فهرست مطالب

Advanced Research in Microbial Metabolite and Technology - Volume:1 Issue:2, 2019
  • Volume:1 Issue:2, 2019
  • تاریخ انتشار: 1398/02/14
  • تعداد عناوین: 6
  • Rasoul Shafiei *, Frank Delvigne Pages 65-78
    Nowadays, vinegar is industrially produced by mesophilic acetic acid bacteria (AAB). However, temperature fluctuation during acetous fermentation is inevitable, and may cause process disturbances. This can be mostly avoided using thermo-tolerant AAB. The main purpose of the present study was to isolate thermo-tolerant AAB. Fermentation performances were then evaluated. Twenty-eight different isolates were isolated from Iranian traditional vinegar. One of the isolates was able to grow and produce acetic acid in minimal culture media containing 5% (w/v) ethanol at 30-42 ºC. 16s rRNA gene analysis showed that the selected thermo-tolerant isolate was Acetobacter tropicalis (L31). Acetous fermentation in Lab-bioreactor showed that Acetobacter tropicalis (L31) grew in minimal culture medium, and produced 5% (w/v) acetic acid at 37°C in batch and semi-continuous fermentation mode. Fermentation time was significantly dependent on dissolved oxygen (DO) concentration and acclimation of cells to low pH and acid stress. In average, acclimated cells produced 2.3-2.7 g L-1h-1 acetic acid during production phase. The final yield was 87% at 37ºC in low and high DO concentrations. Low DO concentration (15%) during acetous fermentation caused longer fermentation time, but a large part of cells (91%) grown under such condition was viable if oxygen flow was interrupted. In contrast, cells grown under high DO concentration were not able to tolerate oxygen deficiency. In conclusion, since Acetobacter tropicalis (L31) grew well in minimal culture medium, and showed tolerance to high temperature and low DO, it seems that it is a potential isolate for vinegar starter production.
    Keywords: Vinegar, Viability, Ethanol, Dissolved oxygen, Acetobacter sp
  • Maryam Ghobadi Dana * Pages 79-90
    In recent years, the demand for the use of natural antimicrobial agents rather than chemicals as food preservatives is rapidly growing. The whole bacterial culture and neutralized supernatants of thirty-nine isolates were examined for antimicrobial activity by the spot-on lawn assay against ten indicator microorganisms. Based on the results, the cultures of all isolates showed antimicrobial activity. The maximum inhibition zone diameter was 38.2±0.1 mm. All the isolates had antimicrobial effects against Bacillus cereus, while 88.88% of the isolates did not show any inhibition zone around Candida albicans. Finally, of eleven selected broad spectrum isolates; only isolate DL200 had antimicrobial activity even in a neutralized supernatant. The range of lactic acid production was 14.2-34.8 mg/g in cultured skim milk. There is a correlation coefficient between lactic acid production and the antimicrobial activity of isolates only against Staphylococcus aureus and Bacillus subtilis. However, there is no correlation between the lactic acid production of isolates and antimicrobial activity against other indicators, like Salmonella typhimurium, Escherichia coli, and Pseudomonas aeruginosa, and increasing lactic acid production did not increase antimicrobial activity. Selected isolates which use galactose as the sole carbon source for the production of CO2, were characterized as facultative heterofermentative and were identified as Lactobacillus paracasei with 99-100% identity based on the alignment results of their 16S rRNA gene. The use of selected isolates as preservatives in food not only inhibits the growth of pathogenic microorganisms but also prevents D-lactic acidosis in the host. Therefore, they are essential for children in the Autism spectrum who have high D-lactate in their system.
    Keywords: Biopreservative, Lactobacillus, Antimicrobial activity, Molecular identification, Spot-on-the-lawn
  • Matia Sadat Borhani, Zahra Etemadifar *, Davood Biria, Eisa Jorjani Pages 91-103
    Improvement of alkaline protease production, one of the most important types of industrial biocatalysts, is essential for commercial purposes. The present study’s aim was to increase alkaline protease production of MSB42, a newly isolated strain of Exiguobacterium sp., through the rotatable central composite design (RCCD). In this regard, parameters affecting MSB42 enzyme production were chosen based on the results of preliminary one-factor-at-a-time (OFAT) experiments. According to the results of RCCD, the enzyme production showed its maximum level (198.48 U/ml) in the presence of 3% w/v glucose, 3% w/v peptone, at 37 °C and pH 9. Overall, the enzyme production was 2 and 3.24 times more than OFAT experiments (98.69 U/ml) and unoptimized conditions (61.29 U/ml), respectively. A polynomial model of MSB42 alkaline protease production was obtained using the experimental date and based on the significant terms. The protease gene of this strain was also amplified using the designed primers (873 bp), and based on the sequencing results, was found to be closely related to the M6 family of metalloprotease domain.
    Keywords: Alkaline protease, Exiguobacterium, One-factor-at-a-time strategy, Response surface methodology
  • Keivan Beheshti Maal * Pages 105-112

    The aggregation of oral Streptococci is resulted in the commence of enamel calcium degradation of the teeth and subsequently emergence of dental caries. The bacteriophages have considerable effects in controlling the populations of various bacteria. The isolation and characterization of specific lytic bacteriophages against oral streptococci were the main goals of this study. The BHI culture medium was used for oral streptococci enrichment from dental plaque. The MSA culture medium was applied to isolate oral streptococci from dental plaque samples. The membrane filtrate of Caspian Sea water was added to streptococcal isolate suspension and cultured using overlay method. The isolated bacterium on MSA according to macroscopic, microscopic and biochemical examinations identified as Streptococcus salivarius. The BLASTN of gtfK gene after DNA sequencing reconfirmed that our isolate was S. salivarius. The strain was named S. salivarius KBM-ISF-2 and its gtfK gene was deposited at GenBank, NCBI under accession number of KJ634208.1 Transmission electron microscopy revealed two specific lytic bacteriophages that attacked S. salivarius we isolated from dental plaques. The first lytic phage was a Tectivirus with icosahedral symmetry measuring 46.67 nm as thickness. The second phage was a Cystovirus with icosahedral symmetry and diameter of 85.56 nm. This is the first report of isolation and characterization of Tectiviruses and Cystoviruses from Caspian Sea and their specific preventing effects on oral streptococci. The lytic specific bacteriophages could be applied as a therapeutic measure for preventing the infectious diseases in human oral cavity.

    Keywords: Bio-controlling, Caspian Sea, Cystoviridae, Dental Plaque, Streptococcus salivarius, Tectiviridae
  • Roohallah Saberi Riseh *, Fariba Fathi, Mojtaba Moradzadeh Eskandari Pages 113-127
    Water deficit is one of the limiting factors of plant productions in arid and semi-arid areas. Many adaptive strategies such as accumulation of osmotic adjustments, phenolic compounds and antioxidant enzymes activity have been developed in plants for dealing with drought stress. The use of microorganisms, including probiotic bacteria, is a type of soil management that is effective in reducing the effects of stress. This experiment aimed to determine the effects of some probiotic bacterial strains on proline, sugar, total phenolic compounds (TPC), phenylalanine ammonia lyase (PAL), photosynthesis pigments and antioxidant activities of cucumber plants under drought stress. A completely randomized design was applied with a factorial arrangement of two factors: irrigation levels and bacteria strains with three replications. The results showed that proline, sugar, TPC, PAL and enzymes activity in control and inoculated plants were increased by increasing drought stresses. By contrast photosynthesis pigments significantly decreased under stress. The use of bacterial strains alleviate the harmful effect of stresses by an accumulation of proline, TPC, sugar, PAL activity and enzyme activity. The results also showed that inoculated plants had higher antioxidant activity compared to control plants under drought. It was found that the use of probiotic bacteria is an effective strategy to enhanced drought stress tolerance in plants.
    Keywords: Cucumber, Drought stress, Enzymes activity, Probiotic bacteria, Prolin
  • Trigonelline antidiabetic metabolite increased in inoculated fenugreek by Trichoderma
    Zahra Hosseini, Tahere Hasanloo, Mojegan Kowsari *, Majid Majidian Pages 129-140
    Trigonelline is known as an antidiabetic substance extracted from plant sources. The trigonelline content and growth factors of two Trigonella foenum ecotypes (Hamedan and Bandarabbas) treated by two Trichoderma harzianum isolates (chit4215MK and T8-7MK) were investigated in greenhouse conditions. The results showed that the two ecotypes are different in terms of growth factors with the Hamedan ecotype having more stem length and the Bandarabbas ecotype having more lateral branches and pod numbers. It was concluded that the Trichoderma strains had a positive effect on the growth of the Hamadan ecotypes stem, and the T8-7MK strain showed better effects than the chit4215MK. However, no shoot length differences were observed between the control and Trichoderma treated plants in the Bandarabbas ecotype. No significant difference was observed for peroxidase activity and total soluble carbohydrate content between the ecotypes, treatments, and the interaction effects of treatment and ecotypes. The highest Trigonelline content (4 mg g-1 DW) was achieved in the Bandarabbas ecotype treated with Trichoderma strain T8-7MK, which was 1.6- fold higher than the control plants. Also, the Hamedan ecotype treated by Trichoderma strain chit4215MK produced a higher content of Trigonelline  (3.5 mg g-1 DW), which was 1.3- fold higher than the control plants. The content of Trigonelline in the treated Hamedan ecotype was lower than the treated Bandarabbas ecotype (1.3 times more). Our results revealed that Trichoderma strains are able to regulate Trigonelline biosynthesis, and different strains showed various effects on different fenugreek ecotypes.
    Keywords: Trichoderma, Bio fertilizer, Fenugreek, Secondary metabolites, Trigonellin