مجله میکروبیولوژی کاربردی در صنایع غذایی
سال هشتم شماره 1 (بهار 1401)

This study was aimed to investigate the total phenols and flavonoids content, antioxidant activity, and antifungal effect of Mentha spicata essential oil on fungi species causing strawberry’s rot (Aspergillus niger, Botrytis cinerea, and Rhizopus stolonifer). For these purposes, the essential oil of M. spicata was firstly extracted by the Clevenger apparatus. The M. spicata essential oil contained 55.15 mg GAE/g total phenols and 29.25 mg QE/g total flavonoids, which show an important role in its antioxidant and antifungal activities. The antioxidant activity (IC50) of the essential oil was found to be 23.35, 19.80, and 27.11 µg/ml, respectively, based on the DPPH radical scavenging, ABTS radical scavenging, and beta-carotene/linoleic acid assays. The antimicrobial tests (disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum fungicidal concentration) showed that the essential oil of M. spicata had a potentially high antifungal activity; Aspergillus niger and Botrytis cinerea were the most sensitive and resistant fungi species to the essential oil. The minimum inhibitory concentration for Aspergillus niger, Botrytis cinerea, and Rhizopus stolonifer was 12.5, 50 and 25 mg/mL, respectively. The minimum fungicidal concentration for Aspergillus niger, Botrytis cinerea, and Rhizopus stolonifer was 100, 200 and 100 mg/mL, respectively. Based on the results, the M. spicata essential oil can be used as an antioxidant and antimicrobial agent in food products.

Today, sodium benzoate and potassium sorbate are mainly used to control microbial contamination, mold and yeast, which have carcinogenic effects. The aim of this study was to evaluate the effect of chitosan (0.06 %w/w) and thyme extract (0.08 %w/w) separately and simultaneously (chitosan 0.03+thyme extract 0.04 %w/w) on physicochemical, microbial and sensory properties of French salad dressing and comparison with control samples (French sauce containing sodium benzoate + potassium sorbate and without preservative). The results showed that the addition of chitosan and thyme extract in comparison with the control sample had no significant effect on changes in pH, water activity and emulsion suspension during storage (p <0.05). Addition of chitosan and thyme extract showed a significant increase and decrease of L * index and a * index in comparison with the control sample and had no significant effect on the amount of b * index. The results of microbial tests showed that treatment with chitosan 0.03% + 0.04% thyme in both MIC and MBC concentrations had a good inhibitory effect on the growth of hetero fermentative lactic acid bacteria, Escherichia coli and mold and yeast at the end of the storage period, no growth was observed. The sample containing chitosan 0.03% + 0.04% thyme received the highest sensory evaluation score. The results of this study showed that the use of natural preservatives of chitosan and thyme extract can significantly reduce the consumption of chemical additives and this is a step in improving the health of the consumer community.

Nisin is a biological bacteriocin with many functions against food pathogenic bacteria. The disadvantages of chemical preservatives in foods have attracted attention to natural preservatives such as nisin. This study evaluated the antimicrobial properties of nisin extracted from Lactococcus lactis isolated from goat milk. Ten goat milk samples were collected from around Kerman city under sterile conditions, and Lactococcus lactis were isolated in the selected environment of Eliker-trimethoprim. Biochemical tests were used to Strain identification and nisin gene confirm by polymerase chain reaction with specific primers was used. HPLC method was used to confirm the presence of nisin using bacterially extracted proteins. The antibacterial properties of nisin were performed by disk diffusion agar method against Staphylococcus aureus, Bacillus cereus, Acinetobacter baumannii, and Pseudomonas aeruginosa. The minimum inhibitory concentration of bacteriocin was performed by Provide serial dilution in a microtiter plate. One of the four strains of Lactococcus lactis was identified and selected with the best growth conditions for further investigation. The presence of the nisin gene in Lactococcus lactis was confirmed by a specific primer and polymerase chain reaction method. The amount of nisin produced protein was 41.5 mg/kg. The diameter of inhibitory zone for Staphylococcus aureus, Bacillus cereus, Acinetobacter baumannii, and Pseudomonas aeruginosa were 13, 17, 14, and 0, respectively, and minimum inhibitory concentrations for extracted nisin were in dilutions of 10-5, 10-6, 10-5 and 10-1, respectively. Therefore, nisin extracted from Lactococcus lactis in goat milk can be a suitable substitute for chemical preservatives.

Increasing antibiotic resistance of Staphylococcus aureus has led to attempts to discover new antimicrobial agents, including the use of nanoparticles. The aim of this study was to synthesize vanosomycin and interferon gamma (IFN-γ) loaded chitosan nanogels and to evaluate the expression of TNF-α gene in mice infected with methicillin-resistant Staphylococcus aureus (MRSA). After synthesis and confirmation of chitosan nanogels, loading of vancomycin and IFN-γ in these nanogels was performed and confirmed by FTIR analysis. Then the antibacterial activity of nanogels was evaluated. At pHs of 6.5 and 7.4, the minimum inhibitory concentration (MIC) for vancomycin-loaded nanogels was 8 and 64 µg/ml, respectively. The MIC was calculated to be 1024 µg/ml for chitosan nanogels and IFN-γ-loaded nanogels and 1 µg/ml for free vancomycin. Then 48 mice were divided into 6 groups: control, MRSA, nanogels, drug nanogels, IFN-γ nanogels and nanogels (drug and IFN-γ). After infecting the groups (except control) with MRSA, 100 mg/kg of nanogels, drug nanogels, IFN-γ nanogels and nanogels (drug and IFN-γ) were added to groups 3 to 6, respectively. Finally, at 6, 12 and 24 hours, a number of mice from each group were anesthetized and their spleen was evaluated for TNF-α gene expression by RT-PCR. The results showed that in groups 4, 5 and 6, compared to the MRSA group, TNF-α gene expression showed a significant decrease after 24 hours. Therefore, it could be concluded that simultaneous injection of drug nanogels and IFN-γ nanogels in infected mice is much more effective than single injection of each of these nanogels.

In order to targeted delivery of probiotics for food and drug applications and their effectiveness in preventing and treating various diseases, designing effective systems in this field can be helpful. In this paper, a new system for targeted delivery of probiotics has been introduced. The objectives of this study included: the efficiency of anti-acid microgels coated by multilayer polyelectrolyte formulation of alginate-chitosan for survivability of probiotic bacteria in gastric and intestinal simulation conditions. Tow Strains of probiotic bacteria including Lactobacillus Rhamnosus and Lactobacillus Plantarum were encapsulated separately in alginate hydrogels and calcium carbonate as an antacid agent (to control pH under acidic conditions) and coated with double bilayer alginate-chitosan by LbL self-assembly technique. The results showed that ( in the presence of pepsin enzyme and at pH=1.8 and in the presence of pancreatin enzyme and at pH=6.8), the survivability of these bacteria increased significantly compared to lactobacillus Plantarum and Lactobacillus rhamnosus 6 log(cfu/g) and 2.5 log(cfu/g) respectively. The number of viable cells in both probiotic strains was higher than the acceptable therapeutic level. In general, these results showed that these microcapsules can be used in controlled delivery of probiotics as food supplements successfully.

This study was done to evaluate the microencapsulated Spirulina platensis powder on intestinal microflora, blood anti-oxidant status, and meat quality of broiler chickens. A total of 160 one-day old Ross 308 broiler chicks (mixed-sex) were assigned to a completely randomized design with four treatments, 4 replicates, and 10 chicks in each replicate. Experimental treatments included basal diet (without additive), basal diet + 0.3, 0.6 or 0.9 % microencapsulated Spirulina powder. Feeding diet contained 0.9 % encapsulated Spirulina powder decreased Coliforms population in the ileum of broiler chickens (P<0.05). Feeding diets contained 0.6 or 0.9 encapsulated Spirulina powder increased ileal Lactobacillus population and the activity of super-oxide dismutase in blood of broiler chickens (P<0.05). Using encapsulated Spirulina powder at the level of 0.9% decreased malondialdehyde of the thigh meat at 30 days after slaughter (P<0.05). In general, results of the present study showed that feeding Spirulina micro-algae to broiler chickens at the level of 0.9 % led to improve the birds̓ anti-oxidant status, decrease the intestinal harmful microbes and oxidation of thigh meat of broiler chickens at 30 days after slaughter.