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Glucoamylase, is an important economic enzyme due to its ability to hydrolyze starch and β-D-glucose polymers. Understanding of factors affecting the thermal stability of the glucoamylase enzyme is critical in the production of isoenzymes with high heat or cold stability.  In this study, the effect of temperature on the structure and properties of each of the isoenzymes of the mesophilic, thermophilic and psychrophilic glucoamylase were studied. For this purpose, molecular dynamics simulation was used to assess these factors and structural differences. 240 nanosecond of MD simulation was done for three isoenzymes of glucoamylase in four temperatures at 300, 350, 400 and 450 K. The variations of each of these parameters were compared for three isoenzymes, and it was found that among the computable factors in molecular dynamics simulation, electrostatic energy of protein with water, van der Waals energy between proteins and water, free energy solubility (∆G_solvation), instability parameter, nonpolar solvent accessible surface, and total solvent accessible surface can be used to predict thermal stability of a protein during increase of temperature.
 

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This research was carried out to study the antifungal effect of aqueous extract and powder of Pistacia atlantica at 0, 0.5, 1, 2.5 and 5% on the growth of Aspergillus flavus and Aspergillus niger. Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) of the baneh extract and powder was certified against Aspergillus niger and Aspergillus flavus in concentrations of 0.5, 0.4, 0.3, 0.2, 0.1 and 0.05 g /ml were determined by Serial Dilution technique. After preparing lactic cheese samples, a 10 mm piece was placed inside the plate and 3 μl Aspergillus flavus and Aspergillus niger was added to its center. Plates were incubated at 26 ° C for 3 weeks and the zone diameter of mold growth was measured. The results showed that by increasing the storage period, the growth zone diameter of Aspergillus flavus and Aspergillus niger in all of treatments increased. The treatments had a greater effect on the control of Aspergillus flavus mold growth than that of Aspergillus niger in lactic cheese. In mold and yeast counting, the highest count was observed for control treatment and the lowest increase was related to treatment containing 5% extract of Pistacia atlantica. The experimental treatments also significantly affected the sensory properties of the cheese samples. The highest taste scores were for samples containing 0.5 and 1% Pistacia atlantica extract. The samples containing more levels of extract (2.5 and 5 %) were less scored in terms of flavor and taste than those containing powder of Pistacia atlantica. From the findings of this study, it can be concluded that extracts and powder of Pistacia atlantica have an appropriate antifungal activity against Aspergillus niger and Aspergillus flavus, Therefore, they can be used in medical pharmacology, food industries and health affairs as drugs and anti-fungal elements.

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Plant essential oils and extracts are the compounds that can inhibit bacterial growth at low concentrations. Also, these materials are mostly strong antioxidants and the presence of these two properties together increases the shelf-life of fish. This study was done to investigate effect of various concentrations of caraway and thyme essences on chemical and microbial quality of common carp fillet. Different concentrations of essential oils (0, 500, 1000 and 2000 mg/l) were added to fish samples and some chemical and oxidation factors, microbial quality and sensory properties of the samples were determined. The results showed the lowest levels of total volatile basic nitrogen was related to 2000 mg/l thyme essential oil (24.6 mg/100 g fillet) and the highest amount of total volatile basic nitrogen were observed in control treatment (75.11 mg/ 100g fillet) at refrigerator temperature. TBA levels in all treatments increased with increasing storage time and at the end of the storage period, except in 500 and 1000 mg/l thyme essences treatments, there was significant difference among all experimental samples (p<0.05). The results showed that various concentrations of essences reduced the total count and Psychrotrophic bacteria compared to the control. At the end of the storage time, treatment of 2000 mg/l caraway essence, 1000 mg/l caraway essence and 2000 mg/l thyme essence had the lower Psychrotrophic bacteria than the other samples. Treatments with 1000 and 2000 mg/l caraway essences in freezing conditions received the most colors score. The highest score of texture was related to 2000 mg/l thyme essential oil at refrigerator temperature. Samples containing 1000 mg/l caraway essence in freezing temperatures had the highest odor score. In general, 1000 and 2000 mg/l concentrations of thyme essence due to acceptance of the organoleptic characteristics from the consumer view as well as reduce microbial growth and chemical factors are recommended.