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Lipases are hydrolytic enzymes which have significant potential for commercial applications, particularly in the breakdown of oil contaminants. Serratia marcescens EGHK-19 isolate exhibited considerable lipase activity. This study investigates the optimization, purification, and characterization of lipase from the Serratia marcescens EGHK-19 isolate. The optimized culture conditions revealed that maximal lipase activity was achieved after 24 hours at 30°C and pH 7, with continuous shaking at 150 rpm. Utilizing a 2% inoculum percentage with 1% diesel and 0.3% tryptone in the presence of Fe2+, Ca2+, Mg2+ salts, and Tween 80 resulted in the highest activity at 17.278 U/ml/min. The purification process involved acetone precipitation and DEAE-Sephadex column chromatography, revealing a molecular weight of approximately 60 kDa on SDS-PAGE. This method exhibited a 0.985-fold purification, and the final yield was limited to 2.097% due to lipase aggregates. Characterization of the purified lipase indicated optimal activity (8.765 U/mL/min) at 40°C a nd p H 7. T he K m a nd V max values w ere c alculated a s 6 .89 m M a nd 6 5.79 µmol/min, respectively. The presence of SDS, Tween 80, and Triton X-100 surfactants resulted in the inhibition of lipase activity. Despite these insuggestss, the biochemical characteristics of the purified lipase suggest its potential as an excellent candidate for various industrial applications. [ABSTRACT FROM AUTHOR]

In this study, three algae (Corallina officillica, Ulva lactuca, and Pterocaldia capallicia) and three aromatic herbs (Ocimum basilicum, Mentha longifoila, and Salvia officinalis) were investigated. Phytochemicals, P. capallicia had the highest total carbohydrate content (17.50%), while M. longifoila had the highest total proteins ratio (17.95%). Mentha longifoila possessed the maximum total lipids percent (32.14%), while C. officillica had the highest ash content (58.83%). As well as, M. longifoila had the highest phenolics and carotenoids values, while U. lactuca had the highest total flavonoids. To antioxidant activity estimated, the S. officinalis (M6) extract showed the highest scavenging activity (89.88%). Regarding antibacterial activities, the C. officillica extract exhibited the most powerful activity against P. aeruginosa ATCC 9027 (44 mm), followed by S. officinalis extract against the same bacterium (40 mm). The GC-MS assessment revealed the existence of several bioactive constituents, involving fatty acids, terpenoids, steroids, flavonoids, carotenoids, phenolic compounds, and other compounds. [ABSTRACT FROM AUTHOR]

Silver nanomaterials are usually applied as antimicrobial agents; however, they can cause toxic effects on human health. The current investigation was performed to study the combined effects of chitosan and silver nanoparticles (AgNPs) using the cell-free supernatant of Escherichia coli (MF062579). The produced chitosan/silver nanocomposite (CS/AgNC) showed good antibacterial activity and high stability. The biosynthesized CS/AgNC contained homogeneous spherical AgNPs with an average size of ~12.3 nm and a net surface charge of +30.9 ± 3.2 mV. CS/AgNC revealed a good minimum inhibitory concentration (MIC) result against Gram-negative (G-ve, E. coli) and Gram-positive (G+ve, Bacillus cereus) bacteria with inhibition ratios of 80.7% and 75.5%, respectively. Nanocomposite-treated cells displayed complete lysis of the bacterial cell, a low amount of DNA, and cell membrane and wall disruption. Glutamate dehydrogenase (GDH) and malate dehydrogenase (MDH) activities of tested bacterial strains were demonstrated using spectrophotometry and electrophoresis on a non-denaturing acrylamide gel. In CS/AgNC-treated strains, enzyme production and activity were fewer than in untreated strains. The obtained results suggested that CS/AgNC seems to be more effective against G-ve than G+ve bacteria. [ABSTRACT FROM AUTHOR]

Central composite design (CCD) as one of response surface designs was employed to optimize the biosynthesis process of silver nanoparticles (AgNPs). In this design, fungal cell-free filtrate of Talaromyces stipitatus was applied as a biosource for the biosynthesis of AgNPs. Different variables with five levels were used to optimize AgNPs biosynthesis. Independent variables were concentration of silver nitrate (AgNO3; mmole), temperature (°C), time, pH and ratio of AgNO3 to cell free extract. While dependent variable was peak intensity of surface plasmon resonance (SPR) at wavelength 420 nm. The predicted optimal setup parameters were AgNO3 concentration of 7 mmol, temperature of 25 °C, time of 91.2 hr, pH of 8 and ratio of AgNO3 solution to cell-free extract of 2:1. The characteristics of biosynthesized AgNPs were revealed using Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta potential, energy dispersive x-ray analysis (EDX), and transmission electron microscopy (TEM). Biosynthesized AgNPs appeared to be spherical, with mean size of 13.95 nm and zeta potential of 9.85 mV. Biosynthesized AgNPs were also examined for their antimicrobial properties against selected bacterial and fungal pathogens including Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Aspergillus flavus, A. niger, Fusarium oxysporum and Alternaria alternata. [ABSTRACT FROM AUTHOR]

The present study aims to search for a nano-delivery system that enables access of antimicrobial compounds to the targeting site of the microbial pathogens. To achieve this obiective, the antimicrobial compounds extracted from the local isolate Streptomyces rimosus were loaded on chitosan (CS) and calcium phosphate (CaP) nanoparticles (NPs) to facilitate drug delivery to some species of bacteria (Escherichia coli ATCC25922, Staphylococcus aureus ATCC25923 and Bacillus cereus ATCC6633) and the yeast Candida albicans ATCC10231. The best incubation period for the production of antifungal and antibacterial compounds, pH, temperature, carbon sources and nitrogen sources were around the third day, 7.0, 30°C, starch and potassium nitrate, respectively. The extracted compounds were identified using gas chromatography-mass spectrometry (GC-MS) analysis which revealed to the identification of nine antimicrobial organic acids. The prepared NPs were characterized using transmission electron microscopy (TEM) and Zeta potential analyser. Results showed those chitosan nanoparticles (CSNPs) were spherical shaped NPs with an average size ≈22 ± 2 nm. The CSNPs loaded with the antimicrobial molecule's diameter was ranged from 55 upto 100 nm. Calcium phosphates nanoparticles (CaPNPs) were also spherical shaped NPs with diameter range from 70 to 95 nm. Loading of antimicrobial compounds onto CaPNPs made them appeared in rod shape with width varying from 14 to 27 nm and length from 274 to 397 nm. The synthesized NPs showed negative values confirming their high dispersity and long-term stability. The tested strains were resistant to solo NPs; but the loaded NPs with the extracted antimicrobial compounds, particularly the CaPNPs, augmented the potency of the isolated antimicrobial compounds, with emergence of differential antimicrobial activity. The activity of the NPs-bound antimicrobial compounds was more evident against bacteria than fungi, Grampositive bacteria than Gram-negative bacteria and against B. cereus than S. aureus. [ABSTRACT FROM AUTHOR]

This study highlights the optimization of extracellular biosynthesis and antimicrobial efficiency of silver nanoparticles (AgNPs) using the crude metabolite of Escherichia coli D8 (MF06257) strain. The bacterial strain had been isolated from a sewage water stream located in Damietta City, Egypt. The optimum conditions for AgNPs production were at temperature 35°C, pH 7 and 1.5mM silver nitrate. The AgNPs biosynthesis was detected in culture filtrate within 1-2 minutes at room temperature (25±2°C) and sunlight. The characterization of AgNPs was studied by UV-Vis spectroscopy (maximum absorbance at 429 nm), X-ray diffraction (XRD) pattern (crystal planes were 110, 111, 200, 211, 220, and 311), transmission electron microscopy (TEM) (AgNPs were spherical in shape ranging from 6 to 17 nm), Fourier transform-infrared (FTIR) spectroscopy (the bands of symmetric and asymmetric amines were assigned at 3421.1 and 2962.13 cm-1, the stretching vibration band of aromatic and aliphatic (C-N) exist at 1392.35 and 1122.37 cm-1 bands), Zeta potential analyser (AgNPs had a negative charge value; -33.6 mV) and size distribution by volume (the presence of capping agent enveloping the AgNPs with a mean size of 136.0-294.3 nm). Nitrate reductase (NR) was assayed as an important partner in the optimized production (the rate of NR reached to 2.18 U/ml). The study demonstrated that AgNPs are potent inhibitors of Staphylococcus aureus, E. coli, Pseudomonas aeruginosa, Alternaria alternata, Fusarium oxysporum and Aspergillus flavus. The antimicrobial activity of AgNPs was studied by TEM. TEM micrographs showed an inhibition of S. aureus cell multiplication. In case of F. oxysporum, a reduction in the size of treated cells, formation of a mucilage matrix connecting the hyphal cells together, the appearance of a big vacuole, lipid droplets an a severe leakage of cytoplasmic contents were detected. AgNPs exhibited MIC values of 6.25μg/ml and 50 μg/ml against S. aureus and Candida albicans, respectively. In addition, AgNPs showed synergy effects by their combination with fluconazole that increased fold areas especially against A. niger, A. flavus and F. oxysporum. [ABSTRACT FROM AUTHOR]

α-Amylase (AmyLa) from Laceyella sp. DS3 was purified 13.8-fold by ammonium sulfate precipitation, gel filtration, and ion exchange chromatography. The purified AmyLa showed an optimum pH of 7 and an optimum temperature 55°C. It had activation energy, Km, and Vmax of 196.1 kJ, 0.81 mg/mL, and 2.85 mg/min, respectively. Co2+, Cu2+, Hg2+, and Na+ were strong inhibitors of AmyLa whereas Cl- was an activator. Although AmyLa is a Ca2+ independent α-amylase, it was activated by Ca2+. The AmyLa gene encoding α-amylase activity was sequenced. It revealed putative triple promoters and an open reading frame of 1449 bp (483 amino acids) including a 29 amino acid putative signal peptide. AmyLa was shown to possess four conserved sequence regions of the GH13 family. Polyacrylamide gel electrophoresis identified 69.2 and 72.5 kDa proteins whose α-amylase activities were confirmed by native gel staining. Modeling of AmyLa revealed three domains A-C with domain A containing a catalytic (α/β)8 barrel. Phylogenetic and evolutionary tree analysis suggests that AmyLa might be have been transferred from fungi to an ancient thermoactinomycete ancestor, then adapted to bacterial genome features. [ABSTRACT FROM AUTHOR]

The optimal conditions for the production of xylanase and peroxidase from Streptomyces sp. K37 were investigated. The production of xylanase and peroxidase increased during the growth phase of the cultures after 72 hours. This indicates that the productions of such enzymes are wholly growth associated in these organisms. The optimum pH for xylanase and peroxidase production from Streptomyces sp. K37 occurred at pH 8.0 and pH 7.0. The optimum temperature for xylanase and peroxidase production by Streptomyces sp. K37 occurred at 50°C and 40°C respectively. Oat spelt xylan was the best carbon source for the production of xylanase and peroxidase from Streptomyces sp. K37. The optimum concentration of ball milled straw for the production of xylanase from Streptomyces sp. K37 was 1.0%, while the concentration for the production of peroxidase was 0.20%. The optimal concentration of yeast extract and casamino acid for the production of xylanase and peroxidase from Streptomyces sp. K37 was found to be 0.2%. [ABSTRACT FROM AUTHOR]

Alpha-amylase production by Bacillus subtilis was studied under different cultivation conditions. The maximum alpha-amylase production occurred after an incubation period of 48 h, temperature 40 degrees C and pH 7.5. Among the defined carbohydrates, starch (1%) was the best carbon source. The organism grew better and produced high levels of alpha-amylase using peptone as nitrogen source. The produced alpha-amylase was immobilized on various carriers by different methods and the properties of the enzyme were compared before and after immobilization. The optimum pH of the immobilized enzyme was changed to acidic range. The optimum reaction temperature of immobilized enzyme was shifted slightly to 70-80 degrees C. Both of Km values and Vmax and thermal stability of immobilized enzyme were found to be higher than that of free one. Among the tested metals CaCl2 exerted a stimulating effect on the activity of alpha-amylase.