JOURNAL OF APPLIED MICROBIOLOGY IN FOOD INDUSTRY
Year:2016 | Volume:2 | Issue:4|Papers Count:6

The aim of this study was to evaluate the survival of Lactobacillus plantarum and Lactobacillus brevis probiotic bacteria and also investigating the qualitative characteristics of fermented olive, under influence of salt percentage (2-10), pH (3-4.5) and preservation temperature (4-37 °C), by response surface methodology for determination the optimum level of mentioned treatments in processing of probiotic fermented olive with high acceptability. After implementation of these treatments, signillcant effect (P<0.05) of salt percentage on survival of L. plantarum by increasing of preservation temperature and pH was clarified. Interaction of preservation temperature increasing by salt percentage decreasing on survival of L. brevis was also significant (P<0.05) in second order model. Interaction of salt percentage increasing by preservation temperature decreasing on color properties of fermented olive was significant (P<0.05) in second order model, too. By considering the results of this study, correlation between survival ofprobiotic bacteria and processing variables was observed. Furthermore, qualitative properties of fermented olive was correlated with survival of inoculated probiotic bacteria under influence of processing parameters and so on, for production high quality probiotic fermented olive, control of interaction of these variables during of processing is necessary.

In this study, Molecular method to measure the rhizopus oryzae Real Time PCR was used in tomato paste. Because of problems mold count HMC method such as Proofer error, low and non-repeatability precision, accuracy and repeatability developing a standard method that can enable high accuracy and repeatability and mold counts it seems necessary. Real Time PCR molecular methods can be used as a suitable method to identity and quantity the precise mold is considered that based on the measurement of absolute and relative genes is the existing molds. Tomato paste samples with different amounts of mold spores (101,103 and 105) were contaminated per gram. After incubation and growth of mold spores and mycelium extraction DNA from each sample was performed using al-sammari method. Then, using Real Time PCR reaction of DNA copy number of molds using SYBR Green reagent and primers of the rhizopus oryzae genus was determined. The results showed that increasing amount of DNA molds in controls and inoculated samples resulted Real Time curve in the lower Cr values are entered logarithmic phase. The correlation coefficient of linear calibration Real Time was R2 = 0.943. This indicate that the accuracy of this test is quantitative detection. The reaction specificity was determined using melting curve of the primers and indicated that the reaction has been completely dedicated.

Silver nanoparticles have been synthesized by several methods, but each of them has disadvantages. Chemical methods, have high toxicity and low stability, and physical methods, are costly and low-efficient More recently, researchers have found a new technique for synthesizing AgNPs, using plants and microorganisms such as bacteria, fungi, and actinomycetes. This method is called "eco-friendly", "green synthesis" or "biosynthesis". The aim of this investigation was, biosynthesis of AgNPs using Saccharomyces cerevisiae, which is one of the safe microorganisms that the AgNPs synthesized by it, are suitable for using in pharmacology and medicine purposes.Saccharomyces cerevisiae was cultured in sabraud dextrose broth and incubated at 28-30°c for 24 h, then it was centrifuged, and its supernatant was added to the silver nitrate solution with the concentration of 0.001, 0.002 and 0.003 Mat pH: 5.6, 7 and 9, then incubated at 28 -35 and 37°c. The formation of AgNPs, was monitored by color­changing, uv-vis spectroscopy, TEM, XRD and FTIR. Antifungal effect of AgNPs on Candida albicans investigated by disc diffusion method. MIC and MFC were also measured.The results, showed that Saccharomyces cerevisiae have had the great potential for syothesizing of AgNPs in the size of 27 nm and have shown the antifungal effect in the concentration of 37±0.29 mg/ml.In this study, we have reported a simple, biological, easy and nontoxic method for synthesis of silver nanoparticles, which have had suitable antifungal effect on Candida albicans, by using one of the nonpathogenic microorganisms.

Enterocins are those bacteriocins that produce by Enterococcus strains. Enterocins have a large variety and any strain of Enterococcus, according to their genetic content and growth environment can produce type or types of Enterocin. In the present study 15 bacterial strains (Enterococcus genus) chose that had isolatated of Kurdish traditional cheese bye cultured-based and molecular methods. Genomic DNA isolation VI kit that was specific for Gram-positive bacteria with hard well, was used to DNA extraction of isolates. Polymerase chain reaction was performed, in order to tracing the Enterocin encoding structural genes. The results showed that the Enterocin gene A was 10 of 15 isolates and had the highest frequency and afier the highest frequency was related to Enterocin gene P with 9 cases and B with 8 cases, respectively. The majority of investigated Enterococcus isolates in this study had Enterocin producing genes. Enterococcus faecalis NRIC0112 and Enterococcus faecalis SK13 had 5 different genes, Enterocin A, Enterocin B, Enterocin P, Enterocin 31 and Enterocin X. 1071, L50, AS48 and KS Enterocin genes was not found in any of the isolates. However, the use of these isolates in industrial and dairy products demands more researches.

The aim of this study was to identify the LAB strains isolated from Chal by the molecular method and to study antifungal activity of Lactobacillus brevis and Enterococcus faecium isolates as a biological preservative against Penicillium chrysogenum. The LAB isolates were identified using PCR technique with universal primers of LAB, sequencing of PCR products and comparing the sequencing results with the data available in NCBI. The antifungal effects were determined using overlay method to investigate the potential application of tested isolates as a biological preservative agent Analysis of 16S rDNA gene sequences revealed two strains as L. brevis, one E. hirae and one E. faecium. The results of antifungal activity showed that both isolates of L. brevis and E. faecium had a strong inhibitory effect against P. chrysogenu so that the growth inhibition, after 48 hours, for strain C6 was more than the other strains. All treatments showed significant differences (P<0.05) with the control samples but were not significantly different (P>0.05) between treatments samples. Inhibitory percentage of both strains of L. brevis (C6 and C17) against P. chrysogenum was stronger than the strain of E. faecium (C8) against the mold. All treatments showed significant differences (P<0.05) with control samples but there were no significant differences (P>0.05) between the treatments samples. According to the results from present work can conclude that the tested isolates have a potential ability to prevent the microbial spoilage, in foods such as cheese that susceptible to spoil with P. chrysogenum, as natural and safe bio-preservative.

One of the novel methods of food preservation for extending the shelf life of food product is biological preservation. In this method, without addition of chemical preservatives and mainly using lactic acid bacteria, the minimum thermal processing is applied for food preservation. In this study, yoghurt samples containing Lb. rhamnosus and Lb. paracasei were prepared. The samples were evaluated for physico-chemical, lactic acid bacteria and viscosity tests, during the first, 10th, and 21th days of shelf life. In addition, the enumeration and viability of Lb. bulgaricus, Lb. paracasei, Lb. rhamnosus and Str. thermophilus in the samples were studied. Not significant pH, total solid and fat changes was showed between samples containing Lb. rhamnosus and Lb. paracasei with blank ones but the viscosity of former samples were significantly increased and the amount of syneresis reduced. The number of Streptucocci bacteria decreased and Lactobacilli population increased during 21 days shelf life of yoghurt samples.