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Research subject: In recent decades, hybrid optimizations methods based on natural phenomenon have placed special position according to their capabilities in finding optimal solutions without expensive computational loads and disassociation on choosing initial points. Artificial Neural Network is used as one of the powerful tools of Artificial Intelligence for process simulation. The employment of the neural network in the modeling of m-Cresol alkylation process of with isopropanol as well as meta-heuristic methods in obtaining the optimal conditions for the catalyst and the reaction can prepare an effective step towards a high efficiency process.
Research approach: In the present study, the artificial neural network is applied to model alkylation of m‐Cresol with isopropanol process. In addition, the bee colony is employed in order to optimize the process yield. To verify its performance, the proposed method is used in prediction of the m‐Cresol conversion and Thymol selectivity of the alkylation process with isopropanol 120 data. In this process, the input variables are Weight Hourly Space Velocity (WHSV), pressure and temperature; m-cresol conversion and thymol selectivity are considered as the output variables of the neural network. Five hidden neurons are considered for the proposed neural network. 120 data is used to train the neural network. The meta-heuristic approach based on bee colony (BC) is applied to maximize the yield of the process.
Main results: The results confirm that the proposed method develops the accurate model with an R² value of greater than 97.5%. The maximum yield is obtained 28.9% by bee colony algorithm with adjustable variables that are WHSV of 0.062 hr^-1, the pressure of 1.5 bar and the temperature of 300^oC. In addition, in order to achieve the better performance of the optimization algorithm, the appropriate values of acceleration coefficient and population size are chosen 100 and 10 during the trial-and-error phase.

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In a marine environment, the biofilm formed on the submerged surfaces leads to fouling of larger organisms. This leads to many environmental and economic problems for the marine industries. Due to the harmful effects of chemical antifouling, the development of environmentally friendly anti-biofilm strategies can be an important step to control fouling.
Therefore, the present study was performed with the aim of isolation of biofilm-forming bacteria from Persian Gulf waters and investigating the antimicrobial effect of thymol against selected bacteria.82 bacterial were isolated and their ability to form biofilm was measured. Among these, 5 isolates were selected and identified using 16S rRNA sequences. The results showed that the 5 selected isolates belonged to the Proteobacteria (genus Vibrio, Kangiella and Psudoaltromonas). In the study of the antibacterial effect of thymol, K. spongicola (PH1) showed the highest sensitivity in disk diffusion method (with a growth inhibition zone diameter of 18 ± 0.57 mm). The minimum inhibitory concentration and minimum bactericidal concentration (at 31.5 and 62.5 μg /ml, respectively) were obtained against the same bacterium. The inhibitory thymol on biofilm formation and performed biofilm by Psudoaltromonas sp. (PH18) showed that thymol at concentrations sub-MIC is able to inhibit biofilm formation. The effect of thymol on the performed biofilm at concentrations higher than MIC is noticeable. Based on the results, due to the anti-biofilm activity of thymol against marine bacteria, its use as a natural compound in antifouling coatings can be suggested.

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The volatility of essential oils and their instability against environmental factors limit their use. However, encapsulating these compounds in polymeric nanoparticles can significantly increase their half-life and make their use possible for longer periods. Chitosan, a biodegradable polymer with controlled release and low toxicity, is one of the polymers utilized in the encapsulation of essential oils. As a result, the present study was carried out with the aim of nanoencapsulation of carvacrol and thymol in chitosan using ionic gelation method and the concentration of chitosan (0.1-0.3%), TPP concentration (0.2-0.1%) and concentration of essential oil (0.1-0.2%) as three variables. The mean particle size of chitosan nanoparticles was optimized using response surface methodology and central composite design. The size and polydispersity index (PDI) were determined by DLS, essential oil loading confirmation was evaluated by FTIR, and the spectrophotometric method was used to measure the encapsulation efficiency. Then, the results of the optimization of nanoparticle synthesis were investigated. The optimum conditions for the synthesis of chitosan-thymol nanoparticles and achieving a size of 101 nm and encapsulation efficiency of 72%, a concentration of 0.11% chitosan, 0.19% TPP and 0.14% thymol were determined. In the case of chitosan-carvacrol nanoparticles, a concentration of 0.13% chitosan, 0.19% TPP and 0.15% carvacrol resulted in the formation of nanoparticles with a size of 95 nm and an encapsulation efficiency of 65%. In general, the results demonstrated the ability of the response surface methodology to predict the particle size and PDI of chitosan nano-formulations containing carvacrol and thymol.

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Currently, consumers are aware of the side-effects of chemical additives and are more interested in natural antibacterial compounds as food preservatives, like herbal essential oils and extracts. In this study, the antimicrobial effect of some main components of the essential oils, including thymol, carvacrol, menthol and eugenol has been evaluated against Bacillus cereus (PTCC 1154), Pseudomonas nigrifacience (ATCC 19375), Erwinia carotorova (PTCC 1675) and Xanthomonas campestris (PTCC 1473) by broth microdilution method and agar disc diffusion method. According to the results, the lowest MIC was reported for Thymol which was 50 ppm (Pseudomonas nigrifacience, Erwinia carotorova and Bacillus cereus) and the maximum MIC for Pseudomonas nigrifacience was 100 ppm due to menthol and 125, 125 and 108 ppm for Bacillus cereus, Erwinia carotorova and Xanthomonas campestris respectively due to Eugenol. Menthol presented the broadest growth inhibitory zone (8.9 mm) for Pseudomonas nigrifacience and the narrowest inhibitory zone was reported for Eugenol against Erwinia carotorova (5.9 mm). Menthol and eugenol were the strongest and weakest antimicrobial agents respectively (p-value<0.05). However, all tested components inhibited the microorganisms at different levels and are potent to be used as food preservatives.

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Vegetables have a short shelf life, and because they are eaten fresh, it is necessary to use healthy and natural methods to increase their shelf life. The present study has investigated the effect of active packaging containing the active ingredient of thymol on the color and pH measurements, microbial evaluation, total mold and yeast count, and the sensory properties of seasonal salad during six-day storage refrigerator temperature. For this purpose, seasonal salads were packed with oriented polypropylene (OPP) and low-density polyethylene (LDPE) films immersed in thymol essential oil for 1, 2, and 3 days. Results show that season salads packed with OPP and LDPE films immersed in thymol essential oil for three days had higher pH and lower mold and yeast count than control and other treatments. The mold and yeast count were significantly lower (p < 0.05) in a sample packed with OPP films containing essential oil compared to the LDPE/ thymol essential oil. The L* and a*values decreased during storage time. The L* and -a * indices of season salads were lower in OPP and LDPE films immersed in thymol essential oil for three days than the neat and other groups. Sensory evaluation showed that immersion in thymol essential oil improved sensory attributes (p <0.05).  The coated films, especially OPP, improved the color, reduced the number of mold and yeast, increased the shelf life, and improved the sensory attributes of seasonal salads. Therefore, films treated with thymol essential oil can act as active packaging.

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 The present study aimed to encapsulate thymol and resveratrol prepared with zein-caseinate composite nanoparticles and to investigate their antioxidant and antimicrobial properties. For this purpose, liquid-liquid dispersion method was used to prepare zein-caseinate composite nanoparticles. In this study, the effect of different concentrations ratio of thymol and resveratrol (zero to 100%) and different ratios of core to coating (1:10 and 1:20) on the ability to inhibit DPPH free radicals, the reducing power of iron ions and antimicrobial activity on Escherichia coli and Listeria monocytogenes was investigated in culture media and milk. The results showed that the sample containing 75% thymol and 25% resveratrol with a ratio of 1 to 10 of core to coating had the highest ability to inhibit DPPH free radicals and the reducing power of iron ions, and it was found that the increase in the coating concentration except for the sample containing 75% thymol, led to an increase in the Inhibition power of DPPH free radicals and reducing power of iron ion. Listeria bacteria in the TSB culture medium were the most sensitive bacteria to the prepared samples, and the strongest prepared nanoparticles, which had the lowest MIC and MBC, belonged to the sample containing 75% thymol and 25% resveratrol with a core-to-wall ratio of 1:10, and in most samples, The bacteria in milk were more resistant to these nanoparticles than the culture medium. Finally, it can be said that the sample containing 75% thymol and 25% resveratrol with a core-to-wall ratio of 1 to 10 can be selected as a combination with appropriate antioxidant and antimicrobial power.
 

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 The quantity and quality of essential oil extracted from the plant is strongly influenced by the extraction conditions, so optimizing the extraction conditions can help us to achieve the most essential oil content with the best quality. Satureja sahendica Bornm. is an endemic medicinal plant of Iran, which is of great importance due to its high essential oil and thymol content. In this research, the effect of plant particle size (mesh size 12, 18 and 35) and the ratio of plant material to water (1:5, 1:10 and 1:15 w/v) on essential oil content and compositions of this plant were evaluated. The essential oils were extracted based on hydro-distillation method by Clevenger’s apparatus and then analyzed using GC/MS and GC/FID. The results indicated that the extracted essential oil decreased with the decrease in the plant particle size. The optimal ratio of plant material to water in order to obtain more essential oil was different depending on the plant particle size. The highest of essential oil content (2.15% v/w) was obtained from plant material with mesh size 12 in the ratio of 1:15 plant material to water. The number, type and amount of essential oil compounds were strongly affected by different treatments. The highest amount of thymol (81.79%) as the most important component of the Satureja sahendica essential oil was obtained from samples with mesh size 35 and a ratio of 1:10 plant material to water. Determining the most appropriate extraction conditions can be different depending on the purpose and desired chemical composition of the essential oil.

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Strawberry is a perishable fruit and gray mold is one of the main reasons which reducing its shelf life. Due to the limitations of using chemical poisons, it seems necessary to use safe methods such as the use of essential oils (EOs) and edible coatings to control this fungus maintain the quality, and increase the storage period. However, the high volatility of EOs and organoleptic effects on agricultural products have hindered the direct application of EOs. This study is designed to enhance the shelf life of strawberries by designing nanoemulsion systems of EO with chitosan as follows: in the first experiment, the effect of nanoemulsion of the thymol, one of the main components of thyme, with a concentration of 5 g/L, alone and in combination with chitosan (CH) biopolymer was investigated on Botrytis cinerea. All treatments significantly reduced fungal growth compared to the control sample. Also, combined treatment showed the highest level of inhibition of B. cinerea. The second experiment was performed to evaluate the quality changes and post-harvest wastes of strawberries during storage. In this section, the fruits were coated with thymol 0.5%, thymol nanoemulsion 0.5%, and thymol nanoemulsion 0.5% + CH 0.5% and kept at 4 °C. Results presented that the application of the applied treatments had a positive effect on the physicochemical and biochemical indicators of strawberry fruit during the post-harvest period and caused better preservation of firmness, prevented weight loss and reduced microbial load. Also, the lowest rate of weight loss, the highest rate of firmness, and the lowest rate of growth of microorganisms were observed in covered fruits with treatment of thymol nanoemulsion 0.5% + CH 0.5%. Finally, this treatment can be suggested as a suitable cover to maintain the quality and reduce post-harvest waste of strawberries.
 

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Satureja sahendica Bornm is an endemic, native, and aromatic plant in Iran, with thymol being its main and major volatile component, which is used in food and pharmaceutical industries. Increasing the oil yield and phenolic compounds in essential oil leads to increased medicinal effects. In this study, the effects of mycorrhizal fungi (Glomus mosseae, G. intraradices, and combination of G. mosseae and G. intraradices) and different levels of water stress [D₁= Control (no water stress), D₂= No irrigation during stem elongation till blooming, D₃= No irrigation at the blooming up to start of flowering, and D₄= No irrigation at 50% flowering up to full flowering] were studied on S. sahendica oil, in two years. When the seedlings were transferred to the field, 10 g of mycorrhiza fertilizer (containing mycorrhizal fungus spores) were added to the rhizosphere of each seedling. The plants were harvested at full flowering and the essential oils were obtained by hydro-distillation and analyzed by GC and GC/MS. The highest amount of oil yield (66.13 kg ha^-1) was obtained using G. intraradices in non-stress conditions in the second year. The highest percentage of thymol was obtained in G. mosseae×control in the first year (74.59%), whereas in the second year, the highest amount of thymol was in G. mosseae×D₄ (61.97%). This study showed that with the use of mycorrhizal fungi, even in conditions of water shortage, S. sahendica produced more essential oil with a higher percentage of thymol. With the use of mycorrhizal fungi, the essential oil can easily be increased and the number of compounds changes.