6941

6483

كارشناسي ارشد

علوم و صنايع غذايي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده كشاورزي

1390

يازده، 107ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

صبيحه سليمانيان زاد، محمود شيخ زين الدين

21/5/91

علي نصيرپور، بهرام شريف نبي

1396/09/18

كتابنامه

كشاورزي

مهندسي كشاورزي

ID6483

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

108 in vitro Study of Antifungal Activity of Native Dairy Starter Cultures Against Food Spoilage Fungi Moslem Shahmoradi m shahmoradi@ag iut ac ir February 28 2012 Department of Food Science and Technology Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Dr S Soleimanian Zad soleiman@cc iut ac irDr M Sheikh Zeinoddin zeinodin@cc iut ac irAbstract Food borne Fungi both yeasts and moulds play an undeniable role in the deterioration of the qualityand hygine of foodstuffs due to their mycellial growth and or production of mycotoxins Development offungal resistance to chemical preservatives besides consumer demand for minimally processed foods andreduced use of chemical preservatives have stimulated researchs on biopreservatives Biopreservation refers to extended shelf life and enhanced safety of foods obtained by using the microorganisms and theirmetabolites Among natural biological antagonists Lactic Acid Bacteria LAB with GRAS status andthe ability to produce variety of antimicrobial compounds are of much importance In this project 42isolates of Lactobacillus delbrueckii subsp bulgaricus and 20 isolates of Streptococcus thermophilus previously isolated from traditional yoghurts of Isfahan region were screened for antifungal activityagainst Penicillium italicum as the indicator mould using Agar Overlay assay The isolate A ofLactobacillus bulgaricus as the most powerful antifungal isolate of all was subjected to examinations forthe evaluation of fungal inhibition spectra and production kinetics of antifungal metabolites Effect of thetype of culture medium and sodium acetate content on antifulngal activity and chemical nature ofantifungal metabolites were also determined Thirty nine out of 42 Lactobacillus bulgaricus isolatespresented antifungal activity by developing inhibition halos while non of Streptoccous thermophilusisolates could create such halos Results showed that the isolate A of Lactobacillus bulgaricus has abroad spectrum inhibitory activity against a variety of fungi species including Aspergillus and Penicilliumspecies The production of antifungal metabolites by the isolate was shown to start at late logarithmicphase and to accelerate during stationary and death phases of growth MRS was the best growth media forthe isolate in order to exhibit its antifungal activity which was also directly affected by sodium acetatecontent of the culture medium Elimination of sodium acetat from MRS led to complete loss ofantifungal activity whereas high levels of the compound in both MRS and Tomato Juice Agar resulted inamplified antifungal activity of the isolate Antifungal effect of the isolate was shown to be only partiallyaffected by severe heat tratment as the cell free supernatant of the isolate retained more than 65 of itsoriginal antifungal activity after being heated for 1 second at 135 C UHT sterilization Organic acidscomprising Lactic acetic and propionic acid were synthesized by the isolate to the respective level of202 78 and 13 mM L as Propionic acid showed the highest fungal inhibitory effect These three organicacids along with peptide compounds were determined as the most significant antifungal metabolites produced by the isolate Keywords Antifungal activity Screening Lactobacillus bulgaricus Organic Acids Peptide Compounds

صبيحه سليمانيان زاد، محمود شيخ زين الدين

علي نصيرپور، بهرام شريف نبي