Shaaban Moussa

Inhibition of microbial pathogens by fungal chitosan

Four fungal chitosan types (CTS) were prepared from Mucor rouxii DSM 1191 and examined for their physico-chemical characteristics. The antimicrobial activity of chitosan types against 11 bacterial strains, including six pathogens, was investigated and the most effective type was chitosan No. 3 which was characterized with the lowest viscosity and molecular weight (3.1 cP and 2.1 x 10(4)Da, respectively), the highest degree of deacetylation (95%) and neutral water solubility. Gram positive bacteria were generally more sensitive to chitosan antimicrobial action than Gram negative strains and this action was notably affected by the environmental growth conditions, i.e. incubation temperature and pH value. The applications of fungal chitosan for the suppression of bacterial pathogens as a natural alternative, reduced risk and biodegradable biocidal agent could be recommended.

Anticandidal action of fungal chitosan against Candida albicans

The anticandidal activity of four fungal chitosan types, produced from Mucor rouxii DSM-1191, against three Candida albicans strains was determined. The most bioactive chitosan type, to inhibit C. albicans growth, had the lowest molecular weight (32 kDa) and the highest deacetylation degree (94%). Water soluble types had stronger anticandidal activity than soluble types in 1% acetic acid solution. Scanning electron micrographs of treated C. albicans with fungal chitosan proved that chitosan principally interact with yeast cell wall, causing severe swelling and asymmetric rough shapes, and subsequent cell wall lyses with the prolonging of exposure time. Fungal chitosan could be recommended for C. albicans control as a powerful and safe alternative to synthetic and chemical fungicides.

Antimicrobial textile treated with chitosan from Aspergillus niger mycelial waste

The waste biomass of Aspergillus niger, following citric acid production, was used as a source for fungal chitosan extraction. The produced chitosan was characterized with deacetylation degree of 89.6%, a molecular weight of 25,000 dalton, 97% solubility in 1% acetic acid solution and comparable FT-IR spectra to standard shrimp chitosan. Fungal chitosan was applied as a cotton fabric finishing agent using pad-dry-cure method. The topographical structure of chitosan-treated fabrics (CTF) was much improved compared with control fabrics. CTF, after durability tests, exhibited a powerful antimicrobial activity against both E. coli and Candida albicans, the captured micrographs for E. coli cells contacted with CTF showed a complete lysis of cell walls with the prolonging contact time. The produced antimicrobial CTF could be proposed as a suitable material for many medical and hygienic applications.

ZnO-modified hybrid polymers as an antibacterial finish for textiles

The antibacterial activity of ZnO is reported by several authors. We present the preparation and application of inorganic–organic hybrid polymers modified/filled with ZnO nanoparticles of varying particle sizes. Inorganic–organic hybrid polymers employed here are based on 3-glycidyloxypropyltrimethoxysilane (GPTMS). ZnO is prepared by hydrolysis of zinc acetate in different solvents (methanol, ethanol or 2-propanol) using lithium hydroxide (LiOH ċ H2O). The hybrid materials prepared are applied to cotton (100%) and cotton/polyester (65/35%) fabrics. The antibacterial performance of these sol-gel derived hybrid materials is exemplarily investigated against Gram-negative bacterium Escherichia coli and Gram–positive Micrococcus luteus. Effects of particle size and concentration for the antibacterial performance are examined. Literature discusses various (active) species and processes responsible for the antibacterial action of ZnO. Therefore, particular attention is paid to investigate active species available in the described systems as well as to observe possible interaction between the nanoparticles and bacteria; the first results are presented.

Evaluation of fungal chitosan as a biocontrol and antibacterial agent using fluorescence-labeling.

Chitosan is a precious biological polysaccharide that could be applied in several fields. Fluorescein isothiocyanate-labeled chitosan (FITC-CTS) was synthesized as a macromolecular fluorophore added to fungal chitosan from Aspergillus niger, to investigate the interaction mechanism and antibacterial performance of (FITC-CTS) against Escherichia coli and Micrococcus leteus. Fluorescence imaging was used to demonstrate chitosan effect on the bacterial cells. Fluorescence density of treated bacteria with FITC-CTS was correlated with viable cell number. Electron micrographs of treated E. coli with fungal chitosan revealed that chitosan principally interact with bacterial cell wall, causing cell wall lyses with exposure time prolongation. Fungal chitosan could be proposed for bacterial growth control as a powerful, natural and safe alternative to synthetic and chemical bactericides. Fluorescence labeling proved to be an efficient tool for determining the antimicrobial activity of chitosan.

Surface Decontamination and Quality Enhancement in Meat Steaks Using Plant Extracts as Natural Biopreservatives

Nine plant extracts were evaluated as biopreservatives to decontaminate and maintain the quality of meat steaks. Most of the extracts exhibited a remarkable antibacterial activity against antibiotic resistant strains from Salmonella Typhimurium and Staphylococcus aureus. The pomegranate peel extract (PPE), cinnamon bark extract (CBE), and lemon grass leaves extract (LGE) were the most effective as bactericides, with minimal inhibitory concentrations (MIC) of 250, 350, and 550 μg/mL, respectively. The most effective treatments, for decontaminating meat steak surfaces, were the application of combined PPE, CBE, and LGE at their MIC values and the treatment with double MIC from PPE; these treatments resulted in complete bacterial inhibitions during the first 2 days of storage period for 7 days. The sensory evaluation of treated steaks revealed that these two treatments had the highest panelist overall scores. The highest scores, for individual attributes, were observed in the treated steaks with double MIC from PPE. Application of plant extracts could be impressively recommended for comprehensive meat decontamination and quality attributes enhancement.

Botryticidal Activity of Nanosized Silver-Chitosan Composite and Its Application for the Control of Gray Mold in Strawberry

Botrytis cinerea Pers, the gray mold fungus, is among the most dangerous plant pathogens that cause great losses in agricultural crops. The botryticidal activities of nanosized silver (nano Ag), fungal chitosan (CTS) irradiated fungal chitosan (IrCTS), and nano Ag-IrCTS composite were investigated. All of the examined materials exhibited powerful antifungal activity against B. cinerea. The most effective compound was nano Ag-IrCTS composite with a minimal inhibitory concentration of 125 μg/mL. The microscopic examination, of treated B. cinerea with the composite, revealed that an obvious alteration in mycelial shape was appeared accompanied and moderate lysis in fungal hyphae. With the prolongation of treatment, most of the fungal mycelia were lysed into small and elastic fragments. The consequence of strawberries coating, with antifungal composite based solution, was the disappearance of gray mold infection signs in 90% of the contaminated fruits after 7 d of storage, treated fruits had a fresh-like appearance at the end of storage. Coating with nano Ag-IrCTS solution could be highly recommended regarding its efficiency in prohibiting B. cinerea growth, preventing gray mold decay and enhancing the overall quality of coated strawberry fruits.

Production of fungal chitosan from date wastes and its application as a biopreservative for minced meat.

Raw and processed meat contaminated with pathogenic microorganisms is a continuing worldwide problem facing health and industry overseers. Fungal chitosan was extracted, purified and characterized from Aspergillus brasiliensis (niger) ATCC 16404 grown in date syrup (dips) and applied as a potential meat biopreservative. The main features of produced chitosan were a deacetylation degree of 81.3%, a molecular weight of 31,000Da, 96% solubility in 1% acetic acid solution and a harmonized IR-spectrum to standard commercial chitosan. The application of fungal chitosan, as a natural and safe biopreservative for minced meat, was conducted in comparison with potassium sorbate, as a commercial meat preservative. Treated meat samples with 0.02% chitosan was the least trials in microbial contents, i.e. total count, coliforms, β-glucuronidase-positive Escherichia coli, Enterobacteriaceae, yeasts and molds, Staphylococcus aureus and coagulase positive staphylococci. The antimicrobial activity of fungal chitosan was considerably greater than that of potassium sorbate or their combination at 0.01% from each. Sensory characteristics, e.g. color, odor and texture, of treated meat with chitosan, were higher than those of control and potassium sorbate treated samples. Fungal chitosan, however, could be recommended as a powerful, natural and eco-friendly alternative for meat preservation and overall quality maintenance.

Antibacterial action of acetic acid soluble material isolated from Mucor rouxii and its application onto textile

Acetic acid soluble material (AcSM) is a chitosan-rich fraction isolated from the fungal cell wall materials. The final step in the traditional production of fungal chitosan is the separation of chitosan from the cell wall AcSM via raising the pH to 9-10 followed by centrifugation. This step results in further undesirable economic and environmental effects. The goal of this paper is to avoid that by investigating the antimicrobial effect of the whole AcSM from Mucor rouxii DSM-1191 cell wall and its application on cotton fabrics. The treated fabrics were characterized through monitoring the textile physical properties and for the antibacterial activity against Escherichia coli and Micrococcus luteus. Results showed that Mucor rouxii DSM-1191 has excellent potentials to be used for cell wall AcSM production on industrial scale with a maximum content of 40% in dry mycelia. The obtained results indicated that the physical properties of the treated fabrics, as well as the antibacterial activity, were improved after treatment with fungal AcSM.