A new bioprocess for the production of prebiotic lactosucrose by an immobilized β-galactosidase

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

Lactose intolerance affects ∼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 ∼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.

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.

Application of electrospun chitosan-based nanofibers as immobilization matrix for biomolecules

Nanofiber meshes from electrospun chitosan, highly modified with biotin and arylazides, are well-suited for application as enzyme immobilization matrices. To test this, catalytically active biomolecules were immobilized onto photocrosslinked nanofibrous nonwovens consisting mainly of biotinylated fungal chitosan and a small amount (10 w%) of poly ethylene oxide. In this study, we show that over 10 μg eugenol oxidase per milligram dry polymer matrix can be loaded on UV-crosslinked chitosan nanofibers. We further demonstrate that bound enzyme activity can be fully retained for over 7 days of storage at ambient conditions in aqueous buffer. Samples loaded at maximum enzyme carrying capacity were tested in a custom-made plug-flow reactor system with online UV-VIS spectroscopy for activity determination. High wettability and durability of the hydrophilic chitosan support matrix enabled continuous oxidation of model substrate vanillyl alcohol into vanillin with constant turnover at flow rates of up to 0.24 L/h for over 6 h. This proves the above hypothesis and enables further application of the fibers as stacked microfluidic membranes, biosensors, or structural starting points for affinity crosslinked enzyme gels. KEY POINTS: • Biotinylated chitosan-based nanofibers retain enzymes via mild affinity interactions • Immobilized eugenol oxidase shows high activity and resists continuous washing • Nanofiber matrix material tolerated high flow rates in a continuous-flow setup.

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.

Gene Expression, Structural Characterization, and Functional Properties of Exopolysaccharide Produced from Potential Probiotic Enterococcus faecalis NOC219 Strain

This study aimed to reveal the structural characterization and functional properties of microbial EPS-NOC219 material produced by the Enterococcus faecalis NOC219 strain with high EPS yield isolated from yogurt, with simultaneously, demonstrating the potential of this EPS for future industrial applications. According to the results of the analyses made for this aim, it was determined that the NOC219 strain contains the epsB, p-gtf-epsEFG, and p-gtf-P1 genes. In addition, it was also revealed that the EPS-NOC219 structure is expressed by the epsB, p-gtf-epsEFG, and p-gtf-P1 genes and has a heteropolymeric feature consisting of glucose, galactose, and fructose units. According to the results of the analyses made for this aim, it was determined that the EPS-NOC219 structure, which was produced from the NOC219 strain containing the epsB, p-gtf-epsEFG, and p-gtf-P1 genes, had a heteropolymeric structure consisting of glucose, galactose, and fructose units. On the other hand, it was shown that this structure had a thickener property, high heat stability exhibited a pseudoplastic flow behavior, and had a high melting point. This showed that the EPS-NOC219 had high heat stability and could be used as a thickener in heat treatment processes. In addition, it was revealed that it is suitable for plasticized biofilm production. On the other hand, the bioavailability of this structure was demonstrated with its high antioxidant activity (55.84%) against DPPH radicals and high antibiofilm activity against Escherichia coli (77.83%) and Listeria monocytogenes (72.14%) pathogens. These results suggest that the EPS-NOC219 structure may be an alternative natural resource for many industries as it has strong physicochemical properties and a healthy food-grade adjunct.

Investigation of biocatalytic production of lactosucrose and fructooligosaccharides using levansucrases and dairy by-products as starting materials

Selected levansucrases (LSs) were investigated for their ability to catalyze the transfructosylation of lactose/sucrose into lactosucrose and fructooligosaccharides (FOSs). Additionally, dairy by-products, including whey permeate (WP) and milk permeate (MP), were assessed for their effectiveness as lactose sources. LSs from Gluconobacter oxydans (LS1), Vibrio natriegens (LS2), Novosphingobium aromaticivorans (LS3), and Burkholderia graminis (LS4) were utilized in three transfructosylation reactions that combined sucrose with either lactose, WP, or MP. All LSs demonstrated a higher transfructosylation activity than hydrolytic one, except for V. natriegens LS2 in the presence of sucrose and MP/sucrose. Furthermore, the bioconversion efficiency of lactose/sucrose into lactosucrose and FOSs exhibited varying time courses and end-product profiles. Both the acceptor specificity of LS and the thermodynamic equilibrium of its reaction modulated the end-product profile. V. natriegens LS2 resulted in the highest lactosucrose production of 328 and 251 g/L with lactose/sucrose and WP/sucrose, respectively. Our results revealed the potential of LS-catalyzed transfructosylation for the biocatalytic production of both lactosucrose and FOSs from abundant biomasses.

Recent trends in the biotechnology of functional non-digestible oligosaccharides with prebiotic potential

Prebiotics as a part of dietary nutrition can play a crucial role in structuring the composition and metabolic function of intestinal microbiota and can thus help in managing a clinical scenario by preventing diseases and/or improving health. Among the different prebiotics, non-digestible carbohydrates are molecules that selectively enrich a typical class of bacteria with probiotic potential. This review summarizes the current knowledge about the different aspects of prebiotics, such as its production, characterization and purification by various techniques, and its link to novel product development at an industrial scale for wide-scale use in diverse range of health management applications. Furthermore, the path to effective valorization of agricultural residues in prebiotic production has been elucidated. This review also discusses the recent developments in application of genomic tools in the area of prebiotics for providing new insights into the taxonomic characterization of gut microorganisms, and exploring their functional metabolic pathways for enzyme synthesis. However, the information regarding the cumulative effect of prebiotics with beneficial bacteria, their colonization and its direct influence through altered metabolic profile is still getting established. The future of this area lies in the designing of clinical condition specific functional foods taking into consideration the host genotypes, thus facilitating the creation of balanced and required metabolome and enabling to maintain the healthy status of the host.

Sources, Processing-Related Transformation, and Gut Axis Regulation of Conventional and Potential Prebiotics

One strategy to achieve a balanced intestinal microbiota is to introduce prebiotics. Some substances present in the diet, such as soybean extracts, koji glycosylceramides, grape extracts, tea polyphenols, and seaweed extracts, can be considered as potential prebiotics, because they can selectively stimulate the proliferation of beneficial bacteria in the intestine. However, the discovery of novel prebiotics also involves advances in screening methods and the use of thermal and non-thermal processing techniques to modify and enhance the properties of beneficial organisms. The health benefits of prebiotics are also reflected by their participation in regulating the microbiota in different gut axes. In the present review, we introduced the field of prebiotics, focusing on potential prebiotic substances, the process of screening potential prebiotics, the transformation of prebiotics by food-processing technologies, and the roles of prebiotics on gut axis regulation, which, it is hoped, will promote the discovery and utilization of novel prebiotics.

Trends in lactose-derived bioactives: synthesis and purification

Lactose obtained from cheese whey is a low value commodity despite its great potential as raw material for the production of bioactive compounds. Among them, prebiotics stand out as valuable ingredients to be added to food matrices to build up functional foods, which currently represent the most active sector within the food industry. Functional foods market has been growing steadily in the recent decades along with the increasing awareness of the World population about healthy nutrition, and this is having a strong impact on lactose-derived bioactives. Most of them are produced by enzyme biocatalysis because of molecular precision and environmental sustainability considerations. The current status and outlook of the production of lactose-derived bioactive compounds is presented with special emphasis on downstream operations which are critical because of the rather modest lactose conversion and product yields that are attainable. Even though some of these products have already an established market, there are still several challenges referring to the need of developing better catalysts and more cost-effective downstream operations for delivering high quality products at affordable prices. This technological push is expected to broaden the spectrum of lactose-derived bioactive compounds to be produced at industrial scale in the near future.

Graphical abstract

Construction and Analysis of Food-Grade Lactobacillus kefiranofaciens β-Galactosidase Overexpression System

Lactobacillus kefiranofaciens contains two types of β-galactosidase, LacLM and LacZ, belonging to different glycoside hydrolase families. The difference in function between them has been unclear so far for practical application. In this study, LacLM and LacZ from L. kefiranofaciens ATCC51647 were cloned into constitutive lactobacillal expression vector pMG36e, respectively. Furtherly, pMG36n-lacs was constructed from pMG36e-lacs by replacing erythromycin with nisin as selective marker for food-grade expressing systems in Lactobacillus plantarum WCFS1, designated recombinant LacLM and LacZ respectively. The results from hydrolysis of o-nitrophenyl-β-galactopyranoside (ONPG) showed that the β-galactosidases activity of the recombinant LacLM and LacZ was 1460% and 670% higher than that of the original L. kefiranofaciens. Moreover, the lactose hydrolytic activity of recombinant LacLM was higher than that of LacZ in milk. Nevertheless, compare to LacZ, in 25% lactose solution the galacto-oligosaccharides (GOS) production of recombinant LacLM was lower. Therefore, two β-galactopyranosides could play different roles in carbohydrate metabolism of L. kefiranofaciens. In addition, the maximal growth rate of two recombinant strains were evaluated with different temperature level and nisin concentration in fermentation assay for practical purpose. The results displayed that 37°C and 20-40 U/ml nisin were the optimal fermentation conditions for the growth of recombinant β-galactosidase strains. Altogether the food-grade Expression system of recombinant β-galactosidase was feasible for applications in the food and dairy 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.

β-Galactosidase-Producing Isolates in Mucoromycota: Screening, Enzyme Production, and Applications for Functional Oligosaccharide Synthesis

β-Galactosidases of Mucoromycota are rarely studied, although this group of filamentous fungi is an excellent source of many industrial enzymes. In this study, 99 isolates from the genera Lichtheimia, Mortierella, Mucor, Rhizomucor, Rhizopus and Umbelopsis, were screened for their β-galactosidase activity using a chromogenic agar approach. Ten isolates from the best producers were selected, and the activity was further investigated in submerged (SmF) and solid-state (SSF) fermentation systems containing lactose and/or wheat bran substrates as enzyme production inducers. Wheat bran proved to be efficient for the enzyme production under both SmF and SSF conditions, giving maximum specific activity yields from 32 to 12,064 U/mg protein and from 783 to 22,720 U/mg protein, respectively. Oligosaccharide synthesis tests revealed the suitability of crude β-galactosidases from Lichtheimia ramosa Szeged Microbiological Collection (SZMC) 11360 and Rhizomucor pusillus SZMC 11025 to catalyze transgalactosylation reactions. In addition, the crude enzyme extracts had transfructosylation activity, resulting in the formation of fructo-oligosaccharide molecules in a sucrose-containing environment. The maximal oligosaccharide concentration varied between 0.0158 and 2.236 g/L depending on the crude enzyme and the initial material. Some oligosaccharide-enriched mixtures supported the growth of probiotics, indicating the potential of the studied enzyme extracts in future prebiotic synthesis processes.

β-galactosidase from Kluyveromyces lactis in genipin-activated chitosan: An investigation on immobilization, stability, and application in diluted UHT milk

The objective of this research was to evaluate the immobilization of the enzyme β-galactosidase in a genipin-activated chitosan support. The influence of the number of spheres and substrate concentration on immobilization yield (IY) and enzyme activity (EA) was analyzed using experimental design. Thermal, operational and storage stabilities were assessed, and the enzymatic derivatives were characterized by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The TGA showed that the enzymatic derivatives kept their thermal behavior, and the SEM images revealed smooth surfaces in all the spheres. The optimized conditions for the immobilization process were 4.57 mg·mL^-1 of spheres and a substrate concentration of 10 mM (IY = 84.13%; EA = 24.97 U·g^-1). Thermal stability was enhanced at 10 and 37 °C, enabling four successive cycles of lactose hydrolysis in diluted UHT milk. Therefore, the immobilized enzyme in genipin-activated chitosan has potential for lactose hydrolysis and applications in the food industry.

Biocatalytic synthesis of lactosucrose using a recombinant thermostable β-fructofuranosidase from Arthrobacter sp. 10138

As a prebiotics, lactosucrose plays an important role in maintaining human gastrointestinal homeostasis. In this study, a thermostable enzyme from Arthrobacter sp. 10138 was screened from six β-fructofuranosidase-producing strains for the lactosucrose production and the coding gene was heterologously expressed in Escherichia coli for efficient expression. Recombinant β-fructofuranosidase was purified and biochemically characterized by MALDI-TOFMS spectrometry. The transfructosylation product by this recombinant enzyme was determined to be lactosucrose rather than other oligosaccharides or polysaccharides by HPLC and LC-MS. Efficient extracellular secretion of β-fructofuranosidase was achieved by the optimization of signal peptide and induction conditions. It was found that with the signal peptide torT, the highest extracellular activity reached 111.01 U/mL, which was 38.4-fold higher than that with the OmpA signal peptide. Under the optimal conditions (pH 6.0, temperature 50°C, enzyme amount 40 μg/ml, sucrose 150 g/L and lactose 150 g/L), 109 g/L lactosucrose was produced with a molar conversion ratio of 49.3%. Here the thermostable β-fructofuranosidase from Arthrobacter sp. 10138 can be used for efficient synthesis of lactosucrose, and this provides a good startpoint for the industrial production of lactosucrose in the future.

Review transglutaminases: part II-industrial applications in food, biotechnology, textiles and leather products

Because of their protein cross-linking properties, transglutaminases are widely used in several industrial processes, including the food and pharmaceutical industries. Transglutaminases obtained from animal tissues and organs, the first sources of this enzyme, are being replaced by microbial sources, which are cheaper and easier to produce and purify. Since the discovery of microbial transglutaminase (mTGase), the enzyme has been produced for industrial applications by traditional fermentation process using the bacterium Streptomyces mobaraensis. Several studies have been carried out in this field to increase the enzyme industrial productivity. Researches on gene expression encoding transglutaminase biosynthesis were performed in Streptomyces lividans, Escherichia coli, Corynebacterium glutamicum, Yarrowia lipolytica, and Pichia pastoris. In the first part of this review, we presented an overview of the literature on the origins, types, mediated reactions, and general characterizations of these important enzymes, as well as the studies on recombinant microbial transglutaminases. In this second part, we focus on the application versatility of mTGase in three broad areas: food, pharmacological, and biotechnological industries. The use of mTGase is presented for several food groups, showing possibilities of applications and challenges to further improve the quality of the end-products. Some applications in the textile and leather industries are also reviewed, as well as special applications in the PEGylation reaction, in the production of antibody drug conjugates, and in regenerative medicine.

Sustainable bioconversion of food waste into high-value products by immobilized enzymes to meet bio-economy challenges and opportunities - A review

Over the past few years, food waste has intensified much attention from the local public, national and international organizations as well as a wider household territory due to increasing environmental, social and economic concerns, climate change and scarcity of fossil fuel resources. On one aspect, food-processing waste represents a substantial ecological burden. On the other hand, these waste streams are rich in carbohydrates, proteins, and lipids, thus hold significant potential for biotransformation into an array of high-value compounds. Indeed, the high sugar, protein, and fat content render food waste streams as attractive feedstocks for enzymatic valorization given the plentiful volumes generated annually. Enzymes as industrial biocatalysts offer unique advantages over traditional chemical processes with regard to eco-sustainability, and process efficiency. Herein, an effort has been made to delineate immobilized enzyme-driven valorization of food waste streams into marketable products such as biofuels, bioactive compounds, biodegradable plastics, prebiotics, sweeteners, rare sugars, surfactants, etc. Current challenges and prospects are also highlighted with respect to the development of industrially adaptable biocatalytic systems to achieve the ultimate objectives of sustainable manufacturing combined with minimum waste generation. Applications-based strategies to enzyme immobilization are imperative to design cost-efficient and sustainable industrially applicable biocatalysts. With a deeper apprehension of support material influences, and analyzing the extreme environment, enzymes might have significant potential in improving the overall sustainability of food processing.

Potential prebiotics and their transmission mechanisms: Recent approaches

Prebiotics are non-digestible carbohydrates which can be used as prime source of energy for gut microflora. These can be naturally occurring in fruit and vegetables or can be made synthetically by enzymatic digestions. New versatile sources of prebiotics had been found nowadays for economic commercialization. This review will decipher on highlighting the importance of prebiotics in immunomodulation and nutrient absorption abilities of gut, as it is important for the anti-effective capacity of the organism especially in the neonatal period. Moreover, new prebiotics transmission strategies with higher penetrating capacity such as microencapsulation and immobilization have been discussed. In addition to this, literature had shown the modulation of gut microflora by the continuous use of prebiotics in many disorders so here, the role of prebiotics in health-related issues such as diabetes and inflammatory bowel disease (IBS) have been explained.

Transforming food waste: how immobilized enzymes can valorize waste streams into revenue streams

Food processing generates byproduct and waste streams rich in lipids, carbohydrates, and proteins, which contribute to its negative environmental impact. However, these compounds hold significant economic potential if transformed into revenue streams such as biofuels and ingredients. Indeed, the high protein, sugar, and fat content of many food waste streams makes them ideal feedstocks for enzymatic valorization. Compared to synthetic catalysts, enzymes have higher specificity, lower energy requirement, and improved environmental sustainability in performing chemical transformations, yet their poor stability and recovery limits their performance in their native state. This review article surveys the current state-of-the-art in enzyme stabilization & immobilization technologies, summarizes opportunities in enzyme-catalyzed valorization of waste streams with emphasis on streams rich in mono- and disaccharides, polysaccharides, lipids, and proteins, and highlights challenges and opportunities in designing commercially translatable immobilized enzyme systems towards the ultimate goals of sustainable food production and reduced food waste.

New β-galactosidase producers with potential for prebiotic synthesis

β-Galactosidases (EC 3.2.1.23) are interesting enzymes with potential application in the pharmaceutical and food industry. In this work, a screening study was carried out to identify new fungal sources of β-galactosidase. A total of 50 fungi were evaluated using a chromogenic test performed in agar plates. The most promising microorganisms were validated as effective β-galactosidase producers under submerged fermentation conditions. The crude β-galactosidases were characterized regarding their optimal pH (3.0-5.5) and temperature (45-65 °C). All enzymes showed ability to synthesize lactose-based prebiotics, namely lactulose (maximal yield 3.3%) and a galacto-oligosaccharide (GOS) (maximal yield 20%). Additionally, some enzymatic extracts with fructosyltransferase activity allowed to produce other type of prebiotics, namely fructo-oligosaccharides (FOS). This work, reports for the first time the simultaneous synthesis of different mixtures of GOS (2-15% yield and 0.07-0.5 g/L·h^-1 productivity) and FOS (4-30% yield and 0.1-1 g/L·h^-1 productivity) by crude extracts exhibiting dual enzymatic activity.

Prebiotic Oligosaccharides: Special Focus on Fructooligosaccharides, Its Biosynthesis and Bioactivity

The bacterial groups in the gut ecosystem play key role in the maintenance of host's metabolic and structural functionality. The gut microbiota enhances digestion processing, helps in digestion of complex substances, synthesizes beneficial bioactive compounds, enhances bioavailability of minerals, impedes growth of pathogenic microbes, and prevents various diseases. It is, therefore, desirable to have an adequate intake of prebiotic biomolecules, which promote favorable modulation of intestinal microflora. Prebiotics are non-digestible and chemically stable structures that significantly enhance growth and functionality of gut microflora. The non-digestible carbohydrate, mainly oligosaccharides, covers a major part of total available prebiotics as dietary additives. The review describes the types of prebiotic low molecular weight carbohydrates, i.e., oligosaccharides, their structure, biosynthesis, functionality, and applications, with a special focus given to fructooligosaccharides (FOSs). The review provides an update on enzymes executing hydrolytic and fructosyltransferase activities producing prebiotic FOS biomolecules, and future perspectives.