High performance biocatalyst based on β-d-galactosidase immobilized on mesoporous silica/titania/chitosan material

A critical review of enzymes immobilized on chitosan composites: characterization and applications

Enzymes with industrial significance are typically used in biological processes. However, instability, high sensitivity, and impractical recovery are the major drawbacks of enzymes in practical applications. In recent years, the immobilization technology has attracted wide attention to overcoming these restrictions and improving the efficiency of enzyme applications. Chitosan (CS) is a unique functional substance with biocompatibility, biodegradability, non-toxicity, and antibacterial properties. Chitosan composites are anticipated to be widely used in the near future for a variety of purposes, including as supports for enzyme immobilization, because of their advantages. Therefor this review explores the effects of the chitosan's structure, molecular weight, degree of deacetylation on the enzyme immobilized, effect of key factors, and the enzymes immobilized on chitosan based composites for numerous applications, including the fields of biosensor, biomedical science, food industry, environmental protection, and industrial production. Moreover, this study carefully investigates the advantages and disadvantages of using these composites as well as their potential in the future.

Genipin crosslinked porous chitosan beads as robust supports for β-galactosidase immobilization: Characterization, stability, and bioprocessing potential

This study aimed to modify the porosity of chitosan beads using Na2CO3 as a porogen agent and to crosslink them with genipin for the immobilization of β-galactosidase from Aspergillus oryzae. Immobilization was performed under four different pH conditions (4.5, 6.0, 7.5, and 9.0), resulting in biocatalysts named B4, B6, B7, and B9, respectively. The immobilized enzymes were characterized for immobilization parameters and stability, including thermal, pH, storage, and operational stability. The optimal conditions for the support were determined as 50 mM Na2CO3. The biocatalyst exhibited nearly 100 % retention of initial activity after 5 h of incubation at different pH conditions and showed improved thermal stability compared to the free enzyme across all pH conditions. After 50 cycles of lactose hydrolysis, all biocatalysts retained at least 71 % of their initial activity, with B6 retaining nearly 100 %. Scanning electron microscopy revealed structural modifications, particularly in B4, leading to weakened support structure after reuse. Continuous lactose hydrolysis showed increased productivity from 41.3 to 48.1 g L-1 h-1 for B6, with 78.1 % retention of initial capacity. All biocatalysts retained >95 % activity when stored at 4 °C for 20 weeks, highlighting their suitability for enzyme immobilization in continuous and discontinuous bioprocesses.

Advances in Low-Lactose/Lactose-Free Dairy Products and Their Production

With increasing health awareness worldwide, lactose intolerance has become a major concern of consumers, creating new market opportunities for low-lactose/lactose-free dairy foods. In recent years, through innovating processes and technologies, dairy manufacturers have significantly improved the variety, and functional and sensory qualities of low-lactose and lactose-free dairy products. Based on this, this paper first covers the pathology and epidemiology of lactose intolerance and market trends. Then, we focus on current advantages and disadvantages of different lactose hydrolysis technologies and improvements in these technologies to enhance nutritional value, and functional, sensory, and quality properties of lactose-free dairy products. We found that more and more cutting-edge technologies are being applied to the production of lactose-free dairy products, and that these technologies greatly improve the quality and production efficiency of lactose-free dairy products. Hopefully, our review can provide a theoretical basis for the marketing expansion and consumption guidance for low-lactose/lactose-free dairy products.

A novel microbial-derived family 19 endochitinase with exochitinase activity and its immobilization

A novel chitinase gene of 888 bp from Streptomyces bacillaris was cloned and expressed in Escherichia coli BL21. The purified recombinant enzyme (SbChiAJ103) was identified as the first microbial-derived family 19 endochitinase that showed exochitinase activity. SbChiAJ103 exhibited the substrate preference for N-acetylchitooligosaccharides with even degrees of polymerization and the capability to specifically hydrolyze colloidal chitin into (GlcNAc)₂. Mono-methyl adipate was employed as a novel linker for the efficient covalent immobilization of chitinase on magnetic nanoparticles (MNPs). The immobilized SbChiAJ103, SbChiAJ103@MNPs, exhibited superior pH tolerance, temperature stability, and storage stability than free SbChiAJ103. Even after incubation at 45 °C for 24 h, SbChiAJ103@MNPs could retain more than 60.0% initial activity. As a result, the enzymatic hydrolysis yield of SbChiAJ103@MNPs increased to 1.58 times that of free SbChiAJ103. Moreover, SbChiAJ103@MNPs could be reused by convenient magnetic separation. After 10 recycles, SbChiAJ103@MNPs could retain almost 80.0% of its initial activity. The immobilization of the novel chitinase SbChiAJ103 paves the way to the efficient and eco-friendly commercial production of (GlcNAc)₂. KEY POINTS: • The first microbial GH19 endochitinase with exochitinase activity was reported. • Mono-methyl adipate was first employed to immobilize chitinase. • SbChiAJ103@MNPs showed excellent pH stability, thermal stability, and reusability.

Galacto-Oligosaccharide (GOS) Synthesis during Enzymatic Lactose-Free Milk Production: State of the Art and Emerging Opportunities

Much attention has recently been paid to β-Galactosidases (β-D-galactoside galactohidrolase; EC 3.2.1.23), commonly known as lactases, due to the lactose intolerance of the human population and the importance of dairy products in the human diet. This enzyme, produced by microorganisms, is being used in the dairy industry for hydrolyzing the lactose found in milk to produce lactose-free milk (LFM). Conventionally, β-galactosidases catalyze the hydrolysis of lactose to produce glucose and galactose in LFM; however, they can also catalyze transgalactosylation reactions that produce a wide range of galactooligosaccharides (GOS), which are functional prebiotic molecules that confer health benefits to human health. In this field, different works aims to identify novel microbial sources of β-galactosidase for removing lactose from milk with the relative GOS production. Lactase extracted from thermophilic microorganisms seems to be more suitable for the transgalactosylation process at relatively high temperatures, as it inhibits microbial contamination. Different immobilization methods, such as adsorption, covalent attachment, chemical aggregation, entrapment and micro-encapsulation, have been used to synthesize lactose-derived oligosaccharides with immobilized β-galactosidases. In this mini-review, particular emphasis has been given to the immobilization techniques and bioreactor configurations developed for GOS synthesis in milk, in order to provide a more detailed overview of the biocatalytic production of milk oligosaccharides at industrial level.

One-step purification of a recombinant beta-galactosidase using magnetic cellulose as a support: Rapid immobilization and high thermal stability

For the first time, this work reported the one-step purification and targeted immobilization process of a β-galactosidase (Gal) with the Cellulose Binding Domain (CBD) tag, by binding it to different magnetic cellulose supports. The process efficiency after β-galactosidase-CBD immobilization on magnetic cellulose-based supports showed values of approximately 90% for all evaluated enzymatic loads. Compared with free Gal, derivatives showed affinity values between β-galactosidase and the substrate 1.2 × higher in the lactose hydrolysis of milk. β-Galactosidase-CBD's oriented immobilization process on supports increased the thermal stability of the immobilized enzyme by up to 7 × . After 15 cycles of reuse, both enzyme preparations showed a relative hydrolysis percentage of 50% of lactose in milk. The oriented immobilization process developed for purifying recombinant proteins containing the CBD tag enabled the execution of both steps simultaneously and quickly and the obtention of β-galactosidases with promising catalytic characteristics for application in the food and pharmaceutical industries.

Predicting the Conformation of Organic Catalysts Grafted on Silica Surfaces with Different Numbers of Tethering Chains: The Silicopodality Concept

Hybrid catalysts are attracting much attention, since they combine the versatility and efficiency of homogeneous organic catalysis with the robustness and thermal stability of solid materials, for example, mesoporous silica; in addition, they can be used in cascade reactions, for exploring both organic and inorganic catalysis at the same time. Despite the importance of the organic/inorganic interface in these materials, the effect of the grafting architecture on the final conformation of the organic layer (and hence its reactivity) is still largely unexplored. Here, we investigate a series of organosiloxanes comprising a pyridine ring (the catalyst model) and different numbers of alkylsiloxane chains used to anchor it to the MCM-41 surface. The hybrid interfaces are characterized with X-ray powder diffraction, thermogravimetric analyses, Fourier-transform infrared spectroscopy, nuclear magnetic resonance techniques and are modeled theoretically through molecular dynamics (MD) simulations, to determine the relationship between the number of chains and the average position of the pyridine group; MD simulations also provide some insights about temperature and solvent effects.