فصلنامه زیست شناسی میکروارگانیسم ها
پیاپی 35 (پاییز 1399)

Inocutis levis is a polypore basidiomycete from the Hymenochaetaceae family. Members of this family have well-known medicinal properties. Recently, anti-diabetic and anti-hypercholesterolemic effects of I. levis have been reported. This study aimed to evaluate antibacterial activities and antioxidant properties of the extracts of I. levis.

After the sampling and fungus identification, the methanolic, ethanolic, and aqueous extracts of the dried fruiting bodies of I. levis were prepared. The antioxidant activities were determined by DPPH method, and antibacterial activities by microdilution method against some gram-positive and gram-negative bacteria. Furthermore, the identification and quantification of phenolic and flavonoid compounds of the extracts were investigated by spectrophotometers and HPLC.

The results showed that the methanolic extract had the highest DPPH scavenging activity, with an IC50 value of 555 µg/ml. The ethanolic and methanolic extracts showed the same antibacterial effects, and Streptococcus mutansATCC35665 was more sensitive than other bacteria, with the MIC and MBC values of 12.5 and 25 mg/ml, respectively. Total phenolic (34.15mg gallic acid) and total flavonoid contents (5.4mg quercetin) per 1 gram dry methanolic extract were higher than other extracts. Furthermore, in the HPLC analysis, ascorbic acid, resorcinol, caffeic acid, catechin and, vanillic acid were determined.

This is the first study presenting the antibacterial and antioxidant properties of I. levis. The results can be considered for future studies in the design of new antibiotics and antioxidant compounds from natural resources applying native fungi.

Sulfate adenylyltransferase catalyzes adenosine phosphosulfate (APS) to generate ATP and sulfate, which is the final stage of the sulfite oxidation to obtain energy, and 4Fe_4S ferredoxin as an enzyme member of the electron transfer chain plays an important role in the oxidation of ferrous iron in the bioleaching system. Efforts to optimize bacterial growth conditions will also increase the gene expression, which will be accompanied by an increase in the efficiency of the microbial leaching system. Accordingly, the present study aimed to investigate the gene expression related to the proteins in Sulfobacillus thermosulfidooxidans along with the application of changing factors in the culture medium.

For culture, different concentrations of chalcopyrite, yeast extract, and ferrous iron ion were added to a 9K medium. Bacteria were purified and bacterial RNA extraction and cDNA synthesis were performed. To investigate the expression level of the genes under study, the Real-time PCR reaction was performed and the results were analyzed by the 2-∆∆CT method. The results were also analyzed by Tukey and Duncan tests using SPSS version 21 with the P-value of ˂0.05.

Using the results of the PCR, the genes in question were identified and primers were confirmed. The highest percentage of copper extraction in the four test environments was in the No. 2 environment with 48.75% in which the 4Fe_4Sferredoxin gene had the highest expression than the other test environments. The highest expression of the Sulfate adenylyltransferase gene was related to the medium No. 4 in which the percentage of copper extraction was 39.16%.

The composition of the bacterial culture medium can change the expression of genes and the percentage of copper extraction. The most suitable test medium was obtained for the extraction of copper in a 10-micron size, the presence of 1.5 g/L ferrous ion, and the absence of yeast extract.

Saccharomyces cerevisiae is the dominant yeast in the bakery industry used throughout the world. One of the most widely used sources of carbon for the bread yeast culture medium is molasses. In recent years, due to the expansion of the fermentation industries and the increased demand for carbon and nitrogen sources in these industries, and the shortage of raw materials and their high cost, the possibility of using by-products produced in food industry factories has been considered.

In this study, the use of corn steep liquor as the nitrogen source and glucose syrup as the carbon source has been studied. The amount of biomass production and yeast activity was measured in the form of carbon dioxide gas production and sugar consumption in separate tests. In all treatments, the fermentation time was 16 hours, and stirring on a shaker was at 30 °C and 150 rpm.

At the optimized point, where the amount of the glucose syrup and corn steep liquor was 12.82 mL/100 mL and 4.31 mL/100 mL, respectively, the amount of produced CO2 increased about 12.5%, and the time of rising of the dough reduced from 25 to 14 minutes showing a significant progress.

To replace the carbon and nitrogen sources in the yeast culture medium, the factors and their levels were selected from previous studies. Because of the shortage of sugar beet molasses, which has recently appeared in Iran's fermentation industry, we tried to introduce two cheap but still valuable replacements, for both the carbon and nitrogen sources. The result showed that using glucose syrup and corn steep liquor is not only feasible but also better than the conventional sources.

Environmental pollution with toxic and heavy metals has been a major problem in recent decades. Therefore, the removal of these pollutants from the environment is very important.

In this study, the biosorption of hexavalent chromium (Cr+ 6) was investigated by brown alga Sargassum ilicifolium. The absorbance of Cr+6 solutions at 540 nm was obtained by UV-VIS. Also, the effective parameters in absorption such as initial metal concentration, amount of algae, pH, temperature, and contact time were investigated. The Langmuir and Freundlich isotherms were used to study the equilibrium studies.

In these conditions, the maximum adsorption capacity was 203 mg/g of Sargassum ilicifolium. Laboratory data with the pseudo-second-order kinetics were described better. Using Response Surface Methodology (RSM), optimum conditions of maximum adsorption capacity were determined at pH 2, adsorbent content of 0.2 g/l, initial metal concentration of 200 mg/L at 25 °C, and the equilibration time of 7 h.

The results showed that the Freundlich isotherm was more suitable for describing the system. Thermodynamic studies have also shown that the process was exothermic and spontaneous and increased with time due to disorder. Due to the functional groups present in the algal cell wall, part of Cr+6 was reduced to Cr+3 and Cr+3 that were remained in solution. Fourier transform infrared spectroscopy of (FT-IR) showed that amino, carboxyl, sulfonic acid, and hydroxyl groups played a major role in the process of chromium uptake by Sargassum ilicifolium.

L-asparaginase has an essential role in the treatment of cancers, especially Acute Lymphoblastic Leukemia. The rapid removal of the enzyme from the bloodstream, glutaminase activity, and also inducing an immune response in the body are disadvantages of commercial enzymes, therefore, the identification of new L-asparaginase with desirable properties is essential. Previously, the coding sequence of L-asparaginase isolated from Halomonas elongata had been cloned in E. coli and had shown to have advantageous properties as a chemotherapeutic agent. However, it was mostly expressed as inclusion bodies.

In this study, soluble enzyme expression was examined in two E. coli hosts, BL21 (DE3) and ArcticExpress strains. After selecting the host, the effects of various factors such as culture media, inducer concentration, inoculum size, induction duration, temperature, and also aeration rate were optimized using the one-factor-at-a-time approach.

Based on the results, the highest amount of active L-asparaginase production was related to Escherichia coli host Bl21 (DE3) strain in LB culture medium by adding 1% inoculum size, after 9 h induction with 0.5 mM IPTG at 37 ˚C, and shaking at 150 rpm. In the next step, the effect of various additives on the culture medium was investigated and it was observed that the addition of ethanol 2% (v/v) or arginine (200 mM) has a significant effect on increasing the specific activity of the enzyme.

Finally, the optimization could increase soluble L-asparaginase production from 1000 U/mg in the basal condition up to approximately 3500 U/mg (more than three times).

Microorganisms that store lipids due to nutrient deficiencies (especially nitrogen) produce microbial oils following inhibition of growth. Based on the structure of fatty acids, microbial oils have industrial applications. The main purpose of this study, the first in Iran, was to evaluate the production of single-cell oil from Rhodococcus erythropolis PTCC 1767 using low-cost materials.

In the present study, Rhodococcus erythropolis PTCC 1767 as bacterial strain, whey, wheat straw, glucose, and glycerol were used for carbon sources and yeast extract was used for the nitrogen source. The bacterial strain was cultured in the MSM medium. FTIR analysis was performed to confirm the presence of carbon groups, GC analysis for identifying fatty acids, and Sudan black staining and imaging with a Transmission Electron Microscope (TEM) for observing the lipid granules stored inside the cell.

The highest lipid production in the presence of carbon sources was related to whey in 96 hours with 23.22% and the maximum lipid production was obtained using wheat straw in 72 hours with 20%.

The results of the present study demonstrated that Rhodococcus strains have the ability of bioconversion of low-cost carbon sources wheat straw and the whey to microbial oils and this can serve as a platform for eco-friendly biotechnological processes.