جستجوی مقالات مرتبط با کلیدواژه « acetic acid » در نشریات گروه « زیست شناسی »

Mexican lime is one of the commercial citrus cultivars in the world, which is commonly used as a citrus rootstock in the southern regions of Iran. This cultivar is one of the most sensitive citrus cultivars to cold stress and is used as a cold-sensitive plant in many citrus studies. This study aimed to investigate the effect of melatonin (0 and 500 μM), mannitol (0 and 50 μM), acetic acid (0 and 15 μM) and their combination on photosynthetic apparatus of Mexican lime seedlings under cold stress (0 and -6 °C). According to the results, the combined application of melatonin, mannitol, and acetic acid, by improving the photosynthetic parameters, reduced the destructive effects of cold stress (0 and -6 ºC) on photosynthetic machinery in Mexican lime seedlings. This treatment led to the highest performance index (PItotal) at both stress levels. The most suitable chlorophyll fluorescence parameters for identifying the best reducing treatment against cold stress were indicator of the activity of the oxygen evolving complex on the donor side of PSII (Fv/F0), variable fluorescence (Fv), maximum quantum yield of PSII photochemistry (Fv/Fm), thermal dissipation quantum yield (F0/Fm), and maximal fluorescence (Fm), respectively. The results of this experiment showed that the exogenous use of natural compounds (melatonin, mannitol) and a cost-effective agent (acetic acid) can protect Mexican lime photosynthetic apparatus under cold stress. Generally, the interactions of melatonin, mannitol, and acetic acid at both 0 and -6 °C provided the best results.

Because of the high energy consumption for fermentor cooling, the isolation of thermo-tolerant Acetobacter strains for vinegar production has a high priority. The aims of this study were the isolation and identification of a high ethanol-thermo-tolerant Acetobacter spp. from grapes as well as the optimization of conditions for increasing the acetic acid production. The grape extract was cultured on Frateur and Carr media. The isolates were characterized against macroscopic, microscopic, and molecular traits. The resistance of the isolates against different concentrations of ethanol as well as high temperatures were measured. The best ethanol- thermo-tolerant isolate using ribotyping was identified as Acetobacter pasteurianus KBMNS-IAUF-2 and its 16s-rDNA sequence was deposited in GenBank, NCBI under the accession number MG547344. This strain was able to grow in Carr medium with 9% (v/v) ethanol after 48h incubation at 40°C. A Taguchi design with L9 analysis revealed that the highest yield of acetic acid production occurred at 34°C in the medium containing of 2% (v/v) ethanol and 2% (w/v) yeast extract. The temperature and yeast extract concentration with 76.70% and 6.29% were the most and least effective factors in acetic acid production, respectively. The acetic acid production yield after 24h under the optimized condition was measured as 97%. This thermo-ethanol-tolerant strain could be applied as an industrial starter for producing vinegar with grapevine flavor.

To increase lactobacillus cells stability, different methods based on entrapment used and their effect on the culturability of entrapped cells was studied. Materials and methods In the present study, sub-lethal acid stress, biofilm-like structure, and the combination of plant gums were used to assess the culturability of entrapped Lactobacillus plantarum during different production phases.

Based on the obtained results, incubation of alginate entrapped cells in MRS broth containing acetic acid increased the survival rate by 29% compared to beads treated in MRS broth. In addition, incubation of alginate entrapped cells in acidic medium resulted in 5% higher survival of biofilm-like cells after the freeze-drying process. To increase the stability of cells during storage, cells were entrapped in alginate plus different plant gums. Incorporation of tragacanth gum and salep gum to alginate showed higher culturability of cells (4.6and 3.1 folds, respectively) in comparison to alginate treated beads. Additionally, the lowest inactivation constant rate (k value), 0.09, and highest D  value, 25 days, obtained for tragacanth gum at 4°C during storageindicating that treatment with tragacanth gum could preserve the cells better in comparison to other treatments under storage condition. Discussion and

The incubation of Lactobacillus plantarum beads in acidic MRS medium can result in increased culturability especially after freeze-drying. This can be due to cross-protection effect. Additionally, due to tragacanth gum traits, this plant gum could protect the entrapped cells better compared to other plant gums in the storage condition. In conclusion, we can use tragacanth gum as a second material for increasing the stability of entrapped L. plantarum cells.