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The accumulation of nisin in the fermentation medium can reduce the process's productivity. This research studied the potential of Nymphaea alba leaf powder (NALP) as a hydrophobic biosorbent for efficient in-situ nisin adsorption from the fermentation medium by docking and experimental analysis. Molecular docking analysis showed that di-galloyl ellagic acid, a phytochemical compound found in N. alba, had the highest affinity towards nisin. Enhancements in nisin adsorption were seen following pre-treatment of NAPL with HCl and MgCl2. A logistic growth model was employed to evaluate the growth dynamics of the biosorption capacity, offering valuable insights for process scalability. Furthermore, optimization through Response Surface Methodology elucidated optimal nisin desorption conditions by Liebig's law of the minimum, which posits that the scarcest resource governs production efficiency. Fourier Transform Infrared (FTIR) spectroscopy pinpointed vital functional groups involved in biosorption. Scanning electron microscopy revealed the changing physical characteristics of the biosorbent after exposure to nisin. The findings designate NALP as a feasible adsorbent for nisin removal from the fermentation broth, thus facilitating its application in the purification of other biotechnological products based on growth and production optimization principles. [ABSTRACT FROM AUTHOR]

Background and Objectives: Recent evidences have shown that methicillin-resistant Staphylococcus aureus (MRSA) can cause severe infections and is resistant to almost all commercially available antibiotics. Therefore, screening unknown sources of biological compounds such as the Thermoactinomycetaceae family as extremophilic bacteria may be helpful to find new antimicrobial agents. Materials and Methods: Various samples were collected from different ecosystems, including desert, volcano, compost, and forest. They were cultured on Soil extract agar and Water agar. The antimicrobial activity of the isolates was evaluated using agar overlay and well diffusion methods. Members of the Thermoactinomycetaceae family were selected for further study: Their ability to grow at different temperatures, NaCl concentrations, and pH values, enzyme production ability, antimicrobial secondary screening, fractionation of their supernatants and so on. Results: According to molecular identification of active isolates against MRSA, three strains, including Laceyella sacchari UTMC 2705, Thermoactinomyces sp. UTMC 2721, and Laceyella sp. UTMC 2731, belonged to Thermoactinomycetaceae were identified. The minimum inhibitory concentrations of their extracts were tested against some pathogenic bacteria, showing their antimicrobial activity with a broad spectrum. The results of TLC bioautography of the extracts showed that the most active fractions were semi-polar. Also, the results of HPLC analysis showed the existence of several UV-active compounds in their extracts. Conclusion: The present study highlighted the importance and potential of Thermoactinomycetaceae members as a lessknown source of antibiotics against pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Recently, there has been a growing demand to develop portable devices for the fast detection of contaminants in food safety, healthcare, and environmental fields. Herein, two biosensing methods were designed by the use of nicotinamide adenine dinucleotide phosphate (NAD(P)H)-dependent TetX2 enzyme activity and thionine as an excellent electrochemical and colorimetric mediator/probe to monitor tetracycline (TC) in milk. The nanoporous glassy carbon electrode (NPGCE) modified with polythionine was first prepared by electrochemically and then TetX2 was immobilized onto the NPGCE using polyethyleneimine. The prepared biosensor provided a high electrocatalytic response toward NAD(P)H by significantly reducing its overpotential. The proposed biosensor exhibited a detection limit of 40 nM with a linear range of 0.1-0.8 µM for TC determination. Besides, the thionine probe was used to develop a novel colorimetric assay using a simple enzymatic color reaction within a few minutes. The limit of detection for TC was experimentally achieved as 60 nM, which was lower than the safety levels established by the World Health Organization (225 nM). The correlation between change in the color of the solution and the concentration of TC was used for quality control of milk samples, as confirmed by the standard high-performance liquid chromatography method. The results show the great potential of the proposed assays as portable instruments for on-site TC measurements. [ABSTRACT FROM AUTHOR]

Probiotics are normal flora of the mouth and digestive tract and have beneficial effects on the health of the consumer by regulating the microflora of the intestine, lowering blood cholesterol, stimulating immune system, improving lactose metabolism and the anti-cancer activities. They are also found in meat, vegetables, and dairy products. Most of probiotic bacteria belong to the Lactic acid bacteria group. Probiotics such as lactobacilli prevent the development of a wide range of human and animal's pathogens through producing antimicrobial compounds. In present study, 83 bacterial strains were isolated from 20 yoghurt samples which were collected from rural area of Kermanshah province, West of Iran. Samples were cultured on MRS agar and incubated at 30°C, in CO2 atmosphere. Gram-positive and catalase negative strains were considered as LAB. The antibacterial activities of these isolates were evaluated against Bacillus subtilis, Bacillus cereus and Escherichia coli, as food-born bacterial models using agar diffusion assay. To reduce antibacterial activity of produced lactic acid by the isolates, the supernatants of their fermentation broth were adjusted at pH 6.The results showed that maximum inhibition activity was belonged to strain 44, 61 and 72. These strains have antimicrobial activity against all tested g+ and g- bacteria. These investigated isolates showed no antibacterial activity on tested starter, including Lactobacillus casei and Lactococcuslactis. 16S rRNA gene analysis of strains 44, 61 and 72 revealed that all three potent LAB are belonged to Enterococcus genus. The results of current study showed that isolated LAB from traditional Kurdish cheeses are able to inhibit the growth of food-born spoilage and pathogenic bacteria. Metabolites of native can be considered as suitable alternatives chemicals with side-effects. [ABSTRACT FROM AUTHOR]