Immobilization of β-Galactosidases from Lactobacillus on Chitin Using a Chitin-Binding Domain

Boosting Biocatalytic Efficiency: Engineering of Chitinase Chit33 with Chitin and Cellulose Binding Domains for Sustainable Chitin Conversion

Endochitinase Chit33 has shown great potential in converting chitin, a recalcitrant waste, into bioactive chitooligosaccharides (COS). This study evaluates how cellulose-binding domain (CBD) and chitin-binding domain (ChBD) affect the hydrolytic activity and product specificity of Chit33. Recombinant proteins were produced and isolated with a simple yeast extracellular medium concentration. The domain functionality was proved using chitin and cellulose supports. ChBD provided more stable immobilization than CBD but reduced the Chit33 activity. CBD enhanced the enzyme activity on both colloidal (α-/β-allomorphs) and crystalline chitin, doubling it on α-chitin, although not on their deacetylated forms. Besides, CBD increased the COS production from the colloidal forms of α-/β-chitin (by 30% and 85%, respectively) and expanded the product diversity from 1 to 9 N-acetylglucosamine units. In contrast, Chit33-ChBD predominantly yielded chitin tetrasaccharides. These findings highlight the importance of selecting appropriate binding domains to tailor product specificity, as polymerization and acetylation degrees directly impact the COS biological properties.

The application of chitin materials in enzymatic catalysis: A review

Enzymatic catalysis offers notable advantages, including exceptional catalytic efficiency, selectivity, and the ability to operate under mild conditions. However, its widespread application is hindered by the high costs associated with enzymes and cofactors. Materials-mediated immobilization technology has proven effective in the recycling of enzymes and cofactors. An optimal carrier material for protein immobilization must be non-toxic, biocompatible, and should not compromise the biological activity or structure of the enzymes. Compared to synthetic polymers, chitin is a promising carrier given its low cost, renewability, abundance of functional groups, and notable biocompatibility and biodegradability. Although numerous reviews on chitosan and other polymers for immobilization have been published, few have addressed using chitin as supports. In this review, chitin-based materials mediated enzyme immobilization, the one-step purification and immobilization of enzymes, as well as co-immobilization of enzymes and cofactors were summarized. Particularly, the significance of chitin materials in the field of enzymatic catalysis was emphasized. This study has the potential to open new avenues for immobilized biocatalysts.

The Impact of Chitinase Binding Domain Truncation on the Properties of CaChi18B from Chitinilyticum aquatile CSC-1

The chitinase binding domain (ChBD) plays a crucial role in the properties of enzymes. To assess its impact, we cloned a truncated mutant of the chitinase gene CaChi18B from the novel chitinase-producing facultative anaerobic bacterium Chitinilyticum aquatile CSC-1, designated as CaChi18B_ΔChBDs. The recombinant chitinase was successfully expressed and purified, exhibiting a specific activity of 3.48 U/mg on colloidal chitin, with optimal conditions at 45 °C and pH 6.0, and retaining over 80% activity at temperatures up to 40 °C. Kinetic analysis revealed that the Km value was 1.159 mg mL-1 and the Vmax was 10.37 μM min-1 mg-1. Compared to CaChi18B_ΔChBD1, which has only the first ChBD truncated at the N-terminus, CaChi18B_ΔChBDs exhibited minor changes in the optimal temperature and pH, while the Km and Vmax values increased significantly. CaChi18B_ΔChBDs exhibited tolerance to various metal ions, with K+ and NH4+ enhancing activity, while Cu2+ significantly inhibited it. Most organic reagents had minimal impact, except for formic acid, which severely reduced activity. The primary hydrolysis product in the initial phase was GlcNAc, contrasting with (GlcNAc)2 for CaChi18B_ΔChBD1. These findings indicated that the ChBD influences the enzyme's Km, Vmax, and product distribution, enhancing our understanding of ChBD's roles and advancing chitin utilization.

Development of a Chitin-Based Purification System Utilizing Chitin-Binding Domain and Tobacco Etch Virus Protease Cleavage for Efficient Recombinant Protein Recovery

This study aims to develop an efficient chitin-based purification system, leveraging a novel design where the target proteins, superfolding green fluorescent protein (sfGFP) and Thermus antranikianii trehalose synthase (TaTS), fused with a chitin-binding domain (ChBD) from Bacillus circulans WL-12 chitinase A1 and a tobacco etch virus protease (TEVp) cleavage site. This configuration allows for the effective immobilization of the target proteins on chitin beads, facilitating the removal of endogenous proteins. A mutant TEVp, H-TEVS219V-ChBD, fused with the His-tag and ChBD, is employed to cleave the target proteins from the chitin beads specifically. Subsequently, fresh chitin beads are added for adsorption to remove H-TEVS219V-ChBD in the solution, thereby significantly improving the purity of the target protein. Our results confirm that this system can efficiently and specifically purify and recover sfGFP and TaTS, achieving electrophoretic-grade purity exceeding 90%. This system holds significant potential for industrial production and other applications.

High-Yield Synthesis of Phosphatidylserine in a Well-Designed Mixed Micellar System

A sustainable enzymatic system is essential for efficient phosphatidylserine (PS) synthesis in industrial production. Conventional biphasic systems face challenges such as excessive organic solvent usage, enzyme-intensive processes, and increased costs. This study introduces a novel approach using chitin nanofibrils (ChNFs) as an immobilization material for phospholipase D (PLD) in a mixed micellar system stabilized by the food-grade emulsifier sodium deoxycholate (SDC). The immobilized enzyme, ChNF-chiA1, was quickly prepared in a one-step process, eliminating the need for purification. By optimizing the reaction conditions, including l-Ser concentration (1.0 M), SDC concentration (10 mM), reaction time (8 h), and enzyme dosage (1.0 U), a remarkable PS yield of 96.74% was achieved in the solvent-free mixed micellar system. The catalytic efficiency of ChNF-chiA1 surpassed that of the free PLD-chiA1 biphasic system by 6.0-fold. This innovative and green biocatalytic technology offers a reusable solution for the high-value enzymatic synthesis of phospholipids, providing a promising avenue for industrial applications.

Invited review: Properties of β-galactosidases derived from Lactobacillaceae species and their capacity for galacto-oligosaccharide production

β-galactosidase (enzymatic class 3.2.1.23) is one of the dairy industry's most important and widely used enzymes. The enzyme is part of a large family known to catalyze hydrolysis and transglycosylation reactions. Its hydrolytic activity is commonly used to decrease lactose content in dairy products, while its transglycosylase activity has recently been used to synthesize galacto-oligosaccharides (GOS). During the past couple of years, researchers have focused on studying β-galactosidase isolated and purified from lactic acid bacteria. This review will focus on β-galactosidase purified and characterized from what used to be the Lactobacillus genera. Furthermore, particular emphasis is given to its kinetics, biochemical characteristics, GOS production, market, and utilization by Lactobacilllaceae species.

PTP4A2 promotes lysophagy by dephosphorylation of VCP/p97 at Tyr805

Overexpression of PTP4A phosphatases are associated with advanced cancers, but their biological functions are far from fully understood due to limited knowledge about their physiological substrates. VCP is implicated in lysophagy via collaboration with specific cofactors in the ELDR complex. However, how the ELDR complex assembly is regulated has not been determined. Moreover, the functional significance of the penultimate and conserved Tyr805 phosphorylation in VCP has not been established. Here, we use an unbiased substrate trapping and mass spectrometry approach and identify VCP/p97 as a bona fide substrate of PTP4A2. Biochemical studies show that PTP4A2 dephosphorylates VCP at Tyr805, enabling the association of VCP with its C-terminal cofactors UBXN6/UBXD1 and PLAA, which are components of the ELDR complex responsible for lysophagy, the autophagic clearance of damaged lysosomes. Functionally, PTP4A2 is required for cellular homeostasis by promoting lysophagy through facilitating ELDR-mediated K48-linked ubiquitin conjugate removal and autophagosome formation on the damaged lysosomes. Deletion of Ptp4a2 in vivo compromises the recovery of glycerol-injection induced acute kidney injury due to impaired lysophagy and sustained lysosomal damage. Taken together, our data establish PTP4A2 as a critical regulator of VCP and uncover an important role for PTP4A2 in maintaining lysosomal homeostasis through dephosphorylation of VCP at Tyr805. Our study suggests that PTP4A2 targeting could be a potential therapeutic approach to treat cancers and other degenerative diseases by modulating lysosomal homeostasis and macroautophagy/autophagy.Abbreviations: AAA+: ATPases associated with diverse cellular activities; AKI: acute kidney injury; CBB: Coomassie Brilliant Blue; CRISPR: clustered regularly interspaced short palindromic repeats; ELDR: endo-lysosomal damage response; GFP: green fluorescent protein; GST: ‎glutathione S-transferase; IHC: immunohistochemistry; IP: immunoprecipitation; LAMP1: lysosomal-associated membrane protein 1; LC-MS: liquid chromatography-mass spectrometry; LGALS3/Gal3: galectin 3; LLOMe: L-leucyl-L-leucine methyl ester; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; PLAA: phospholipase A2, activating protein; PTP4A2: protein tyrosine phosphatase 4a2; PUB: NGLY1/PNGase/UBA- or UBX-containing protein; PUL: PLAP, Ufd3, and Lub1; TFEB: transcription factor EB; UBXN6/UBXD1: UBX domain protein 6; UPS: ubiquitin-proteasome system; VCP/p97: valosin containing protein; VCPIP1: valosin containing protein interacting protein 1; YOD1: YOD1 deubiquitinase.

Efficient production of inositol from glucose via a tri-enzymatic cascade pathway

Inositol is an essential intermediate in cosmetics, food, medicine and other industries. However, developing an efficient biotransformation system for large-scale production of inositol remains challenging. Herein, a tri-enzymatic cascade route with three novel enzymes including polyphosphate glucokinase (PPGK) from Thermobifida fusca, inositol 3-phosphate synthase (IPS) from Archaeoglobus profundus DSM 5631 and inositol monophosphatase (IMP) from Thermotoga petrophila RKU-1 was designed and reconstructed for the production of inositol from glucose. The problem of poor cooperativity of the cascade reactions was addressed by ribosome binding site (RBS) optimization of PPGK and replication of IPS. Under the optimum biotransformation conditions, the engineered whole-cell immobilized with colloidal chitin transformed 120 g/L glucose to 110.8 g/L inositol with 92.3% conversion in four cycles of reuse, representing the highest titer of inositol to date. Furthermore, this is the first study for inositol production using a three-enzyme coordinated immobilized single-cell.

Production and Digestibility Studies of β-Galactosyl Xylitol Derivatives Using Heterogeneous Catalysts of LacA β-Galactosidase from Lactobacillus Plantarum WCFS1

The synthesis of β-galactosyl xylitol derivatives using immobilized LacA β-galactosidase from Lactobacillus plantarum WCFS1 is presented. These compounds have the potential to replace traditional sugars by their properties as sweetener and taking the advantages of a low digestibility. The enzyme was immobilized on different supports, obtaining immobilized preparations with different activity and stability. The immobilization on agarose-IDA-Zn-CHO in the presence of galactose allowed for the conserving of 78% of the offered activity. This preparation was 3.8 times more stable than soluble. Since the enzyme has polyhistidine tags, this support allowed the immobilization, purification and stabilization in one step. The immobilized preparation was used in synthesis obtaining two main products and a total of around 68 g/L of β-galactosyl xylitol derivatives and improving the synthesis/hydrolysis ratio by around 30% compared to that of the soluble enzyme. The catalyst was recycled 10 times, preserving an activity higher than 50%. The in vitro intestinal digestibility of the main β-galactosyl xylitol derivatives was lower than that of lactose, being around 6 and 15% for the galacto-xylitol derivatives compared to 55% of lactose after 120 min of digestion. The optimal amount immobilized constitutes a very useful tool to synthetize β-galactosyl xylitol derivatives since it can be used as a catalyst with high yield and being recycled for at least 10 more cycles.

Engineering of a chitosanase fused to a carbohydrate-binding module for continuous production of desirable chitooligosaccharides

Chitooligosaccharides (CHOS) with multiple biological activities are usually produced through enzymatic hydrolysis of chitosan or chitin. However, purification and recycling of the enzyme have largely limited the advancement of CHOS bioproduction. Here, we engineered a novel enzyme by fusing the native chitosanase Csn75 with a carbohydrate-binding module (CBM) that can specifically bind to curdlan. The recombinase Csn75-CBM was successfully expressed by Pichia pastoris and allowed one-step purification and immobilization in the chitosanase immobilized curdlan packed-bed reactor (CICPR), where a maximum adsorption capacity of 39.59 mg enzyme/g curdlan was achieved. CHOS with degrees of polymerization of 2-5 (a hydrolysis yield of 97.75%), 3-6 (75.45%), and 3-7 (73.2%) were continuously produced by adjusting the ratio of enzyme and chitosan or the flow rate of chitosan. Moreover, the CICPR exhibited good stability and reusability after several cycles. The recombinase Csn75-CBM has greatly improved the efficiency of the bioproduction of CHOS.

Engineering a carbohydrate binding module to enhance chitinase catalytic efficiency on insoluble chitinous substrate

Development of a high-performance chitinase for efficient biotransformation of insoluble chitinous substrate would be highly valuable in industry. In this study, the chitin-binding domains (ChBDs) of chitinase SaChiA4 were successfully modified to improve the enzymatic activity. The engineered substitution variant R-SaChiA4, which had the exogenous ChBD of chitinase ChiA1 from Bacillus circulans WL-12 (ChBD_ChiA1) substituted for its original ChBD_ChiA4, increased its activity by nearly 54% (28.0 U/mg) towards chitin powder, and by 49% towards colloidal chitin, compared with the wild-type. The substrate-binding assay demonstrated that the ChBD could enhance the capacity of enzymatic hydrolysis by promoting substrate affinity, and molecular dynamics simulations indicated that this could be due to hydrophobic interactions in different substrate binding modes. This work advances the understanding of the role of the ChBD, and provides a step towards the achievement of industrial-scale hydrolysis and utilization of insoluble chitin.

Cadaverine Production From L-Lysine With Chitin-Binding Protein-Mediated Lysine Decarboxylase Immobilization

Lysine decarboxylase (CadA) can directly convert L-lysine to cadaverine, which is an important platform chemical that can be used to produce polyamides. However, the non-recyclable and the poor pH tolerance of pure CadA hampered its practical application. Herein, a one-step purification and immobilization procedure of CadA was established to investigate the cadaverine production from L-lysine. Renewable biomass chitin was used as a carrier for lysine decarboxylase (CadA) immobilization via fusion of a chitin-binding domain (ChBD). Scanning electron microscopy, laser scanning confocal microscopy, fourier transform infrared spectra, elemental analysis, and thermal gravimetric analysis proved that the fusion protein ChBD-CadA can be adsorbed on chitin effectively. Furthermore, the fusion protein (ChBD-CadA) existed better pH stability compared to wild CadA, and kept over 73% of the highest activity at pH 8.0. Meanwhile, the ChBD-CadA showed high specificity toward chitin and reached 93% immobilization yield within 10 min under the optimum conditions. The immobilized ChBD-CadA (I-ChBD-CadA) could efficiently converted L-lysine at 200.0 g/L to cadaverine at 135.6 g/L in a batch conversion within 120 min, achieving a 97% molar yield of the substrate L-lysine. In addition, the I-ChBD-CadA was able to be reused under a high concentration of L-lysine and retained over 57% of its original activity after four cycles of use without acid addition to maintain pH. These results demonstrate that immobilization of CadA using chitin-binding domain has the potential in cadaverine production on an industrial scale.

Immobilization of β-Galactosidases on the Lactobacillus Cell Surface Using the Peptidoglycan-Binding Motif LysM

Lysin motif (LysM) domains are found in many bacterial peptidoglycan hydrolases. They can bind non-covalently to peptidoglycan and have been employed to display heterologous proteins on the bacterial cell surface. In this study, we aimed to use a single LysM domain derived from a putative extracellular transglycosylase Lp_3014 of Lactobacillus plantarum WCFS1 to display two different lactobacillal β-galactosidases, the heterodimeric LacLM-type from Lactobacillus reuteri and the homodimeric LacZ-type from Lactobacillus delbrueckii subsp. bulgaricus, on the cell surface of different Lactobacillus spp. The β-galactosidases were fused with the LysM domain and the fusion proteins, LysM-LacLMLreu and LysM-LacZLbul, were successfully expressed in Escherichia coli and subsequently displayed on the cell surface of L. plantarum WCFS1. β-Galactosidase activities obtained for L. plantarum displaying cells were 179 and 1153 U per g dry cell weight, or the amounts of active surface-anchored β-galactosidase were 0.99 and 4.61 mg per g dry cell weight for LysM-LacLMLreu and LysM-LacZLbul, respectively. LysM-LacZLbul was also displayed on the cell surface of other Lactobacillus spp. including L. delbrueckii subsp. bulgaricus, L. casei and L. helveticus, however L. plantarum is shown to be the best among Lactobacillus spp. tested for surface display of fusion LysM-LacZLbul, both with respect to the immobilization yield as well as the amount of active surface-anchored enzyme. The immobilized fusion LysM-β-galactosidases are catalytically efficient and can be reused for several repeated rounds of lactose conversion. This approach, with the β-galactosidases being displayed on the cell surface of non-genetically modified food-grade organisms, shows potential for applications of these immobilized enzymes in the synthesis of prebiotic galacto-oligosaccharides.

Efficient Immobilization of Bacterial GH Family 46 Chitosanase by Carbohydrate-Binding Module Fusion for the Controllable Preparation of Chitooligosaccharides

Chitooligosaccharide has been reported to possess diverse bioactivities. The development of novel strategies for obtaining optimum degree of polymerization (DP) chitooligosaccharides has become increasingly important. In this study, two glycoside hydrolase family 46 chitosanases were studied for immobilization on curdlan (insoluble β-1,3-glucan) using a novel carbohydrate binding module (CBM) family 56 domain from a β-1,3-glucanase. The CBM56 domain provided a spontaneous and specific sorption of the fusion proteins onto a curdlan carrier, and two fusion enzymes showed increased enzyme stability in comparison with native enzymes. Furthermore, a continuous packed-bed reactor was constructed with chitosanase immobilized on a curdlan carrier to control the enzymatic hydrolysis of chitosan. Three chitooligosaccharide products with different molecular weights were prepared in optimized reaction conditions. This study provides a novel CBM tag for the stabilization and immobilization of enzymes. The controllable hydrolysis strategy offers potential for the industrial-scale preparation of chitooligosaccharides with different desired DPs.

One-step immobilization-purification of enzymes by carbohydrate-binding module family 56 tag fusion

Immobilization of enzymes is an essential strategy with outstanding prospects in biocatalytic processes. Nontoxic, inexpensive immobilized enzyme approach is especially important for food enzymes. We here demonstrate that a carbohydrate-binding module family 56 domain (CBM56-Tag) mediates the immobilization of fusion enzymes with the curdlan (β-1,3-glucan) particle support, thereby enabling the one-step immobilization-purification of target enzymes. CBM56-Tag exhibits an immunoglobulin-like β-sandwich fold, which can be adsorbed by curdlan via hydrogen bond-mediated binding. The maximum adsorption capacity of a fusion chitosanase (CBM56-GsCsn46A) on curdlan is 50.72 mg/g. The immobilized enzyme could be directly used in the packed-bed reactor. This immobilization strategy utilizes a natural polysaccharide without any treatment, avoiding the negative environmental effects. Moreover, the one step immobilization-purification simplifies the purification step, which reduces the use of chemicals. Our study provides a nontoxic and inexpensive immobilization strategy for the biocatalytic reaction in food industry.