Growth and survival of Bacillus cereus in mageu, a sour maize beverage (original) (raw)
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Journal of Food Safety, 2005
The growth and survival of Bacillus cereus , a known pathogen commonly found in cereals, during lactic acid fermentation of boza, a traditional Turkish cereal beverage, was studied. In the boza base inoculated with both the starter culture and B. cereus , the acidity developed to pH 2.6 and 0.8% titratable acidity after 72 h; the growth of B. cereus was reduced from 3.9 log cfu/mL to 1 log cfu/mL within 72 h. The control boza base to which starter was not added had a pH of 3, titratable acidity of 0.8%. The B. cereus in this boza base to which no starter culture was added dropped to 1 log cfu/mL after 72 h. No strains of lactic acid bacteria were found to produce bacteriocins antagonistic to B. cereus. Low pH and acidity were found to be the major factors inhibiting growth of B. cereus in boza.
Properties of Bacillus cereus Collected from Different Food Sources
Turkish Journal of Biology
Bacillus cereus spores and vegetative forms are frequent inhabitants of a wide range of environments, including soils and clays, sediment, dust, mineral water, vegetation, and many food types, especially cereals and cereal derivatives, milk and dairy products, meat, and raw and processed foods and vegetables (1-4). The organism sometimes causes food poisoning and this is due to poor temperature control during the preparation or storage of food, which allows B. cereus to reach hazardous levels of >10 5 cfu g-1. It can cause 2 different types of illness, the diarrhoeal form and the emetic form, attributed to consumption of foods containing large numbers of this organism. The first and
Frontiers in microbiology, 2013
Microorganisms are able to adapt to different environments and evolve rapidly, allowing them to cope with their new environments. Such adaptive response and associated protections toward other lethal stresses, is a crucial survival strategy for a wide spectrum of microorganisms, including food spoilage bacteria, pathogens, and organisms used in functional food applications. The growing demand for minimal processed food yields to an increasing use of combination of hurdles or mild preservation factors in the food industry. A commonly used hurdle is low pH which allows the decrease in bacterial growth rate but also the inactivation of pathogens or spoilage microorganisms. Bacillus cereus is a well-known food-borne pathogen leading to economical and safety issues in food industry. Because survival mechanisms implemented will allow bacteria to cope with environmental changes, it is important to provide understanding of B. cereus stress response. Thus this review deals with the adaptive ...
International Journal of Food Microbiology, 2012
Ingestion of B. cereus can result in diarrhea, if these bacteria survive gastrointestinal passage and achieve growth and enterotoxin production in the small intestine. The gastrointestinal survival of vegetative cells and spores of the diarrheal food poisoning strain B. cereus NVH 1230-88 was investigated during in vitro batch experiments simulating the stomach, duodenum and ileum using simulation media and competing intestinal microbiota. All spores and approx. 30% of the vegetative B. cereus cells survived the 2 h incubation in gastric medium with pH 4.0. Sterile intestinal medium induced germination of spores and enabled outgrowth of vegetative cells to approx. 7 log CFU/mL. The behavior of B. cereus in the intestinal environment with competing intestinal bacteria was determined by their relative concentrations. Besides the numbers of intestinal bacteria, the nutrition and composition of the intestinal community were also very important for the growth inhibition of B. cereus.
Acid stress in the food pathogen Bacillus cereus
Journal of Applied Microbiology, 2002
The pathogen Bacillus cereus, which is associated with a number of foods including dairy products, was studied for its response to acid stress during the exponential phase. Methods and Results: Bacillus cereus was found to adapt to acid stress (pH 4á6) when preexposed to a non-lethal, inducing pH of 6á3 or to inducing concentrations of heat, ethanol, salt or hydrogen peroxide. Cells were found to maintain their internal pH at a higher level than the external acid pH and adapted cells had a higher internal pH than unadapted cells. A constitutive acid-sensitive mutant that was also heat-and ethanol-sensitive was found to be capable of high levels of adaptation despite its lack of induction of proteins induced in the wild type by exposure to moderate pH (6á3) values. Conclusions: A number of proteins were found to be underexpressed in the mutant compared with the wild type at pH 6á3, including some with homology to ribosomal proteins and to the sporulation regulator RapK, while one differentially expressed band contained two proteins, one of which was homologous to the competence regulator CodY. Signi®cance and Impact of the Study: The work has implications for the processing of B. cereus-associated foods by acidi®cation. The linked developmental processes of stationary phase, sporulation and possibly competence appear to be involved in the response to acid stress.
Journal of Microbiology and Antimicrobials
The present study is concerned with the taxonomy and influences of some cultural conditions on growth and antimicrobial metabolite production of a strain of Bacillus cereus, isolated from Alba'qa, Jordan, and designated NBS1, which is a highly active against a variety of Gram positive bacteria, and less activity was noted against filamentous fungi and yeasts, whereas no activity was detected against tested Gram negative bacteria. In order to optimize the culture conditions for the production of antimicrobial metabolite, the effect of different carbon and nitrogen sources were determined. Effects of nutritional compounds on production of antimicrobial compounds showed that the highest antimicrobial activity was obtained when arabinose and glycerol at 3.5 g/100 (w/v) level was used as sole carbon source. Ca(NO 3) 2 was identified as a nitrogen source that significantly affected antibiotic production. The results showed that strain NBS1 was a potential soil microorganism with antimicrobial activity and may be used for pharmaceutical and biotechnological purposes.
International Journal of Food Microbiology, 2007
The influence of temperature (10 to 50°C), initial pH (4.0 to 6.0) and sodium chloride concentration (0.5 to 3.0%) on the growth in nutrient broth and in meat extract of Bacillus cereus after mild heat treatment (90°C-10 min) was determined. B. cereus spores survived after heating and they were able to germinate and grow in both media when post-treatment conditions were favourable. Heated B. cereus did not grow at 10 and 50°C or in a medium with pH 4.0. Decreasing pH values and increasing levels of sodium chloride decreased growth rate and increased the lag phase of B. cereus. pH 4.5 was unable to prevent the growth of heated spores in a meat substrate with 0.5% NaCl at 12°C. The combination of pH ≤4.5, NaCl concentration ≥ 1.0% and temperatures ≤12°C was sufficient to inhibit B. cereus growth after heat treatment at 90°C for 10 min, for at least 50 days in nutrient broth and in meat extract. Re-heating at temperatures ≥60°C could control heated B. cereus ATCC 7004 growth.
Growth of Bacillus cereus on solid media as affected by agar, sodium chloride, and potassium sorbate
Journal of food protection, 2000
The effect of two independent variables: microstructure, as modified by the agar content (1.0, 4.0, 7.0%), and water activity (a(w)), as modified by the NaCl content (0.5, 2.5, 4.5%), in the absence or in the presence of potassium sorbate (0.0; 2,000 ppm) on Bacillus cereus growth on solid media was studied. The time to visible growth (TVG) and the radial growth rate (RGR) of colonies were evaluated. TVG was not affected by microstructure and K-sorbate, although when a(w) was reduced, TVG tended to increase. RGR depended on linear effects of microstructure and a(w) variables and their interaction. When K-sorbate was added to cultural media, RGR was reduced significantly. However, in the presence of K-sorbate, RGR was found to change only when a(w) vas varied.