Production of Cell Membrane-Bound α- and β-Glucosidase by Lactobacillus acidophilus

Hydrolytic enzymes, viz. α- and β-glucosidase, were produced from indigenous isolate, Lactobacillus acidophilus, isolated from fermented Eleusine coracana. Production of these enzymes was enhanced by optimizing media using one factor at a time followed by response surface methodology. The optimized media resulted in a 2.5- and 2.1-fold increase in α- and β-glucosidase production compared with their production in basal MRS medium. Localization studies indicated 80% of the total activity to be present in the cell membrane-bound fraction. Lack of sufficient release of these enzymes using various physical, chemical, and enzymatic methods confirmed their unique characteristic of being tightly cell membrane bound. Enzyme characterization revealed that both α- and β-glucosidase exhibited optimum catalytic activity at 50 °C and pH 6.0 and 5.0, respectively. K _m and V _max of α-glucosidase were 4.31 mM and 149 μmol min⁻¹ mL⁻¹ for p-nitrophenyl-α-d-glucopyranoside as substrate and 3.8 mM and 120 μmol min⁻¹ mL⁻¹ for β-glucosidase using p-nitrophenyl-β-d-glucopyranoside as the substrate.     

Partial Purification and Characterization of Extracellular Fructofuranosidase with Transfructosylating Activity from <Emphasis Type="Italic">Candida</Emphasis> sp.

The present work was carried out with the aim to investigate some properties of an extracellular fructofuranosidase enzyme, with high transfructosylating activity, from Candida sp. LEB-I3 (Laboratory of Bioprocess Engineering, Unicamp, Brazil). The enzyme was produced through fermentation, and after cell separation from the fermented medium, the enzyme was concentrated by ethanol precipitation and than purified by anion exchange chromatography. The enzyme exhibited both fructofuranosidase (FA) and fructosyltransferase (FTA) activities on a low and high sucrose concentration. With sucrose as the substrate, the data fitted the Michaellis–Menten model for FA, showing rather a substrate inhibitory shape for fructosyltransferase activity. The K _m and v _max values were shown to be 13.4 g L⁻¹ and 21.0 μmol mL⁻¹ min⁻¹ and 25.5 g L⁻¹ and 52.5 μmol mL⁻¹ min⁻¹ for FA and FTA activities, respectively. FTA presented an inhibitory factor K _i of 729.8 g L⁻¹. The optimum conditions for FA activity were found to be pH 3.25–3.5 and temperatures around 69 °C, while for FTA, the optimum condition were 65 °C (±2 °C) and pH 4.00 (±0.25). Both activities were very stable at temperatures below 60 °C, while for FA, the best stability occurred at pH 5.0 and for FTA at pH  4.5–5.0. Despite the strong fructofuranosidase activity, causing hydrolysis of the fructooligosaccharides (FOS), the high transfructosilating activity allows a high FOS production from sucrose (44%).     

Determination of Histamine in Some Foods by Isotachophoretic Method with Simple Sample Preparation

A one-dimensional capillary isotachophoretic method in cationic system of the separation has been applied for histamine determination in food samples. The proposed electrolyte system consisted of 0.01 M potassium hydroxide with l-valine to pH = 9.9 as the leading electrolyte and 0.02 M 2-amino-2-hydroxymethyl-propane-1,3-diol adjusted to pH = 8.3 with 0.1 M hydrochloric acid as terminating electrolyte. Proposed method was characterized by linearity range 5–50 mg L⁻¹ and R ² = 0.9982, accuracy (recoveries ranged from 95% to 102%), detection (2.10 mg L⁻¹), and quantification (7.01 mg L⁻¹) limits. The sample preparation for proposed electrophoretic method included only simple extraction with trichloroacetic acid with filtration and derivatisation stage are avoided. The histamine concentration was determined in meat (turkey, chicken, beef and pork) and meat products (ripened sausage and dry-cured ham), fish (smoked salmon and mackerel), and different kind of mildew and mold ripened cheeses samples. The histamine content ranged from not detected level for fresh meat to 29.63 mg 100 g⁻¹ for cheese samples. The reversed phase HPLC was applied as reference method and the F-Snedecor test and the t test were employed to compare the precision and accuracy of the both methods. Positive correlations were found between the two analytical methods for histamine determination in food products. The obtained results indicate that the proposed electrophoretic method is simple, precise, accurate, and convenient.     

Evaluation of Functional Properties in Protein Hydrolysates from Bluewing Searobin (Prionotus punctatus) Obtained with Different Microbial Enzymes

Enzymatic hydrolysis of proteins from low commercial value fish could be produced for uses like functional ingredients in a wide and always increasing zone of application in different food products. The objective of this work was to evaluate the functional properties and the amino acid profile of enzymatic hydrolysates from Bluewing searobin (Prionotus punctatus), using two microbial enzymes, Alcalase and Flavourzyme. The enzymatic hydrolysate obtained through the addition of the enzyme Alcalase reached the maximum solubility (42%) at pH 9, water holding capacity (WHC) of 2.4 g_water  g_protein ⁻¹, 4.5 g_oil g_protein ⁻¹ of oil holding capacity (OHC) and an emulsifying activity index (EAI) of 54 m² g_solids ⁻¹ at pH 3. On the other hand, the hydrolysate obtained from Flavourzyme attained 38% of solubility at pH 9, 3.7 g_water  g_protein ⁻¹ and 5.5 g_oil g_protein ⁻¹ for the holding capacities, and an EAI of 71 m² g_solids ⁻¹ at pH 11. The hydrolysate with Flavourzyme produced best results for WHC, OHC, and EAI because it had solubility lower than the hydrolysate of Alcalase. The hydrolysate produced by Alcalase had a higher amino acid content compared with Flavourzyme’s hydrolysate. However, both showed a good essential amino acid amounts. In general, these results indicate the potential utilization of the hydrolysate from Bluewing searobin in food formulations for the direct human consumption.     

Production and Application of Xylanase from Penicillium sp. Utilizing Coffee By-products

The lignocellulosic coffee by-products such as coffee pulp, coffee cherry husk, silver skin, and spent coffee were evaluated for their efficacy as a sole carbon sources for the production of xylanase in solid-state fermentation using Penicillium sp. CFR 303. Among the residues, coffee cherry husk was observed to produce maximum xylanase activity of 9,475 U/g. The process parameters such as moisture (50%), pH (5.0), temperature (30 °C), particle size (1.5 mm), inoculum size (20%), fermentation time (5 days), carbon source (xylose), and nitrogen source (peptone) were optimized and the enzyme activity was in the range of 19,560–20,388 U/g. The enzyme production was further improved to 23,494 U/g with steam as a pre-treatment. The extracellular xylanase from the fungal source was purified to homogeneity from culture supernatant by ammonium sulfate fractionation, DE32-cellulose with a recovery yield of 25.5%. It appeared as a single band on SDS-PAGE gel with a molecular mass of approximately 27 kDa. It had optimum parameters of 50 °C temperature, pH 5.0, K _m 5.6 mg/mL, and V _max 925 μmol mg⁻¹ min⁻¹ with brichwood xylan as a substrate. The crude enzyme hydrolysed lignocellulosic substrate as well as industrial pulp. Production of xylanase utilizing coffee by-products constitutes a renewable resource and is reported for the first time.     

Microwave treatment of dietary gelatin does not generate cis-4-hydroxy-l-proline, an inhibitor of collagen biosynthesis

 Aqueous solutions (5 g/100 ml) of commercial preparations of (a) an enzymatic partial hydrolysate of gelatin and (b) type A gelatin were subjected to threefold heating to boiling in a domestic microwave oven at 750 W and to conventional heating. Then samples were totally hydrolyzed (6 M hydrochloric acid, 110  °C, 24 h) and investigated for the presence of eight possible stereoisomers of 3- and 4-hydroxyproline (Hyp) using capillary gas chromatography. Amino acids were analyzed as N(O)-trifluoroacetyl 2-propyl esters on Chirasil-l-Val and detected by selected ion monitoring mass spectrometry. Blanks of (a) and (b) were analyzed in parallel. Relative amounts of 5.0±0.2% cis-4-d-Hyp were generated from native trans-4-l-Hyp as a result of total hydrolysis in all samples and independent of previous treatment. Notably, neither cis-3-l-Hyp nor cis-4-l-Hyp could be detected in either of the gelatin samples. Thus a report on the generation of antifibrotic and therefore potentially hazardous cis-3-l-Hyp and cis-4-l-Hyp from protein-bonded native trans-3-l-Hyp and trans-4-l-Hyp on microwave heating of infant formulae could not be confirmed.     

Benzyloxybenzaldehydethiosemicarbazone: Extractive Spectrophotometric Reagent for the Determination of Cu(II) in Food and Water Samples

Benzyloxybenzaldehydethiosemicarbazone (BBTSC) was prepared and developed a new method for the simple, highly selective, and extractive spectrophotometric determination of copper(II) with BBTSC at wavelength 370 nm. The metal ion formed a bluish green colored complex with BBTSC in acetate buffer of pH 5.0, which was easily extractable into n-butanol with 1:1(metal/ligand) composition. The method obeys Beer’s law in the range of 0.5–5.2 ppm. The molar absorptivity and Sandell’s sensitivity were found to be 1.5 × 10⁴ l mol⁻¹ cm⁻¹ and 0.00412 g cm⁻², respectively. The correlation coefficient of the Cu(II)–BBTSC complex was 0.998, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD; n = 10), which was 0.377% and its detection limit 0.0204 μg ml⁻¹. The interfering effect of various cations and anions were also studied. The proposed method was successfully applied to the determination of copper(II) in food and water samples. Comparing the results with those obtained using an atomic absorption spectrophotometer tested the validity of the method.     

Stability of naturally occurring 2,5-dimethyl-4-hydroxy-3 [2H]-furanone derivatives

The stability, in aqueous buffer solutions at different pH values (pH 2.0–8.0, interval: 1.5 pH units), of 2,5-dimethyl-4-hydroxy-3[2H]-furanone (Furaneol, DMHF, 1), its methoxy derivative 2,5-dimethyl-4methoxy-3[2H]-furanone (methoxyfuraneol, mesifurane, DMMF, 2 and the glycosidically bound forms DMHF β-D-glucopyranoside 3 and DMHF 6′-O-malonyl-β-Dglucopyranoside 4 was investigated over a period of 32 days at 23 °C. Only slight decomposition of 2 and 3 was observed, whereas 1 and 4 were found to be unstable at all pH values. In addition, 3 and 4 were subjected to enzymatic hydrolysis. In contrast to the rapid hydrolysis of 3, the malonylated glycoside, 4, remained unaffected by enzymatic treatment with β-glucosidase (Emulsin). Using a pectinolytic enzyme preparation (Rohapect D5L; R?hm, Darmstadt, Germany) with esterase activities, hydrolysis of 4 was achieved. Received: 25 September 1996     

Electrochemical Determination of Phenothrin in Agricultural Formulations, Vegetables, and Storage Bags of Wheat and Rice by Differential Pulse Adsorptive Stripping Voltammetry (DP-AdSV)

An electroanalytical method has been developed for the determination of the pesticide phenothrin by differential pulse adsorptive stripping voltammetry on a hanging mercury drop electrode in universal buffer as supporting electrolyte. The best adsorption conditions were found to be pH 6.0, an accumulation potential of −0.6 V, and an accumulation time of 75 s. Effects of stirring rate, scan rate, pulse amplitude, and purge time were examined for the optimization of instrumental conditions. Calibration curve is linear in the range 2 × 10⁻⁹ to 2 × 10⁻⁷ mol l⁻¹ with a detection limit of 1.9 × 10⁻¹⁰ mol l⁻¹. The correlation coefficient and relative standard deviation were 0.995% and 1.1%. The method is applied to the determination of the phenothrin in agricultural formulations, vegetables, and storage bags of wheat and rice under Food Corporation of India’s storage system.     

Simple Phosphate Buffer Extraction for the Determination of Fumonisins in Masa,Maize, and Derived Products

An accurate determination of fumonisins in masa can be troublesome because of difficulties often experienced in obtaining satisfactory recoveries. In this study, a new extraction method, effective both for masa and for maize and derived products, has been developed. The method extracts fumonisins using a 0.4 M phosphate buffer (PB) at pH 7.5, without any organic solvent; the purification of the extract is performed by an immunoaffinity column and the quantification by HPLC–MS/MS. The average recovery percentages were 95.5 ± 1.9% and 96.7 ± 2.1% for fumonisin B₁ and B₂, respectively. The limit of detection and of quantification for both fumonisins were 10 and 30 μg kg⁻¹, respectively. For masa and tortillas, PB pH 7.5 gave significantly higher results when compared with AOAC and other published extraction methods; for maize flour, PB gave generally higher results, even if the difference with the other extraction methods was not always significant.     

Evaluation of Protease-producing Ability of Fish Gut Isolate Bacillus cereus for Aqua Feed

Extracellular protease production by Bacillus cereus isolated from the intestine of fish Mugil cephalus has been investigated in shake-flask experiment using different preparations of tuna-processing waste such as raw fish meat, defatted fish meat, alkali hydrolysate, and acid hydrolysate as nitrogen source. Among the tuna preparations tested, defatted fish meat supported the maximum protease production (134.57 ± 0.47 U ml⁻¹), and 3% concentration of the same was found to be optimum for maximizing the protease production (178.50 ± 0.28 U ml⁻¹). Effect of carbon sources on protease production in the optimized concentration of defatted tuna fish meat revealed that galactose aided the higher protease production (259.83 ± 0.04 U ml^–1) than the other tested carbon sources and a concentration of 1.5% galactose registered as optimum to enhance the protease production (289.40 ± 0.16 U ml⁻¹). The halotolerancy of B. cereus for protease production indicated that 3% of sodium chloride was optimum to yield maximum protease (301.63 ± 0.20 U ml⁻¹). Among the surfactants tested, protease production was high in Triton X 100-added medium (298.63 ± 0.12 U ml⁻¹) when compared to other surfactants, and its optimum concentration recorded was 0.8% (320.57 ± 0.17 U ml⁻¹) for more protease production. Partial characterization of crude enzyme revealed that pH 7.0 (278.90 ± 0.08 U ml⁻¹) and 60°C temperature (332.37 ± 0.18 U ml⁻¹) were optimum for better protease activity by B. cereus.     

Application of Catalytic Hydrogen Evolution in the Presence of Neonicotinoid Insecticide Clothianidin

Clothianidin, a new generation of pesticide, was determined in spiked tap water, apple juice, and soil by square-wave adsorptive stripping voltammetry. The method of determination is based on the hydrogen evolution reaction catalyzed by clothianidin at the hanging mercury drop electrode. The optimal signal was detected at −1.4 V versus Ag/AgCl in citrate buffer at pH 2.2. Various parameters such as pH, buffer concentration, frequency, amplitude, step potential, accumulation time, and potential were investigated to enhance the sensitivity of the determination. The optimal results were recorded at an accumulation potential of −0.35 V, accumulation time of 7 s, amplitude of 100 mV, frequency of 200 Hz, and step potential of 7 mV. The mechanism of catalytic hydrogen evolution was considered under experimental and theoretical conditions. This electroanalytical procedure enabled to determine clothianidin in the concentration range 9 × 10⁻⁹–4 × 10⁻⁶ mol L⁻¹ in supporting electrolyte and tap water, 1 × 10⁻⁷–4 × 10⁻⁶ mol L⁻¹ in diluted apple juice, and 2 × 10⁻⁷–1 × 10⁻⁶ mol L⁻¹ in soil. The detection and quantification limits in supporting electrolyte and diluted apple juice were found to be 2.6 × 10⁻⁹, 8.6 × 10⁻⁹ and 3 × 10⁻⁸, and 1 × 10⁻⁷ mol L⁻¹, respectively. A standard addition method was successfully used to determine clothianidin in spiked tap water, spiked apple juice, and spiked soil.     

Synthesis of oligosaccharides with lactose and N-acetylglucosamine as substrates by using β-d-galactosidase from Bacillus circulans

In the present study, β-d-galactosidase from Bacillus circulans was proved to be a suitable biocatalyst for the production of N-acetyl-oligosaccharides with lactose and N-acetylglucosamine (GlcNAc) as biocatalyst. During the hydrolysis of lactose, apart from no ultraviolet absorption oligosaccharides such as β-d-Galp-(1 → 6)-d-Glcp (6′-allolactose) and β-d-Galp-(1 → 4)-β-d-Galp-(1 → 4)-d-Glcp (4′-galactosyl-lactose), the formation of four N-acetyl-oligosaccharides was followed by high-performance liquid chromatography with a diode-array detector. The four N-acetyl-oligosaccharides were isolated from the reaction mixture and identified to be as β-d-Galp-(1 → 4)-d-GlcpNAc (LacNAc, I), β-d-Galp-(1 → 6)-d-GlcpNAc (allo-LacNAc, II), β-d-Galp-(1 → 4)-β-d-Galp-(1 → 4)-d-GlcpNAc (III), β-d-Galp-(1 → 4)-β-d-Galp-(1 → 4)-β-d-Galp-(1 → 4)-d-GlcpNAc (IV) by authentic standards and the spike technique or high-resolution mass spectrometry with an electrospray ionization source and nuclear magnetic resonance spectroscopy. Furthermore, the effects of synthetic conditions including reaction temperature, concentration of substrate, molar ratio of donor/acceptor and enzyme concentration on the formation of N-acetyl-oligosaccharides were examined. We found that the optimal synthetic conditions were different for production of oligosaccharides with β-(1 → 4) linkages and β-(1 → 6) linkage. The optimal reaction conditions for I, III and IV were 40 °C, 0.50 M lactose and 0.50 M GlcNAc and 1.0 U/mL of enzyme. Under such conditions, the N-acetyl-oligosaccharides formed were composed of 28.75% of I, 2.29% of II, 9.47% of III and 5.67% of IV. On the other hand, suitable reaction conditions found for II were 40 °C, 0.50 M lactose and 0.50 M GlcNAc and 2.0 U/mL of enzyme.     

Flocculation Properties of Poly(��-Glutamic Acid) Produced from Bacillus subtilis Isolate

Bacillus subtilis R 23 produced extracellular biopolymer showing excellent flocculation activity. The biopolymer was confirmed as poly(γ-glutamic acid) (PGA) using high-performance liquid chromatography profile and product characterization. The production, characteristics, and flocculation properties of PGA were studied. PGA produced by B. subtilis R 23 was devoid of any polysaccharides and had a molecular weight of 6.2 × 10⁶ Da. The flocculating activity of PGA in the kaolin suspension was markedly stimulated by the addition of bivalent and trivalent cations in optimum concentration. The pH of reaction mixture also influenced the flocculating activity. Response surface methodology was used to establish the optimum parameters for maximum flocculating activity and to study their interactions. A maximum flocculating activity of 30.32 ± 1.4 1/optical density was obtained with 7.5 mg/L of PGA in combination with 8.0 mM of Ca⁺² at pH 7.5.     

Flavonoid glycosides from cowpea seeds (Vigna sinensis K.) inhibit LDL oxidation

Six flavonoid glycosides were isolated from the n-butanol fraction of cowpea seeds (Vigna sinensis K.) through silica gel (SiO₂) and octadecyl silica gel (ODS) column chromatographies. Based on their chemical structures determined via interpretation of spectroscopic data including NMR, MS, and IR, the compounds were identified as kaempferol 3-O-β-d-sophoroside (1), quercetin 3-O-β-d-sophoroside (2), isoquercitrin (3), hyperin (4), catechin 7-O-β-d-glucopyranoside (5), and quercetin 3-O-β-Dglucopyranosyl( 1→6)-O-β-d-galactopyranoside (6). This is the first report of the isolation of these flavonoids from this plant. Among these flavonoids, compound 2, 5, and 6 significantly inhibited LDL oxidation exhibiting 96.0±0.1 (IC₅₀: 3.9 μM), 96.8±1.7 (IC₅₀: 2.9 μM), and 97.4±0.1% (IC₅₀: 3.5 μM) inhibition, respectively, at a concentration of 40 μM.     

Direct Determination of Molybdenum in Milk and Infant Food Samples Using Slurry Sampling and Graphite Furnace Atomic Absorption Spectrometry

A fast and efficient method to determine molybdenum, Mo, in milk and other infant food by atomic absorption spectrometry with electrothermal atomization employing slurry sampling was developed. Slurries were prepared in ultrapure water with 5 to 20 min of sonication in concentrations of 10% w/v. The injection of 5.0 μL of a 0.1% (v/v) cetyl trimethyl ammonium chloride solution before the temperature program reduced the effect of build-up of carbonaceous residues within the atomizer. Europium (chemical modifier) and niobium (permanent modifier) were chosen for use from several potential modifiers. The parameters of merit were obtained in the optimized conditions T _a  =  2,700 oC, T _p  = 2,000 oC, tp = 20 s, and Eu 5.0 μg + permanent Nb 500.0 μg. These parameters were linear working range up to 100.0 μg/L, limit of detection (1.1 ± 0.1) μg/L, aqueous calibration, and standard addition curves with r ² > 0.9900 and relative standard deviation of 0.6% to 8.7%. The accuracy was evaluated by recovery tests and by certified material analysis; the agreement among these numbers validated the method. The powdered sample concentrations were between 39 and 1,570 μg/kg.     

Storage Properties of Low Fat Fish and Rice Flour Coextrudates

In the present study, response surface method (RSM) and genetic algorithm (GA) were used to study the effects of process variables like screw speed, rpm (x ₁), L/D ratio (x ₂), barrel temperature (°C; x ₃), and feed mix moisture content (%; x ₄), on flow rate of biomass during single-screw extrusion cooking. A second-order regression equation was developed for flow rate in terms of the process variables. The significance of the process variables based on Pareto chart indicated that screw speed and feed mix moisture content had the most influence followed by L/D ratio and barrel temperature on the flow rate. RSM analysis indicated that a screw speed > 80 rpm, L/D ratio > 12, barrel temperature > 80 °C, and feed mix moisture content > 20% resulted in maximum flow rate. Increase in screw speed and L/D ratio increased the drag flow and also the path of traverse of the feed mix inside the extruder resulting in more shear. The presence of lipids of about 35% in the biomass feed mix might have induced a lubrication effect and has significantly influenced the flow rate. The second-order regression equations were further used as the objective function for optimization using genetic algorithm. A population of 100 and iterations of 100 have successfully led to convergence the optimum. The maximum and minimum flow rates obtained using GA were 13.19 × 10⁻⁷ m³/s (x ₁ = 139.08 rpm, x ₂ = 15.90, x ₃ = 99.56 °C, and x ₄ = 59.72%) and 0.53 × 10⁻⁷ m³/s (x ₁ = 59.65 rpm, x ₂ = 11.93, x ₃ = 68.98 °C, and x ₄ = 20.04%).     

Analytical Methods for the Evaluation of α-<Emphasis Type="SmallCaps">l</Emphasis>-Fucosidase Activity in Sheep Milk

The lack of analytical methods for measuring the activity of highly thermolable endogenous enzymes in sheep milk is a factor that hampers the protection of typical Protected Designation of Origin (PDO) dairy products made from raw milk. In order to provide a solution, this study assesses, tests, and fully validates analytical procedures for the determination of α-l-fucosidase activity in sheep milk. While the UV–VIS method has been optimized for this matrix in order to solve clarification problems before the spectrophotometric reading, a reversed phase high-performance liquid chromatography literature method proposed for bovine milk has been successfully applied also to sheep milk. Both methods have been fully validated in terms of sensitivity, linearity, precision, and accuracy, displaying low detection and quantification limits, excellent linearity over a wide enzymatic activity interval, very good repeatability and reproducibility, and the lack of any bias. The analysis of a number of real samples of whole sheep milk has allowed the evaluation of an average value (46.78 ± 5.49 U mL⁻¹) and range (from 29.27 ± 2.60 to 72.64 ± 1.17 U mL⁻¹) of α-l-fucosidase activity. Such activity does not seem to differ substantially from those measured for bovine milk. Finally, marked seasonal variability has been observed in this preliminary dataset.     

Purification and application of α-galactosidase from germinating coffee beans (<Emphasis Type="Italic">Coffea arabica</Emphasis>)

The objective of this study was to prepare and purify α-galactosidase (α-Gal) from germinating coffee beans. The molecular weight of purified α-Gal from germinating coffee beans was determined to be 38.8 kDa by SDS-PAGE. Then the purified α-Gal was applied to synthesize galactosyl β-cyclodextrin using melibiose as donor and β-cyclodextrin as acceptor. Galactosyl β-cyclodextrin was isolated by preparative high-performance liquid chromatography (HPLC) and its structure was analyzed and elucidated by HPLC, fourier transform infrared spectrometer, electro spraying ionization-mass spectrometry, and ¹³C nuclear magnetic resonance. Our results strongly demonstrate that the synthesized product is a mono-6-O-α-d-galactopyranosyl-β-cyclodextrin and the purified α-galactosidase could transfer one galactosyl residue directly to the β-cyclodextrin ring and synthesize the mono-6-O-α-d-galactosyl β-cyclodextrin.     

A Rapid Spectrophotometric Method for Trace Determination of Zinc

A simple, sensitive, and highly selective method is proposed for the determination of zinc(II) using a bis-azo dye, 2,6-bis(1-hydroxy-2-naphthylazo)pyridine as spectrophotometric reagent. At pH 7.8, in 50% (v/v) ethanol–water medium, the complex is found to obey Beer’s law up to 1.3 mg/L with an optimum concentration range between 0.19 and 1.0 mg/L. Sandell’s sensitivity of the color reaction was calculated to be 0.0011 μg cm⁻² with molar absorptivity of 6.0 × 10⁴ L mol⁻¹ cm⁻¹ at 560 nm. The optimum conditions for the determination of Zn(II) with the reagent were ascertained. The complexation at different pH was studied in water–ethanol medium. The composition of the complex is 1:2. The action of some interfering ions was verified, and the developed method applied successfully for the estimation of zinc levels in food and milk samples, and the results were then compared with those obtained by using AAS.