Cell surface engineering of α-l-rhamnosidase for naringin hydrolysis

α-L-rhamnosidase: production, properties, and applications

α-L-rhamnosidase [EC 3.2.1.40] belongs to glycoside hydrolase (GH) families (GH13, GH78, and GH106 families) in the carbohydrate-active enzymes (CAZy) database, which specifically hydrolyzes the non-reducing end of α-L-rhamnose. Αccording to the sites of catalytic hydrolysis, α-L-rhamnosidase can be divided into α-1, 2-rhamnosidase, α-1, 3-rhamnosidase, α-1, 4-rhamnosidase and α-1, 6-rhamnosidase. α-L-rhamnosidase is an important enzyme for various biotechnological applications, especially in food, beverage, and pharmaceutical industries. α-L-rhamnosidase has a wide range of sources and is commonly found in animals, plants, and microorganisms, and its microbial source includes a variety of bacteria, molds and yeasts (such as Lactobacillus sp., Aspergillus sp., Pichia angusta and Saccharomyces cerevisiae). In recent years, a series of advances have been achieved in various aspects of α-validates the above-described-rhamnosidase research. A number of α-L-rhamnosidases have been successfully recombinant expressed in prokaryotic systems as well as eukaryotic systems which involve Pichia pastoris, Saccharomyces cerevisiae and Aspergillus niger, and the catalytic properties of the recombinant enzymes have been improved by enzyme modification techniques. In this review, the sources and production methods, general and catalytic properties and biotechnological applications of α-L-rhamnosidase in different fields are summarized and discussed, concluding with the directions for further in-depth research on α-L-rhamnosidase.

Shrimp protected from a virus by feed containing yeast with a surface-displayed viral binding protein

Recombinant Pichia pastoris biomass surface-expressing the viral binding protein PmRab7 (YSD-PmRab7) was prepared by fed-batch, aerobic fermentation with methanol induction for 48 h. By cell based ELISA assay, immunofluorescence and flow cytometry, 45% of the YSD-PmRab7 cells were positive for PmRab7. Freeze dried YSD-PmRab7 cells were added to formulated shrimp feed pellets at 0.25 g and 0.5 g per g feed and fed to 2 shrimp groups for 7 days prior to challenge with white spot syndrome virus (WSSV). Controls consisted of 1 shrimp group fed normal pellets and one fed pellets containing P. pastoris carrying an empty gene cassette. At 10 days post challenge, survival in the two control groups was 6.7 ± 6.6%, while it was 26.7 ± 6.6% in the 0.25 g YSD-PmRab7 group and significantly higher (p < 0.05) in the 0.5 g YSD-PmRab7 group at 46.7 ± 10.1%. Nested PCR assays and histopathological analysis revealed significantly lower WSSV replication levels in the 0.5 g YSD-PmRab7 group. The results indicated potential for development of YSD-PmRab7 cells as an oral prophylactic against WSSV in shrimp.

Screening and characterization of a GH78 α-l-rhamnosidase from Aspergillus terreus and its application in the bioconversion of icariin to icaritin with recombinant β-glucosidase

In this study, a GH78 α-L-rhamnosidase AtRha from Aspergillus terreus CCF3059 was screened and expressed in Pichia pastoris KM71H. The maximum enzyme activity of AtRha was 1000 U/mL after 12 days. AtRha was most active at 65 °C and pH 6.5, displaying excellent thermal stability and pH stability. The kinetic parameters Km, Vmax, kcat and kcat/Km values for pNPR were 0.481 mM, 659 μmol/min·mg, 1065 s-1 and 2214 s-1mM-1, respectively. AtRha could be inhibited by Fe2+, Hg2+ and Cu2+. Moreover, it displayed good tolerance to organic reagents with 52.6% activity in 15%(w/v) methanol. AtRha can hydrolyze icariin containing the α-1 rhamnoside linkage. Furthermore, AtRha and β-glucosidase TthBg3 showed excellent selectivity to cleave the rhamnose at the 3rd position and the glucosyl at the C-7 group of icariin, which established an effective and green method to produce the more pharmacological active icaritin. In addition, the optimal enzyme addition schemes and the reaction conditions were screened and optimized. After a two-stage transformation under optimized conditions, 0.5 g/L of icariin was transformed into 0.25 g/L of icaritin, with a corresponding molar conversion rate of 91.2%. Our findings provide a new, specific and cost-effective method for the production of icaritin in the industry.

The Efficacy of Citrus maxima Peels Aqueous Extract Against Cryptosporidiosis in Immunecompromised Mice

INTRODUCTION

 Cryptosporidiosis is an opportunistic globally distributed parasitic disease caused by protozoan Cryptosporidium where its development is closely related to the host's immune status. New therapeutic agents are a high priority as chemotherapeutics are impractical and vaccines are unavailable for young as well as immune-compromised patients or animals. The current study was designed to evaluate the therapeutic effect of the internal white (albedo) and external yellow (flavedo) peels of Citrus maxima (C. maxima) as an alternative medicinal plant. MATERIALS AND METHODS : Parasitological examination for oocysts in the stool was determined. Histopathological alterations and immunohistochemical expression of APC and cyclin D1 as well as an assessment of interferon-γ (IFN-γ) and interleukin 1β (IL-1β) in ileal tissues was carried out. In addition, the biochemical examination of serum albumin, globulin and liver enzymes were evaluated. Results revealed a significant decrease of oocysts count correlated with an amelioration of histopathological and immunohistochemical changes in ileal tissue with an enhancement of liver enzymes and inflammatory cytokines levels.

CONCLUSION

 It could be concluded that treatment with C. maxima peel extracts have a potential therapeutic and an immunoregulatory efficacy against Cryptosporidiosis. Obtained results showed that the white peel was found to have more immunological effect that could significantly enhance inflammatory cytokines response towards normal status. Hence, it can be used in the daily animal diet to give protective effects against infection.

A facile preparation of immobilized naringinase on polyethyleneimine-modified Fe3O4 magnetic nanomaterials with high activity

Polyethyleneimine-modified Fe3O4 nanoparticles (Fe3O4-PEI) were synthesized by the one-step co-precipitation method, and the resulting material was used to immobilize naringinase from the fermentation broth of Aspergillus niger FFCC uv-11. The immobilized naringinase activity could reach up to 690.74 U per g-support at the conditions of initial naringinase activity of 406.25 U mL-1, immobilization time of 4 h, glutaraldehyde concentration of 40% (w/v), immobilization temperature of 35 °C, and pH value of 5.5, with naringinase-carrying rate and naringinase activity recovery of 92.93% and 20.89%, respectively. In addition, the immobilized naringinase exhibited good pH and temperature stability in a pH range of 3.5-6.0 and temperature range of 40-70 °C, and the optimal reaction pH and reaction temperature were optimized as 5.5 and 60 °C, respectively. Besides, the immobilized naringinase could maintain 60.58% of the original activity after 10 reuse cycles, indicating that the immobilized naringinase had good reusability. Furthermore, the immobilized naringinase also performed excellent storage stability, 87.52% of enzyme activity still remained as stored at 4 °C for one month. In conclusion, the Fe3O4-PEI could be considered as a promising support for naringinase immobilization, with the advantages of high enzyme activity loading, good reusability, storage stability and rapid recovery.

Novel Strategy of Mussel-Inspired Immobilization of Naringinase with High Activity Using a Polyethylenimine/Dopamine Co-deposition Method

Mussel-inspired surface chemistry is recognized as a simple, efficient, and mild surface modification method and has become a research hotspot in many fields. In this study, polyethylenimine/dopamine was coated on the surface of SBA-15 using a co-deposition method, making it possible to immobilize naringinase with high activity and operation stability. The optimal modification and immobilization conditions as well as enzyme properties were investigated. The naringinase activity can reach up to 753.78 U/g carrier, which was much higher than those of the previous works. Besides, the residual naringinase activity still kept 78.91% of the initial activity after one month of storage and maintained 60.79% after 8 cycles. Therefore, the strategy of mussel-inspired enzyme immobilization could be recognized as a promising and universal enzyme immobilization method, with the advantages of high relative enzyme activity, enzyme carrying rate, enzyme activity recovery rate, and good reusability and storage stability.

Crystal structure of native α-L-rhamnosidase from Aspergillus terreus

α-L-Rhamnosidases cleave terminal nonreducing α-L-rhamnosyl residues from many natural rhamnoglycosides. This makes them catalysts of interest for various biotechnological applications. The X-ray structure of the GH78 family α-L-rhamnosidase from Aspergillus terreus has been determined at 1.38 Å resolution using the sulfur single-wavelength anomalous dispersion phasing method. The protein was isolated from its natural source in the native glycosylated form, and the active site contained a glucose molecule, probably from the growth medium. In addition to its catalytic domain, the α-L-rhamnosidase from A. terreus contains four accessory domains of unknown function. The structural data suggest that two of these accessory domains, E and F, might play a role in stabilizing the aglycon portion of the bound substrate.

"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.

Development and characterization of an α-l-rhamnosidase mutant with improved thermostability and a higher efficiency for debittering orange juice

The glycoside hydrolase, α-l-rhamnosidase, could remove the bitter taste of naringin from citrus juices. However, most α-l-rhamnosidases are easily deactivated at high temperatures, limiting the practice in debittering citrus juices. The V529A mutant of the α-l-rhamnosidase r-Rha1 from Aspergillus niger JMU-TS528 was developed with improved thermostability using directed evolution technology and site-directed mutagenesis. The enzyme mutant had a half-live of thermal inactivation T_(1/2) of 1.92 h, 25.00 min, and 2 min at 60, 65, and 70 °C, respectively. In addition, it had improved substrate affinity and better resistance to the inhibition of glucose. The improved substrate affinity was related to its lowered binding energy. Most significantly, the naringin content was reduced to below the bitter taste threshold by treatment with 75 U/mL of the mutant during the preheating process of orange juice production. The comprehensive results indicate that thermostability improvement could promote the practical value of α-l-rhamnosidase in citrus juice processing.

Rhamnosidase activity of selected probiotics and their ability to hydrolyse flavonoid rhamnoglucosides

Bioavailability of flavonoids is low, especially when occurring as rhamnoglucosides. Thus, the hydrolysis of rutin, hesperidin, naringin and a mixture of narcissin and rutin (from Cyrtosperma johnstonii) by 14 selected probiotics was tested. All strains showed rhamnosidase activity as shown using 4-nitrophenyl α-l-rhamnopyranoside as a substrate. Hesperidin was hydrolysed by 8–27% after 4 and up to 80% after 10 days and narcissin to 14–56% after 4 and 25–97% after 10 days. Rutin was hardly hydrolysed with a conversion rate ranging from 0 to 5% after 10 days. In the presence of narcissin, the hydrolysis of rutin was increased indicating that narcissin acts as an inducer. The rhamnosidase activity as well as the ability to hydrolyse flavonoid rhamnoglucosides was highly strain specific. Naringin was not hydrolysed by rhamnosidase from probiotics, not even by the purified recombinant enzyme, only by fungal rhamnosidase. In conclusion, rhamnosidases from the tested probiotics are substrate specific cleaving hesperidin, narcissin and to a small extent rutin, but not naringin.

Protective effect of naringin against ankylosing spondylitis via ossification, inflammation and oxidative stress in mice

Naringin is an abundant flavanone in pomelo, grapefruit as well as lime and its variants, has been shown to exhibit certain antioxidative, anti-inflammatory, anti-cancer and hypoglycemic effects. The aim of the current study was to evaluate the protective effects of naringin against ankylosing spondylitis (AS) and to elucidate the potential underlying mechanism. Firstly, a mouse model of ankylosing spondylitis (AS) was established. Next, osteocalcin (OC), alkaline phosphatase (ALP) and triglyceride (TG) activity values, inflammatory factor and oxidative stress were evaluated in the AS mice. Then, the Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) protein expression levels in the AS mice were investigated using western blot analysis. The results showed that naringin increased OC, ALP and TG activity values in the AS mouse model. Furthermore, inflammatory factor and oxidative stress levels in the AS mice were restrained by treatment with naringin. Furthermore, JAK2 and STAT3 protein expression levels were reduced by treatment with naringin. In conclusion, the present results indicated that the protective effects of naringin against AS are exerted via the induction of ossification, suppression of inflammation and oxidative stress and the downregulation of JAK2/STAT3 in mice.

Enzymatic Synthesis of Rhamnose Containing Chemicals by Reverse Hydrolysis

Rhamnose containing chemicals (RCCs) are widely occurred in plants and bacteria and are known to possess important bioactivities. However, few of them were available using the enzymatic synthesis method because of the scarcity of the α-L-rhamnosidases with wide acceptor specificity. In this work, an α-L-rhamnosidase from Alternaria sp. L1 was expressed in Pichia pastroris strain GS115. The recombinant enzyme was purified and used to synthesize novel RCCs through reverse hydrolysis in the presence of rhamnose as donor and mannitol, fructose or esculin as acceptors. The effects of initial substrate concentrations, reaction time, and temperature on RCC yields were investigated in detail when using mannitol as the acceptor. The mannitol derivative achieved a maximal yield of 36.1% by incubation of the enzyme with 0.4 M L-rhamnose and 0.2 M mannitol in pH 6.5 buffers at 55°C for 48 h. In identical conditions except for the initial acceptor concentrations, the maximal yields of fructose and esculin derivatives reached 11.9% and 17.9% respectively. The structures of the three derivatives were identified to be α-L-rhamnopyranosyl-(1→6')-D-mannitol, α-L-rhamnopyranosyl-(1→1')-β-D-fructopyranose, and 6,7-dihydroxycoumarin α-L-rhamnopyranosyl-(1→6')-β-D-glucopyranoside by ESI-MS and NMR spectroscopy. The high glycosylation efficiency as well as the broad acceptor specificity of this enzyme makes it a powerful tool for the synthesis of novel rhamnosyl glycosides.

Uncommon Glycosidases for the Enzymatic Preparation of Glycosides

Most of the reports in literature dedicated to the use of glycosyl hydrolases for the preparation of glycosides are about gluco- (α- and β-form) and galacto-sidase (β-form), reflecting the high-availability of both anomers of glucosides and of β-galactosides and their wide-ranging applications. Hence, the idea of this review was to analyze the literature focusing on hardly-mentioned natural and engineered glycosyl hydrolases. Their performances in the synthetic mode and natural hydrolytic potential are examined. Both the choice of articles and their discussion are from a biomolecular and a biotechnological perspective of the biocatalytic process, shedding light on new applicative ideas and on the assortment of biomolecular diversity. The hope is to elicit new interest for the development of biocatalysis and to gather attention of biocatalyst practitioners for glycosynthesis.