Razi Journal of Medical Sciences

  Introduction : Kefir is a probiotic mixture of bacteria and yeast originating from Qafqaz region. The Kefir grain contain s both Lactic acid bacteria (Lactobacillus,Lactococcus,Leuconostoc,Acetobacte and Streptococcus spp.) and yeast (Kluyveromyces, Torula, Candida and Saccharomyces spp.). Kefir is claimed to have therapeutic effect. This study looked at the antimicrobial activity of Kefir on Pseudomonas aeruginosa.

  Methods: The antimicrobial activity of Kefir extract were determined on Pseudomonas aeruginosa (ATCC 27853) and on those isolated from burned patient. Effect of antibacterial extracts Kefir fermentation time in both 48 and 72 hours at a temperature of 35 degrees Celsius were determined with the disk plate and well test in vitro. The MIC was defined as the lowest antimicrobial concentration able to completely inhibited bacterial growth up to 24 h. MIC values were determined by microdilution method. The lactic acid contents of the Kefir extracts were determined by reverse-phase HPLC (high performance liquid chromatography).

  Result: The result showed that the highest antimicrobial activity of Kefir extract on Pseudomonas aeruginosa (ATCC 27853) and the burned patient isolation, ranged from 250 mg/mL(MIC) to 250 mg/mL(MBC) on time 96h.

  Discussion: The Kefir extract showed significant antimicrobial activity on Pseudomonas aeruginosa (ATCC 27853) and the clinical isolate of Pseudomonas aeruginosa.

Background: It is better to use agricultural by-products or waste for microbial production to reduce costs in the industry. Whey is one of the by-products that are rich in nutrients like vitamins, proteins and essential amino acids. Low-intensity ultrasound stimulation can improve membrane permeability and also help optimize the growth and reproduction of cells. According to high efficiency of Saccharomyces cerevisiae in the fermentation industry, the purpose of this study was to investigate the effect of ultrasound and the use of whey as alternative substrate carbohydrate substrates on the growth of Saccharomyces cerevisiae.

Methods: PDB medium was formulated by adding a certain amount of dextrose and 1% whey. Ultrasound was applied to the medium containing yeast with three powers (2, 6 and 10 W) at different time periods (10, 20, 30 sec). The amount of cell mass was measured after fermentation process for control and treated samples.

Results: Optimum operating conditions obtained from RSM was the power of ultrasound 6 W, sonication time of 20 seconds and Add 10% glucose. Results showed that ultrasonic waves (with a power of 6 kW and 30 seconds) and medium containing whey increased the growth of yeast (from 8/14 to 6/64 mg).

Conclusion: Based on the results, the low-power ultrasound can expedite fermentation process up to 4 times, also using nutritious compounds in whey new media could be created to increase fermentation output and prevent possible pollutions. Whey is used as a novel and applied method to enhance the growth of the Saccharomyces cerevisiae, which will ultimately increase the growth efficiency of the microorganisms.

Background: In Iran, bread is mainly baked from flours with high extraction rate and low fermentation time that results in increasing amount of phytic acid causing low absorption and bioavailability of important minerals in the body. In this study, effect of  baker’s yeast  and several lactic acid bacteria on phytic acid of baguette bread is compared.

 Methods:  Two groupes of dough samples were provided (with yeast, without yeast).  To each ones, bacterial suspension containing 10⁸ (cfu / g) Lactobacillus strains was inoculated separately and held for 20 hours at 37 °C. After baking, the amount of phytic acid in each two groupes of samples evaluated and compared together. Phytic acid content was determined by spectrophotometric method (the total phosphorus content was determined using the Molybdovanadate Method). 

Results: In the first group of dough samples (with yeast),  the means of phytic acid content in sourdough lactic acid bacteria were 138.84 (fermentum), 126.22 (acidophilus) , 148.31 (casei) and 129.37 (plantarum) mg per 100g, respectively. In the second group of  dough samples (without yeast), the means of phytic acid content  in sourdough lactic acid bacteria were 268.22 (fermentum), 255.60 (acidophilus), 274.53 (casei) and 261.91 (plantarum) mg per 100g, respectively. The results showed that yeast and lactic acid bacteria have a significant effect  on reducing the amount of phytic acid (P ˂0.05 ).

Conclusion: Baker’s yeast and lactic acid bacteria, significantly reduced levels of phytic acid of  baguette bread.