Simultaneous hydrolysis of cheese whey and lactulose production catalyzed by β-galactosidase from Kluyveromyces lactis NRRL Y1564

Innovative approaches for enzyme immobilization in milk processing: advancements and industrial applications

The dairy industry is progressively integrating advanced enzyme technologies to optimize processing efficiency and elevate product quality. Among these technologies, enzyme immobilization has emerged as a pivotal innovation, offering considerable benefits in terms of enzyme reusability, stability, and overall process sustainability. This review paper explores the latest improvements in enzyme immobilization techniques and their industrial applications within milk processing. It examines various immobilization strategies, including adsorption, affinity binding, ionic and covalent binding, entrapment, encapsulation, and cross-linking, highlighting their effectiveness in improving the performance of key enzymes such as lactases, lipases, proteases and transglutaminases. The paper also delves into the economic and ecological benefits of enzyme immobilization, emphasizing its role in reducing production costs and environmental impact while maintaining or enhancing the quality of dairy products. By analyzing current trends and technological developments, this review provides a comprehensive overview of how innovative enzyme immobilization approaches are transforming milk processing. It concludes with a discussion on future research directions and potential industrial applications, underscoring the importance of continued innovation in this field to meet the increasing demands of the global dairy market.

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.

A yeast surface display platform for screening of non-enzymatic protein secretion in Kluyveromyces lactis

Enhancing the secretion of recombinant proteins, particularly non-enzymatic proteins that predominate in food and pharmaceutic protein products, remains a significant challenge due to limitations in high-throughput screening methods. This study addresses this bottleneck by establishing a yeast surface display system in the food-grade microorganism Kluyveromyces lactis, enabling efficient display of model target proteins on the yeast cell surface. To assess its potential as a universal high-throughput screening tool for enhanced non-enzymatic protein secretion, we evaluated the consistency between protein display levels and secretion efficiency under the influence of various genetic factors. Our results revealed a strong correlation between these two properties. Furthermore, screening in a random mutagenesis library successfully identified a mutant with improved secretion. These findings demonstrate the potential of the K. lactis surface display system as a powerful and universal tool for high-throughput screening of strains with superior non-enzymatic protein secretion capacity. We believe this study could pave the way for efficient large-scale production of heterologous food and therapeutic proteins in industries. KEY POINTS: • A YSD (yeast surface display) system was established in Kluyveromyces lactis • This system enables high-throughput screening of non-enzymatic protein secretion • This technology assists industrial production of food and therapeutic proteins.

Recent Advances and Perspectives on Food-Grade Immobilisation Systems for Enzymes

The use of enzyme immobilisation is becoming increasingly popular in beverage processing, as this method offers significant advantages, such as enhanced enzyme performance and expanded applications, while allowing for easy process termination via simple filtration. This literature review analysed approximately 120 articles, published on the Web of Science between 2000 and 2023, focused on enzyme immobilisation systems for beverage processing applications. The impact of immobilisation on enzymatic activity, including the effects on the chemical and kinetic properties, recyclability, and feasibility in continuous processes, was evaluated. Applications of these systems to beverage production, such as wine, beer, fruit juices, milk, and plant-based beverages, were examined. The immobilisation process effectively enhanced the pH and thermal stability but caused negative impacts on the kinetic properties by reducing the maximum velocity and Michaelis-Menten constant. However, it allowed for multiple reuses and facilitated continuous flow processes. The encapsulation also allowed for easy process control by simplifying the removal of the enzymes from the beverages via simple filtration, negating the need for expensive heat treatments, which could result in product quality losses.

Aspergillus oryzae β-D-galactosidase immobilization on glutaraldehyde pre-activated amino-functionalized magnetic mesoporous silica: Performance, characteristics, and application in the preparation of sesaminol

Aspergillus oryzae β-D-galactosidase (β-Gal) efficiently hydrolyzes sesaminol triglucoside into sesaminol, which has higher biological activity. However, β-Gal is difficult to be separate from the reaction mixture and limited by stability. To resolve these problems, β-Gal was immobilized on amino-functionalized magnetic nanoparticles mesoporous silica pre-activated with glutaraldehyde (Fe3O4@mSiO2-β-Gal), which was used for the first time to prepare sesaminol. Under the optimal conditions, the immobilization yield and recovered activity of β-Gal were 57.9 ± 0.3 % and 46.5 ± 0.9 %, and the enzymatic loading was 843 ± 21 Uenzyme/gsupport. The construction of Fe3O4@mSiO2-β-Gal was confirmed by various characterization methods, and the results indicated it was suitable for heterogeneous enzyme-catalyzed reactions. Fe3O4@mSiO2-β-Gal was readily separable under magnetic action and displayed improved activity in extreme pH and temperature conditions. After 45 days of storage at 4 °C, the activity of Fe3O4@mSiO2-β-Gal remained at 92.3 ± 2.8 %, which was 1.29 times than that of free enzyme, and its activity remained above 85 % after 10 cycles. Fe3O4@mSiO2-β-Gal displayed higher affinity and catalytic efficiency. The half-life was 1.41 longer than free enzymes at 55.0 °C. Fe3O4@mSiO2-β-Gal was employed as a catalyst to prepare sesaminol, achieving a 96.7 % conversion yield of sesaminol. The excellent stability and catalytic efficiency provide broad benefits and potential for biocatalytic industry applications.

Chitosan-based oral hydrogel formulations of β-galactosidase to improve enzyme supplementation therapy for lactose intolerance

β-Galactosidase supplementation plays an important role in the life of people with lactose intolerance. However, these formulations are rendered ineffective by the low pH and pepsin in the stomach and pancreatic proteases in the intestine. Therefore, it is necessary to develop oral transport systems for carrying this enzyme in the active form up to the intestine, where the lactose digestion occurs. In this research, a new hydrogel was developed that could potentially be used for enzyme supplement therapy. In this regard, the chitosan-based β-Gal formulations described in the manuscript are an alternative long-acting preparation to the so far available preparations that allow for enzyme protection and mucosal targeting. These hydrogels were prepared from chitosan and polyethylene glycol and contained a covalently immobilized β-galactosidase from Aspergillus oryzae. The β-galactosidase in the hydrogel was protected from degradation in a gastric medium at a pH of 2.5 and retained 75 % of its original activity under subsequent intestinal conditions. In the case of a simulated gastric fluid with a pH of 1.5, a copolymer containing methacrylic acid functional groups was sufficient to protect the hybrid hydrogel from the extremely acidic pH. In addition, the surface of the hydrogel was chemically modified with thiol and amidine groups, which increased the binding to intestinal mucin by 20 % compared with the unmodified hydrogel. These results represent a promising approach for oral transport as a reservoir for β-galactosidase in the small intestine to reduce the symptoms of hypolactasia.

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.

Magnetic CLEAs of β-Galactosidase from Aspergillus oryzae as a Potential Biocatalyst to Produce Tagatose from Lactose

β-galactosidase is an enzyme capable of hydrolysing lactose, used in various branches of industry, mainly the food industry. As the efficient industrial use of enzymes depends on their reuse, it is necessary to find an effective method for immobilisation, maintaining high activity and stability. The present work proposes cross-linked magnetic cross-linked enzyme aggregates (mCLEAs) to prepare heterogeneous biocatalysts of β-galactosidase. Different concentrations of glutaraldehyde (0.6%, 1.0%, 1.5%), used as a cross-linking agent, were studied. The use of dextran-aldehyde as an alternative cross-linking agent was also evaluated. The mCLEAs presented increased recovered activity directly related to the concentration of glutaraldehyde. Modifications to the protocol to prepare mCLEAs with glutaraldehyde, adding a competitive inhibitor or polymer coating, have not been effective in increasing the recovered activity of the heterogeneous biocatalysts or its thermal stability. The biocatalyst prepared using dextran-aldehyde presented 73.6% recovered activity, aside from substrate affinity equivalent to the free enzyme. The thermal stability at 60 °C was higher for the biocatalyst prepared with glutaraldehyde (mCLEA-GLU-1.5) than the one produced with dextran-aldehyde (mCLEA-DEX), and the opposite happened at 50 °C. Results obtained for lactose hydrolysis, the use of its product to produce a rare sugar (D-tagatose) and operational and storage stability indicate that heterogeneous biocatalysts have adequate characteristics for industrial use.

Past, Present, and Future Perspectives on Whey as a Promising Feedstock for Bioethanol Production by Yeast

Concerns about fossil fuel depletion and the environmental effects of greenhouse gas emissions have led to widespread fermentation-based production of bioethanol from corn starch or sugarcane. However, competition for arable land with food production has led to the extensive investigation of lignocellulosic sources and waste products of the food industry as alternative sources of fermentable sugars. In particular, whey, a lactose-rich, inexpensive byproduct of dairy production, is available in stable, high quantities worldwide. This review summarizes strategies and specific factors essential for efficient lactose/whey fermentation to ethanol. In particular, we cover the most commonly used strains and approaches for developing high-performance strains that tolerate fermentation conditions. The relevant genes and regulatory systems controlling lactose utilization and sources of new genes are also discussed in detail. Moreover, this review covers the optimal conditions, various feedstocks that can be coupled with whey substrates, and enzyme supplements for increasing efficiency and yield. In addition to the historical advances in bioethanol production from whey, this review explores the future of yeast-based fermentation of lactose or whey products for beverage or fuel ethanol as a fertile research area for advanced, environmentally friendly uses of industrial waste products.

Application of cellulosic materials as supports for single-step purification and immobilization of a recombinant β-galactosidase via cellulose-binding domain

This study aimed to develop single-step purification and immobilization processes on cellulosic supports of β-galactosidase from Kluyveromyces sp. combined with the Cellulose-Binding Domain (CBD) tag. After 15 min of immobilization, with an enzymatic load of 150 U/g_support, expressed activity values reached 106.88 (microcrystalline cellulose), 115.03 (alkaline nanocellulose), and 108.47 IU/g (acid nanocellulose). The derivatives produced were less sensitive to the presence of galactose in comparison with the soluble purified enzyme. Among the cations assessed (Na⁺, K⁺, Mg²⁺, and Ca²⁺), magnesium provided the highest increase in the enzymatic activity of β-galactosidases immobilized on cellulosic supports. Supports and derivatives showed no cytotoxic effect on the investigated cell cultures (HepG2 and Vero). Derivatives showed high operational stability in the hydrolysis of milk lactose and retained from 53 to 64% of their hydrolysis capacity after 40 reuse cycles. This study obtained biocatalyzers with promising characteristics for application in the food industry. Biocatalyzers were obtained through a low-cost one-step sustainable bioprocess of purification and immobilization of a β-galactosidase on cellulose via CBD.

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.

Characterization and Application of a New β-Galactosidase Gal42 From Marine Bacterium Bacillus sp. BY02

β-Galactosidase plays an important role in medicine and dairy industry. In this study, a new glycoside hydrolase family 42 (GH42) β-galactosidase-encoding gene, gal42, was cloned from a newly isolated marine bacterium Bacillus sp. BY02 and expressed in Escherichia coli. Structural characterization indicated that the encoding β-galactosidase, Gal42, is a homotrimer in solution, and homology modeling indicated that it retains the zinc binding sites of the Cys cluster. The reaction activity of Gal42 was significantly increased by Zn²⁺ (229.6%) and other divalent metal ions (Mn²⁺, Mg²⁺, and Co²⁺), while its activity was inhibited by EDTA (53.9%). Meanwhile, the thermo-stability of the Gal42 was also significantly enhanced by 5 and 10 mM of zinc ion supplement, which suggested that the “Cys-Zn” motif played important roles in both structural stability and catalytic function. Furthermore, Gal42 showed effective lactose hydrolysis activity, which makes the enzyme hydrolyze the lactose in milk effectively. These properties make Gal42 a potential candidate in food technology.

β-galactosidase GALA from Bacillus circulans with high transgalactosylation activity

β-galactosidase catalyzes lactose hydrolysis and transfers reactions to produce prebiotics such as galacto-oligosaccharides (GOS) with potential applications in the food industry and pharmaceuticals. However, there is still a need for improved transgalactosylation activity of β-galactosidases and reaction conditions of GOS production in order to maximize GOS output and reduce production costs. In this study, a β-galactosidase gene, galA, from Bacillus circulans was expressed in Pichia pastoris, which not only hydrolyzed lactose but also had strong transgalactosylation activity to produce GOS. Response surface methodology was adopted to investigate the effects of temperature, enzyme concentration, pH, initial lactose concentration, and reaction time on the production of GOS and optimize the reaction conditions for GOS. The optimal pH for the enzyme was 6.0 and remained stable under neutral and basic conditions. Meanwhile, GALA showed most activity at 50°C and retained considerable activity at a lower temperature 30–40°C, indicating this enzyme could work under mild conditions. The enzyme concentration and temperature were found to be the critical parameters affecting the transgalactosylation activity. Response surface methodology showed that the optimal enzyme concentration, initial lactose concentration, temperature, pH, and reaction time were 3.03 U/mL, 500 g/L, 30°C, 5.08, and 4 h, respectively. Under such conditions, the maximum yield of GOS was 252.8 g/L, accounting for approximately 50.56% of the total sugar. This yield can be considered relatively high compared to those obtained from other sources of β-galactosidases, implying a great potential for GALA in the industrial production and application of GOS.

Polylactic acid production from biotechnological routes: A review

Polylactic acid (PLA) has been highlighted as an important polymer due to its high potential for applicability in various areas, such as in the chemical, medical, pharmaceutical or biotechnology field. Very recently, studies have reported its use as a basic component for the production of personal protective equipment (PPE) required for the prevention of Sars-Cov-2 contamination, responsible for the cause of coronavirus disease, which is currently a major worldwide sanitary and social problem. PLA is considered a non-toxic, biodegradable and compostable plastic with interesting characteristics from the industrial point of view, and it emerges as a promising product under the concept of "green plastic", since most of the polymers produced currently are petroleum-based, a non-renewable raw material. Biotechnology routes have been mentioned as potential methodologies for the production of this polymer, especially by enzymatic routes, in particular by use of lipases enzymes. The availability of pure lactic acid isomers is a fundamental aspect of the manufacture of PLA with more interesting mechanical and thermal properties. Due to the technological importance that PLA-based polymers are acquiring, as well as their characteristics and applicability in several fields, especially medical, pharmaceutical and biotechnology, this review article sought to gather very recent information regarding the development of research in this area. The main highlight of this study is that it was carried out from a biotechnological point of view, aiming at a totally green bioplastic production, since the obtaining of lactic acid, which will be used as raw material for the PLA synthesis, until the degradation of the polymer obtained by biological routes.

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.

Production of beta-galactosidase fused to a cellulose-binding domain for application in sustainable industrial processes

This study aimed to produce and characterize a recombinant Kluyveromyces sp. β-galactosidase fused to a cellulose-binding domain (CBD) for industrial application. In expression assays, the highest enzymatic activities occurred after 48 h induction on Escherichia coli C41(DE3) strain at 20 °C in Terrific Broth (TB) culture medium, using isopropyl β-d-1-thiogalactopyranoside (IPTG) 0.5 mM (108.77 U/mL) or lactose 5 g/L (93.10 U/mL) as inducers. Cultures at bioreactor scale indicated that higher product yield values in relation to biomass (2000 U/g) and productivity (0.72 U/mL.h) were obtained in culture media containing higher protein concentration. The recombinant enzyme showed high binding affinity to nanocellulose, reaching both immobilization yield and efficiency values of approximately 70% at pH 7.0 after 10 min reaction. The results of the present study pointed out a strategy for recombinant β-galactosidase-CBD production and immobilization, aiming toward the application in sustainable industrial processes using low-cost inputs.

The β-galactosidase immobilization protocol determines its performance as catalysts in the kinetically controlled synthesis of lactulose

In this paper, 3 different biocatalysts of β-galactosidase from Kluyveromyces lactis have been prepared by immobilization in chitosan activated with glutaraldehyde (Chi_Glu_Gal), glyoxyl agarose (Aga_Gly_Gal) and agarose coated with polyethylenimine (Aga_PEI_Gal). These biocatalysts have been used to catalyze the synthesis of lactulose from lactose and fructose. Aga-PEI-Gal only produces lactulose at 50 °C, and not at 25 or 37 °C, Aga_Gly_Gal was unable to produce lactulose at any of the assayed temperatures while Chi_Glu_Gal produced lactulose at all assayed temperatures, although a lower yield was obtained at 25 or 37 °C. The pre-incubation of this biocatalyst at 50 °C permitted to obtain similar yields at 25 or 37 °C than at 50 °C. The use of milk whey instead of pure lactose and fructose produced an improvement in the yields using Aga_PEI_Gal and a decrease using Chi_Glu_Gal. The operational stability also depends on the reaction medium and of biocatalyst. This study reveals how enzyme immobilization may greatly alter the performance of β-galactosidase in a kinetically controlled manner, and how medium composition influences this performance due to the kinetic properties of β-galactosidase.

Integration of elastin-like polypeptide fusion system into the expression and purification of Lactobacillus sp. B164 β-galactosidase for lactose hydrolysis

An elastin-like polypeptide (ELP) sequence fused with Lactobacillus sp. B164 β-galactosidase modified with 6x-Histidine (β-Gal-LH) to produce recombinant β-Gal-Linker-ELP-His (β-Gal-LEH) was expressed in E. coli and purified via inverse thermal cycling (ITC) and nickel-nitrilotriacetic acid (Ni-NTA) resin. The β-galactosidase integrated with ELP-system showed an improved purification at 1.75 M (NH₄)₂SO₄ after 1 round ITC (95.66% recovery rate and 13.04 purification fold) with better enzyme activity parameters compared to Ni-NTA. The enzyme maintained an optimal temperature (40 °C) and pH (7.5) for both β-Gal-LEH and β-Gal-LH. The results further showed that the ELP-fusion system improved the enzyme's thermal and storage stability. Moreover, the enzyme secondary structure was not changed by ELP-tag. Enzyme activity was completely inactivated by Hg²⁺, Cd²⁺ and Cu²⁺, unaffected by Ca²⁺, EDTA and urea, but partially activated by Mn²⁺ at lower concentration. Compared to commercial β-galactosidases, β-Gal-LEH exhibited similar biocatalytic efficiency on lactose and could potentially catalyze transgalactosylation.

Potential of "coalho" cheese whey as lactose source for β-galactosidase and ethanol co-production by Kluyveromyces spp. yeasts

The present study evaluated the co-production of β-galactosidase and ethanol by Kluyveromyces marxianus ATCC 36907 and Kluyveromyces lactis NRRL Y-8279 using as carbon source the lactose found on "coalho" cheese whey. Cheese whey was subjected to partial deproteinization, and physicochemical parameters were assessed. Cultivations were carried out in an shaker to evaluate two carbon/nitrogen (C:N) ratios. The best C:N ratio (1.5:1) was carried to 1.5-L bioreactor cultivation in order to increase co-production yields. The stability of β-galactosidase was assessed against different temperatures and pH, and in the presence of metal ions. Concerning the co-production of β-galactosidase and ethanol, K. lactis proved to be more efficient in both the C:N ratios, reaching 21.09 U·mL^-1 of activity and 7.10 g·L^-1 of ethanol in 16 h. This study describes the development of a viable and value-adding biotechnological process using a regional cheese by-product from Northeast Brazil for co-production of biomolecules of industrial interest.