Background and objectives: Aflatoxin B1 (AFB1) is the most toxic aflatoxin produced by a large number of Aspergillus species. Successful detoxification of this toxin is an important attempt to improve community health. The aim of this study was to evaluate reducing effects of yeasts isolates from KEFIR and traditional KEFIR-like fermented beverages on AFB1 in a broth medium. Methods: Polymerase chain reaction-sequencing was carried out to identify the yeast isolates from KEFIR and KEFIR-like beverages. Effects of the isolates on AFB1 adsorption and biotransformation in peptone dexterose broth medium were evaluated by using high performance liquid chromatography. Results: Saccharomyces cerevisiae and Kluyveromyces marxianus were isolated from KEFIR and KEFIR-like beverages and resulted in 46% and 53% AFB1 adsorption, respectively. The isolates 27Y and 2Y caused 7% toxin biotransformation, while 10% toxin biotransformation was achieved by the isolate 18Y. Conclusion: Our results indicate that the yeast isolates from KEFIR and traditional KEFIR-like products can bind to and detoxify AFB1, thereby reducing its harmful effects.

Background: Mycotoxins naturally occur in foods. Aflatoxins can cause serious health problems in consumers. Nowadays, biological detoxification method is considered to decrease the aflatoxins level in foods. The aim of this study was to evaluate the effect of KEFIR starter microorganisms to decrease the aflatoxin M1 (AFM1) levels in milk.Methods: The study was carried out at Shabestar branch, Islamic Azad University in 2016. AFM1 at three levels 150, 200 and 250 ng/L was added to milk samples. Then a pool of lactic acid bacteria (LAB), yeasts and full KEFIR starter culture was added to milk samples. After cool storage of samples in 4 °C for 7 d, all samples were collected and the level of AFM1 determined by HPLC method. All samples were prepared in triplicate.Results: The highest reduction percentage of AFM1 was observed in yeast (65.33%-68.89%) and LAB pool (65%). Samples with full KEFIR starter showed the reduction percent range of 11.67-34.66% that was lower in compare with other treatment groups.Conclusion: These findings support the ability of LAB and yeasts to bind to aflatoxins in foods.KEFIR drink in countries with high contamination by AFM1 in milk can be a safe dairy product choice for consumers.

KEFIR is fermented milk that has a unique flavor because of acetaldehyde, diacetyl, acetoin and ethanol. The aim of this study was to evaluate flavor and aroma compounds present in KEFIR. Two types of starter (Christian Hansen and Sacco) and three levels of temperatures (30, 33 and 35oC) were used for the preparation of KEFIR samples. The samples were analyzed for acetaldehyde, diacetyl, acetoin and ethanol by GC equipped with FID detector. Levels of acetaldehyde, diacetyl, acetoin and ethanol were increased with raising the temperature and decreased during cold storage from the first day until the 14th day. pH was decreased and acidity was increased in all samples during cold storage. After organoleptic evaluation, the prepared sample by Sacco at 35oC was known as the best sample and then the prepared samples by Sacco at 33 and 30oC were recognized as the favorable samples.

Background: Probiotic products contain metabolites that have positive effects on the intestinal microorganisms and well-being of the host as well as possess antimicrobial properties. Objective: This study aimed to investigate the antifungal activities of the water-soluble peptides (WSPs) found in ewe and cow milk KEFIR fermented by the traditional KEFIRan of Semnan (Semnan province, Iran). Materials and Methods: KEFIR samples were prepared by inoculating Iranian traditional KEFIRan into pasteurized milk. WPSs were extracted and antifungal activity was evaluated. Results: During the 28-day storage, the concentration of the amino acids increased except for a decrease detected in the concentration of arginine, aspartic acid, cysteine, and glycine,and the total amino acid concentration in ewe milk and KEFIR was higher than that in cow’, s milk and KEFIR. The WSPs of both KEFIR samples showed considerable inhibitory activities against the growth of Candida albicans and Aspergillus niger, but Penicillium sp. had the lowest sensitivity when treated with WSPs. The antifungal activity of WSPs of ewe KEFIR was significantly higher than that of cow KEFIR. The highest growth inhibitory potential of WSPs between two KEFIR samples was found for C. albicans. The antifungal potential of WSPs of ewe KEFIR was considerably higher than that of cow KEFIR. Conclusion: The higher antifungal potential of ewe KEFIR was likely associated with the high concentration of protein, extensive degradation of proteins, and diversity of amino acids produced during the fermentation.

Background: Inhibition of biofilm formation is essential for the prevention and treatment of urinary tract infection. This study was aimed to identify the probiotic potential of Lactobacillus strains isolated from KEFIR and evaluate their antimicrobial and antibiofilm activities against Uropathogenic Escherichia coli (UPEC). Methods: Twelve Lactobacillus strains were evaluated. Antimicrobial and antibiofilm activities of Cell Free Supernatant (CFS) of the Lactobacillus strains against UPEC isolates were evaluated by agar well diffusion method and crystal violet assay, respectively. Probiotic potential of selected isolates was assessed by analyzing their tolerance to acidic pH and bile salts, auto-aggregation ability, co-aggregation with Escherichia coli (E. coli) and hemolytic activity. The isolates were identified by phenotypic and 16S rRNA gene sequencing. Results: The CFS of all lactobacilli strains was able to inhibit UPEC isolates even after neutralization. Four out of 12 isolates inhibited the biofilm formation by UPEC in the range 62-75%. The viability under acidic condition varied among the isolates ranging from 6-89. 8%. All the isolates could tolerate the 0. 3% bile and eight isolates showed the adaptation time of less than 1 hr. All the strains exhibited co-aggregation with E. coli. Auto-aggregation was highly correlated with co-aggregation of all lactobacilli strains with E. coli (r=0. 889, p<0. 001). The isolates with satisfactory probiotic potential and higher ability of biofilm inhibition and antibacterial activity belonged to the species Lactobacillus rhamnosus and Lactobacillus paracasei. Conclusion: All four selected probiotic strains exhibited antimicrobial and antibiofilm activities, which suggest potential applications for controlling or preventing infections caused by UPEC.

KEFIR drink is a popular natural probiotic beverage in the Middle East. It is the fermentation product of a variety of probiotic microorganisms- live microorganisms added to the diet in sufficient quantities to improve the health condition- present in the KEFIR grain of the milk (1). Different KEFIR grains may have various microbial complexes (2). Generally, knowing the microbial characterizations of probiotic products is needed for the safety confirmation. On the other hand, the beneficial effects of probiotics vary from strain to strain and condition to condition (3).