Hulya Yagar

Optimization of α‐Amylase Immobilization in Calcium Alginate Beads

Abstract α‐Amylase enzyme was produced by Aspergillus sclerotiorum under SSF conditions, and immobilized in calcium alginate beads. Effects of immobilization conditions, such as alginate concentration, CaCl2 concentration, amount of loading enzyme, bead size, and amount of beads, on enzymatic activity were investigated. Optimum alginate and CaCl2 concentration were found to be 3% (w/v). Using a loading enzyme concentration of 140 U mL−1, and bead (diameter 3 mm) amount of 0.5 g, maximum enzyme activity was observed. Beads prepared at optimum immobilization conditions were suitable for up to 7 repeated uses, losing only 35% of their initial activity. Among the various starches tested, the highest enzyme activity (96.2%) was determined in soluble potato starch hydrolysis for 120 min at 40°C.

Comparison of antioxidant activities of juice, peel, and seed of pomegranate (Punica granatum L.) and inter-relationships with total phenolic, Tannin, anthocyanin, and flavonoid contents

In this study, the antioxidant activities of juice, peel, and seed parts of pomegranate were investigated by using DPPH scavenging activity, β-carotene bleaching method, reducing power, and metal chelating activity. Sample of pomegranates which are named Punica granatum L. cv. Hicaznar, genotype 19–121, genotype 17–67, and genotype 19–66 obtained from BATEM (West Mediterranean Agricultural Research Institute) in Anlalya. The EC50 values of DPPH scavenging activities in peel extracts (PE) had 23.4-fold higher than the juice extracts (JE), and the seed extracts (SE) had 2.3-fold higher than JE. The reducing power in peel extracts was found to be 4.7-fold higher than SE and 10.5-fold higher than the JE. The highest metal chelating capacity (37.22%) was determined in peel, while the lowest (7.151%) in seed. Generally, in peel, the total polyphenol, flavonoid, tannin contents, and in juice, the total polyphenol, anthocyanin, tannin contents, and acidity significantly affected to antioxidant activities.

Some Properties of Free and Immobilized α‐Amylase from Penicillium griseofulvum by Solid State Fermentation

Abstract α‐Amylase was produced from Penicillium griseofulvum by an SSF technique. α‐Amylase was immobilized on Celite by an adsorption method. Various parameters, such as effect of pH and temperature, substrate concentration, operational and storage stability, ability to hydrolyze starch and products of hydrolysis were investigated; these findings were compared with the free enzyme. The activity yield of immobilization was 87.6%. The optimum pH and temperature for both enzymes were 5.5°C and 40°C, respectively. The thermal, and the operational and storage stabilities of immobilized enzyme were better than that of the free enzyme. Km and Vmax were calculated from Lineweaver–Burk plots for both enzymes. Km values were 9.1 mg mL−1 for free enzyme, and 7.1 mg mL−1 for immobilized enzyme. The Vmax of the immobilized enzyme was approximately 40% smaller than that of the free enzyme. The hydrolysis ability of the free and immobilized enzyme were determined as 99.3% and 97.9%, respectively. Hydrolysis products of the α‐amylase from P. griseofulvum were maltose, unidentified oligosaccharides, and glucose.

Effects of hot air and freeze drying methods on antioxidant activity, colour and some nutritional characteristics of strawberry tree (Arbutus unedo L) fruit

Antioxidant activity, colour and some nutritional properties of hot air and freeze-dried strawberry tree (Arbutus unedo L.) fruits were investigated. Additionally, the effects of two pre-treatments, namely ethyl oleate and water blanching, were compared in terms of drying characteristics. For determination of antioxidant activities in ethanol extracts, two different analytical methods were used: 1,1-diphenyl-2-picrylhydrazyl scavenging activity and β-carotene bleaching activity. As a result, the ethyl oleate pre-treatment shortened the drying time by hot air method and gave a higher 1,1-diphenyl-2-picrylhydrazyl scavenging activity (82.16 ± 0.34%), total phenolic content (7.62 ± 1.09 µg GAE/g extract), ascorbic acid content (236.93 ± 20.14 mg/100 g), besides hydromethylfurfural was not observed. Freeze-dried fruits exhibited higher ascorbic acid content (368.63 ± 17.16 mg/100 g) than those fresh fruits (231.33 ± 19.51 mg/100 g) and nearly 1,1-diphenyl-2-picrylhydrazyl activity (93.52 ± 0.41 %) to fresh fruits (94.03 ± 1.18%). Colour characteristics, sugar content and mineral contents of fruits were significantly affected by pre-treatments and drying methods (p < 0.05). It is concluded that the drying of strawberry tree fruits should bring a valuable and attractive foodstuff to food industry due to the rich nutritional components, antioxidant activity and colour. Another conclusion from this study is that the freeze-drying is the best drying method to keep the nutritional value, antioxidant activity and sensory properties of fruits.

Comparison of Some Properties of Free and Immobilized α‐Amylase by Aspergillus sclerotiorum in Calcium Alginate Gel Beads

Abstract Some properties of immobilized α‐amylase by Aspergillus sclerotiorum within calcium alginate gel beads were investigated and compared with soluble enzyme. Optimum pH and temperature were found to be 5.0 and 40°C, respectively, for both soluble and immobilized enzymes. The immobilized enzyme had a better Km value, but kcat/Km values were the same for both enzymes. Entrapment within calcium alginate gel beads improved, remarkably, the thermal and storage stability of α‐amylase. The half life values of immobilized enzyme and soluble enzyme at 60°C were 164.2, and 26.2 min, respectively. The midpoint of thermal inactivation (Tm) shifted from 56°C (for soluble enzyme) to 65.4°C for immobilized enzyme. The percentages of soluble starch hydrolysis for soluble and immobilized α‐amylase were determined to be 97.5 and 92.2% for 60 min, respectively.

Comparison of Polyphenol Oxidases Prepared From Different Parts of Artichoke (Cynara Scolymus L.)

Artichoke polyphenol oxidases (PPOs) were obtained by (NH4)2SO4 precipitation using ascorbic acid, polyvinylpyrrolidone, and Triton X-100. The PPO content of artichoke head (AHPPO) was 8820 units (mg protein)−1 as compared with 3370 units (mg protein)−1 in artichoke leaves-and-stem (ALSPPO) by using catechol as a substrate. The substrates of both AHPPO and ALSPPO are o-diphenols, such as catechol, pyrogallol, and L-DOPA. Optimum pH and temperature of both PPOs were determined. AHPPO had higher thermal stability than ALSPPO. Also, Tm (the midpoint of thermal inactivation) and t1/2 (half-life) values were determined. Km and Vmax of both PPOs were observed to be similar. Twelve inhibitors were tested and their I50 values were determined. The most effective inhibitors were found to be potassium cyanide, ascorbic acid, L-cysteine, and thiourea. Sodiumdodecylsulfate, urea, and cupric sulfate caused an increase about 20–30% in the PPO activity.

Optimization of Polyphenol Oxidase Immobilization in Copper Alginate Beads

Abstract Polyphenol oxidase (PPO, EC 1.14.18.1) was isolated from artichoke head (Cynara scolymus L.) by using 0.1 M Tris-HCl buffer (pH 7.0), concentrated by (NH4)2SO4 precipitation, and immobilized in copper-alginate beads. Immobilization yield was determined to be 70%. The cresolase and catecholase activities of enzyme immobilized at optimum immobilization conditions were found to be 13.3 and 670 U g beads min−1, respectively. Effects of immobilization conditions such as alginate concentration, CaCl2 concentration, amount of loading enzyme, bead size, and amount of beads on enzymatic activity were investigated. Optimum alginate and CuCl2 concentration were found to be 2 % and 3 % (w/v), respectively. Using bead (diameter 3 mm) amount of 0.25 g maximum enzyme activities were observed for both polyphenol activities. The initial concentrations of loading free enzyme were 6.5U mL−1 and 5815 U mL−1 for cresolase activity and catecholase activities, respectively. Beads prepared at optimum immobilization conditions were suitable for up to 8 repeated uses.

Determination of Antioxidant Properties of Lyophilized Olive Leaf Water Extracts Obtained from 21 Different Cultivars

The objective of this study was to compare the antioxidant activities of lyophilized olive leaf water extracts (OLWExtracts) from 21 different olive tree cultivars. The highest total phenolic content (102.69±1.63 μg GAE/mg extract) was found in cultivar ‘Esek Zeytini’ and the lowest content (78.52±2.18 μg GAE/mg extract) was in ‘Uslu’. The highest total flavonoid content (12.47±0.12 μg QE/mg extract) obtained from ‘Frantoio’. According to EC50 values, ‘Domat’ have the highest DPPH scavenging activity (EC50 =59 μg/mL), reducing power (EC50 =180 μg/mL), and superoxide radical scavenging capacity (EC50=44 μg/mL). While, ‘Ascolana’ showed the highest metal chelating capacity (EC50=163 μg/mL), ‘Memecik’ showed the highest hydrogen peroxide (H2O2) scavenging capacity. Research results exhibited that OLWExtracts are comparable to synthetic antioxidants. The correlation study showed that while total phenolic content correlated with DPPH scavenging activity and reducing power (p<0.01), total flavonoid content correlated with metal chelating and superoxide radical scavenging capacity (p<0.05).

Entrapment of laurel lipase in chitosan hydrogel beads.

Abstract Laurel seed lipase was entrapped within chitosan beads with ionotropic gelatin method using tripolyphosphate (TPP) as multivalent covalent counter ion. Immobilization yield was 78%. First, optimum immobilization conditions were determined, and morphology of chitosan beads was characterized by scanning electron microscopy. Optimum pH and temperature were evaluated as 6.0 and 40 °C, respectively. The immobilized beads saved about 55% of its activities at 60° while saved about 32% at 70 °C for 30 min. Vmax/Km values were determined as 31.75 and 2.87 using olive oil as substrate for immobilized beads and free enzyme, respectively. Immobilized beads showed the activities during 30 days at +4 °C.

Comparison of some biochemical properties of artichoke polyphenol oxidase entrapped in alginate-carrageenan and alginate gels

Abstract Polyphenol oxidase (PPO, EC.1.14.18.1) isolated from artichoke (Cynara scolymus) was entrapped within alginate and alginate+ carrageenan beads, and the catecholase and cresolase activities of both entrapped enzymes were determined. Some properties of these immobilized enzymes such as optimum pH and temperature, kinetic parameters (Km and Vmax), thermal, and storage stability were determined and compared to each other. The highest catecholase activity was observed in alginate gel (370 U/g bead) while the highest cresolase activity was in alginate+ carrageenan gel (90 U/g bead). For catecholase and cresolase activities, optimum pHs of alginate and alginate+ carrageenan beads were determined to be 7.0 and 4.0, respectively. Optimum temperatures for catecholase activity were determined to be 40°C for both entrapped enzymes. These values for cresolase activity were 30°C and 20°C, respectively. Immobilized artichoke PPOs greatly preserved their thermal stability which exists anyway. The catalytic efficiency value (Vmax/Km) of the alginate beads is approximately high as two-and-a-half folds of that of alginate+κ-carrageenan beads for cresolase activity. These values were very close for catecholase activity. Immobilized beads saved their both activities after 30 days of storage at 4°C.