β-galactosidase: Biotechnological applications in food processing

Immobilization and characterization of β-galactosidase from Aspergillus oryzae in PVA-CMC hydrogel

Creating new formulations of immobilized enzymes has been a major focus of modern biotechnology. In this study, the industrially significant β-galactosidase was immobilized by being trapped in a polyvinyl alcohol and carboxymethyl cellulose (PVA-CMC) gel. The immobilized enzyme was optimized and characterized, and the results were compared with those obtained using free enzymes. The data show that 40 °C to 50 °C is the ideal temperature range for the enzyme after immobilization. The activity rose, the Vmax value increased from 1.94 U/mg to 6.01 U/mg, and the Km value fell from 4.86 mM to 3.35 mM at pH 5, the optimal pH. β-galactosidases immobilized on PVA-CMC gels exhibited 70 % activity at the end of the fifth week and 50 % activity at the end of the eighth week, depending on the storage stability of the immobilized enzyme. After three reuses, the initial activity of the enzymes decreased, yet the thermal stability of the immobilized enzyme remained superior to that of the free form, retaining 82 % of its initial activity. Thus, it might be claimed that immobilization amplifies the enzyme's catalytic impact. Consequently, it has been discovered that immobilized β-galactosidase exhibits stronger enzymatic characteristics than free β-galactosidase, making it potentially more useful in industrial operations.

Isolation, characterization, and immobilization of β-galactosidase from Klebsiella michiganensis B5582Y for enhanced transgalactosylation

β-Galactosidases are highly desirable in various biotechnological applications. However, research on those obtained from Klebsiella strains has been noticeably restricted. The present investigation centers on the isolation, purification, and characterization of a β-galactosidase enzyme derived from Klebsiella michiganensis (GALB5582Y). Additionally, the study aims to immobilize GALB5582Y onto functionalized graphene oxide (GO)-based polystyrene electrospun nanofibrous membranes (ENMs). The ultimate goal is to enhance the enzyme's transgalactosylation and catalytic efficiency, thereby expanding its range of potential applications. The GALB5582Y gene was sequenced, revealing a 3354 bp sequence that encodes 1024 amino acids. This discovery provides vital information about the gene's structural arrangement. The effectiveness of functionalized graphene oxide (GO)-based engineered nanomaterials (ENMs) in immobilising GALB5582Y was confirmed using SEM, FTIR, and XRD investigations. Significant stability was reported during assessments, with the enzyme activity remaining extended. Additionally, it was shown that the enzyme was efficiently distributed across the surface of the ENM. Although there have been breakthroughs in enzyme production and immobilisation techniques, there is still room for improvement in maximizing the effectiveness of GALB5582Y immobilisation and increasing the yield of galactooligosaccharides (GOS). This calls for additional investigation and refinement.

Structural determinants of cold activity and glucose tolerance of a family 1 glycoside hydrolase (GH1) from Antarctic Marinomonas sp. ef1

Cold-active enzymes support life at low temperatures due to their ability to maintain high activity in the cold and can be useful in several biotechnological applications. Although information on the mechanisms of enzyme cold adaptation is still too limited to devise general rules, it appears that very diverse structural and functional changes are exploited in different protein families and within the same family. In this context, we studied the cold adaptation mechanism and the functional properties of a member of the glycoside hydrolase family 1 (GH1) from the Antarctic bacterium Marinomonas sp. ef1. This enzyme exhibits all typical functional hallmarks of cold adaptation, including high catalytic activity at 5 °C, broad substrate specificity, low thermal stability, and higher lability of the active site compared to the overall structure. Analysis of the here-reported crystal structure (1.8 Å resolution) and molecular dynamics simulations suggest that cold activity and thermolability may be due to a flexible region around the active site (residues 298-331), whereas the dynamic behavior of loops flanking the active site (residues 47-61 and 407-413) may favor enzyme-substrate interactions at the optimal temperature of catalysis (Topt) by tethering together protein regions lining the active site. Stapling of the N-terminus onto the surface of the β-barrel is suggested to partly counterbalance protein flexibility, thus providing a stabilizing effect. The tolerance of the enzyme to glucose and galactose is accounted for by the presence of a "gatekeeping" hydrophobic residue (Leu178), located at the entrance of the active site.

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.

Enzyme stability in polymer hydrogel-enzyme hybrid nanocarrier containing phosphorylcholine group

Enzymes are biological catalysts with good biocompatibility and high efficiency and have been widely used in many fields, such as wastewater treatment, biosensors, and the medical industry. However, their inherently low stability under conditions of practical use limits further applications. Zwitterionic polymers possessing a pair of oppositely charged groups in their repeating units can increase protein stability because of their good biocompatibility and high water content. In this study, zwitterionic copolymer nanogels comprising poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-methacrylic acid-N-hydroxy succinimide ester (MNHS)) (PMS) were synthesized via reversible addition-fragmentation chain-transfer polymerization (RAFT). β-Galactosidase (β-gal) was post-modified within zwitterionic polymer nanogels with a covalently-bound spacer and the activity was compared with that of directly immobilized β-gal and free β-gal. Compared with direct immobilization, covalent immobilization with a spacer could reduce the structural change of β-gal, as confirmed by the circular dichroism spectra. Although the activity of β-gal decreased after immobilization, the hybrids of the β-gal immobilized nanogels, termed hybrid nanogel-enzymes, demonstrated superior stability compared to the free enzymes. The hybrid nanogel-enzymes maintained their function against inactivation by organic solvents and proteinases owing to their high water content, anti-biofouling properties, and limited mass transfer. They can also withstand protein aggregation at high temperatures and maintain their activity. Compared to direct immobilization, immobilization with a spacer resulted in a dramatic increase in the enzyme activity and a slight decrease in the stability. These results indicate that polymer nanogels containing phosphorylcholine units are promising materials for enzyme immobilization, expanding the scope of enzyme applications.

Adsorption features of reduced aminated supports modified with glutaraldehyde: Understanding the heterofunctional features of these supports

Immobilization of enzymes on aminated supports using the glutaraldehyde chemistry may involve three different interactions, cationic, hydrophobic, and covalent interactions. To try to understand the impact this heterofunctionality, we study the physical adsorption of the beta-galactosidase from Aspergillus niger, on aminated supports (MANAE) and aminated supports with one (MANAE-GLU) or two molecules of glutaraldehyde (MANAE-GLU-GLU). To eliminate the chemical reactivity of the glutaraldehyde, the supports were reduced using sodium borohydride. After enzyme adsorption, the release of the enzyme from the supports using different NaCl concentrations, Triton X100, ionic detergents (SDS and CTAB), or different temperatures (4 °C to 55 °C) was studied. Using MANAE support, at 0.3 M NaCl almost all the immobilized enzyme was released. Using MANAE-GLU, 0.3 M, and 0.6 M NaCl similar results were obtained. However, incubation at 1 M or 2 M NaCl, many enzyme molecules were not released from the support. For the MANAE-GLU-GLU support, none of the tested concentrations of NaCl was sufficient to release all enzyme bound to the support. Only using high temperatures, 0.6 M NaCl, and 1 % CTAB or SDS, could the totality of the proteins be released from the support. The results shown in this paper confirm the heterofunctional character of aminated supports modified with glutaraldehyde.

β-Galactosidase: a traditional enzyme given multiple roles through protein engineering

β-Galactosidases are crucial carbohydrate-active enzymes that naturally catalyze the hydrolysis of galactoside bonds in oligo- and disaccharides. These enzymes are commonly used to degrade lactose and produce low-lactose and lactose-free dairy products that are beneficial for lactose-intolerant people. β-galactosidases exhibit transgalactosylation activity, and they have been employed in the synthesis of galactose-containing compounds such as galactooligosaccharides. However, most β-galactosidases have intrinsic limitations, such as low transglycosylation efficiency, significant product inhibition effects, weak thermal stability, and a narrow substrate spectrum, which greatly hinder their applications. Enzyme engineering offers a solution for optimizing their catalytic performance. The study of the enzyme's structure paves the way toward explaining catalytic mechanisms and increasing the efficiency of enzyme engineering. In this review, the structure features of β-galactosidases from different glycosyl hydrolase families and the catalytic mechanisms are summarized in detail to offer guidance for protein engineering. The properties and applications of β-galactosidases are discussed. Additionally, the latest progress in β-galactosidase engineering and the strategies employed are highlighted. Based on the combined analysis of structure information and catalytic mechanisms, the ultimate goal of this review is to furnish a thorough direction for β-galactosidases engineering and promote their application in the food and dairy industries.

Expression and Characterization of a β-Galactosidase from the Pacific Oyster, Crassostrea gigas, and Evaluation of Strategies for Testing Substrate Specificity

β-Galactosidases (EC 3.2.1.23) are exoglycosidases that catalyze the cleavage of glycoconjugates with terminal β-D-galactose residues in β1,3-, β1,4- or β1,6-linkage. Although this family of exoglycosidases has been extensively studied in vertebrates, plants, yeast, and bacteria, little information is available for mollusks. Mollusks are a diverse and highly successful group of animals that play many different roles in their ecosystems, including filter feeders and detritivores. Here, the first β-galactosidase from the Pacific oyster, Crassostrea gigas was discovered, biochemically characterized, and compared to our previously characterized slug enzyme from Arion vulgaris (UniProt Ref. Nr.: A0A0B7AQJ9). Overall, the mussel enzyme showed similar biochemical parameters to the snail enzyme. The enzyme from C. gigas was most active in an acidic environment (pH 3.5) and at a reaction temperature of 50 °C. Optimal storage conditions were up to 37 °C. In contrast to the enzyme from A. vulgaris, the supplementation of cations (Ni2+, Co2+, Mn2+, Mg2+, Ca2+, Cu2+, Ba2+) increased the activity of the enzyme from C. gigas. Substrate specificity studies of the β-galactosidases from the mussel, C. gigas, and the slug, A. vulgaris, revealed activity towards terminal β1,3- and β1,4-linked galactose residues for both enzymes. Using the same substrates in labeled and unlabeled form, we were able to detect the effect of labeling on the β-galactosidase activity using MALDI-TOF MS, HPTLC, and HPLC. While lactose was cleaved by the enzymes in an unlabeled or labeled state, galacto-N-biose was not cleaved as soon as a 2-amino benzoic acid label was added. In this study we present the biochemical characterization of the first recombinantly expressed β-galactosidase from the Pacific oyster, C. gigas, and we compare different analytical methods for the determination of β-galactosidase activity using the enzyme from C. gigas and A. vulgaris.

Involvement of Versatile Bacteria Belonging to the Genus Arthrobacter in Milk and Dairy Products

Milk is naturally a rich source of many essential nutrients; therefore, it is quite a suitable medium for bacterial growth and serves as a reservoir for bacterial contamination. The genus Arthrobacter is a food-related bacterial group commonly present as a contaminant in milk and dairy products as primary and secondary microflora. Arthrobacter bacteria frequently demonstrate the nutritional versatility to degrade different compounds even in extreme environments. As a result of their metabolic diversity, Arthrobacter species have long been of interest to scientists for application in various industry and biotechnology sectors. In the dairy industry, strains from the Arthrobacter genus are part of the microflora of raw milk known as an indicator of hygiene quality. Although they cause spoilage, they are also regarded as important strains responsible for producing fermented milk products, especially cheeses. Several Arthrobacter spp. have reported their significance in the development of cheese color and flavor. Furthermore, based on the data obtained from previous studies about its thermostability, and thermoacidophilic and thermoresistant properties, the genus Arthrobacter promisingly provides advantages for use as a potential producer of β-galactosidases to fulfill commercial requirements as its enzymes allow dairy products to be treated under mild conditions. In light of these beneficial aspects derived from Arthrobacter spp. including pigmentation, flavor formation, and enzyme production, this bacterial genus is potentially important for the dairy industry.

A Review on the Various Sources of β-Galactosidase and Its Lactose Hydrolysis Property

β-Galactosidase is a glycoside hydrolase enzyme that possesses both hydrolytic and transgalactosylation properties and has several benefits and advantages in the food and dairy industries. The catalytic process of β-galactosidase involves the transfer of a sugar residue from a glycosyl donor to an acceptor via a double-displacement mechanism. Hydrolysis prevails when water acts as an acceptor, resulting in the production of lactose-free products. Transgalactosylation prevails when lactose acts as an acceptor, resulting in the production of prebiotic oligosaccharides. β-Galactosidase is also obtained from many sources including bacteria, yeast, fungi, plants, and animals. However, depending on the origin of the β-galactosidase, the monomer composition and their bonds may differ, thereby influencing their properties and prebiotic efficacy. Thus, the increasing demand for prebiotics in the food industry and the search for new oligosaccharides have compelled researchers to search for novel sources of β-galactosidase with diverse properties. In this review, we discuss the properties, catalytic mechanisms, various sources and lactose hydrolysis properties of β-galactosidase.

Sensory Assessment of Bi-Enzymatic-Treated Glucose-Galactose Syrup

There are a variety of ways to make glucose-galactose syrup (GGS) and other products of lactose hydrolysis; therefore, research is still ongoing and will undoubtedly result in improved methods and lower costs. The aim of the study was to use a two-stage fermentation approach to increase the sweetness of glucose-galactose syrup. Comparing lactose hydrolysis with β-galactosidases, the enzyme Ha-Lactase 5200 (K. lactis) showed the highest hydrolysis yield but NOLA™ Fit5500 (B. licheniformis) and GODO-YNL2 (K. lactis) hydrolysis yields varied. After the two-stage fermentation, the syrups from sweet whey permeate had shown the highest sweet taste intensity scores; the sweetest samples were 1NFS and 1HLS with a score of 9.2 and 9.3, respectively. The presence of fructose in the range of 14 ± 3 to 25 ± 1 %, significantly (p < 0.05) increased the sweetness of the syrups. Obtained syrups from whey permeates using enzymes NOLA™ Fit5500 and Ha-Lactase 5200 contained less than 10% lactose. Additionally, results indicate that hydrolysis of lactose and subsequent enhancement of sweetness through glucose isomerisation may provide additional benefits through the production of galacto-oligosaccharides (GOS) in the range of 2 ± 1 to 34 ± 7%.

A Review on Psychrophilic β-D-Galactosidases and Their Potential Applications

The majority of the Earth's ecosystem is frigid and frozen, which permits a vast range of microbial life forms to thrive by triggering physiological responses that allow them to survive in cold and frozen settings. The apparent biotechnology value of these cold-adapted enzymes has been targeted. Enzymes' market size was around USD 6.3 billion in 2017 and will witness growth at around 6.8% CAGR up to 2024 owing to shifting consumer preferences towards packaged and processed foods due to the rising awareness pertaining to food safety and security reported by Global Market Insights (Report ID-GMI 743). Various firms are looking for innovative psychrophilic enzymes in order to construct more effective biochemical pathways with shorter reaction times, use less energy, and are ecologically acceptable. D-Galactosidase catalyzes the hydrolysis of the glycosidic oxygen link between the terminal non-reducing D-galactoside unit and the glycoside molecule. At refrigerated temperature, the stable structure of psychrophile enzymes adjusts for the reduced kinetic energy. It may be beneficial in a wide variety of activities such as pasteurization of food, conversion of biomass, biological role of biomolecules, ambient biosensors, and phytoremediation. Recently, psychrophile enzymes are also used in claning the contact lens. β-D-Galactosidases have been identified and extracted from yeasts, fungi, bacteria, and plants. Conventional (hydrolyzing activity) and nonconventional (non-hydrolytic activity) applications are available for these enzymes due to its transgalactosylation activity which produce high value-added oligosaccharides. This review content will offer new perspectives on cold-active β-galactosidases, their source, structure, stability, and application.

Identification, Characterization, and Expression of a β-Galactosidase from Arion Species (Mollusca)

β-Galactosidases (β-Gal, EC 3.2.1.23) catalyze the cleavage of terminal non-reducing β-D-galactose residues or transglycosylation reactions yielding galacto-oligosaccharides. In this study, we present the isolation and characterization of a β-galactosidase from Arion lusitanicus, and based on this, the cloning and expression of a putative β-galactosidase from Arion vulgaris (A0A0B7AQJ9) in Sf9 cells. The entire gene codes for a protein consisting of 661 amino acids, comprising a putative signal peptide and an active domain. Specificity studies show exo- and endo-cleavage activity for galactose β1,4-linkages. Both enzymes, the recombinant from A. vulgaris and the native from A. lusitanicus, display similar biochemical parameters. Both β-galactosidases are most active in acidic environments ranging from pH 3.5 to 4.5, and do not depend on metal ions. The ideal reaction temperature is 50 °C. Long-term storage is possible up to +4 °C for the A. vulgaris enzyme, and up to +20 °C for the A. lusitanicus enzyme. This is the first report of the expression and characterization of a mollusk exoglycosidase.

Use of soil actinomycetes for pharmaceutical, food, agricultural, and environmental purposes

In this article, we reviewed the international scientific production of the last years on actinomycetes isolated from soil aiming to report recent advances in using these microorganisms for different applications. The most promising genera, isolation conditions and procedures, pH, temperature, and NaCl tolerance of these bacteria were reported. Based on the content analysis of the articles, most studies have focused on the isolation and taxonomic description of new species of actinomycetes. Regarding the applications, the antimicrobial potential (antibacterial and antifungal) prevailed among the articles, followed by the production of enzymes (cellulases and chitinases, etc.), agricultural uses (plant growth promotion and phytopathogen control), bioremediation (organic and inorganic contaminants), among others. Furthermore, a wide range of growth capacity was verified, including temperatures from 4 to 60 °C (optimum: 28 °C), pH from 3 to 13 (optimum: 7), and NaCl tolerance up to 32% (optimum: 0-1%), which evidence a great tolerance for actinomycetes cultivation. Streptomyces was the genus with the highest incidence among the soil actinomycetes and the most exploited for different uses. Besides, the interest in isolating actinomycetes from soils in extreme environments (Antarctica and deserts, for example) is growing to explore the adaptive capacities of new strains and the secondary metabolites produced by these microorganisms for different industrial interests, especially for pharmaceutical, food, agricultural, and environmental purposes.

An acid-tolerant and cold-active β-galactosidase potentially suitable to process milk and whey samples

A novel β-galactosidase gene (gal_M) was cloned from an aquatic habitat metagenome. The analysis of its translated sequence (Gal_M) revealed its phylogenetic closeness towards Verrucomicrobia sp. The sequence comparison and homology structure analysis designated it a member of GH42 family. The three-dimensional homology model of Gal_M depicted a typical (β/α)8 TIM-barrel containing the catalytic core. The gene (gal_M) was expressed in a heterologous host, Escherichia coli, and the purified protein (Gal_M) was subjected to biochemical characterization. It displayed β-galactosidase activity in a wide range of pH (2.0 to 9.0) and temperature (4 to 60 °C). The heat exposed protein showed considerable stability at 40 and 50 °C, with the half-life of about 100 h and 35 h, respectively. The presence of Na, Mg, K, Ca, and Mn metals was favorable to the catalytic efficiency of Gal_M, which is a desirable catalytic feature, as these metals exist in milk. It showed remarkable tolerance of glucose and galactose in the reaction. Furthermore, Gal_M discerned transglycosylation activity that is useful in galacto-oligosaccharides' production. These biochemical properties specify the suitability of this biocatalyst for milk and whey processing applications. KEY POINTS: • A novel β-galactosidase gene was identified and characterized from an aquatic habitat. • It was active in extreme acidic to mild alkaline pH and at cold to moderate temperatures. • The β-galactosidase was capable to hydrolyze lactose in milk and whey.

Engineering the optimum pH of β-galactosidase from Aspergillus oryzae for efficient hydrolysis of lactose

β-Galactosidase (lacA) from Aspergillus oryzae is widely used in the dairy industry. Its acidic pH optimum and severe product inhibition limit its application for lactose hydrolysis in milk. In the present study, structure-based sequence alignment was conducted to determine the candidate mutations to shift the pH optimum of lacA to the neutral range. The Y138F and Y364F mutants shifted the pH optimum of lacA from 4.5 to 5.5 and 6.0, respectively. The acid dissociation constant (pKa) values of catalytic acid/base residues with upwards shift were consistent with the increased pH optimum. All variants in the present study also alleviated galactose inhibition to various extents. Molecular dynamics demonstrated that the less rigid tertiary structures and lower galactose-binding free energy of Y138F and Y364F might facilitate the release of the end product. Both Y138F and Y364F mutants exhibited better hydrolytic ability than lacA in milk lactose hydrolysis. The higher pH optimum and lower galactose inhibition of Y138F and Y364F may explain their superiority over lacA. The Y138F and Y364F mutants in the present study showed potential in producing low-lactose milk, and our studies provide a novel strategy for engineering the pH optimum of glycoside hydrolase.

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.

A Comparative Analysis of Weizmannia coagulans Genomes Unravels the Genetic Potential for Biotechnological Applications

The production of biochemicals requires the use of microbial strains with efficient substrate conversion and excellent environmental robustness, such as Weizmannia coagulans species. So far, the genomes of 47 strains have been sequenced. Herein, we report a comparative genomic analysis of nine strains on the full repertoire of Carbohydrate-Active enZymes (CAZymes), secretion systems, and resistance mechanisms to environmental challenges. Moreover, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) immune system along with CRISPR-associated (Cas) genes, was also analyzed. Overall, this study expands our understanding of the strain's genomic diversity of W. coagulans to fully exploit its potential in biotechnological applications.

Characterization of a halotolerant GH2 family β-galactosidase GalM from Microvirga sp. strain MC18

A new glycoside hydrolase family 2 (GH2) β-galactosidase encoding gene galM was cloned from Microvirga sp. strain MC18 and overexpressed in Escherichia coli. The recombinant β-galactosidase GalM showed optimal activity at pH 7.0 and 50 °C, with a stability at pH 6.0-9.0 and 20-40 °C, which are conditions suitable for the diary environment. The K_m and V_max values for o-nitrophenyl-β-d-galactopyranoside (oNPG) were 1.30 mmol/L and 15.974 μmol/(min·mg), respectively. GalM showed low product inhibition by galactose with a K_i of 73.18 mM and high tolerance for glucose that 86.5% activity retained in the presence of 500 mM glucose. It was also stable and active in 20% of methanol, ethanol and isopropanol. In addition, the enzyme activity of GalM was activated significantly over 0-2 mol/L NaCl (1.6-4.3 fold). These favorable properties make GalM a potential candidate for the industrial application.

Advances in solid-state fermentation for bioconversion of agricultural wastes to value-added products: Opportunities and challenges

The increase in solid waste has become a common problem and causes environmental pollution worldwide. A green approach to valorise solid waste for sustainable development is required. Agricultural residues are considered suitable for conversion into profitable products through solid-state fermentation (SSF). Agricultural wastes have high organic content that is used as potential substrates to produce value-added products through SSF. The importance of process variables used in solid-phase fermentation is described. The applications of SSF developed products in the food industry as flavouring agents, acidifiers, preservatives and flavour enhancers. SSF produces secondary metabolites and essential enzymes. Wastes from agricultural residues are used as bioremediation agents, biofuels and biocontrol agents through microbial processing. In this review paper, the value addition of agricultural wastes by SSF through green processing is discussed with the current knowledge on the scenarios, sustainability opportunities and future directions of a circular economy for solid waste utilisation.

β-Galactosidase from Kluyveromyces lactis: Characterization, production, immobilization and applications - A review

A review on the enzyme β-galactosidase from Kluyveromyces lactis is presented, from the perspective of its structure and mechanisms of action, the main catalyzed reactions, the key factors influencing its activity, and selectivity, as well as the main techniques used for improving the biocatalyst functionality. Particular attention was given to the discussion of hydrolysis, transglycosylation, and galactosylation reactions, which are commonly mediated by this enzyme. In addition, the products generated from these processes were highlighted. Finally, biocatalyst improvement techniques are also discussed, such as enzyme immobilization and protein engineering. On these topics, the most recent immobilization strategies are presented, emphasizing processes that not only allow the recovery of the biocatalyst but also deliver enzymes that show better resistance to high temperatures, chemicals, and inhibitors. In addition, genetic engineering techniques to improve the catalytic properties of the β-galactosidases were reported. This review gathers information to allow the development of biocatalysts based on the β-galactosidase enzyme from K. lactis, aiming to improve existing bioprocesses or develop new ones.

Engineering of a β-galactosidase from Bacillus coagulans to relieve product inhibition and improve hydrolysis performance

Most β-galactosidases reported are sensitive to the end product (galactose), making it the rate-limiting component for the efficient degradation of lactose through the enzymatic route. Therefore, there is ongoing interest in searching for galactose-tolerant β-galactosidases. In the present study, the predicted galactose-binding residues of β-galactosidase from Bacillus coagulans, which were determined by molecular docking, were selected for alanine substitution. The asparagine residue at position 148 (N148) is correlated with the reduction of galactose inhibition. Saturation mutations revealed that the N148C, N148D, N148S, and N148G mutants exhibited weaker galactose inhibition effects. The N148D mutant was used for lactose hydrolysis and exhibited a higher hydrolytic rate. Molecular dynamics revealed that the root mean square deviation and gyration radius of the N148D-galactose complex were higher than those of wild-type enzyme-galactose complex. In addition, the N148D mutant had a higher absolute binding free-energy value. All these factors may lead to a lower affinity between galactose and the mutant enzyme. The use of mutant enzyme may have potential value in lactose hydrolysis.

Challenges and perspectives of the β-galactosidase enzyme

The enzyme β-galactosidase has great potential for application in the food and pharmaceutical industries due to its ability to perform the hydrolysis of lactose, a disaccharide present in milk and in dairy by-products. It can be used in free form, in batch processes, or in immobilized form, which allows continuous operation and provides greater enzymatic stability. The choice of method and support for enzyme immobilization is essential, as the performance of the biocatalyst is strongly influenced by the properties of the material used and by the interaction mechanisms between support and enzyme. Therefore, this review showed the main enzyme immobilization techniques, and the most used supports for the constitution of biocatalysts. Also, materials with the potential for immobilization of β-galactosidases and the importance of their biotechnological application are presented. KEY POINTS: • The main methods of immobilization are physical adsorption, covalent bonding, and crosslinking. • The structural conditions of the supports are determining factors in the performance of the biocatalysts. • Enzymatic hydrolysis plays an important role in the biotechnology industry.

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

A new support for the immobilization of β-d-galactosidase from Kluyveromyces lactis was developed, consisting of mesoporous silica/titania with a chitosan coating. This support presents a high available surface area and adequate pore size for optimizing the immobilization efficiency of the enzyme and, furthermore, maintaining its activity. The obtained supported biocatalyst was applied in enzyme hydrolytic activity tests with o-NPG, showing high activity 1223 Ug^-1, excellent efficiency (74%), and activity recovery (54%). Tests of lactose hydrolysis in a continuous flow reactor showed that during 14 days operation, the biocatalyst maintained full enzymatic activity. In a batch system, after 15 cycles, it retained approximately 90% of its initial catalytic activity and attained full conversion of the lactose 100% (±12%). Additionally, with the use of the mesoporous silica/titania support, the biocatalyst presented no deformation and fragmentation, in both systems, demonstrating high operational stability and appropriate properties for applications in food manufacturing.

Immobilization of β-galactosidase by halloysite-adsorption and entrapment in a cellulose nanocrystals matrix

BACKGROUND

Immobilization allows easy recovery and reuse of enzymes in industrial processes. In addition, it may enhance enzyme stability, allowing prolonged use. A simple and novel method of immobilizing β-galactosidase is reported. Effects of immobilization on the enzyme characteristics are explained. β-Galactosidase is well established in dairy processing and has emerging applications in novel syntheses.

METHODS

β-Galactosidase was immobilized by physical adsorption on halloysite, an aluminosilicate nanomaterial. Optimal conditions for adsorption were identified. The optimally prepared halloysite-adsorbed enzyme was then entrapped in a porous matrix of nanocrystals of sulfated bacterial cellulose, to further enhance stability.

RESULTS

Under optimal conditions, 89.5% of the available protein was adsorbed per mg of halloysite. The most active and stable final immobilized biocatalyst had 1 part by mass of the enzyme-supporting halloysite particles mixed with 2 parts of cellulose nanocrystals. Immobilization raised the optimal pH of the catalyst to 7.5 (from 6.0 for the native enzyme) and temperature to 55 °C (40 °C for the native enzyme). During storage at 25 °C, the immobilized enzyme retained 75.8% of initial activity after 60 days compared to 29.2% retained by the free enzyme.

CONCLUSION

The immobilization method developed in this work enhanced enzyme stability during catalysis and storage. Up to 12 cycles of repeated use of the catalyst became feasible.

GENERAL SIGNIFICANCE

The simple and rapid immobilization strategy of this work is broadly applicable to enzymes used in diverse bioconversions.

β-Galactosidase: From its source and applications to its recombinant form

Carbohydrate-active enzymes are a group of important enzymes playing a critical role in the degradation and synthesis of carbohydrates. Glycosidases can hydrolyze glycosides into oligosaccharides, polysaccharides, and glycoconjugates via a cost-effective approach. Lactase is an important member of β-glycosidases found in higher plants, animals, and microorganisms. β-Galactosidases can be used to degrade the milk lactose for making lactose-free milk, which is sweeter than regular milk and is suitable for lactose-intolerant people. β-Galactosidase is employed by many food industries to degrade lactose and improve the digestibility, sweetness, solubility, and flavor of dairy products. β-Galactosidase enzymes have various families and are applied in the food-processing industries such as hydrolyzed-milk products, whey, and galactooligosaccharides. Thus, this enzyme is a valuable protein which is now produced by recombinant technology. In this review, origins, structure, recombinant production, and critical modifications of β-galactosidase for improving the production process are discussed. Since β-galactosidase is a valuable enzyme in industry and health care, a study of its various aspects is important in industrial biotechnology and applied biochemistry.

Cold-Active β-Galactosidases: Insight into Cold Adaption Mechanisms and Biotechnological Exploitation

β-galactosidases (EC 3.2.1.23) catalyze the hydrolysis of β-galactosidic bonds in oligosaccharides and, under certain conditions, transfer a sugar moiety from a glycosyl donor to an acceptor. Cold-active β-galactosidases are identified in microorganisms endemic to permanently low-temperature environments. While mesophilic β-galactosidases are broadly studied and employed for biotechnological purposes, the cold-active enzymes are still scarcely explored, although they may prove very useful in biotechnological processes at low temperature. This review covers several issues related to cold-active β-galactosidases, including their classification, structure and molecular mechanisms of cold adaptation. Moreover, their applications are discussed, focusing on the production of lactose-free dairy products as well as on the valorization of cheese whey and the synthesis of glycosyl building blocks for the food, cosmetic and pharmaceutical industries.

Magnetic graphene oxide nanocomposites as an effective support for lactase immobilization with improved stability and enhanced photothermal enzymatic activity

Magnetic graphene oxide-immobilized lactase with high loading capacity, improved stabilities, and photothermal enhancement of activity has been reported.

The Biotechnological Potentials of Bacteria Isolated from Parsık Cave, Turkey : Measuring the enzyme profiles, antibiotic resistance and antimicrobial activity in bacteria

Since cave ecosystems have extraordinary environmental conditions, these ecosystems offer opportunities for microbiological studies. In this study, cultivable bacteria isolated from Parsık cave, Turkey, were investigated regarding enzyme profiles, antibiotic resistance and potential for production of antimicrobial agents. The metabolic properties of 321 bacterial isolates were determined. The most produced enzyme by the isolates was found to be tyrosine arylamidase. The enzymatic reactions of the bacteria showed that Parsık cave isolates have high aminopeptidase activity. The highest antibiotic resistance frequency of the isolates was 38.6% against ampicillin. While the isolates displayed variable inhibition rates against tested pathogenic microorganisms, they showed the highest inhibition against Candida albicans. The results show that the bacteria isolated from Parsık cave have potential for further studies related to biotechnological applications. The study findings contribute increased knowledge on metabolic peculiarities of bacteria isolated from cave ecosystems.

Production of β-galactosidase by Trichoderma sp. through solid-state fermentation targeting the recovery of galactooligosaccharides from whey cheese

AIMS

Optimization of β-galactosidase production by Trichoderma sp. under solid-state fermentation using wheat bran as solid substrate through an experimental design and its application targeting the recovery of galactooligosaccharides (GOS) from whey cheese.

METHODS AND RESULTS

The β-galactosidase production by Trichoderma sp. increased 2·3-fold (2·67 U g^-1 of substrate) culturing the fungus at 30°C for 187 h, at an inoculum of 10⁵ spores per ml, and a 1 : 1·65 (w/v) ratio of wheat bran to tap water. The best enzyme activity was obtained at 55°C and pH 4·5. The catalytic activity was maintained for up to 180 min incubating at 35-45°C, and above 50% at acidic or alkaline pH for up to 24 h. It also presented resistance to chemical compounds. β-galactosidase catalysed the hydrolysis of the lactose and the transgalactosylation reaction leading to the production of GOS.

CONCLUSION

Trichoderma sp. produced β-galactosidase with transgalactosylation activity that may be used to recover GOS, products with high added value, from whey cheese.

SIGNIFICANCE AND IMPACT OF THE STUDY

β-galactosidases are used in different industrial sectors. Therefore, the Trichoderma β-galactosidase is a promising alternative for the production of GOS as prebiotic from the dairy effluents, contributing to the reduction in the environmental impact.

Forty years of study on the thermostable β-glycosidase from S. solfataricus: Production, biochemical characterization and biotechnological applications

The aim of this paper is to make the point on the fortieth years study on the β-glycosidase from Sulfolobus solfataricus. This enzyme represents one of the thermophilic biocatalysts, which is more extensively studied as witnessed by the numerous literature reports available since 1980. Comprehensive biochemical studies highlighted its broad substrate specificity for β-d-galacto-, gluco-, and fuco-sides and also showed its remarkable exo-glucosidase and transglycosidase activities. The enzyme demonstrated to be active and stable over a wide range of temperature and pHs, withstanding to several drastic conditions comprising solvents and detergents. Over the years, a great deal of studies were focused on its homotetrameric tridimensional structure, elucidating several structural features involved in the enzyme stability, such as ion pairs and post-translational modifications. Several β-glycosidase mutants were produced in the years in order to understand its peculiar behavior in extreme conditions and/or to improve its functional properties. The β-glycosidase overproduction was also afforded reporting numerous studies dealing with its production in the mesophilic host Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, and Lactococcus lactis. Relevant applications in food, beverages, bioenergy, pharmaceuticals, and nutraceutical fields of this enzyme, both in free and immobilized forms, highlighted its biotechnological relevance.

Prebiotic galactooligosaccharides production from lactose and lactulose by Lactobacillus delbrueckii subsp. bulgaricus CRL450

Galactooligosaccharides (GOS) are useful dietary ingredients recognized worldwide as prebiotics.

Modular Molecular Nanoplastics

In view of their facile fabrication and recycling, functional materials that are built from small molecules ("molecular plastics") may represent a cost-efficient and sustainable alternative to conventional covalent materials. We show how molecular plastics can be made robust and how their (nano)structure can be tuned via modular construction. For this purpose, we employed binary composites of organic nanocrystals based on a perylene diimide derivative, with graphene oxide (GO), bentonite nanoclay (NC), or hydroxyethyl cellulose (HEC), that both reinforce and enable tailoring the properties of the membranes. The hybrids are prepared via a simple aqueous deposition method, exhibit enhanced mechanical robustness, and can be recycled. We utilized these properties to create separation membranes with tunable porosity that are easy to fabricate and recycle. Hybrids 1/HEC and 1/NC are capable of ultrafiltration, and 1/NC removes heavy metals from water with high efficiency. Hybrid 1/GO shows mechanical properties akin to covalent materials with just 2-10% (by weight) of GO. This hybrid was used as a membrane for immobilizing β-galactosidase that demonstrated long and stable biocatalytic activity. Our findings demonstrate the utility of modular molecular nanoplastics as robust and sustainable materials that enable efficient tuning of structure and function and are based on self-assembly of readily available inexpensive components.

Genome Insights into the Novel Species Microvirga brassicacearum, a Rapeseed Endophyte with Biotechnological Potential

Plants harbor a diversity of microorganisms constituting the plant microbiome. Many bioinoculants for agricultural crops have been isolated from plants. Nevertheless, plants are an underexplored niche for the isolation of microorganisms with other biotechnological applications. As a part of a collection of canola endophytes, we isolated strain CDVBN77^T. Its genome sequence shows not only plant growth-promoting (PGP) mechanisms, but also genetic machinery to produce secondary metabolites, with potential applications in the pharmaceutical industry, and to synthesize hydrolytic enzymes, with potential applications in biomass degradation industries. Phylogenetic analysis of the 16S rRNA gene of strain CDVBN77^T shows that it belongs to the genus Microvirga, its closest related species being M. aerophila DSM 21344^T (97.64% similarity) and M. flavescens c27j1^T (97.50% similarity). It contains ubiquinone 10 as the predominant quinone, C19:0 cycloω8c and summed feature 8 as the major fatty acids, and phosphatidylcholine and phosphatidylethanolamine as the most abundant polar lipids. Its genomic DNA G+C content is 62.3 (mol %). Based on phylogenetic, chemotaxonomic, and phenotypic analyses, we suggest the classification of strain CDVBN77^T within a new species of the genus Microvirga and propose the name Microvirga brassicacearum sp. nov. (type strain CDVBN77^T = CECT 9905^T = LMG 31419^T).

Small-molecule fluorescent probes for specific detection and imaging of chemical species inside lysosomes

In the past few years, the preparation of novel small-molecule fluorescent probes for specific detection and imaging of chemical species inside lysosomes has attracted considerable attention because of their wide applications in chemistry, biology, and medical science. This feature article summarizes the recent advances in the design and preparation of small-molecule fluorescent probes for specific detection of chemical species inside lysosomes. In addition, their properties and applications for the detection and imaging of pH, H2O2, HOCl, O2˙-, lipid peroxidation, H2S, HSO3-, thiols, NO, ONOO-, HNO, Zn2+, Cu2+, enzymes, etc. in lysosomes are discussed as well.