSF treatment protocol. In conclusion, DSF affects the viability of metabolically active phagocytes by inducing mitochondrial stress and secondly attenuates phagocytosis and migration in some long-lived phagocytes.

Microbial Lipases and Their Potential in the Production of Pharmaceutical Building Blocks

Processes involving lipases in obtaining active pharmaceutical ingredients (APIs) are crucial to increase the sustainability of the industry. Despite their lower production cost, microbial lipases are striking for their versatile catalyzing reactions beyond their physiological role. In the context of taking advantage of microbial lipases in reactions for the synthesis of API building blocks, this review focuses on: (i) the structural origins of the catalytic properties of microbial lipases, including the results of techniques such as single particle monitoring (SPT) and the description of its selectivity beyond the Kazlauskas rule as the "Mirror-Image Packing" or the "Key Region(s) rule influencing enantioselectivity" (KRIE); (ii) immobilization methods given the conferred operative advantages in industrial applications and their modulating capacity of lipase properties; and (iii) a comprehensive description of microbial lipases use as a conventional or promiscuous catalyst in key reactions in the organic synthesis (Knoevenagel condensation, Morita-Baylis-Hillman (MBH) reactions, Markovnikov additions, Baeyer-Villiger oxidation, racemization, among others). Finally, this review will also focus on a research perspective necessary to increase microbial lipases application development towards a greener industry.

Coimmobilization and colocalization of a glycosyltransferase and a sucrose synthase greatly improves the recycling of UDP-glucose: Glycosylation of resveratrol 3-O-β-D-glucoside

Glycosylation is one of the most efficient biocompatible methodologies to enhance the water solubility of natural products, and therefore their bioavailability. The excellent regio- and stereoselectivity of nucleotide sugar-dependent glycosyltransferases enables single-step glycosylations at specific positions of a broad variety of acceptor molecules without the requirement of protection/deprotection steps. However, the need for stoichiometric quantities of high-cost substrates, UDP-sugars, is a limiting factor for its use at an industrial scale. To overcome this challenge, here we report tailor-made coimmobilization and colocalization procedures to assemble a bi-enzymatic cascade composed of a glycosyltransferase and a sucrose synthase for the regioselective 5-O-β-D-glycosylation of piceid with in situ cofactor regeneration. Coimmobilization and colocalization of enzymes was achieved by performing slow immobilization of both enzymes inside the porous support. The colocalization of both enzymes within the porous structure of a solid support promoted an increase in the overall stability of the bi-enzymatic system and improved 50-fold the efficiency of piceid glycosylation compared with the non-colocalized biocatalyst. Finally, piceid conversion to resveratrol 3,5-diglucoside was over 90% after 6 cycles using the optimal biocatalyst and was reused in up to 10 batch reaction cycles accumulating a TTN of 91.7 for the UDP recycling.

Glycosynthase reaction meets the flow: Continuous synthesis of lacto-N-triose II by engineered β-hexosaminidase immobilized on solid support

The D746E variant of Bifidobacterium bifidum β‐N‐acetyl‐hexosaminidase is a promising glycosynthase (engineered glycosidase deficient in hydrolase activity) for the synthesis of lacto‐N‐triose II (LNT II), a core structural unit of human milk oligosaccharides. Here, we develop a flow process for the glycosynthase reaction, which is the regioselective β‐1,3‐glycosylation of lactose from a d‐glucosamine 1,2‐oxazoline donor. Using the glycosynthase immobilized on agarose beads (∼30 mg/g) packed into a fixed bed (1 ml), we show stable continuous production of LNT II (145–200 mM) at quantitative yield from the donor substrate. The wild‐type β‐N‐acetyl‐hexosaminidase used under exactly comparable conditions gives primarily (∼85%) the hydrolysis product d‐glucosamine. By enabling short residence times (2 min) that are challenging for mixed‐vessel types of reactor to establish, the glycosynthase flow reactor succeeds in an effective uncoupling of the LNT II formation (∼80–100 mM/min) from the slower side reactions (decomposition of donor substrate, enzymatic hydrolysis of LNT II) to obtain optimum synthetic efficiency. Our study thus provides a strong case for the application of flow chemistry principles to glycosynthase reactions and by that, it reveals the important synergy between enzyme and reaction engineering for biocatalytic synthesis of oligosaccharides.

Intraparticle pH Sensing Within Immobilized Enzymes: Immobilized Yellow Fluorescent Protein as Optical Sensor for Spatiotemporal Mapping of pH Inside Porous Particles

pH is a fundamental variable in enzyme catalysis and its measurement therefore is crucial for understanding and optimizing enzyme-catalyzed reactions. Whereas measurements within homogeneous bulk liquid solution are prominently used, enzymes immobilized inside porous particles often suffer from pH gradients due to partition effects and heterogeneously catalyzed biochemical reactions. Unfortunately, the measurements of intraparticle pH are not available due to the lack of useful suitable methodologies; as a consequence the biocatalyst characterization is hampered. Here, a fully biocompatible methodology for real-time optical sensing of pH within porous materials is described. A genetically encoded ratiometric pH indicator, the superfolder yellow fluorescent protein (sYFP), is used to functionalize the internal surface of enzyme carrier supports. By using controlled, tailor-made immobilization, sYFP is homogeneously distributed within these materials, and so enables, via self-referenced imaging analysis, pH measurements in high accuracy and with useful spatiotemporal resolution. The hydrolysis of penicillin by a penicillin acylase, taking place in solution or confined to the solid surface of the porous matrix is used to show the monitoring of evolution of internal pH. Thus, pH sensing based on immobilized sYFP represents a broadly applicable technique to the study of the internally heterogeneous environment of immobilized enzymes into solid particles.

Immobilization of cellulase in the non-natural ionic liquid environments to enhance cellulase activity and functional stability

Ionic liquids (ILs) have been applied as an environmentally friendly solvent in the pretreatment of lignocellulosic biomass for more than a decade. The ILs involved pretreatment processes for cellulases mediated saccharification lead to both the breakdown of cellulose crystallinity and the decrease of lignin content, thereby improving the solubility of cellulose and the accessibility of cellulase. However, most cellulases are partially or completely inactivated in the presence of even low amount of ILs. Immobilized cellulases are found to perform improved stability and higher apparent activity in practical application compared with its free counterparts. Enzyme immobilization therefore has become a promising way to relieve the deactivation of cellulase in ILs. Various immobilization carriers and methods have been developed and achieved satisfactory results in improving the stability, activity, and recycling of cellulases in IL pretreatment systems. This review aims to provide detailed introduction of immobilization methods and carrier materials of cellulase, including natural polysaccharides, synthetic polymers, inorganic materials, magnetic materials, and newly developed composite materials, and illustrate key methodologies in improving the performance of cellulase in the presence of ILs. Especially, novel materials and concepts from the recently representative researches are focused and discussed comprehensively, and future trends in immobilization of cellulases in non-natural ILs environments are speculated in the end.

Biobased, Internally pH-Sensitive Materials: Immobilized Yellow Fluorescent Protein as an Optical Sensor for Spatiotemporal Mapping of pH Inside Porous Matrices

The pH is fundamental to biological function and its measurement therefore crucial across all biosciences. Unlike homogenous bulk solution, solids often feature internal pH gradients due to partition effects and confined biochemical reactions. Thus, a full spatiotemporal mapping for pH characterization in solid materials with biological systems embedded in them is essential. In here, therefore, a fully biocompatible methodology for real-time optical sensing of pH within porous materials is presented. A genetically encoded ratiometric pH sensor, the enhanced superfolder yellow fluorescent protein (sYFP), is used to functionalize the internal surface of different materials, including natural and synthetic organic polymers as well as silica frameworks. By using controlled, tailor-made immobilization, sYFP is homogenously distributed within these materials and so enables, via self-referenced imaging analysis, pH measurements in high accuracy and with useful spatiotemporal resolution. Evolution of internal pH is monitored in consequence of a proton-releasing enzymatic reaction, the hydrolysis of penicillin by a penicillin acylase, taking place in solution or confined to the solid surface of the porous matrix. Unlike optochemical pH sensors, which often interfere with biological function, labeling with sYFP enables pH sensing without altering the immobilized enzyme's properties in any of the materials used. Fast response of sYFP to pH change permits evaluation of biochemical kinetics within the solid materials. Thus, pH sensing based on immobilized sYFP represents a broadly applicable technique to the study of biology confined to the internally heterogeneous environment of solid matrices.

Construction of an Immobilized Thermophilic Esterase on Epoxy Support for Poly(ε-caprolactone) Synthesis

Developing an efficient immobilized enzyme is of great significance for improving the operational stability of enzymes in poly(ε-caprolactone) synthesis. In this paper, a thermophilic esterase AFEST from the archaeon Archaeoglobus fulgidus was successfully immobilized on the epoxy support Sepabeads EC-EP via covalent attachment, and the immobilized enzyme was then employed as a biocatalyst for poly(ε-caprolactone) synthesis. The enzyme loading and recovered activity of immobilized enzyme was measured to be 72 mg/g and 10.4 U/mg using p-nitrophenyl caprylate as the substrate at 80 °C, respectively. Through the optimization of reaction conditions (enzyme concentration, temperature, reaction time and medium), poly(ε-caprolactone) was obtained with 100% monomer conversion and low number-average molecular weight (M_n < 1300 g/mol). Further, the immobilized enzyme exhibited excellent reusability, with monomer conversion values exceeding 75% during 15 batch reactions. Finally, poly(ε-caprolactone) was enzymatically synthesized with an isolated yield of 75% and M_n value of 3005 g/mol in a gram-scale reaction.

Highly stable and reusable immobilized formate dehydrogenases: Promising biocatalysts for in situ regeneration of NADH

This study aimed to prepare robust immobilized formate dehydrogenase (FDH) preparations which can be used as effective biocatalysts along with functional oxidoreductases, in which in situ regeneration of NADH is required. For this purpose, Candida methylica FDH was covalently immobilized onto Immobead 150 support (FDHI150), Immobead 150 support modified with ethylenediamine and then activated with glutaraldehyde (FDHIGLU), and Immobead 150 support functionalized with aldehyde groups (FDHIALD). The highest immobilization yield and activity yield were obtained as 90% and 132%, respectively when Immobead 150 functionalized with aldehyde groups was used as support. The half-life times (t_1/2) of free FDH, FDHI150, FDHIGLU and FDHIALD were calculated as 10.6, 28.9, 22.4 and 38.5 h, respectively at 35 °C. FDHI150, FDHIGLU and FDHIALD retained 69, 38 and 51% of their initial activities, respectively after 10 reuses. The results show that the FDHI150, FDHIGLU and FDHIALD offer feasible potentials for in situ regeneration of NADH.