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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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There is a global interest to study lactic acid bacteria (LAB) of artisanal fermented products like yoghurt for improving or replacing current strains used in commercial starter cultures. In this work, five traditional yoghurt samples were collected from different areas of Khorasan-e-Razavi. Grouping and identification of isolates were carried out on the basis of physiological and biochemical tests (non-molecular),as well as ARDRA technique and sequencing (molecular methods). Totally, 71 isolates including 33 Streptococcus thermophilus, 30 Lactobacillus delbrueckii (subsp. Bulgaricus and lactis), were identified as dominant strains in all yoghurt samples. Also 8 other isolates belonging to Lactobacillus helveticus, Pediococcus pentosaceus and Weissella cibaria were observed. Results of this research show the diversity of LAB population in collected samples.