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  • Küçük Resim
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    Biofilm characteristics and evaluation of the sanitation procedures of thermophilic Aeribacillus pallidus E334 biofilms
    (Taylor & Francis Ltd, 2017) Kilic, Tugba; Karaca, Basar; Ozel, Beste Piril; Ozcan, Birgul; Cokmus, Cumhur; Cihan, Arzu Coleri
    The ability of Aeribacillus pallidus E334 to produce pellicle and form a biofilm was studied. Optimal biofilm formation occurred at 60 degrees C, pH 7.5 and 1.5% NaCl. Extra polymeric substances (EPS) were composed of proteins and eDNA (21.4kb). E334 formed biofilm on many surfaces, but mostly preferred polypropylene and glass. Using CLSM analysis, the network-like structure of the EPS was observed. The A. pallidus biofilm had a novel eDNA content. DNaseI susceptibility (86.8% removal) of eDNA revealed its importance in mature biofilms, but the purified eDNA was resistant to DNaseI, probably due to its extended folding outside the matrix. Among 15 cleaning agents, biofilms could be removed with alkaline protease and sodium dodecyl sulphate (SDS). The removal of cells from polypropylene and biomass on glass was achieved with combined SDS/alkaline protease treatment. Strong A. pallidus biofilms could cause risks for industrial processes and abiotic surfaces must be taken into consideration in terms of sanitation procedures.
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    CONTROL OF THERMOPHILIC SPORES BY SPORICIDAL AGENTS AND THERMAL INACTIVATION
    (Slovak Univ Agriculture Nitra, 2022) Karakaya, Ayse Busra; Karaca, Basar; Ozcan, Birgul; Cihan, Arzu Coleri
    In this study, the adhesion patterns of thermophilic spores of Geobacillus thermodenitrificans DSM 465(T), Geobacillus thermoglucosidans B84a, Anoxybacillus kamchatkensis subp. asaccharedens F81 and Anoxybacillus flavithermus DSM 2641(T), all of which are biofilm producers in dairy products, were investigated by epifluorescence microscopy on 6 different abiotic surfaces commonly used in the dairy industry. The spores of G. thermodenitrificans DSM 465(T) and A. kamchatkensis subp. asaccharedens F81 were found to adhere mainly to rubber, polycarbonate, PTFE and stainless steel surfaces. In addition, the efficacy of sporicidal agents on the spores of these bacteria was investigated and only peracetic acid, cetylpyridinium chloride and formaldehyde were found to be the most effective of the sporicidal agents tested. Among the sporicidal agents that showed high efficacy against spores, peracetic acid and nitric acid were selected because they had the shortest contact time, low toxicity and cost. Binary combination effects were tested by determining the LD50 values of the selected agents and it was found that there was a synergistic effectbetween these two effective chemicals. In addition, the thermal resistance profiles of planktonic and sessile spores of A. flavithermus DSM 2641(T) and G. thermodenitrificans DSM 465(T) were evaluated.
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    Öğe
    Rapid detection of Geobacillus and Anoxybacillus species by quantitative qPCR (qPCR) in commercial dairy products
    (Wiley, 2022) Karaca, Basar; Karakaya, Ayse Busra; Ozcan, Birgul; Cihan, Arzu Coleri
    Thermophilic spore-forming bacteria, especially Anoxybacillus and Geobacillus species, are a major problem for dairy industry. The presence of these thermophilic bacilli in the dairy products is considered a poor hygiene indicator during product processing. The commonly preferred culture-dependent detection methods are time consuming. Therefore, the development of rapid and reliable molecular approaches for the detection of these problematic microorganisms in food processing is essential. In this context, specific primers for the gene (spo0A) that initiates sporulation were designed for Anoxybacillus kamchatkensis subsp. asaccharedens (F81) and Geobacillus thermodenitrificans (DSM 465(T)), which have been shown to be strong biofilm producers in dairy products. For this purpose, a quantitative polymerase chain reaction (qPCR) assay was developed. The qPCR standard curves obtained with these primers allowed a total viable cell count in the range of 10(1)-10(8) CFU/ml for G. thermodenitrificans, while the spore count was in the range of 10(3)-10(8) CFU/ml. The primer developed for A. kamchatkensis subsp. asaccharedens was able to detect viable total cells and spores with much higher sensitivity (10(1)-10(8) CFU/ml viable total cells, 10(2)-10(8) CFU/ml spores). The primers developed in this study allowed separate detection of Anoxybacillus and Geobacillus in dual culture experiments. The primers and method developed in this study can also be used for rapid detection of Anoxybacillus and Geobacillus contamination in mixed cultures.