Pinus residue/pectin-based composite hydrogels for the immobilization of β-D-galactosidase

Enhanced flexibility of high-yield bamboo pulp fibers via cellulase immobilization within guar gum/polyacrylamide/polydopamine interpenetrating network hydrogels

Softness is a crucial criterion in assessing the comfort and usability of tissue paper. Flexible fibers contribute to the softness of the tissue paper by allowing the sheets to conform to the contours of the skin without feeling rough or abrasive. This study focuses on developing innovative CGG/APAM/PDA hydrogels with interpenetrating networks consisting of cationic guar gum, anionic polyacrylamide, and polydopamine for cellulase immobilization, aimed at improving bamboo fiber flexibility. Cellulase biomolecules are efficiently immobilized on CGG/APAM/PDA hydrogels through the Schiff base reaction. Immobilized cellulases have a wider pH applicability than free cellulases, good storage stability, and can maintain high relative activity at relatively high temperatures. The treatment of bamboo fibers with immobilized cellulase results in a significant increase in flexibility, reaching 6.90 × 1014 N·m2, which is 7.18 times higher than that of untreated fibers. The immobilization of cellulases using CGG/APAM/PDA hydrogels as carriers results in a substantial enhancement of storage stability, pH applicability, and inter-fiber bonding strength, as well as the capacity to sustain high relative enzymatic activity at elevated temperatures. The immobilization of cellulase within CGG/APAM/PDA interpenetrating network hydrogels presents a viable strategy for enhancing bamboo fiber flexibility, thereby expanding the accessibility of tissue products.

Immobilization of the β-galactosidase enzyme by encapsulation in polymeric matrices for application in the dairy industry

Lactose intolerance affects approximately 65% of the global adult population, leading to the demand for lactose-free products. The enzyme β-galactosidase (βG) is commonly used in the industry to produce such products, but its recovery after lactose hydrolysis is challenging. In this scenario, the study aims to encapsulate βG within capsules, varying in dimensions and wall materials, to ensure their suitability for efficient industrial recovery. The enzyme βG was encapsulated through ionic gelation using alginate and its blends with pectin, maltodextrin, starch, or whey protein as wall materials. The capsules produced underwent evaluation for encapsulation efficiency, release profiles, activity of the βG enzyme, and the decline in enzyme activity when reused over multiple cycles. Alginate at 5% wt/vol concentrations, alone or combined with polymers such as maltodextrin, starch, or whey protein, achieved encapsulation efficiencies of approximately 98%, 98%, 80%, and 88%, respectively. The corresponding enzyme recovery rates were 34%, 19%, 31%, and 48%. Capsules made with an alginate-pectin blend exhibited no significant hydrolysis and maintained an encapsulation efficiency of 79%. Encapsulation with alginate alone demonstrated on poor retention of enzyme activity, showing a loss of 74% after just 4 cycles of reuse. Conversely, when alginate was mixed with starch or whey protein concentrate, the loss of enzyme activity was less than 40% after 4 reuses. These results highlight the benefits of combining encapsulation materials to improve enzyme recovery and reuse, offering potential economic advantages for the dairy industry.

Stabilization of β-D-galactosidase in solution containing chitosan-based membrane: Central composite rotatable design

β-D-galactosidase is a hydrolase enzyme capable of hydrolyzing lactose in milk-based foods. Its free form can be inactivated in solution during the production of low-dosage lactose foods. Then, it is important to study strategies for avoiding the free enzyme inactivation with the aim of circumventing this problem. The stabilization of β-D-galactosidase in aqueous solution after interactions with chitosan/eucalyptus sawdust composite membrane proved to be a potential strategy when optimized by central composite rotatable (CCR) design. In this case, the best experimental conditions for β-D-galactosidase partitioning and stability in an aqueous medium containing the chitosan-based composite membrane reinforced with eucalyptus sawdust were i) enzyme/buffer solution ratio of 0.0057, ii) pH 5.6, iii) membrane mass of 50 mg, and iv) temperature lower than 37 °C. Significance was found for the linear enzyme/buffer solution ratio, linear temperature, and quadratic pH (p < 0.05) in the interval between 0 and 60 min of study. In the interval between 60 and 120 min, there was significance (p < 0.12) for linear temperature, the temperature-enzyme/buffer solution ratio interaction and the interaction between linear pH and linear enzyme/buffer solution ratio. The Pareto charts and response surfaces clearly showed all the effects of the experimental variables on the stabilization of β-D-galactosidase in solution after interactions with the chitosan composite membrane. In this case, industrial food reactors covered with chitosan/eucalyptus sawdust composite membrane could be a strategy for the hydrolysis of lactose during milk-producing processes.

Protein-polymer bioconjugation, immobilization, and encapsulation: a comparative review towards applicability, functionality, activity, and stability

Polymer-based biomaterials have received a lot of attention due to their biomedical, agricultural, and industrial potential. Soluble protein-polymer bioconjugates, immobilized proteins, and encapsulated proteins have been shown to tune enzymatic activity, improved pharmacokinetic ability, increased chemical and thermal stability, stimuli responsiveness, and introduced protein recovery. Controlled polymerization techniques, increased protein-polymer attachment techniques, improved polymer surface grafting techniques, controlled polymersome self-assembly, and sophisticated characterization methods have been utilized for the development of well-defined polymer-based biomaterials. In this review we aim to provide a brief account of the field, compare these methods for engineering biomaterials, provide future directions for the field, and highlight impacts of these forms of bioconjugation.

Pectin extracted from Premna Microphylla Turcz for preparation of a "sandwich" multi-property sensor film involved with deep eutectic solvent

An acidic deep eutectic solvent (DES, choline chloride/citric acid) was used to efficiently extract edible pectin from Premna microphylla Turcz (PMTP) and further prepare the film sensor with the purpose of "four birds with one stone" with the roles of extractant, coalescent, conductivity promoter and bacteriostatic agent. The optimized extraction process accorded with pseudo second-order kinetics, which was carried out at 78.2 °C for 1.29 h with the solid-liquid ratio of 1:34.66 g/mL with the yield up to 0.8210 g/g. After comprehensive characterizations of pectin product, a simple casting method was used to prepare the PMTP-DES based composite film. It showed that the composite film has promising compatibility, smooth surface, good breathability and ideal homogeneity. After 30 power on/power off cycles at 10 V, it exhibited satisfied conductivity stability. Moreover, the PMTP-DES film could be simply assembled as the flexible visual temperature sensor, with sensitive response at breathing or finger touch; it exhibited the highest sensitivity of 134 %/°C when the external temperature changed from 15 to 55 °C. Besides, the composite film also has preferable antimicrobial activity. The whole results and findings were aimed to contribute for the raw material, composition, preparation, and functions of the existing flexible functional materials.

Modulating the performance of lipase-hydrogel microspheres in a "micro water environment"

In our previous work, we successfully stimulated lipase activity in an anhydrous reaction system using porous polyacrylamide hydrogel microsphere (PPAHM) as a carrier of lipase and free water. However, the effect of the existence state and content of water in lipase-porous polyacrylamide hydrogel microsphere (L-PPAHM) on the interfacial activation remained unclear. In this work, L-PPAHM with different water contents were obtained by water mist rehydration and were used to catalyze the synthesis of conjugated linoleic acid ethyl ester (CLA-EE). The results revealed that there were three existence states of water in L-PPAHM: bound water, semi-bound water and free water, and free water provided the "micro water environment" for the interfacial activation of lipase. The reusability of L-PPAHM with different water contents showed that the activity and stability of L-PPAHM could be achieved by varying the water content of L-PPAHM. The proportion of free water in L-PPAHM increased, and the activity of L-PPAHM increased, but the strength of hydrogen bond interaction between PPAHM and lipase weakened, resulting in the decrease of stability. L-PPAHM with 2/3 of water absorption could ensure sufficient immobilized lipase activity and stability, and its water absorption property could reduce the free water generated during esterification, thus increasing the yield of CLA-EE.

Hydrogen-bonded lipase-hydrogel microspheres for esterification application

Lipase is the most widely used enzyme in industry. Due to its unique "lid" structure, lipase can only show high activity at the oil-water interface, which means that water is needed in the catalytic esterification process. However, the traditional lipase catalytic system cannot effectively control "micro-water" in the esterification environment, resulting in the high content of free water, which hinders the esterification reaction and reduces the yield. In this paper, a promising strategy of esterification catalyzed by polyacrylamide hydrogel immobilized lipase is reported. The porous polyacrylamide hydrogel microspheres (PHM) prepared by inverse emulsion polymerization are used as carrier to adsorb lipase by hydrogen bonding interaction. These hydrogel microspheres provide a "micro-water environment" for lipase in the anhydrous reaction system, and further provide an oil-water interface for "interface activation" of lipase. The obtained lipase-porous polyacrylamide hydrogel microspheres (L-PHMs) exhibit higher temperature and pH stability compared with free lipase, and the optimum enzymatic activity reach 1350 U/g (pH 6, 40 °C). L-PHMs can still remain about 49% of their original activity after 20 reuses. Furthermore, L-PHMs have been successfully applied to catalyze the synthesis of conjugated linoleic acid ethyl ester. The results suggest that this immobilization method opens up a new way for the application of lipase in ester synthesis.

Synthesis of lipase-hydrogel microspheres and their application in deacidification of high-acid rice bran oil

The main challenge of rice bran oil (RBO) as a highly nutritional edible oil is the high content of free fatty acids.

Expanding the Biocatalytic Scope of Enzyme-Loaded Polymeric Hydrogels

In recent years, polymeric hydrogels have appeared promising matrices for enzyme immobilization to design, signify and expand bio-catalysis engineering. Therefore, the development and deployment of polymeric supports in the form of hydrogels and other robust geometries are continuously growing to green the twenty-first-century bio-catalysis. Furthermore, adequately fabricated polymeric hydrogel materials offer numerous advantages that shield pristine enzymes from denaturation under harsh reaction environments. For instance, cross-linking modulation of hydrogels, distinct rheological behavior, tunable surface entities along with elasticity and mesh size, larger surface-volume area, and hydrogels' mechanical cushioning attributes are of supreme interest makes them the ideal candidate for enzyme immobilization. Furthermore, suitable coordination of polymeric hydrogels with requisite enzyme fraction enables pronounced loading, elevated biocatalytic activity, and exceptional stability. Additionally, the unique catalytic harmony of enzyme-loaded polymeric hydrogels offers numerous applications, such as hydrogels as immobilization matrix, bio-catalysis, sensing, detection and monitoring, tissue engineering, wound healing, and drug delivery applications. In this review, we spotlight the applied perspective of enzyme-loaded polymeric hydrogels with recent and relevant examples. The work also signifies the combined use of multienzyme systems and the future directions that should be attempted in this field.

Methylene Blue Release from Chitosan/Pectin and Chitosan/DNA Blend Hydrogels

Chitosan/DNA blend hydrogel (CDB) and chitosan/pectin blend hydrogel (CPB) were synthesized using an emulsion (oil-in-water) technique for the release of methylene blue (model molecule). Both hydrogels were characterized by swelling assays, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), before and after the methylene blue (MB) loading. Higher swelling degrees were determined for both hydrogels in simulated gastric fluid. FT-IR spectra inferred absorption peak changes and shifts after MB loading. The TGA results confirmed changes in the polymer network degradation. The SEM images indicated low porosities on the hydrogel surfaces, with deformed structure of the CPB. Smoother and more uniform surfaces were noticed on the CDB chain after MB loading. Higher MB adsorption capacities were determined at lower initial hydrogel masses and higher initial dye concentrations. The MB adsorption mechanisms on the hydrogel networks were described by the monolayer and multilayer formation. The MB release from hydrogels was studied in simulated gastric and intestinal fluids, at 25 °C and 37 °C, with each process taking place at roughly 6 h. Higher release rates were determined in simulated gastric fluid at 25 °C. The release kinetics of MB in chitosan/DNA and chitosan/pectin matrices follows a pseudo-second-order kinetic mechanism.

Biodegradable gelatin composite hydrogels filled with cellulose for chromium (VI) adsorption from contaminated water

Biopolymers are promising materials for water treatment applications due to their abundance, low cost, expandability, and chemical structure. In this work, gelatin hydrogels filled with cellulose in the form of pristine eucalyptus residues (PER) or treated eucalyptus residues (TER) were prepared for adsorption and chromium removal in contaminated water. PER is a lignocellulosic compound, with cellulose, hemicellulose, and lignin, while TER has cellulose as a major component. FT-Raman Spectroscopy and FTIR analysis confirmed the crosslink reaction with glutaraldehyde and indicated that fillers altered the gelatin molecular vibrations and formed new hydrogen bonds, impacting the hydrogels' crystalline structure. The hydrogen bond energy was altered by the cellulosic fillers' addition and resulted in higher thermal stability (~10 °C). Hydrogels presented a Fickian diffusion, where gelatin hydrogel showed the highest swelling ability (466%), and composites showed lower values with the filler content increase. The chromium adsorption capacity presented values between 12 and 13 mg/g, i.e., featuring an excellent removal capacity which is related with hydrogel crosslinked structure and fibers surface hydroxyl groups, highlighting gelatin hydrogel TER 5% with better removal capacity. The developed hydrogels were produced from biomacromolecules with low-cost and potential application in contaminated water.

Improvement of biodiesel production from palm oil by co-immobilization of Thermomyces lanuginosa lipase and Candida antarctica lipase B: Optimization using response surface methodology

Candida antarctica lipase B (CALB) and Thermomyces lanuginose lipase (TLL) were co-immobilized on epoxy functionalized silica gel via an isocyanide-based multicomponent reaction. The immobilization process was carried out in water (pH 7) at 25 °C, rapidly (3 h) resulting in high immobilization yields (100%) with a loading of 10 mg enzyme/g support. The immobilized preparations were used to produce biodiesel by transesterification of palm oil. In an optimization study, response surface methodology (RSM) and central composite rotatable design (CCRD) methods were used to study the effect of five independent factors including temperature, methanol to oil ratio, t-butanol concentration and CALB:TLL ratio on the yield of biodiesel production. The optimum combinations for the reaction were CALB:TLL ratio (2.1:1), t-butanol (45 wt%), temperature (47 °C), methanol: oil ratio (2.3). This resulted in a FAME yield of 94%, very close to the predicted value of 98%.