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Citric acid is one of the industrial products with extensive applications which are used in the food, pharmaceutical, cosmetics and chemical industries. Although to 1965 Aspergillus niger was single strain to production of citric acid but yeasts are good candidate for citric acid production because growth on cheap and disposal substrates such as hydrocarbon and oils, low sensitive to trace elements in raw material. In this study, citric acid producing yeasts were isolated. Among 340 isolated yeast strains from dairy, meat and food products from Isfahan factories on screening media. 12 strains cultivated in citric acid production medium have been chosen for further study. Production of citric acid was determined by colorimetric method and Megazyme kit during 192 hours. One of the isolated yeasts with 55.5 g/g citric acid production along 144 hours after inoculation had the best yield. Biochemical and molecular tests showed that this strain belonged to the species Yarrowia lipolytica, molecular tests confirmed by sequencing; therefore it was named as Y. lipolytica M7 with accession number HM011048 in Genbank..

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  Date palm is one of important and strategic crops in, Iran. Microbial contamination is the most important factor in wasting of date palm. In this study, Sayer or Stamaran cultivar that is the most predominant cultivar in Khuzestan province, was studied and its microbial profile and characteristics including: total  count ( T.C), mold and yeast, and coli form were determined. During six months storage at 2 different temperatures environment temperature (25^°C   ) and cold storage ( 4 ^°C   ). Samples of date fruits were taken randomly after harvesting from ten trees and were then packed in plastic containers and stored as mentioned until the day of experiment for microbial analysis and analyzed in 3 replicates.Date samples homogenized with stomacher and then diluted with serum physiology.Standard plate count agar, sabroud Dextrose Agar and Violet Red Bile Lactose Agar media were used for total count,mold and yeast and coliform determination,respectively. Results showed that cold storage had inhibitory effect on microbial growth and microbial profile especially mold and yeast has had increasing trend in environment temperature and decreasing trend in cold storage during 6 month.With respect to mold and yeast log cfu had increased from 3.63 to 5.32 in room or environmental temperature and had decreased from 5.36 to 3 in cold or refrigerator temperature.No clear trend had been seen in total count and coliforms in both temperatures. Finally according to the results, the best condition for date palm storage is the cold storage or refrigerator temperature (4 ^°C) that this temperature has the inhibitory effect on microbial growth.

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In this research the effects of kind and quantity of leavening agent on dough rheological properties and organoleptical quality of Iranian flat breads were studied. The amount of compressed yeast and active dry yeast were 1.5, 2 and 2.5 percents of the bread formula. Rheological properties of samples were studied by farinograph method, and some factors such as water absorption, dough development time and etc were measured. Sangak bread had stronger flour comparing to the other flours including Barbari and Lavash. Thus water absorption, dough development time, stability and dough strength were more than other flours, but farinograph results didn't show any change. Some changes occurred in extensograph results by addition of 1.5, 2 and 2.5 percents of compressed yeast. Sensory analysis results indicated that bread samples had better quality with addition of various contents of compressed yeast. Addition of active dry yeast decreased the quality of dough and it cause disruption of dough samples and finally decreased quality of products.

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Production of recombinant proteins such as β-NGF using prokaryotic hosts is the topic of many recent researches. However, bacterial cell culture media are cheaper than eukaryotic cell culture media, but in industrial production scale they are not cost effective at all for biotech companies. Therefore, survey to find inexpensive cell culture medium that bacterial cells not only can grow in it but also produce recombinant proteins is very important. In this study, for the first time date syrup and yeast extract mixture was used as an inexpensive medium. In RSM (response surface methodology) studies different concentrations of date syrup and yeast extract were used as carbon and nitrogen sources respectively. The results indicate that the 20 g/lit of carbon and 5 g/lit of nitrogen are optimum for bacterial growth. Also the data show that recombinant bacteria not only can grow but also can produce recombinant proteins such as β-NGF using this synthetic medium.

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The present study was to evaluate the effect of dietary yeast cell wall (Saccharomyces cerevisiae) and cinnamon essential oil (Cinnamomum verum) supplementation on growth indices, serum biochemical parameters and immunity of rainbow trout (Oncorhynchus mykiss) fingerlings. Using a 2×2 factorial experiment, 276 fingerlings (9.67 ± 1.20 g) were fed four different experimental diets (including control diet, diet supplemented with 1.5 % yeast cell wall or 1 % cinnamon essential oil and a diet containing 1.5 % yeast cell wall and 1 % cinnamon essential oil) for a 60-day period. At the end of the trial, specific growth rate and weight gain significantly decreased in fish fed diet supplemented with 1% cinnamon essential oil (P≤0.05), however, feed conversion ratio was not statistically differed amongst treatments (P>0.05). Fish fed diets containing 1% cinnamon essential oil had the highest hepatosomatic index (P≤0.05). The highest red blood cell count and blood hemoglobin content belonged to group fed diet containing 1% cinnamon essential oil (P≤0.05). Simultaneous feeding with yeast cell wall and cinnamon essential oil significantly resulted in higher hematocrit value. Serum alkaline phosphatase activity was significantly increased in group fed diet containing 1.5% yeast cell wall. Dietary cinnamon essential oil supplementation also resulted in lower alkaline phosphatase, aspartate aminotransferase and gamma glutamyltransferase activity of serum (P≤0.05). The highest serum total protein and globulin content and lysozyme activity were observed in fish fed diet only supplemented with yeast cell wall (P≤0.05). In conclusion, dietary cinnamon essential oil and yeast cell wall inclusion resulted in improved immunity of rainbow trout fingerlings.

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Witches' broom disease of lime (WBDL) is a lime disease that has destroyed several citrus orchards in Oman, United Arab Emirates and Iran. WBDL is caused by a bacterium ''Candidatus Phytoplasma aurantifolia'' which is spread through the citrus orchards by a leafhopper, Hishimonus phycitis (Distant) (Hemiptera: Cicadellidae). Leafhoppers are associated with symbiotic microorganisms which provide them with essential amino acids lacking in their diets. Yeast-like relationships with insects are known as common and obligate symbiotic relationship. A prerequisite for the development of future strategies for the symbiotic control of insect pests and insect-vector competence is the identification of insect-associated yeast-like symbionts. In the present study, yeast-like symbionts housed in H. phycitis were investigated in insects collected from 13 districts of citrus orchards distributed in southern Iran (Hormozgan, Kerman, Sistan-Balushestan and Fars provinces). Insects were collected from infected lime trees by a D-Vac and stored at -20 ºC up to the DNA extraction. Total DNA was extracted and PCR was conducted with specific primer sets targeting 18S rRNA and 26S rRNA genes of the symbionts. Results revealed that the vector harboured two yeast symbionts, namely Yeast like symbiont of H. phycitis (Hp-YLS)and Candida pimensis,with a similarity of (98-99%) to those reported from the other Cicadellids. These results substantiate the association of these two endosymbiotic microbiota with H. phycitis which may suggest their ecological interactions. To establish any endosymbiotic relationship and probable interfering in pathogen transmission, further studies are needed.

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Beheshti University, M.C., Tehran,Iran   Spices are used all over the world to prepare foods mainly because of their flavoring properties however , these are grown and harvested in warm, humid areas of the world where the growth of a wide variety of microorganisms is readily supported. The aims of the present work were to evaluate the hygienic quality of some spices,in the chain stores of Tehran . We collected 151 packed samples of three kinds of spices, black pepper, turmeric , cinnamon in the chain stores of Tehran .we investigated to determine their microbial status based on ISIRI.we found these results: average of total aerobic mesophilic  count for turmeric was 3/6 ×  10⁷ cfu/ gr , black pepper: 7× 10⁶  cfu/gr .cinnamon: 1/92×10⁴ cfu/gr  average of coliforms count was: tumeric : 6/26×10³ cfu/gr , black pepper : 8/83×10³ cfu/gr ,cinnamon:4/7×10³ cfu/gr. Feacal coliform tests for 3 kinds of spices were: turmeric 13%  , black pepper34%  ,cinnamon 6%  ,average of yeast and mold count was for turmeric:1/23×10³ cfu/gr, black pepper : 2/94×10³ cfu/gr and cinnamon  2/9×10³ cfu/gr. We compere our results to ISIRI standard and we found that ,some of them were out of standard limit, therefor: it is suggested to provide legislation on the sanitary and hygienic quality of spices in our country.

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Microcerotermes diversus Silvestri (Isoptera: Termitidae) is an extremely destructive structural wood pest in Khuzestan province, Iran. One of the effective methods for subterranean termites control is the use of baiting systems that have recently evolved as an environmentally safe tactic to protect structures. In this research, several factors for the preparation of bait were evaluated involving the bait composition. In the no-choice test of bait composition, termites had the highest levels of feeding on bagasse + molasses + yeast, bagasse + molasses, bagasse + yeast, and bagasse, respectively. In the further experiment, termites had the highest levels of feeding on bait containing bagasse + molasses + yeast compared to control. Termites showed the highest levels of feeding on the bait in the stems of the cane, raw bait, cooked bait and pill-shaped bait, respectively. In the field phase, significant differences were not observed among the treatments but termites had the highest levels of feeding on the bait in the stems of the cane, pill-shaped bait, cooked bait and raw bait, respectively. Both field and laboratory conditions, indicate that the target termite has shown a greater tendency to baits in the cane. Findings of this study suggests that the design of the bait and its shape can also affect the bait’s attraction and its acceptance by the termite. Therefore, in addition to the ingredients of the bait, its shape, size, softness and texture quality also affect the amount of bait consumption.
 

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  In this study, binding ability of Saccharomayces cerevisiae to aflatoxin of pistachio was investigated. Results indicate that the yeast has aflatoxin surface binding ability of 40% (with initial concentration of 10 ppb aflatoxin) in exponential phase. Acid and heat treatment increase this ability 60% and 55%, respectively. Binding appears to be a physical phenomenon that reaches to saturation point within first 2-3 hours of process. Also, results showed that yeast immobilization on aflatoxin contaminated pistachio in order to toxin reduction, have no effect on color factor. In this condition, Hunter Lab factors (L^*, a^*, b^*) indicate no significant changes.  Yeast cells, viable or nonviable, are effective in aflatoxin binding and this property, especially for foods having high risk of aflatoxin contamination is considered as a good solution.

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Production of recombinant proteins in Escherichia coli has been very common in recent decades. Many studies and experiments have been done in order to optimize the production and expression of recombinant proteins in E.coli. One strategy is using high cell density to increase recombinant protein production such as β-NGF in the cell. Therefore, in this study for the first time bacterial cell culture in high cell density was done using glycerol and yeast extract as carbon and nitrogen sources and MgCl2 as a growth effective factor. Also the effects of overnight culture conditions on bacterial growth were evaluated. Meanwhile culture conditions were optimized using response surface methodology (RSM) and the optimum conditions were as follows: 18/23 g/lit glycerol, 14.44 g/lit yeast extract and 10mM MgCl2. Also the obtained results indicated that the 14 hours incubation at 37 °C and 180 rpm were optimum conditions for the overnight culture. Our results showed that the rate of cell growth and recombinant β-NGF production in optimized condition is significantly higher than in basic medium.

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Cellulase is one of the industrial enzymes which its production and utilization is increasingly taking into consideration due to global heed to second-generation bioethanol production. Cellulase produced by different organisms such as fungi, bacteria, insects, and plants. With increase in utilization of this enzyme and need for reduction in the enzymes price for production of second-generation bioethanol, the production of recombinant enzyme has been considered noticeably.
In this study, by investigation of corn steep liquor as nitrogen source and second carbon source after glycerol, a new medium is designed based on SYN6 salt medium then biomass and endoglucanase II production by methylotrophic yeast was optimized. Experiments designed by one-factor and response surface methodology used for optimization.
Results showed that optimum conditions for biomass and endoglucanase production are 5.5% (w/v) and 6.15% (w/v) of corn steep liquor respectively. New optimized conditions increased 41.4% and 69.7% for biomass and recombinant enzyme production respectively.

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  In the present study, some industrial active dry yeasts were compared regarding CO2 production which is a factor for determining the fermentation ability. The industrial baking strains of Saccharomyces cerevisiae were isolated from commercial active dry yeast, afterwards the amount of CO2 production was measured in a model liquid dough media using the gas measuring system. The comparison between the amounts of CO2 production by standard and industrial strains of Saccharomyces cerevisiae revealed that rapid CO2 production in moderate sugar medium is the most important phenotype in strains which are suitable for producing the baker's yeast. This method is considered as a fast screening way for strains of Saccharomyces cerevisiae in laboratory scale for the purpose of selecting the optimum strains for producing bakers yeast. The more osmoresistance strains are more active in high sucrose medium. Therefore, these strains are useful for producing baker's yeast in the confectionary industry. One strain named K, showed appropriate biomass production. This strain had been highly active in high sucrose medium which makes it a good candidate for the production of bakers yeast in bakery and confectionary industry.   

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Effects of adding whole soy flour and different extrusion conditions on microbial properties of spaghetti were investigated. Results showed that although the number of colonies of microorganisms in some treatments more than the limit, but not found relationship among microbial counts and added soy flour or production conditions. Thus it seems that because of high pollution due to use of raw materials with high microbial flora, conventional drying method, contamination after processing, high humidity of the final product and unsuatable packaging materials. However, moisture content of treatments among the formula components, influence in determining the number of microorganisms found. The interaction among water temperature, formulation and extruder screw speed increases microorganisms was counted.

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  A lot of reasons are effective on growth of microorganisms during the storage of sugar beet in the silos. In this study, effect of the size of sugar beet (in 4 levels) and height of storage them (in 4 levels) in silos, in duration of 18 days, on growth changes of microorganism are investigated. In our study we observed that maximum activity microorganism growth (bacteria, mould, yeast and total count) in smallest sugar beets and minimum activity in biggest sugar beets. Also, maximum activity of microorganism growth belongs to the sugar beets that stored on 3 meter height and minimum activity belongs to stored on 5 meter height.

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Nowadays, aromatic componds are widely used in food, pharmaceutical, cosmetic and chemical industries. Due to the growing tendency of consumers to use natural products, biotransformation by microorganisms is an interesting method for the production of aromatic compounds. Gamma-decalactone is a cyclic aroma with a peach-like flavor. The non-conventional yeast Yarrowia lipolytica can bioconversion the inexpensive castor oil substrate into the valuable gamma-decalactone. The process begins with the hydrolysis of castor oil by the lipase to ricinoleic acid, then continues by shortening the chain by beta-oxidation, and finally ends by lactonization. In this study, gamma-decalactone production was optimized via Response surface methodology (RSM) by a mutant strain of this yeast with the ability to produce high amounts of lipase. For this purpose, castor oil, yeast extract, peptone and pH were studied as factors at five levels. Based on statistical analysis of the relationships between the experimental variables, a mathematical model was obtained for the governing relationships between the experimental variables. Based on the results, the best values were obtained for castor oil 35 ml/l, yeast extract 6 g/l, peptone 8.5 g/l and pH 4. To validate the mathematical model, the proposed values were tested and 126 mg/L of gamma-decalactone was produced by the yeast strain, which shows a 46% increase compared to non-optimal conditions. The results of this study can be used to make cost-effective production of gamma-decalactone from castor oil by microbial biotransformation process.

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  Traditional dairy products harbor a complex microbiota composed by several microbial groups, including lactic acid bacteria (LAB) and yeasts. The common method to detect LAB is to culture the products on media containing cycloheximide (CHX) to prevent yeast growth by interfering with protein synthesis. However, some yeast species and strains show natural or acquired resistance to this antibiotic and thus can be specifically selected in media with CHX. The aim of this research was to identify such CHX-resistant yeasts. To this purpose, 25 samples of home-made dairy products were plated on MRS medium with 0.01% CHX; after incubation (48 h, 30˚C), 32 colonies of presumptive yeasts were picked up. Catalase test and morphological investigation confirmed that 19 were yeasts. After DNA isolation, randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) with primer M13 was applied to gain information on genomic relatedness among isolates. Visual comparison of RAPD-PCR pattern allowed selecting five representative isolates for further analysis. Primers ITS1 and ITS4 were used for specific amplification, and the PCR-products were sequenced after purification. The results of sequencing revealed that all isolates belong to Kluyveromyces marxianus, a species with a high technological potential.  

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Objective: Fungal nail infection (onychomycosis) is a common disease in all communities consisting about 50 percent of nail disorders. Yeasts are one of the important causative agents of onychomycosis. Identification of the yeast species is important in the epidemiological and therapeutical point of views. The aim of the present study is the precise species identification of the pathogenic yeast isolated from fungal nail infections, using the DNA-based methods. Materials and Methods: The isolates were preliminary studied according to study of morphological characteristics. For species identification, the genomic DNA of each sample was extracted by boiling method and the ITS region of ribosomal DNA was amplified by polymerase chain reaction (PCR). The amplified DNA was digested by the restriction enzyme MspI and each isolate was identified according to the electrophoretic patterns. A new enzymatic profile was used for final differentiation of Candida albicans and C. dubliniensis. A few of yeast isolates were identified by using ITS-sequensin. Results: C. albicans with the prevalence of 45.6% was the most common isolate, followed by C. parapsilosis with 22.5% and C. tropicalis with 21.8%. The less common species were C. glabrata, C. krusei, C. kefyr, C. lusitaniae, C. guilliermondii and C. pulcherrima that consisted 2.72%, 2%, 1.36%, 0.68% and 0.68% of the isolates, respectively. No C. dubliniensis was found among C. albicans isolates. Two isolates (1.36%) were identified as Trichosporon spp. The most common group of the patients was in the age range of 40-70 years old and the majority (83.2%) of the patients were women with finger nail infections. Conclusion: Although C. albicans is still the most prevalent isolates of nail candidiasis, the increasing number of non-albicans species is notable. The study showed that for identification of some rare species, the routine phenotypical approaches are not efficient and application of the ITS-PCR-RFLP can improve the level of differentiation up to 98%. The remaining isolates can be identified by more expensive methods such as sequencing.

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Today, many studies are doing to identify the lipolytic microorganisms because of the important role of them in the production of microbial lipases. Oilseed meals are a good place to achieve these microorganisms. In this field, yeasts are more important in comparison with other microorganisms. In this study, we isolated 27 types of fungi from Yazd sesame meal. After the evaluation of macro and micro morphological features, it was identified that 16 of them were from yeast group. Lipolytic yeasts were screened using Tween 80 agar medium and were identified to genus and species by colony and cell morphology observations and evaluation of fermentation reactions and the use of carbon and nitrogen sources. 4 lipolytic  screened  yeasts were included Sporidiobolus pararoseus, Sporobolomyces salmonicolor, Cryptococcus albidus and Yarrowia lipolytica .The ratio of areola diameter to the well diameter was  between 2.314 – 2.714. S. pararoseus showed  the maximum ratio of areola to well diameter (2.714) .Lipase activity of these four types of yeasts was measured in submerged cultures with Cezepek Dox medium for 7 days at 30 °C and 200 rpm by using of photometry method and p-nitrophenyl palmitate substrate. Lipase activity range was between 0.866 – 4.333 U/ml, and Cryptococcus albidus had the highest lipase activity 4.333 U / ml, while it showed the least biomass growth among other yeasts (OD= 0.577). Yarrowia lipolytica showed lipase activity of 3.466 U/ml and also, the highest biomass growth OD =0.806.