Influência genotípica de estirpes de Bacillus cereus na adesão e na resistência a sanitizantes químicos

• Autor(a) principal: Sá, João Paulo Natalino de
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2930
• topic: Laticínios; Bacillus cereus; Adesão bacteriana; Resistência a sanitizantes; Dairy; Bacillus cereus; Adhesion bacterial; Resistance to sanitizing; CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS

Among several micro-organisms contaminants in food industry, Bacillus cereus is a pathogen that may cause poisoning emetic and/or diarrheal and, furthermore, spoil foods production of proteolytic or lipolytic enzymes. In this research, the multiplication rate (&#956;), the lag time (&#955;) and maximum multiplication rate (&#956;max) of four genotypes of Bacillus cereus with genes for the production from different enterotoxins were evaluated at temperatures of 10 °C, 15 °C, 25 °C, 32 °C and 42 °C. Multiplying quantitation was performed byspectrophotometer, with readings from optical density at 600 nm. The DMFit software was used to fit the data to curves of Baranyi and Roberts model. The maximum multiplication rate (&#956;max) was evaluated by modified Ratkowsky et al. model. Also in the experiment, adhesion of genotypes of B. cereus, vegetative cell or spore, to stainless steel 304 # 4, at 10 ° C and 32 ° C was evaluated. The interaction between the surface of stainless steel and genotypes was studied by tension interfacial characteristics and measure of the contact angle of surfaces. In addition, we evaluated the removal of genotypes adhered to the stainless steel surface using six hygienic procedures through simulated use test of cleaning in place (CIP). As result, no significant effect was found (p> 0.05) for values of &#956; between genotypes, at the same temperature. However, was observed significant effects (p <0.05) among genotypes for this parameter (&#956;) for different incubation temperatures (10 °C, 15 °C, 25 °C, 32 ° C and 42 °C) and also for the lag time (&#955;). At 10 ° C, the values of &#956; and &#956;max were lower and the lag time (&#955;) was higher for all vegetative cells of genotypes. At 32 °C there was an opposite behavior for all kinetic parameters. In this study, no difference was observed (p> 0.05) in the ability of adhesion to stainless steel between the genotypes at the same temperature (10 °C and 32 °C). However, significant differences (p <0.05) in adhesion in relation to physiological structures was observed for temperatures of 10 °C or 32 °C. At 10 °C, the vegetative form adhered less than sporulated. This may correlate to low values of &#956; and &#956;max, and long period of &#955;. The variation of 22 °C in temperature was sufficient for that adhesion of all vegetative cells genotypes were almost two log cycles higher than at 10 °C, confirming the importance and influence of temperature on adhesion process. The effect of temperature on the adhesion of vegetative cells and spores of B. cereus, can be explained, among other factors, by hydrophobic interactions. These interactions are governed by the entropy of the system, thus increasing temperature favors the entropic component. Thus, when temperature increases the hydrophobic interactions are become stronger, favoring adhesion. According to results, removal of spores and vegetative cells for genotypes of B. cereus is dependent (p <0.05) of the treatment applied, however, the action of these agents was not affected by physiological structure (vegetative and spore), or by genotypes. Formulations containing sodium dodecylbenzene sulfonate combined with sodium dichloroisocyanurate or peracetic acid were more efficient, resulting in hygienization of stainless steel with a count of B. cereus below 50 cfu.cm-2. We observed that all genotypes in the vegetative form were considered hydrophilic (&#916;Gsws TOT> 0), independent of temperature (10 °C and 32 °C). However, all genotypes in the spore form were hydrophobic (&#916;Gsws TOT <0). The adhesion to stainless steel was thermodynamically favorable (&#916;Gadhesion < 0) for all the genotypes at 10 °C and 32 °C for both physiological structures except for the cell vegetative genotype G4 at 10 °C and 32 °C, where the adhesion was thermodynamically unfavorable (&#916;Gadhesion > 0).