مجله میکروبیولوژی کاربردی در صنایع غذایی
سال ششم شماره 3 (پاییز 1399)

Integrated control is a program that uses several methods to reduce the consumption of high-risk chemicals and is cost-effective. The aim of this study was to investigate the combined control of trichoderma fungi and chemical toxins (carbendazim and mancozeb) in onion gray rot caries. For this purpose, isolation of Trichoderma from fungal onions in Kahnouj city was carried out on a specific medium and isolates were identified using Gaussian and Twenty keys. Also, gray rot fungi were isolated and identified from onion molds infected with gray mold from the warehouses of Kahnouj city. Then, combined control of gray rot fungi was investigated by Trichoderma and two Mancosb and Carbendazim toxins. The results showed that the average inhibition of growth of Trichoderma fungi against Botrytis was 51.61percent in vitro. The average inhibitory percentages for growth of volatile metabolites were 38.14percent and nonvolatile metabolites in two treatments of 5 and 10 ml, respectively. The results of the analysis of catalase and peroxidase enzymes in onion samples treated with trichoderma showed an increase in both. Simultaneous use of trichoderma and two carbendazim and mancozeb toxins 100percent inhibited the growth of Butrititis in laboratory and storage conditions. Whereas, application of Trichoderma alone 68.18percent inhibited the growth of Botrytis in laboratory conditions. In addition, the concentration of the pesticides used was 500 ppm, which is lower than that of the conventional pesticides. Therefore, the results indicate that the fungal control of gray rot factor by trichoderma and the two toxins carbendazim and mancozeb are successful.

Microbial contamination and spoilage caused by pathogenic microorganisms cause irreparable damage to fruit and vegetable producers annually. For this reason, chemical pesticides are used to prevent the growth of spoilage microorganisms in vegetables and fruits, which has caused problems such as environmental pollution, human poisoning, high costs, and the development of resistant microorganisms. Today, plant essential oils are one of the most important natural compounds used to control fungal contamination. The aim of this study was to investigate the chemical composition of Origanum vulgare essential oil, its phenol and total flavonoid content, antioxidant activity and antifungal effect on Rhizopus stolonifer, Aspergillus niger, and Botrytis cinerea. In this study, the essential oil of Origanum vulgare was extracted by hydrodistillation method and its main chemical compounds, total phenol and flavonoid contents, antioxidant activity, and antifungal effect against strawberry’ rot species (Rhizopus stolonifer, Aspergillus niger, and Botrytis cinerea) were investigated. Among 19 identified compounds (96.49% of the total essential oil compounds), carvacrol (29.15%) and linalyl acetate (22.25%) were the main chemical compounds in the essential oil, respectively. Also, the total phenol content of the essential oil was 48.38 ± 0.26 mg GAE/g and the total flavonoid content was found to be 36.26 ± 0.52 mg QE /g. DPPH free radical scavenging effect (IC50), ABTS free radical scavenging activity (IC50), and β-carotene/linoleic acid bleaching inhibitory effect were 24.27 ± 0.39 μg/ml, 19.15 ± 0.22 μg/ml, and 59.65± 0.62%, respectively. Antifungal effect results (disk diffusion agar, well diffusion agar, minimum inhibitory concentration, minimum fungicidal concentration) showed that A. niger and B. cinerea were the most sensitive and resistant strains to the essential oil, respectively. Due to its high antioxidant and antifungal properties, O. vulgare essential oil can be used as a natural antimicrobial and antioxidant compound.

Saccharomyces cerevisiae has many different uses such as baker's yeast and bioethanol production. Response surface methodology (RSM) is a complex of statistical techniques for experimental model creation. In this study was done to determination of optimal condition of bioethanol production from starch by yeast using RSM. Initially saccharomyces cerevisiae was proliferated on agar then by α-amylase, dextranase and amyloglucosidase respectively, then starch 5% was hydrolyzed to glucose. 250 ml glucose was put at 30 ºC and velocity of 150 rpm for 36 h. Bioethanol quantity was evaluated by dichromate oxidation and ethanol measurement methods and temperature, time and pH variables were considered at 25-98 ºC, 1 to 6 weeks and 3 to7, respectively. The highest bioethanol production was 12.5 ml at 30 ºC, pH 4 also at 80 ºC, and pH 7 for 5 weeks. The lowest bioethanol production was 3 ml at 98 ºC, pH 7 for 1 week which was practically compatible. Regarding the results, RSM method has many benefits such as increase in efficiency of chemical reactions, prevention of wasting raw material, time, money and energy which could use in different biological reactions.

Listeria monocytogenes has been identified as a major cause of human Listeriosis, which has now become a major public health concern. So the main purpose of this study was to screen Listeria monocytogenes from ready-to-eat nugget samples to determine the seromolecular typing of the isolates. For this purpose, 40 chicken nuggets were bought from different area of Shiraz city and had transferred to the microbiological laboratory. 25 gram of each nugget was transferred to Palcom Broth medium and subsequently Palcam Agar. Then the isolates were identified by biochemical tests, also specific primers were used for seromolecular typing. For determination of antibiotic susceptibility of the isolates, effect of Oxacillin (OX1), Erythromycin (E15), Amikacin (AN30), Penicillin (P10), Tobramycin (Tob10), Gentamicin (Gm10), Ceftriaxone (CRO30), Clindamycin (CC2), Vancomycin (V30), Ciproflexocacin (CP5), Tetracycline (TE30) and Trimethoprim Sulfomethoxazole (SXT23) were checked on the isolates by using disk diffusion method and Vet01-A4 CLSI protocol. Data were analyzed by SPSS software and ANOVA test. Out of all isolated bacteria, 4 isolates from chicken nugget belong to Listeria monocytogenes was identified by biochemical tests. Based on molecular testing, Seromoleculartyping including 1/2a, 3a and 1/2b, 3b were identified and their frequency was 50%. Out of all the most antibiotics resistant belong to the (OX), (CRO), (P) were100 percent, 100 percent and 58/3 percent respectively and the less belong to (TE), (GM), (CP), (V), (SXT), (TOB), (AN), all of them was 100 percent.

The aim of the current study was to investigate the antioxidant activity of Hawthorn's woods ethanol and acetone extracts and the effect of their antimicrobial on Escherichia coli, Staphylococcous aureus and Bacillus cereus bacteria. Extraction was performed by maceration method with two acetone and ethanol (96 percent) solvents at a ratio of 1:20 of sample to solvent. Total phenol content was measured by Folin– Ciocalteu method, and also the antioxidant properties were measured. Antibacterial activity of the extracts was determined at 0.7, 0.8, 0.9 and 1 percent (v/v) concentrations by well diffusion and test broth macro dilution method, respectively. The results showed that TPC and the percentage of inhibition of DPPH and ABTS free radicals of acetone extract were higher than methanol extract, and the highest effect on the diameter of the non–growth zone was related to 1 percent (v/v) of both extracts. Also, the results of antibacterial tests showed that the minimum inhibitory bactericidal were obtained with 1 percent of the extracts against B. cereus. The results of GC/MS also showed several functional compounds in the acetone extract.

Physicochemical characteristics, viability of probiotic bacteria, and sensory specification were investigated during three weeks of refrigerated storage with various concentration of oat bran extract and carbon dioxide in orange flavor beverage. It was observed that the acidity of the beverage samples significantly increased by increasing the percentage of oat bran extract and carbon dioxide, while the Brix decreased. The viability of the bacteria was significantly enhanced by increasing the amount of carbon dioxide and oat bran extract concentration until the 14th day after fermentation. The viability extremely decreased with increasing the storage time to 21 days. Oat bran is a rich source of nutrients including carbohydrates, protein, minerals, vitamins and soluble β-glucan. The use of oat bran as a profitable substrate to produce a non-dairy orange flavor probiotic beverage was examined. Due to high viability of the Lactobacillus acidophilus after two weeks of storage at 4 °C, the formulation was characterized with 15percent (w/v) oat bran extract and 1percent carbon dioxide. The highest sensory score was obtained by 10percent (w/v) oat bran extract and 0.5percent carbon dioxide sample. Therefore, incorporation of the oat bran in formulated orange flavor probiotic could enhance the nutritional value of the beverage.