Germination and Heat Resistance of Bacillus cereus Spores from Strains Associated with Diarrheal and Emetic Food-Borne Illnesses

Bacillus cereus has been implicated as the cause of both diarrheal and emetic forms of food-borne illness. Spores of eight strains of B. cereus, representing diairheal, emetic and atoxigenic origins, were examined for heat resistance and germination responses. No correlation was observed between heat resistance at 85° or 90°C and origin of the strain. Germination of spores in Trypticase soy broth at 30°C, measured by loss of heat resistance, was more extensive for diarrheal strains than for emetic strains. These data should be useful in evaluating potential hazards from B. cereus in foods.     

Influence of Heating and Cooling Rates on Bacillus cereus Spore Survival and Growth in a Broth Medium and in Rice

Survival, spore germination, and growth of emetic and diarrheal type strains of Bacillus cereus were evaluated in broth and rice media during heating and cooling. Samples were heated to 80°C (20C°/hr or 40C°/hr) or 90°C (ca. 900C°/hr), prior to cooling to 10°C (5C°/hr or 10C°/hr). Following heating to 80°C, growth occurred during 5C°/hr cooling. After heating to 90°C, inactivation of three strains occurred during cooling from 90 to 80°C and again from 50 to 40°C. Great variability was observed among the responses of the four strains. Emetic strains exhibited greater survival than diarrheal strains. Rice reduced low temperature inactivation, and did not favor emetic strains. Significant two and three way interactions existed among media, strains, heating and cooling rates.     

蜡样芽孢杆菌在营养肉汤和维也纳香肠中的预测模型及其在生产中的应用

本文比较了蜡样芽孢杆菌在营养肉汤和维也纳香肠中的生长曲线,发现它们具有很好的相关性,可用芽孢杆菌在营养肉汤中的生长情况指导维也纳香肠的生产.然后根据蜡样芽孢杆菌在营养肉汤的生长情况,提出维也纳香肠在生产中应注意的事项,为维也纳香肠的生产提供参考.     

Effect of Ethylenediaminetetraacetic Acid (EDTA) on Growth from Spores of Bacillus cereus

Germination and growth from spores of toxigenic B. cereus strain USDA 201 in BHI broth containing Na²EDTA were studied. Reduced growth was effected by low EDTA concentrations (< 300 ppm). Little or no growth was observed after incubation for 48 hr in broth containing from 300–1,000 ppm of EDTA EDTA did not affect percent spore germination, or release of Ca following heat activation and subsequent incubation. However, delayed colony development was observed as EDTA concentrations increased in the broth, and atypically small colonies formed on Plate Count Agar. Growth inhibition by 500 ppm EDTA was evident over the pH range 5–9, with the highest spore resistance observed at pH 7. Addition of Fe, Zn, and Ca to the media reversed the growth inhibitory action, whereas Mg was less effective.     

Model for Combined Effects of Temperature, pH and Water Activity on Thermal Inactivation of Bacillus cereus Spores

Initially, the effect of water activity (a_w) on heat resistance of Bacillus cereus spores (decimal reduction time) was investigated. A linear relationship was found between log D and 1-a_w. The combined effects of temperature (85-105°C), pH (4.5-6.5) and water activity (0.80-1) were then studied. A four parameter model was fitted to the data. This model appeared to be parsimonious with each parameter having a biological significance. Interactions between factors were observed but they accounted for <2.4% of the total variation and they were not taken into account by the model.     

Effects of Electrolyzed Oxidizing Water on Inactivation of Bacillus subtilis and Bacillus cereus Spores in Suspension and on Carriers

Spores of some Bacillus species are responsible for food spoilage and foodborne disease. These spores are highly resistant to various interventions and cooking processes. In this study, the sporicidal efficacy of acidic electrolyzed oxidizing (EO) water (AEW) and slightly acidic EO water (SAEW) with available chlorine concentration (ACC) of 40, 60, 80, 100, and 120 mg/L and treatment time for 1, 2, 3, 4, 5, and 6 min were tested on Bacillus subtilis and Bacillus cereus spores in suspension and on carrier with or without organics. The reduction of spore significantly increased with increasing ACC and treatment time (P < 0.05). Nondetectable level of B. cereus spore in suspension occurred within 2 min after exposure to both EO waters containing 120 mg/L ACC, while only SAEW at 120 mg/L and 2 min treatment achieved >6 log reductions of B. subtilis spore. Both types of EO water with ACC of 60 mg/L and 6 min treatment achieved a reduction of B. subtilis and B. cereus spores to nondetectable level. EO water with ACC of 80 mg/L and treatment time of 3 min on carrier test without organics addition resulted in reductions of B. subtilis spore to nondetectable level. But, addition of 0.3% organics on carrier decreased the inactivation effect of EO water. This study indicated that EO water was highly effective in inactivation of B. subtilis and B. cereus spores in suspension or on carrier, and therefore, rendered it as a promising disinfectant to be applied in food industry.     

Control of Bacillus cereus Spores and Spoilage Microflora in Sous Vide Chicken Breast

Safety of sous vide chicken breast with respect to Bacillus cereus and effect of processing parameters on natural microflora were evaluated. B. cereus, a facultatively anaerobic sporeformer, may cause foodborne illness and has been isolated from poultry. Product was inoculated and processed to 77°C or 94°C. Populations were reduced by 0.5- to 1.0-log and by 3-log in products heated to 77°C and 94°C, respectively. Spores germinated within 1 day at 10°C yet detectable changes in populations were not evident through 28 days storage. Lactate did not influence B. cereus populations or spore germination. Natural microflora was reduced by processing and remained low through 28 days storage at 4°C and 10°C.     

Growth of Bacillus cereus in soyabean tempeh

Bacillus cereus strains isolated from retail samples of tempeh were added in levels of approx. 10⁵ cfu/g to soaking soyabeans intended for tempeh manufacture. Their growth was prevented and tempeh of good quality was obtained when the soaking resulted in acidification of the beans to pH 4.85, but B. cereus could grow well (approx. 10⁸ cfu/g) in tempeh and cause its spoilage when the soaking did not cause acidification (bean pH 5.70–6.00). Acidification of soyabeans by addition of lactic acid prior to fungal fermentation required pH ≤ 4.4 to prevent B. cereus growth; at this pH, tempeh of good quality was obtained. Acidification of soyabeans with addition of acetic acid inhibited at pH ≤ 5.5 both B. cereus and Rhizopus oligosporus, the mould responsible for tempeh formation; hence, no tempeh could be obtained. Mixed inocula of R. oligosporus and either Lactobacillus plantarum, L. casei ssp. alactosus or L. fermentum produced tempeh of excellent quality. However, mixed inocula containing lactobacilli were not able to prevent B. cereus growth and subsequent spoilage when added to unacidified soyabeans of pH 6.6. This indicates that soyabean acidification, either by biological or by chemical means, is essential to inhibit B. cereus growth during the tempeh fermentation.     

地衣芽孢杆菌在营养肉汤中生长模型的建立

考察了温度、Na Cl质量分数及p H值对地衣芽孢杆菌在营养肉汤中生长特性的影响,建立了15~45℃下地衣芽孢杆菌的生长模型。结果表明:地衣芽孢杆菌的最适的生长温度范围为30~37℃,Na Cl质量分数范围为0~3%,p H值范围为5.0~8.0。在15、20、25℃时其生长曲线用MMF模型拟合较好,在30、37℃用Richards模型拟合较好,其相关系数较高,均大于0.998。相反,在45℃其生长曲线只能用Logistic方程拟合,且相关系数较低,仅为0.907。     

蜡样芽孢杆菌发酵液对苹果保鲜作用的初步研究

本文研究了蜡样芽孢杆菌发酵液对苹果的保鲜作用.在实验研究的时间内,经蜡样芽孢杆菌发酵液的浸泡处理,可在一定程度上防止苹果水分的蒸发,减缓苹果的褐变,抑制由于霉菌等霉腐微生物的生长而导致的苹果腐烂,减少苹果营养成分,如VC、糖、蛋白质等的损失,因而对苹果具有保鲜作用.     

食用菌发酵液对热干面中蜡样芽孢杆菌的抑制作用

为确定鲜湿热干面中主要腐败微生物,本研究通过16Sr DNA序列和生化鉴定对从热干面中分离的微生物进行鉴定,确定从中分离出一株蜡样芽孢杆菌。为利用食用菌发酵液抑制蜡样芽孢杆菌生长,以菌丝生长速度为筛选指标,从香菇、黑木耳、血耳、猴头菇和蛹虫草5个品种26个菌株中各筛选1个菌株进行液体发酵,并通过不同品种菌株发酵液对蜡样芽孢杆菌生长抑制效果评价,筛选最佳食用菌品种及菌株,最后,利用微量二倍稀释法确定发酵液的最小抑菌浓度。结果表明,5个食用菌品种中,血耳的麻城血耳菌株对所分离蜡样芽胞杆菌生长抑制效果最好,在300 min检测周期内其抑制率始终保持在95%以上。通过微量二倍稀释法确定麻城血耳发酵液对蜡样芽孢杆菌的最小抑菌浓度为31.25μL/m L。本研究为血耳发酵液应用于鲜湿热干面的生产和保鲜提供参考,并为食用菌发酵液应用于鲜湿面条营养和功效提升奠定基础。     

Effect of Pulsed Light Treatment on the Germination of Bacillus subtilis Spores

Food and Bioprocess Technology - The loss of cell culturability (spore counts), spore germination and subsequent vegetative growth of Bacillus subtilis were evaluated after pulsed light (PL)...     

蜡样芽孢杆菌在草莓中的生长及预测模型的建立

在对草莓的病源微生物污染调查中发现蜡样芽孢杆菌具有高的检出率。为比较不同温度和不同包装方式的草莓表面蜡样芽孢杆菌数量的变化情况,测定了7℃、15℃、25℃、30℃的温度条件下,采用保鲜盒包装和保鲜膜包装方式的草莓表面蜡样芽孢杆菌生长数据;选用Baranyi Roberts模型为初级模型,拟合不同温度和不同包装方式的草莓中蜡样芽孢杆菌生长曲线,并对模型进行验证。结果显示,7℃冷藏的蜡样芽孢杆菌均增长缓慢而与包装方式无关;15℃低温贮藏过程中,膜装与盒装延滞期基本相同,但膜装比盒装降低了0.7 lg cfu/g的生长势,说明保鲜膜在此温度下有一定的抑菌作用;在25℃、30℃储藏下两种包装方式的比生长速率和延滞期基本相同,蜡样芽孢杆菌在42 h后分别增长了2.9 lg cfu/g、3.2 lg cfu/g,表明贮藏温度是影响蜡样芽孢杆菌的主要因素。因此在高温条件下蜡样芽孢杆菌会带来潜在的食用安全风险。本研究结果为微生物定量风险评估提供重要信息。     

蜡样芽胞杆菌生长特性及大蒜精油对其抑菌活性的研究

主要研究了37℃条件下3种蜡样芽胞杆菌在营养肉汤中的生长状况,建立了37℃下蜡样芽胞杆菌在营养肉汤中的Boltzmann牛长模犁,3条牛长曲线相关系数鼯均大于0．97;检测了不同培养时间蜡样芽胞杆菌的产芽胞情况,结果表明1号菌株和14号菌株较早产芽胞,培养相同时间,产芽胞数：1号菌株,4号菌株〉标准菌株;采用牛沣杯法和平板计数法研究了大蒜精油对蜡样芽胞杆菌的抑制效果,结果表明浓度为lO。的人蒜精油对3种蜡样芽胞杆菌都有很好的抑制效果,3种菌株中l号菌株最难抑制。     

基于环介导等温扩增技术的产呕吐毒素 蜡样芽胞杆菌特异性检测

本研究旨在建立食品中产呕吐毒素蜡样芽胞杆菌的快速检测方法.基于产呕吐毒素蜡样芽胞杆菌合成酶基因cesB靶基因,设计4条特异性引物(2条内引物、2条外引物),建立环介导等温扩增技术(LAMP).然后采用2株产呕吐毒素蜡样芽胞杆菌、19株蜡样芽胞杆菌和41株非蜡样芽胞杆菌验证了该LAMP具有很好的特异性.LAMP检测的灵敏...     

Distribution and Characteristics of Bacillus cereus Isolated from Rice in Taiwan

Sixty-six strains of Bacillus cereus were isolated from 12 kinds of rice samples collected in Taiwan by employing polymyxin pyruvate egg yolk mannitol bromothymol blue agar(PEMBA). It was found that in Taiwan B. cereus could be detected in various rice samples (less than 200 CFU per gram). The isolates generally grew poorly under acidic conditions. Spore suspensions prepared from six isolates of B. cereus were used to detect their ability to resist heat. The D_100°C- and _D92°C- values for these six isolates in rice broth ranged from 4.2-6.5 min and 16–36 min, respectively. Most of the isolates were sensitive to chloramphenicol (30 mcg), erythromycin (15 mcg), gentamicin (10 mcg) and streptomycin (10 mcg).