Zeinat Kamel

Evaluation of free and immobilized Aspergillus niger NRC1ami pectinase applicable in industrial processes.

The Aspergillus niger NRC1ami pectinase was evaluated according to its hydrolysis efficiency of dry untreated orange peels (UOP), HCl-treated orange peels and NaOH-treated orange peels (HOP and NOP). Pectinase was entrapped in polyvinyl alcohol (PVA) sponge and the optimum pH and temperature of the free and immobilized enzymes were shifted from 4, 40 °C to 6, 50 °C respectively. The study of pH stability of free and immobilized pectinase showed that the immobilization process protected the enzyme strongly from severe alkaline pHs. The immobilization process improved the enzyme thermal stability to great instant. The unique feature of the immobilization process is its ability to solve the orange juice haze problem completely. Immobilized enzyme was reused 12 times in orange juice clarification with 9% activity loss from the original activity. Maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) of the partially purified form were significantly changed after immobilization.

Optimization of cultural and nutritional conditions for carboxymethylcellulase production by Aspergillus hortai

Abstract The potential production of carboxymethylcellulase (CMCase) by Aspergillus hortai in liquid state fermentation was studied. Cultural and nutritional factors affecting CMC production were also investigated in order to optimize the fermentation conditions for the maximization of production. The obtained results revealed that, the maximum CMCase production (0.23U/ml) was achieved after 96h in a liquid medium (PH7) inoculated with 10% v/v, at temperature 37°C, containing (gL−1) CMC, 5.0; yeast extract, 0.1; (NH4)SO4, 0.5; KH2PO4, 10.0; MgSO4·7H2O, 0.1 and NaCl, 0.2. and the activity remained almost stable between pH 6 and 7. The highest CMCase activity (1.18U/ml) was obtained at a lactose concentration of 5.0gL-1.

Biodegradation of lignocellulosic substances and production of sugars and lignin degradation intermediates by four selected microbial strains

Abstract The relative ability of four microbial strains to grow on and degrade soft and hard lignocellulosic materials was examined. The most active strain was Phanerochaete chrysosporium NRRL 6361. The percentage weight loss was different for the three tested lignocellulosic samples (3.9–51.9%). The fungi degraded more carbohydrates and less lignin in sugarcane bagasse; on the other substrates both carbohydrate and lignin were extensively degraded. All tested strains released significant amounts of low molecular weight intermediates and reducing sugars, varying with the strain and the substrate.

Toxicity of cadmium to twoStreptomyces species as affected by clay minerals

SummaryThe effect of cadmium on the growth ofStreptomyces rimosus andS. bottropensis (both isolated from soil) was investigated. The modifying effect of the presence of the clay minerals kaolinite, bentonite and vermiculte on Cd toxicity was also included. After four days no growth was observed at 100 ppm CdCl2 ofS. bottropensis and at 150 ppm in case ofS. rimosus. After six days some growth ofS. rimosus occurred at 150 ppm CdCl2 and ofS. bottropensis at 100 ppm. Addition of the three clay minerals decreased the Cd toxicity considerably.

Antimicrobial potential of licorice: Leaves versus roots

Medicinal plants play a vital role in covering the basic health needs. They may offer a new source of antibacterial agents. The aim of this study was to screen in-vitro the antimicrobial activity of some Egyptian medicinal plants against clinical methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from different hospitals in Egypt followed by studying the MIC and cytotoxicty of the most active one. Screening of antimicrobial activities of 70% ethanolic extracts obtained from 19 plants against 59 MRSA clinical isolates were tested by agar well diffusion method. Licorice showed the highest antimicrobial effect against all 59 MRSA isolates (leaves were more active than roots). Minimum inhibitory concentrations (MICs) of licorice leaves were 8 μg/ml, whereas that of Flucloxacillin range between 32 to <128 ug/ml when tested against five MRSA strains. Colorimetric cytotoxicity assay of licorice leaves extract was done on HEPG2 and HCTI16 cell lines and revealed that the IC50 were 19.5 and 15 µg/ml respectively. Separation of the components in licorice leaves using thin layer chromatography (TLC) results in two active fractions identified with the help of spectroscopic analysis as inflacoumarin A and Licochalcone A. Our results reveal that the Egyptian licorice leaves extract represent a new candidate for antimicrobial agent against MRSA more than that achieved by root. This is the first report which highlights the antimicrobial activity of licorice leaves.

Detoxification of Patulin by Kombucha tea culture

Kombucha is a refreshing beverage, obtained by fermenting sugared tea with a symbiotic culture of acetic acid bacteria and yeast, consumed for its positive effects on human health. In this study, the potential of kombucha supernatant for reduction of patulin (PAT) of three toxigenic fungal strains (Penicillium expansum LC015096, Talaromyces purpureogenus LC015095, and Acremonium implicatum LC015097) in liquid medium and apple fruit was investigated. In liquid medium, kombucha up to 10% (v/v) significantly inhibited PAT production of P. expansum by 77.2% and that of T. purpureogenus and A. implicatum by 100%. In apple fruit, inhibition percent of PAT accumulation by the respective fungal strains was 49.8%, 100%, and 53%. In aqueous solution, kombucha cells showed a relative greater PAT uptake capacity than Sacchromyces cerevisiae. The maximum PAT uptake (64.67% and 60.69%) by viable and heat-treated kombucha cells was achieved at pH 3.0 throughout 48 h incubation, respectively.

Conjunctival microbiota and Antibiotic Resistance Pattern in Patients Submitted to Cataract Surgery and Antibacterial Activity of Some Plant Essential Oils

Objective: The objective of this study was to identify the conjunctival microbiota of patients undergoing cataract surgery and evaluate its antibiotic resistance pattern. Also to in-vitro evaluate the antimicrobial effects of some essential oils against multidrug resistant isolates. Methodology: Ocular samples were collected using swabs and polymethyl-metaacrylate (PMMA) intraocular lenses from seventy patients submitted to cataract surgery. Isolation and identification of bacteria was performed using conventional microbiological methods. Antibiotic sensitivity was done by disc diffusion method. The sensitivity of 16 essential oils against isolated bacteria was tested using well diffusion method. Results: Thirty six strains were isolated from patients submitted to cataract surgery. Gram positive microorganisms represent 75% of the isolates with coagulase-negative Staphylococci (CoNS) the most common isolate (47.2%) followed by S.aureus (19.4%), whereas gram negative occurred in 25% of cases, with Moraxella spp. the most frequent Gram negative isolate. Antibiotic sensitivity test revealed that the highest antibiotic resistance was exhibited against ceftazidime (100%) followed by clindamycin (86%), ampicillin (80.5%), erythromycin (72.2%) and tetracycline (69.4%). Gentamycin displayed the best activity (55.5%) followed by chloramphenicol (44.4%) and vancomycin (38.88%). Fifteen essential oils showed antibacterial effect against one or more bacterial strains. The most potent oils were peppermint oil, dill oil, cinnamon oil which showed promising inhibitory activity against most tested bacterial species, whereas cotton, ginger, chamomile, blue green, cod liver and parsley oil were the least active against tested strains. Olive oil failed to inhibit any of the tested strains. In general, St. pneumoniae was the most susceptible organism as it inhibited by ten oils. Conclusion: Our results indicate a promising antibacterial effect of peppermint oil, dill oil and cinnamon oil against conjunctival microorganisms.

Cinnamon oil: A possible alternative for contact lens disinfection.

OBJECTIVE To investigate the antibacterial activity of cinnamon oil alone and in combination with a multipurpose contact lens disinfectant solution (MPS) as well as tobramycin against multi drμg resistant conjunctival bacteria both in planktonic and sessile forms. METHODS Minimum inhibitory concentrations (MIC) of tobramycin and cinnamon oil against 19 bacterial strains were investigated against planktonic and sessile cells by micro-dilution methods. Synergistic effects were determined by well diffusion and micro-dilution tissue culture plate methods for planktonic and sessile cells respectively. Time kill assay was performed to study the bactericidal effect of cinnamon oil in concentrations ranging from 5% to 0.312% combined with an MPS with respect to time. RESULTS MICs of cinnamon oil against planktonic bacteria ranged from 0.04% to 1.25% versus 0.156% to 5% for sessile cells. Combination of cinnamon oil with tobramycin had a synergistic effect against most tested organisms. The MIC values of cinnamon oil in combination with tobramycin was significantly lower than cinnamon oil alone against biofilm production (P=0.004). Time kill assay revealed that combination of cinnamon oil and disinfectant successfully eradicated the tested microorganisms at all tested concentrations within 2h contact time except for 0.312% concentration (3h) versus 24h for MPS alone. CONCLUSION Cinnamon oil has a promising antimicrobial effect. It could be a probable candidate for contact lens disinfection.

Optimization of a Growth Medium for Antibiotic Production by Streptomyces anandii var. Taifiensis

Trials were conducted to determine the optimal culture conditions for the production of the antibiotic SA-53 by a strain of Streptomyces anandii isolated from a Saudi Arabian soil. The influences exerted by initial pH values of the medium, different carbon and nitrogen sources, and various concentrations of these supplements on the yield of the antibiotic were determined.