Recombinant α-L-rhamnosidase ofAspergillus terreusimmobilization in polyvinylalcohol hydrogel and its application in rutin derhamnosylation

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.

Immobilization and characterization of β-galactosidase from Aspergillus oryzae in polyvinyl alcohol hydrogels

One of the main goals of contemporary biotechnology has been the development of novel immobilized enzyme formulations. In the present study, the industrially important β-galactosidase was trapped in a polyvinyl alcohol (PVA) gel to immobilize it. The optimization of immobilization method and characterization of the immobilized enzyme were studied. The results were compared with free enzymes. The results indicate that the optimal temperature range for the enzyme to be at following immobilization is between 40°C and 50°C. At pH 7, the optimal pH, the activity increased, the Vmax value increased from 1.936 to 2.495 U mg‒1, and the Km value decreased from 4.861 to 0.982 mM. Depending on how stable the immobilized enzyme when stored, β-galactosidases immobilized on PVA gels showed 52.87% activity at the end of the seventh week and 58.86% activity at the end of the fifth week. Their initial activity subsided after three reuses. The final result was 66%. Therefore, one may argue that it increases the catalytic effect of the enzyme. As a result, it has been found that immobilized β-galactosidase has more potent enzymatic properties than free β-galactosidase, which may make it more advantageous for industrial processes. Further studies could delve deeper into the mechanistic aspects of the immobilization process in an effort to improve optimization and tailor the immobilized enzyme to specific industrial needs.

Immobilization of Ene Reductase in Polyvinyl Alcohol Hydrogel

In this study, ene reductase (ER) was entrapped in polyvinyl alcohol hydrogel, adsorbed on montmorillonite and immobilized covalently on glutaraldehyde activated 3-aminopropyl-functionalized silica gel. Although protein recovery yields were at least 85% for adsorption and covalent immobilization, only the encapsulated ER showed activity. The activity of free and entrapped ER preparations was measured by following NADPH-dependent reduction of 2-cyclohexen-1-one. The both protein recovery and activity recovery yields were calculated as 100% when 1 mg protein was used for immobilization. The both free and entrapped ER preparations showed the same optimum pH and temperature as 7.0 and 30 °C, respectively. The entrapped ER showed 34.4-fold more thermal stability than that of the free ER at 30 °C. Michaelis-Menten constant and maximum velocity values were 0.25 mM and 1.2 U/mg protein, respectively for the free ER towards 2-cyclohexen-1-one. The corresponding values were 1.5 mM and 0.9 U/mg protein for the entrapped ER. The results of time-course reduction of 2-cyclohexen-1-one showed that the entrapped ER catalyzed the reaction as effectively as the free ER. The entrapped ER remained 85% of its initial activity after 10 reused cycles.

Continuous process technology for glucoside production from sucrose using a whole cell-derived solid catalyst of sucrose phosphorylase

Advanced biotransformation processes typically involve the upstream processing part performed continuously and interlinked tightly with the product isolation. Key in their development is a catalyst that is highly active, operationally robust, conveniently produced, and recyclable. A promising strategy to obtain such catalyst is to encapsulate enzymes as permeabilized whole cells in porous polymer materials. Here, we show immobilization of the sucrose phosphorylase from Bifidobacterium adolescentis (P134Q-variant) by encapsulating the corresponding E. coli cells into polyacrylamide. Applying the solid catalyst, we demonstrate continuous production of the commercial extremolyte 2-α-D-glucosyl-glycerol (2-GG) from sucrose and glycerol. The solid catalyst exhibited similar activity (≥70%) as the cell-free extract (~800 U g-1 cell wet weight) and showed excellent in-operando stability (40 °C) over 6 weeks in a packed-bed reactor. Systematic study of immobilization parameters related to catalyst activity led to the identification of cell loading and catalyst particle size as important factors of process optimization. Using glycerol in excess (1.8 M), we analyzed sucrose conversion dependent on space velocity (0.075-0.750 h-1) and revealed conditions for full conversion of up to 900 mM sucrose. The maximum 2-GG space-time yield reached was 45 g L-1 h-1 for a product concentration of 120 g L-1. Collectively, our study establishes a step-economic route towards a practical whole cell-derived solid catalyst of sucrose phosphorylase, enabling continuous production of glucosides from sucrose. This strengthens the current biomanufacturing of 2-GG, but also has significant replication potential for other sucrose-derived glucosides, promoting their industrial scale production using sucrose phosphorylase. KEY POINTS: • Cells of sucrose phosphorylase fixed in polyacrylamide were highly active and stable. • Solid catalyst was integrated with continuous flow to reach high process efficiency. • Generic process technology to efficiently produce glucosides from sucrose is shown.

Immobilization of alpha-L-rhamnosidase on a magnetic metal-organic framework to effectively improve its reusability in the hydrolysis of rutin

α-L-Rhamnosidase (Rha) is a biotechnologically important enzyme that degrades biomass containing natural rhamnoside. Herein, the recombinant Rha was successfully immobilized on magnetic metal-organic frameworks (MOFs), and used to hydrolyze rutin. Magnetic MOFs were constructed by binding Cu²⁺ and PABA to the surface of Fe₃O₄ nanoparticles coated with a polydopamine film through coordinate covalent bonds, and the enzyme was attached to the MOFs using the cross-linking agents EDC/NHS. The immobilized enzyme Rha@MOF reached an activity of 25.09 U/g with a lower apparent K_m value compared with the free enzyme. The conversion rate of 20 g/L rutin was 91.42%, corresponding to an isoquercitrin productivity of 12.78 g/L/h. Rha@MOF also exhibited significantly improved reusability; the conversion rate was still 73.55% after 30 cycles at 60 °C. These results indicated that the magnetic MOF-immobilized enzyme was a feasible biocatalyst for the conversion of flavonoids with low aqueous solubility.

Bioproduction of Quercetin and Rutinose Catalyzed by Rutinosidase: Novel Concept of "Solid State Biocatalysis"

Quercetin is a flavonoid largely employed as a phytochemical remedy and a food or dietary supplement. We present here a novel biocatalytic methodology for the preparation of quercetin from plant-derived rutin, with both substrate and product being in mostly an undissolved state during biotransformation. This "solid-state" enzymatic conversion uses a crude enzyme preparation of recombinant rutinosidase from Aspergillus niger yielding quercetin, which precipitates from virtually insoluble rutin. The process is easily scalable and exhibits an extremely high space-time yield. The procedure has been shown to be robust and was successfully tested with rutin concentrations of up to 300 g/L (ca 0.5 M) at various scales. Using this procedure, pure quercetin is easily obtained by mere filtration of the reaction mixture, followed by washing and drying of the filter cake. Neither co-solvents nor toxic chemicals are used, thus the process can be considered environmentally friendly and the product of "bio-quality." Moreover, rare disaccharide rutinose is obtained from the filtrate at a preparatory scale as a valuable side product. These results demonstrate for the first time the efficiency of the "Solid-State-Catalysis" concept, which is applicable virtually for any biotransformation involving substrates and products of low water solubility.

An alkali tolerant α-l-rhamnosidase from Fusarium moniliforme MTCC-2088 used in de-rhamnosylation of natural glycosides

Analkali tolerant α-l-rhamnosidase has been purified to homogeneity from the culture filtrate of a new fungal strain, Fusarium moniliforme MTCC-2088, using concentration by ultrafiltration and cation exchange chromatography on CM cellulose column. The molecular mass of the purified enzyme has been found to be 36.0 kDa using SDS-PAGE analysis. The K_m value using p-nitrophenyl-α-l-rhamnopyranoside as the variable substrate in 0.2 M sodium phosphate buffer pH10.5 at50 °C was 0.50 mM. The catalytic rate constant was15.6 s^-1giving the values of k_cat/K_m is 3.12 × 10⁴M^-1 s^-1. The pH and temperature optima of the enzyme were 10.5 and 50 °C, respectively. The purified enzyme had better stability at 10 °C in basic pH medium. The enzyme derhamnosylated natural glycosides like naringin to prunin, rutin to isoquercitrin and hesperidin to hesperetin glucoside. The purified α-l-rhamnosidase has potential for enhancement of wine aroma.

"Sweet Flavonoids": Glycosidase-Catalyzed Modifications

Natural flavonoids, especially in their glycosylated forms, are the most abundant phenolic compounds found in plants, fruit, and vegetables. They exhibit a large variety of beneficial physiological effects, which makes them generally interesting in a broad spectrum of scientific areas. In this review, we focus on recent advances in the modifications of the glycosidic parts of various flavonoids employing glycosidases, covering both selective trimming of the sugar moieties and glycosylation of flavonoid aglycones by natural and mutant glycosidases. Glycosylation of flavonoids strongly enhances their water solubility and thus increases their bioavailability. Antioxidant and most biological activities are usually less pronounced in glycosides, but some specific bioactivities are enhanced. The presence of l-rhamnose (6-deoxy-α-l-mannopyranose) in rhamnosides, rutinosides (rutin, hesperidin) and neohesperidosides (naringin) plays an important role in properties of flavonoid glycosides, which can be considered as "pro-drugs". The natural hydrolytic activity of glycosidases is widely employed in biotechnological deglycosylation processes producing respective aglycones or partially deglycosylated flavonoids. Moreover, deglycosylation is quite commonly used in the food industry aiming at the improvement of sensoric properties of beverages such as debittering of citrus juices or enhancement of wine aromas. Therefore, natural and mutant glycosidases are excellent tools for modifications of flavonoid glycosides.

Influence of Three Commercial Graphene Derivatives on the Catalytic Properties of a Lactobacillus plantarum α-l-Rhamnosidase When Used as Immobilization Matrices

The modification of carbon nanomaterials with biological molecules paves the way toward their use in biomedical and biotechnological applications, such as next-generation biocatalytic processes, development of biosensors, implantable electronic devices, or drug delivery. In this study, different commercial graphene derivatives, namely, monolayer graphene oxide (GO), graphene oxide nanocolloids (GOCs), and polycarboxylate-functionalized graphene nanoplatelets (GNs), were compared as biomolecule carrier matrices. Detailed spectroscopic analyses showed that GO and GOC were similar in composition and functional group content and very different from GN, whereas divergent morphological characteristics were observed for each nanomaterial through microscopy analyses. The commercial α-l-rhamnosidase RhaB1 from the probiotic bacterium Lactobacillus plantarum, selected as a model biomolecule for its relevant role in the pharma and food industries, was directly immobilized on the different materials. The binding efficiency and biochemical properties of RhaB1-GO, RhaB1-GOC, and RhaB1-GN composites were analyzed. RhaB1-GO and RhaB1-GOC showed high binding efficiency, whereas the enzyme loading on GN, not tested in previous enzyme immobilization studies, was low. The enzyme showed contrasting changes when immobilized on the different material supports. The effect of pH on the activity of the three RhaB1-immobilized versions was similar to that observed for the free enzyme, whereas the activity-temperature profiles and the response to the presence of inhibitors varied significantly between the RhaB1 versions. In addition, the apparent K_m for the immobilized and soluble enzymes did not change. Finally, the free RhaB1 and the immobilized enzyme in GOC showed the best storage and reutilization stability, keeping most of their initial activity after 8 weeks of storage at 4 °C and 10 reutilization cycles, respectively. This study shows, for the first time, that distinct commercial graphene derivatives can influence differently the catalytic properties of an enzyme during its immobilization.

Immobilization of cells and enzymes to LentiKats®

Biocatalyst immobilization is one of the techniques, which can improve whole cells or enzyme applications. This method, based on the fixation of the biocatalyst into or onto various materials, may increase robustness of the biocatalyst, allows its reuse, or improves the product yield. In recent decades, a number of immobilization techniques have been developed. They can be divided according to the used natural or synthetic material and principle of biocatalyst fixation in the particle. One option, based on the entrapment of cells or enzymes into a synthetic polyvinyl alcohol lens with original shape, is LentiKats® immobilization. This review describes the preparation principle of these particles and summarizes existing successful LentiKats® immobilizations. In addition, examples are compared with other immobilization techniques or free biocatalysts, pointing to the advantages and disadvantages of LentiKats®.

Upscale of recombinant α-L-rhamnosidase production by Pichia pastoris Mut(S) strain

Pichia pastoris is currently one of the most preferred microorganisms for recombinant enzyme production due to its efficient expression system. The advantages include the production of high amounts of recombinant proteins containing the appropriate posttranslational modifications and easy cultivation conditions. α-L-Rhamnosidase is a biotechnologically important enzyme in food and pharmaceutical industry, used for example in debittering of citrus fruit juices, rhamnose pruning from naringin, or enhancement of wine aromas, creating a demand for the production of an active and stable enzyme. The production of recombinant α-L-rhamnosidase cloned in the Mut(S) strain of P. pastoris KM71H was optimized. The encoding gene is located under the control of the AOX promoter, which is induced by methanol whose concentration is instrumental for these strain types. Fermentation was upscaled in bioreactors employing various media and several methanol-feeding strategies. It was found that fed batch with BSM media was more effective compared to BMMH (Buffered Methanol-complex Medium) media due to lower cost and improved biomass formation. In BSM (Basal Salt Medium) medium, the dry cell weight reached approximately 60 g/L, while in BMMH it was only 8.3 g/L, without additional glycerol, which positively influenced the amount of enzyme produced. New methanol feeding strategy, based on the level of dissolved oxygen was developed in this study. This protocol that is entirely independent on methanol monitoring was up scaled to a 19.5-L fermenter with 10-L working volume with the productivity of 13.34 mgprot/L/h and specific activity of α-L-rhamnosidase of 82 U/mg. The simplified fermentation protocol was developed for easy and effective fermentation of P. pastoris Mut(S) based on dissolved oxygen monitoring in the induction phase of an enzyme production.