Kinetic study of the activation of banana juice enzymatic browning by the addition of maltosyl-beta-cyclodextrin

Progress in cyclodextrins as important molecules regulating catalytic processes of glycoside hydrolases

Cyclodextrins (CDs) are important starch derivatives and commonly comprise α-, β-, and γ-CDs. Their hydrophilic surface and hydrophobic inner cavity enable regulation of enzyme catalysis through direct or indirect interactions. Clarifying interactions between CDs and enzyme is of great value for enzyme screening, mechanism exploration, regulation of catalysis, and applications. We summarize the interactions between CDs and glycoside hydrolases (GHs) according to two aspects: 1) CD as products, substrates, inhibitors and activators of enzymes, directly affecting the reaction process; 2) CDs indirectly affecting the enzymatic reaction by solubilizing substrates, relieving substrate/product inhibition, increasing recombinant enzyme production and storage stability, isolating and purifying enzymes, and serving as ligands in crystal structure to identify functional amino acid residues. Additionally, CD enzyme mimetics are developed and used as catalysts in traditional artificial enzymes as well as nanozymes, making the application of CDs no longer limited to GHs. This review concerns the regulation of GHs catalysis by CDs, and gives insights into research on interactions between enzymes and ligands.

What do we learn from enzyme behaviors in organic solvents? - Structural functionalization of ionic liquids for enzyme activation and stabilization

Enzyme activity in nonaqueous media (e.g. conventional organic solvents) is typically lower than in water by several orders of magnitude. There is a rising interest of developing new nonaqueous solvent systems that are more "water-like" and more biocompatible. Therefore, we need to learn from the current state of nonaqueous biocatalysis to overcome its bottleneck and provide guidance for new solvent design. This review firstly focuses on the discussion of how organic solvent properties (such as polarity and hydrophobicity) influence the enzyme activity and stability, and how these properties impact the enzyme's conformation and dynamics. While hydrophobic organic solvents usually lead to the maintenance of enzyme activity, solvents carrying functional groups like hydroxys and ethers (including crown ethers and cyclodextrins) can lead to enzyme activation. Ionic liquids (ILs) are designable solvents that can conveniently incorporate these functional groups. Therefore, we systematically survey these ether- and/or hydroxy-functionalized ILs, and find most of them are highly compatible with enzymes leading to high activity and stability. In particular, ILs carrying both ether and tert-alcohol groups are among the most enzyme-activating solvents. Future direction is to learn from enzyme behaviors in both water and nonaqueous media to design biocompatible "water-like" solvents.

Effects of α-, β- and maltosyl-β-cyclodextrins use on the glucoraphanin-sulforaphane system of broccoli juice

Cyclodextrins (CDs) are macromolecules with several industrial applications, being particularly used in the food industry as health-promoting compounds protection agents, as flavour stabilizers, or to eliminate undesired tastes and browning reactions, among others. This study shows the effects of α- (10, 30 and 40 mmol L^-1 ), β- (3, 6 and 10 mmol L^-1 ) and maltosyl-β-CDs (30, 60 and 90 mmol L^-1 ) use on the health-promoting glucoraphanin-sulforaphane system of a broccoli juice up to 24 h at 22 °C. Maltosyl-β-CD (90 mmol L^-1 ) highly retained glucoraphanin content after 24 h at 22 °C, showing better effectiveness than β-CD (10 mmol L^-1 ). Sulforaphane was efficiently encapsulated with β-CD at just 3 mmol L^-1 , and the sulforaphane formed was stable during 3 h at 22 °C. On the other hand, 40 mmol L^-1 α-CD retained a high glucoraphanin content in broccoli juice. In contrast, glucoraphanin levels in juice without CDs decreased by 71% after 24 h. Consequently, CDs addition may potentially preserve glucoraphanin in this broccoli juice during industrial processing with the possibility to be later transformed by endogenous myrosinase after ingestion to the health-promoting sulforaphane. © 2018 Society of Chemical Industry.

Comparative study of the banana pulp browning process of 'Giant Dwarf' and FHIA-23 during fruit ripening based on image analysis and the polyphenol oxidase and peroxidase biochemical properties

This work presents a novel method to associate the polyphenol oxidase (PPO) and the peroxidase (POD) activities with the ripening-mediated color changes in banana peel and pulp by computational image analysis. The method was used to follow up the de-greening of peel and browning of homogenized pulp from 'Giant Dwarf' (GD: Musa AAA, subgroup Cavendish) and FHIA-23 (tetraploid hybrid, AAAA) banana cultivars. In both cultivars, the color changes of peel during the ripening process clearly showed four stages, which were used to group the fruit into ripening stages. The PPO and POD were extracted from pulp of fruit at these ripening stages, precipitated, and partially purified by gel filtration chromatography. Moreover, the pulp browning was digitally monitored after homogenization for a span time of up to 120 min. The browning level was higher for GD than FHIA-23 tissues. This fact correlated with an 11.7-fold higher PPO activity in the GD cultivar, as compared with that of FHIA-23. POD activity was 8.1 times higher for GD as compared that that of FHIA-23.

Enhancement of umami taste of hydrolyzed protein from wheat gluten by β-cyclodextrin

BACKGROUND

Wheat gluten was hydrolyzed by Flavourzyme and Neutrase at pH 7.0 and 50 °C for 8 h with β-cyclodextrin (β-CD) employed in the reaction. The hydrolysates were enzyme deactivated, cooled and centrifuged at 1500 × g for 15 min.

RESULTS

Sensory and chemical characterization of wheat gluten hydrolysates WGH-1 (reaction conducted without β-CD), WGH-2 (reaction conducted with β-CD) and WGH-3 (β-CD added to WGH-1) was performed. WGH-2 revealed enhanced umami taste and higher hydrolyzing degree, total free amino acid amount, protein yield and umami taste amino acid (Glu + Asp) amount. High-performance liquid chromatography showed that the proportion of molecular weight 180-500 Da in WGH-2 was 11.5% higher than that in WGH-1. Further research indicated that β-CD had multiple effects on the hydrolysis. It could not only increase the solubility of wheat gluten but also form inclusion complexes with resultants. This can both promote the hydrolysis and protect oligopeptides from degradation.

CONCLUSION

β-CD was found to have the ability to increase the umami taste of enzyme-hydrolyzed vegetable protein from wheat gluten. The reasons analyzed were that β-CD could take part in the hydrolysis process by improving the solubility of wheat gluten and form inclusion complexes with resultants. © 2016 Society of Chemical Industry.

Experimental and Theoretical Investigations on the Supermolecular Structure of Isoliquiritigenin and 6-O-α-D-Maltosyl-β-cyclodextrin Inclusion Complex

Isoliquiritigenin (ILTG) possesses many pharmacological properties. However, its poor solubility and stability in water hinders its wide applications. The solubility of bioactive compounds can often be enhanced through preparation and delivery of various cyclodextrin (CD) inclusion complexes. The 6-O-α-d-maltosyl-β-CD (G₂-β-CD), as one of the newest developments of CDs, has high aqueous solubility and low toxicity, especially stable inclusion characteristics with bioactive compounds. In this work, we for the first time construct and characterize the supermolecular structure of ILTG/G₂-β-CD by scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffractometry (XRD). The solubility of ILTG in water at 25 °C rises from 0.003 to 0.717 mg/mL by the encapsulation with G₂-β-CD. Our experimental observations on the presence of the ILTG/G₂-β-CD inclusion complex are further supported by the ONIOM(our Own N-layer Integrated Orbital molecular Mechanics)-based QM/MM (Quantum Mechanics/Molecular Mechanics) calculations, typically substantiating these supermolecular characteristics, such as detailed structural assignments, preferred binding orientations, selectivity, solvent effects, interaction energies and forces of the ILTG/G₂-β-CD inclusion complex. Our results have elucidated how ILTG interacts with G₂-β-CD, demonstrating the primary host-guest interactions between ILTG and G₂-β-CD, characterized by hydrogen bonds, hydrophobic interactions, electrostatic forces, and conformational effects, are favored for the formation of the ILTG/G₂-β-CD inclusion.

Cyclodextrin-Based Solid-Gas Clathrates

"Cyclodextrin-gas" clathrates were obtained by crystallization from water solution of α-, β-, and γ-cyclodextrins (CDs) under pressure of the gas to be entrapped into the CD molecules. When the pressure is released, these clathrates are stable at ambient conditions and dissociate at elevated temperature, which makes them interesting for various applications as foam boosters in food and other industries. It was found that under these conditions α-CD forms clathrates with all of the gases used in this study (N2, N2O, CO2, Ar), whereas β- and γ-CDs can form clathrates only with N2. The concentration of the cyclodextrin and the temperature and pressure of the gas were varied for achieving higher clathrate yield and larger amount of embedded gas. Highest values of about 2 wt % were found for α-CD-N2O, as it releases in the temperature range of 40-60 °C.

Interaction of polyphenol oxidase of Solanum tuberosum with β-cyclodextrin: Process details and applications

Polysaccharides differing in structure and chemical nature were screened for their ability to bind non-covalently with polyphenol oxidase (PPO) from potato (as a model) and their effect on enzyme activity. All the polysaccharides selected inhibited the PPO but β-cyclodextrin showed maximum inhibition under optimum conditions. Process details for the inhibition of PPO were studied with respect to concentration of β-cyclodextrin, temperature, pH, and time. Higher inhibition constant and lower half life was obtained at 40 °C than at 30 °C in the presence of inhibitor. β-Cyclodextrin showed mixed type of inhibition of PPO. β-Cyclodextrin was further exploited as anti-browning agent in selected fruit juices. It not only showed a significant anti-browning effect on freshly prepared potato juice but was also effective in other fruit juices. Better effect was seen in pineapple, apple and pear as compared to banana, sugarcane and guava fruit juices.

Bridging of a substrate between cyclodextrin and an enzyme's active site pocket triggers a unique mode of inhibition

BACKGROUND

Methionyl-7-amino-4-methylcoumarin (MetAMC) serves as a substrate for the Escherichia coli methionine aminopeptidase (MetAP) catalyzed reaction, and is routinely used for screening compounds to identify potential antibiotic agents. In pursuit of screening the enzyme's inhibitors, we observed that 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), utilized to solubilize hydrophobic inhibitors, inhibited the catalytic activity of the enzyme, and such inhibition was not solely due to sequestration of the substrate by HP-β-CD.

METHODS

The mechanistic path for the HP-β-CD mediated inhibition of MetAP was probed by performing a detailed account of steady-state kinetics, ligand binding, X-ray crystallographic, and molecular modeling studies.

RESULTS

X-ray crystallographic data of the β-cyclodextrin-substrate (β-CD-MetAMC) complex reveal that while the AMC moiety of the substrate is confined within the CD cavity, the methionine moiety protrudes outward. The steady-state kinetic data for inhibition of MetAP by HP-β-CD-MetAMC conform to a model mechanism in which the substrate is "bridged" between HP-β-CD and the enzyme's active-site pocket, forming HP-β-CD-MetAMC-MetAP as the catalytically inactive ternary complex. Molecular modeling shows that the scissile bond of HP-β-CD-bound MetAMC substrate does not reach within the proximity of the enzyme's catalytic metal center, and thus the substrate fails to undergo cleavage.

CONCLUSIONS

The data presented herein suggests that the bridging of the substrate between the enzyme and HP-β-CD cavities is facilitated by interaction of their surfaces, and the resulting complex inhibits the enzyme activity.

GENERAL SIGNIFICANCE

Due to its potential interaction with physiological proteins via sequestered substrates, caution must be exercised in HP-β-CD mediated delivery of drugs under pathophysiological conditions.

Evaluation of the Freezing and Thawing Cryoconcentration Process on Bioactive Compounds Present in Banana Juice from Three Different Cultivars

In this research, we produced concentrates of banana juices from three different cultivars of bananas (Enano gigante and two hybrids FHIA-17 and FHIA-23) by the freezing and thawing method. To track the cryoconcentration process, different parameters were monitored in the melted fractions, such as variation of the content of soluble solids, concentration of polyphenols (Folin–Ciocalteu), reducing sugar (DNS assay), minerals (K, Mg, Ca, P, Na, Mn, Cu and B) by inductively coupled plasma-optical emission spectroscopy and the main volatile compounds by headspace-GC–MS. It was found that the solution obtained during thawing showed higher concentrations than the original solution. The concentrations of polyphenols were duplicated in FHIA-17 cultivar (758.53 mg/100 ml), and the concentrates obtained in this study proved to be good sources of K and Mg 5,054.6 mg/l and 485.4 mg/l with around 70% and 40% of the recommended daily intake (RDI), respectively. In addition, the concentrates contained a very low level of Na around 1% of the RDI. Furthermore, the cryoconcentration process of the bioactive compounds presented a sigmoid behavior, and the inflexion point in the function was proposed as stop point of the process. Finally, the main volatile compounds reported as responsible for the banana aroma were identified, and its cryoconcentration proved. These results suggest that consumption of banana juice concentrates obtained by the freezing and thawing method can provide bioactive compounds needed for health.

Microencapsulation of Banana Juice from Three Different Cultivars

In order to effectively process and utilize surplus bananas and those without the quality for export, in this research it is proposed to microencapsulate the banana juice by means of spray drying and using maltodextrin as the covering material. Three cultivars Enano gigante (Musa AAA, subgroup Cavendish), and the tetraploids hybrids (AAAA), FHIA-17 and FHIA-23 were selected for this research. Being Enano gigante, the cultivar shows the highest glass transition temperature. The drying parameters were established, depending upon the ratio of juice/maltodextrin and the drying air temperature. The optimal drying air temperature was 220°C for the three cultivars with a 20% juice/maltodextrin ratio for both the Enano Gigante and the FHIA-23, while in the FHIA-17 there were no significant differences between the juice/maltodextrin ratios. The morphology and size distribution of the microcapsules were observed by a scanning electron microscopy. The number of particles is directly proportional to the temperature and inversely proportional to the juice/maltodextrin ratio. A Weibull particle size distribution was common to all treatments. There is a correlation between the principal components and clustering analyses with the optimization of the system. The principal components analysis considers three Weibull parameters (obtained from the particle size distribution) and the powders moisture percentage.

Comparative effect of the addition of α-, β-, or γ-cyclodextrin on main sensory and physico-chemical parameters

Although α-, β-, and γ-cyclodextrins (CDs) have been widely used to improve the color of different fruit juices, a comparative study of the effect of these natural CDs on other properties that also influence pear juice quality, such as odor and aroma, have not been reported yet. In this study, the comparative effect of the addition of α-, β-, and γ-cyclodextrin, the only CDs authorized to be used in the food industry by U.S. Food and Drug Administration (FDA) and European Union, on the pear juice quality was evaluated for the first time. Several instrumental and sensory properties of this fruit juice, such as color, volatile composition, odor, and aroma have been evaluated in the absence and presence of α-, β-, and γ-CD. A study of the aroma profile of pear juice showed that esters, aldehydes, alcohols, and terpenes were the most important chemical families. However, the addition of α-, β-, and γ-CD had different effects on both the concentration of individual volatile compounds and their chemical grouping. Furthermore, a trained sensory panel was used to evaluate color, overall odor, overall aroma, and overall quality of pear juice in the presence or absence of CDs.

PRACTICAL APPLICATION

After comparing the effects of the addition of α-, β-, and γ-CD on pear juice, our final recommendation is to add α-CD (the natural CD formed by 6 units of glucose) to pear juice because it will significantly increase the global quality of the juice by reducing its browning but without producing a significant reduction in the aroma quality.

Preparation and characterization of the inclusion complex of chlorpyrifos in cyclodextrins to improve insecticide formulations

The chemical control of crops by organophosphate insecticide treatment is usually limited because the insecticides do not maintain their efficiency for long periods for several reasons, including environmental conditions or rapid degradation of the active ingredient. Chlorpyrifos is an organophosphate insecticide used worldwide to control a variety of soil insects and arthropods in a wide range of crops. It is easily soluble in organic solvents but shows poor water solubility. The inclusion of chrorpyrifos in cyclodextrins (CDs) improves its water solubility, bioavailability, and insecticidal activity and helps prevent overdosing, leading to more cost-effective and more environmentally friendly agricultural practices. Solubility studies of chlorpyrifos in the presence of different types of CDs show G2-beta-CDs to be the most effective CDs in the complexation process, giving 1:2 complexes, with complexation constant (Kc) values of 12.34 +/- 3.1 M(-1) for K1 and 3895 +/- 183 M(-1) for K2. These complexation constant values were corroborated by applying a fluorimetric method.