فهرست مطالب سارا تقوی

Microbial enzymes isolated from marine environments have found special applications in various industries, due to their unique properties. The Persian Gulf is a pristine place for the isolation of bacterial strains with the potential to produce new enzymes due to its rich biodiversity. Protease, lipase, and amylase are among the most widely used enzymes in various industries and due to the increasing importance and demand for microbial-marine enzymes in industry, this study aims to optimize and partial purify these enzymes from new strains isolated in port. Choubdeh (north of the Persian Gulf) was performed for the first time. Sampling was performed in November 2019 from 10 different stations (water and sediment samples). A new strain, Aeromonas taiwanensis - Persiangulf ST16 (accession number: OM189448) capable of producing protease, lipase, and amylase were identified by phylogenetic analysis of 16 SrRNA sequences. Optimal conditions for the growth of this bacterium included temperature of 30-37 ° C, pH 6, and salt concentration of 2.5%. The highest enzyme activity was observed for all three enzymes on the second day of incubation. The highest production of protease was reported at 37 ° C, pH 7, with the presence of maltose as a source of carbon and casein as a source of nitrogen, and the lowest was observed in the presence of dextrose and Beaf extract. The optimal conditions for lipase production at 37 ° C were 6-7 pH, and in the presence of olive oil and tryptone. The use of tween 20 and casein produced the lowest amount of enzyme. Optimal amylase production was observed at 35 ° C, pH 7, and the use of starch and yeast extract, but sorbitol and ammonium sulfate-induced the lowest production. During the purification steps, the specific activity of all three enzymes increased so that in the last stage of purification, protease, lipase, and amylase enzymes were purified by 16.23, 2.69, and 2.43 times respectively compared to the crude enzyme. Optimization of production of all three enzymes with significant activity by Aeromonas taiwanensis-Persiangulf ST16 showed that this bacterium could be a good candidate for further studies and use in industry.

colicins are a group of bacteriocins produce by Escherichia coli and act against pathogenic bacteria Escherichia coli. Today, the use of colicinogenic strains as probiotic microorganisms and replace them instead of the combination of antibiotics are taken into consideration. Therefore, this study was conducted to identify the different types of colicins in commensal Escherichia coli. This research was a descriptive - analytic study was performed on 120 stool samples that randomly was isolated from the commensal Escherichia coli in children referred to health centers in the Yasuj city. Firstly, E. coli isolates were determined by common biochemical tests. Then colicin gene existence was analyzed using specific primers 9. Data were analyzed by chi-square test. Of the 120 commensal E. coli in 85 cases (71%) colicin gene has been identified, so that 34/11% of samples containing a gene, 45/89% contain two genes and 20% of the samples had more than two genes. A strain was observed with six different colicin. The highest and lowest frequencies were related to colicin-coding genes IaIb and ANS4. the strains with more than one colicin gene showed a high frequency. These strains have a selective advantage for inhibition sensitive strains. The presence of colicin in the gastrointestinal tract, an important factor is to inhibit other pathogenic Escherichia coli.