Título da Tese: Alicyclobacillus spp.: Habilidade na formação de biofilme e resistência ao tratamento por UV-C 

Orientador: Prof. Dr. Benício Alves de Abreu Filho

 Data da Defesa: 28/02/2019



INTRODUCTION. Alicyclobacillus spp. are acid-resistant microorganisms and are often associated with the deterioration of reconstituted orange juice, causing unpleasant taste and odor to the product. Brazil is the largest producer and exporter of concentrated orange juice in the world, and the presence of this bacteria in juices can cause damages to our country's economy. Some processes are inefficient to eliminate all forms of microbial life, especially when it comes to bacteria that have the capacity to form spores as is the case of the genus Alicyclobacillus. If these spores are present in concentrated orange juice industrialized, they can germinate and grow after reconstitution and pasteurization of the juice. In addition, these microorganisms may be present in the food industry by forming biofilms on contact surfaces such as stainless steel, contributing to product contamination; however, bacteria of this genus isolated from the orange juice industry to date do not were evaluated for biofilm formation. Therefore, the industry seeks effective alternatives for the removal of these biofilms, since most of the time only the applied hygiene is not enough. In this search for alternatives, it is important to emphasize the importance of searching for clean and refreshing sources that do not compromise the environment, such as ultraviolet short-wave (UV-C) radiation. UV-C radiation is a safe method to control microorganisms in liquid foods, water and food contact surfaces undergoing approval at various country health agencies (FDA, for example). AIMS. To evaluate the capacity of isolates of Alicyclobacillus spp. to form biofilms formation and to evaluate the effect of (UV-C) radiation on the reduction of spores and biofilms of Alicyclobacillus spp. on stainless steel and rubber surfaces using industrialized orange juice as a culture medium. MATERIAL AND METHODS. Five isolates of Alicyclobacillus spp. of the orange juice industry and a reference strain of Alicyclobacillus acidoterrestris 0244T for the formation of biofilm under stainless steel surface using orange juice as culture medium at different temperatures (28 °C and 45 °C), (30 °C and 45 °C), and (45 °C and 60 °C), and different contact times (24, 72 and 120 h). The degree of hydrophobicity and the survival time on the abiotic surface were also investigated, as well as biofilm confirmation by Scanning Electron Microscopy. To evaluate the effect of radiation (UV-C) on the reduction of spores and biofilms of Alicyclobacillus spp. on stainless steel and rubber surfaces industrialized orange juice was used as culture medium. Four reference species of Alicyclobacillus spp. and different doses of UV-C. Scanning Electron Microscopy of the spores of the A. acidoterrestris was carried out after the treatment. RESULTS AND DISCUSSION. The results showed biofilm formation of Alicyclobacillus isolates and reference strain 0244T from 24 h of contact in at least one temperature tested. There was variation of the biofilm formed in 10 relation to the different incubation times and temperatures. Alicyclobacillus spp. presented variations in the degree of hydrophobicity. We verified that all isolates of Alicyclobacillus spp. survived on the stainless steel surface for 30 days. It was observed that after 20 min (16.8 kJ/m2 ) exposure to UV-C the spores of Alicyclobacillus acidoterrestris, Alicyclobacillus herbarius and Alicyclobacillus cycloheptanicus decreased dramatically, with counts below the detection limit of the method (


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