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Abstract  

Fiber of Japanese food natto (Bacillus subtilis) is known to be superabsorbent poly(-glutamic acid) (PGA). NaCl particles precipitate in FeCl2-absorbed crosslinked PGA when heated at crystallization temperature of 320 °C for 10 to 60 min. After heat treatment the Mössbauer spectrum of FeCl2-crosslinked PGA consists of a quadrupole doublet due to FeCl2·2H2O. The Mössbauer spectrum of anhydrous FeCl2 reagent heated under the same condition shows an intense sextet due to -Fe2O3 . These results prove that the superabsorbent polymer, crosslinked PGA, has higher heat resistance.

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Direct bioautography performed with luminescence gene-tagged bacteria enables almost real-time detection of antimicrobial compounds in plant extracts. This method for the detection of chamomile ( Matricaria recutita ) components with antibacterial effect against Bacillus subtilis soil bacteria was more sensitive than commonly used bioautographic visualization by staining with a tetrazolium salt. Some compounds had a strong inhibiting effect only via the bioluminescence measurement. Extraction of antibacterial components of chamomile flowers was most effective with 50% ethanol; slightly lower efficiency was achieved with acetone and methanol, and hexane was least effective. The results were confirmed by using luminescent Pseudomonas syringae pv. maculicola plant pathogen bacteria.

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The main volatile compounds from three medicinal plants belonging to Lamiaceae family were screened for their biological properties. The plants were Salvia officinalis, Thymus vulgaris, and Mentha × piperita containing as the main volatile constituents thujone, thymol, and menthol, respectively. The applied chromatographic system was silica gel developed with toluene-ethyl acetate (93:7). Thin-layer chromatography — direct bioautography (TLC-DB) against Escherichia coli and Bacillus subtilis was used for detection of antibacterial activity of the plant extracts and essential oils. The bioautographic fingerprints were compared with the fingerprints obtained after derivatization with anisaldehyde.

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Commercially available hop pellets of different origins were extracted by use of ethanol and water, chromatographed on silica layers by use of nonaqueous eluents, chemically derivatized and observed in ultraviolet (UV) light for the localization of component bands. The plates were developed in optimized systems, and direct bioautographic method by use of Bacillus subtilis and Escherichia coli strains was applied for the examination of the antimicrobial activities of hop components. The method enables for the identification of bactericidal/bacteriostatic components in the extracts of different polarities and shows differences in the composition of extracts from various varieties from an antimicrobial point of view.

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Acta Alimentaria
Authors:
A. Mouwakeh
,
P. Radácsi
,
ZS. Pluhár
,
É. Németh Zámboriné
,
G. Muránszky
,
CS. Mohácsi-Farkas
, and
G. Kiskó

Nigella sativa L. (black cumin) is well known for its benefits in the field of traditional medicine. The aim of this study was to determine the chemical composition and investigate the antimicrobial activity of cold pressed oil (CO) and essential oil (EO) of Nigella sativa L. on food-borne pathogenic and spoilage bacteria. The microdilution method was used to determine the minimal inhibitory concentration (MIC) of Nigella sativa crude oil (CO) and essential oil (EO) against 4 Gram-positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, and Listeria monocytogenes) and 3 Gram-negative (Salmonella Hartford, Pseudomonas aeruginosa, and Escherichia coli) foodborne pathogenic and spoilage bacteria occurring in food products. Total fatty acid composition of CO was analysed by GLC, while the EO was analysed by GC-MS to detect its active compounds. The results showed that the major fatty acid of CO was palmitic acid (C16:0), as saturated fatty acid, however, linoleic acid (C18:2) was the main unsaturated fatty acid. The major compounds of the EO were p-cymene and thymoquinone. The inhibition on all tested bacteria of EO was 10 times higher than of CO, and the lowest concentration value was observed in case of Bacillus subtilis (0.003%). Hence, results reinforce the ambition to apply Nigella sativa oils in food as natural preservative.

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The leaf blight disease caused by Lasiodiplodia theobromae is an important foliar disease in coconut that results in a yield reduction of 10–24 per cent in Tamil Nadu, India. In the present study, five Trichoderma viride isolates, Pseudomonas fluorescens and Bacillus subtilis strains were isolated from the coconut rhizosphere and tested against L. theobromae. P. fluorescens Pf1, B. subtilis (Km1) and T. viride (TNAU) isolates were found highly effective against the leaf blight pathogen under in vitro conditions and hence, all the three antagonists were combined together to develop microbial consortia and tested against leaf blight disease under field conditions. Soil application of microbial consortia formulated using talc as a carrier material at 150 g (50 g each) and 300 g (100 g each) doses at different intervals (quarterly, half-yearly and annually) was evaluated for three years from 2011 to 2013. Among the treatments, the fungicide carbendazim was found to be the most effective against coconut leaf blight. Among the treatments with bioagents, soil application of microbial consortia @ 300 g+5 kg of farm yard manure at quarterly interval/palm/year was the best treatment which was followed by the treatment with TNAU Bacillus subtilis (Bs1) mixture in two locations. Confirmatory results were obtained in similar experiments carried out at two different locations during 2013–2014, too.

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Studies were carried out on bacteria which usually infect spawns and culture plates of Psathyrella atroumbonata (Pegler) and Schizophyllum commune (Fr. ex. Fr.), two Nigerian edible mushrooms. During the vegetative propagation of these higher fungi, six different bacterial species were isolated and characterized from 14-day-old spawns and mycelial ramified PDA culture plates. These bacteria include Bacillus licheniformis, Bacillus subtilis, Leuconostoc mesenteroides, Pseudomonas aeruginosa, Bacillus cereus and Staphylococcus aureus. The average bacteria count was 1.0 x 106 cfu/ml and these bacteria grew within pH range of 5.0 and 9.0. The optimum temperature range of growth is between 30 °C and 37 °C. The significance of these findings to the cultivation of P. atroumbonata and S. commune in Nigeria was discussed.

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Acta Alimentaria
Authors:
M. Benhanifia
,
K. Shimomura
,
I. Tsuchiya
,
S. Inui
,
S. Kumazawa
,
W. Mohamed
,
L. Boukraa
,
M. Sakharkar
, and
H. Benbarek

The chemical analysis and antibacterial activity of propolis collected from some parts of Western Algeria were investigated. The ethanolic extracts of propolis (EEP) were evaluated for further investigation. The major constituents in EEP were identified by high-performance liquid chromatography (HPLC) analysis. All EEP samples were active against Gram positive bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus), but no activity was found against Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli). The mean diameters of growth inhibition of the EEP ranged between 8.05 and 21.4 mm. The propolis extract obtained from Sidi bel Abbés (SFS-SBA) was more active than other samples as well as showed unique HPLC profile. These results support the idea that propolis can be a promising natural food preservative in food industry and alternative candidate for management of bacterial infections caused by drug-resistant microorganisms.

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Wrightia tinctoria leaf hexane, methanol and ethanol extracts were screened against skin bacteria and dermatophytes by in vitro. The extracts were tested using agar dilution method and broth micro dilution method. Methanol and ethanol extracts showed antibacterial activity; the MIC was 0.5 mg/ml for Bacillus subtilis and Staphylococcus epidermidis; 0.25 mg/ml for Staphylococcus aureus. The hexane extract showed antifungal activity against Trichophyton rubrum and Trichophyton tonsurans at 2 mg/ml. The MIC of 2 mg/ml was observed for methanol extract against Trichophyton mentagrophytes and IC50 (2 mg/ml) was determined for Trichophyton rubrum and Epidermophyton floccosum. To summarise Wrightia tinctoria leaves possessed potent antimicrobial properties against dermatophytic microbes. In particular, methanol and ethanol extracts were active against bacteria and hexane extract was active against dermatophytic fungi, suggesting that the active principles may be useful in the topical treatment of superficial skin infections.

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The Juniperus excelsa is considered an important medicinal plant by the local population of Balochistan, Pakistan. The species is facing a grave threat by a parasitic and epiphytic angiosperm, dwarf mistletoe, Arceuthobium oxycedri (DC.) M. Bieb. (Viscaceae). The methanolic extract of A. oxycedri was studied for its chemical composition and biologically active compounds for the first time. The extract was assayed for antibacterial, antifungal, phytotoxic, cytotoxic and insecticidal activities. The antibacterial and antifungal activities of the extract were determined against ten bacterial and ten fungal strains by agar well diffusion and disc diffusion assay. The extract was highly effective against three bacteria Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis and a fungus Candida albicans . The phytotoxic effects showed that it was extremely toxic for Lemna acquinoctialis . It showed high cytoxicity for brine shrimps at all concentrations and was found to be significantly cytotoxic against Candida albicans when checked by flow cytometer. However, the extract was not effective against the pests tested.

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