No abstract

T HE PRESENT study investigated the physicochemical, antioxidant, and microbiological properties of six types of honey obtained from Alexandria, Egypt. Physicochemical properties showed that optical density in the tested honey samples ranged from 0.50 to 1.65, while the pH was in the acidic range. Moisture contents and electrical conductivity in honey samples ranged from 0.5 to 0.64, and 0.29-0.79 mScm-1 , respectively. Total phenol varied from 5500 and 14120 mg/kg in the samples. Flavonoid contents were between 926-1657 mg/kg. The greater amount of phenolic and flavonoid compounds leads to more potent radical scavenging effect as shown by Cotton, Eucalyptus, and Black seed honey samples. Microbiological characteristics showed that Black seed followed by Eucalyptus honey extracts gave the maximum antibacterial activity against K. pneumonia, P. aeruginosa, P. mirabilis, E. coli and S. mutans with maximum inhibition zones equal to 42.67, 39.00, 36.00, 27.33 and 18.67 mm at 100 µl, respectively, for Black seed honey, and 41, 38.33 and 35.67 mm and approximately equal inhibition zones of 13.67 mm against E. coli and S. mutans at 100 µl, respectively, for Eucalyptus honey. The minimum inhibitory concentration values against the pathogenic bacteria showed that, at 25% concentration, Black seed and Eucalyptus honey had an effect on E. coli and K. pneumonia, while Clover honey had an effect on P. aeruginosa and P. mirabilis. Thus, honey can be used for nutritional, medicinal and industrial purposes and can be an important commodity in the international market.

An alginate lyase with high specific enzyme activity was purified from Pseudomonas stutzeri MSEA04, isolated from marine brown algae. The alginate lyase was purified by precipitation with ammonium sulphate, acetone and ethanol individually. 70% ethanol fraction showed maximum specific activity (133.3 U/mg). This fraction was re-purified by anion exchange chromatography DEAE-Cellulose A-52. The loaded protein was separated into 3 peaks. The second protein peak was the major one which contained 48.2% of the total protein recovered and 79.4% of the total recovered activity. The collected fractions of this peak were subjected to further purification by re-chromatography on Sephadex G-100. Alginate lyase activity was fractionated in the Sephadex column into one major peak, and the specific activity of this fraction reached 116 U/mg. The optimal substrate concentration, pH and temperature for alginate lyase activity were 8 mg/ml, pH 7.5 and 37 °C, respectively. While, K m and V max values were 1.07 mg alginate/ ml and 128.2 U/mg protein, respectively. The enzyme was partially stable below 50 °C, and the activity of the enzyme was strongly enhanced by K + , and strongly inhibited by Ba +2 , Cd +2 , Fe +2 and Zn +2 . The purified enzyme yielded a single band on SDS-PAGE with molecular weight (40.0 kDa).

L-glutaminase (E.C.3.5.2.1) is an antineoplastic enzyme and in the present study, an extracellular L-glutaminase was produced from a marine local strain identified as Pseudomonas sp. RAS123. The enzyme was produced from free cultures and from cultures immobilized on and in different supports. Pseudomonas sp. RAS123 L-glutaminase produced from immobilized cultures was purified to homogeneity. The specific activity of the enzyme reached 698.655 U/mg protein, with Km and Vmax value of 3.2 mg/ml and 2000 U/ml, respectively. A single band with a molecular weight of about 32.0 kDa was produced by the purified enzyme on SDS-PAGE. Further findings indicated that the pure enzyme's maximum activity occurred at 50°C and pH 9. The enzyme was stable at 60°C for 60 min and in the pH range of 8.0 to 10.0, The effect of chemicals showed that Mn2+, Mg2+, Ni2+ and Fe2+activated the enzyme, while SDS (10% w/v) strongly inhibited the activity of the enzyme. The purified enzyme showed cytotoxic activity against HCT-116, HepG2, MCF-7, HeLa, and CCL-86 cell lines tested with IC50 values of 122, 175, 195, 306, and > 500 µg/ml, respectively. Also, the antibacterial effect of the enzyme showed activity against Staphylococcus aureus, Bacillus subtilis, Streptococcus mutants, Enterobacter cloacae and Escherichia coli. These findings demonstrate that L-glutaminase might be used in numerous biotechnological applications, particularly food and pharmaceutical processing.

Among six marine isolates grown on minimal medium, an isolate AA4 was chosen based on its high alginase lyase specific activity (1.69 U/mg biomass), in comparison to other isolates. The isolate AA4 was identified as Bacillus subtilis, based on a partial sequence of the 16S rDNA gene. A 2 n factorial design was applied to elucidate media compositions that significantly affect alginate lyase formation. Sixteen trials were investigated and one with positive levels of yeast extract, peptone, sodium alginate and sodium chloride showed a 15-fold increase in specific enzyme activity. The F ratio revealed that two factors, sodium chloride and alginate, whether separately or combined are positively effective at a 1% level of significance.