Activity-loss characteristics of spores of Bacillus thuringiensis during spray drying

Survival of spores of Bacillus thuringiensis was determined under various processing conditions for spray drying. The results indicated that the viable spores number of B. thuringiensis decreased with increased inlet air temperature, outlet air temperature and atomising air pressure. When the inlet air temperature ranged from 170 °C to 250 °C, the outlet air temperature (75 °C) and atomising air pressure (0.15 MPa) were fixed, the pseudo-z value (one logarithmic cycle reduction) was 238.1 °C; when the outlet air temperature ranged from 65 °C to 95 °C, the inlet air temperature (200 °C) and atomising air pressure (0.15 MPa) were fixed, the pseudo-z value was 85.5 °C, the activation energy calculated according to the outlet air temperature was 59.96 kJ mol⁻¹; when the atomising air pressure ranged from 0.10 MPa to 0.25 MPa, the inlet air temperature (200 °C) and outlet air temperature (75 °C) were fixed, the pseudo-z value was 3.49 MPa, the variance analysis showed that the atomising air pressure has no significant influence to the spores. The diluting solutions between Tween-80 solution and phosphate buffer have significant influence on the plate count of spores.

The B. thuringiensis powder prepared by spray drying with inlet air temperature 250 °C, outlet air temperature 97 °C, the spores count of powder decreased obviously. But when the inlet air temperature of 155–165 °C, outlet air temperature of 66–70 °C were employed, the spores count of powder approaches to that of freeze drying powder. The spores count of oven drying powder was lower than that of the freeze drying powder, but close to the spray drying powder which inlet air temperature was 200 °C, outlet air temperature was 75 °C.     

Toxin producing Bacillus cereus persist in ready-to-reheat spaghetti Bolognese mainly in vegetative state

The potential of Bacillus cereus to cause a diarrheal toxico-infection is related to its ability to perform de novo enterotoxin production in the small intestine. A prerequisite for this is presence of sufficient numbers of B. cereus that have survived gastro-intestinal passage. It is known that the percentage of survival is much smaller for vegetative cells in comparison to spores and it is therefore important to know the state in which B. cereus is ingested. The results of the current study performed on twelve B. cereus strains, comprising both diarrheal and emetic type, indicate that exposure via contaminated foods mainly concerns vegetative cells. Inoculated vegetative cells grew to high counts, with the growth dynamic depending on the storage temperature. At 28 °C growth to high counts resulted in spore formation, in general, after 1 day of storage. One strain was an exception, producing spores only after 16 days. At 12 °C obtained high counts did not result in spore formation for 11 of 12 tested strains after two weeks of storage. The highest counts and time to sporulation were different between strains, but no difference was observed on the group level of diarrheal and emetic strains. The spore counts were always lower than vegetative cell counts and occurred only when food was obviously sensory spoiled (visual and odor evaluation). Similar observations were made with food inoculated with B. cereus spores instead of vegetative cells. Although the prospect of consuming spores was found very weak, the numbers of vegetative B. cereus cells were high enough, without obvious sensory deviation, to survive in sufficient level to cause diarrheal toxico-infection.     

High Pressure Destruction Kinetics of Clostridium Sporogenes Spores in Salmon Slurry at Elevated Temperatures

Salmon slurry containing C. sporogenes spores was subjected to high pressure (HP) treatments (700–900 MPa; 80–100°C, and 0–24 min). Destruction rates (D value) and pressure/temperature sensitivity parameters (Z_P and Z_T ) were evaluated. Thermal treatment D values were an order of magnitude higher than those under HP. Higher pressures and temperatures accelerated the spore destruction rates. Z_P values were 14.5, 17.3 and 15.5°C at 700, 800 and 900 MPa respectively, while Z_T values (at constant temperature) were 440, 540, 550 MPa at 80, 90, and 100°C, respectively. The z value under thermal treatment was 8.8°C. The spores were relatively more sensitive to temperature than to pressure.     

Use of endospore-forming bacteria as an active oxygen scavenger in plastic packaging materials

The incorporation of active oxygen scavengers in polymer packaging materials is essential to allow packaging of oxidation sensitive products. Opposed to the currently available chemical oxygen scavengers, systems based upon natural and biological components could have advantages towards consumer perception and sustainability. A modelsystem for a new oxygen scavenging poly(ethylene terephthalate) (PET) bottle is proposed using an endospore-forming bacteria genus Bacillus amyloliquefaciens as the active ingredient. Spores were incorporated in poly(ethylene terephthalate, 1,4-cyclohexane dimethanol) (PETG), an amorphous PET copolymer having a considerable lower processing temperature and higher moisture absorption compared to PET. To asses spore viability after incorporation, a method was optimized to extract spores from PETG using a chloroform/water mixture. Samples were also analyzed using a Live/Dead BacLight Bacterial Viability kit. It was shown that endospores were able to survive incorporation in PETG at 210 °C. Incorporated spores could actively consume oxygen for minimum 15 days, after an activation period of 1–2 days at 30 °C under high humidity conditions.

Industrial relevance

The study describes a modelsystem for the use of incorporated spores genus Bacillus amyloliquefaciens as an active oxygen scavenger in PET multilayer bottles using PETG as the middle layer material. Industrially, oxygen scavengers using incorporated viable spores as the active compound could have advantages towards consumer perception, recyclability, safety, material compatibility, production costs, … compared to currently available chemical oxygen scavengers.     

Process Control For Ozonation Systems: A Novel Real-Time Approach

For real-time control of ozonation processes in water works, a sequencing batch reactor was constructed to measure the ozone decay rate constant (k_O3) in short time intervals of about 15 min. The batch reactor is filled during the production process, immediately after dissolving ozone in water by a static mixer. On the basis of k_O3 and the initial ozone concentration ([O₃]₀), and the experimentally determined ratio of the concentrations of ^?OH radicals to ozone (R_ct), the degradation of micropollutants in ozone reactors (modeled as Continuously Stirred Tank Reactors - CSTRs) were calculated for compounds with known reaction rate constants with ozone and ^?OH radicals. Calculated degradation of atrazine, iopromide, benzotriazole and acesulfame are in good agreement with measured data. For acesulfame the following rate constants were determined in this study at 20 ^oC: reaction rate constant with ozone = 88 M^?1s^?1, reaction rate constant with ^?OH radical = 4.55?×?10⁹ M^?1s^?1. For the ozone reaction an activation energy of 35 kJ/mol was determined. Similarly to micropollutants, the relative inactivation of microorganisms (N/N₀) can be calculated based on the inactivation rate constant for ozone and if applicable the lag phase. The pI-value (=??logN/N₀) was introduced and implemented in the process management system to calculate online the log inactivation of reference microorganisms such as B. subtilis spores. The system was tested for variation of pH (6.5–8.5), DOC (1.2–4.2 mg/L) flowrate 3.2–12 m³/h and temperature (5.7–9 ^oC). Furthermore, a given pI-value, e.g. 1 for a 1-log inactivation of B. subtilis spores, can be set as control parameter in the process management system. The ozone gas flow is then adjusted until the set pI-value is reached. The process control concept was validated with B. subtilis spores. Generally, a good agreement was found between calculated and measured inactivation data. It was also demonstrated, that a constant ozone residual may lead to insufficient disinfection or overdosing of ozone. The new process control concept for ozonations based on onsite measurement of the ozone decay rate constant and the pI-value allows to assess disinfection and degradation processes quantitatively in real-time.     

Effects of ozone exposure on the xerophilic fungus, Eurotium amstelodami IS-SAB-01, isolated from naan bread

Xerophilic moulds cause contamination and spoilage of low moisture foods. This study examined the effect of ozone fumigation on growth of a Eurotium species isolated from naan bread. Two ozone treatments were used — a low-level long-term exposure (0.4 μmol/mol for 21 days) and high-level short-term exposure (300 μmol/mol for 5 to 120 min). For the low level exposure the combination of different media sucrose concentrations (0, 5, 10 and 20% w/v) with ozone treatment was also assessed. The growth of the isolate was found to be sensitive to low-level ozone fumigation depending on the media sucrose concentration and duration of the exposure. Low-level ozone exposure significantly (p < 0.05) reduced the number of asexual spores formed in media with no added sucrose, an effect not observed in media with higher sucrose levels. Electron microscope observations of colonies indicated that ozone exposed cultures produced lower numbers of cleistothecia. High-level ozone exposure for short durations reduced spore viability although 100% reduction in viability was achieved only after 120 min exposure. This work demonstrates that ozone may be used to reduce spore production in Eurotium but that the ozone effect can be mediated by sucrose levels in the growth medium.     

Middle–Upper Jurassic palynology of the South Sallum well,North Western Desert,Egypt

Palynological analyses have been carried out on some samples of Middle–Upper Jurassic from the South Sallum well, North Western Desert, Egypt. A refinement of the original chronostratigraphy has been suggested and the stages of Bathonian – Callovian and the Callovian – Oxfordian are recognized. Two biozones were identified that are Dichadogonyaulax sellwoodi i – Wanaea acollaris – Wanaea digitata Assemblage Zone in the Bathonian – Callovian and Amphorula dodekovae Interval Zone in the Callovian – Oxfordian. Other important dinoflagellates and miospores of Middle–Upper Jurassic are recorded in the samples. The palaeoenvironmental settings are interpreted on the basis of statistical relative abundances of the palynomorphs, in the course of their ecological preferences. Depositional regime fluctuates between marginal marine to normal marine. A warm-humid climate prevails throughout the deposition, as indicated by the abundance of ferns, and other hygrophilous spores, and rare xerophytes.     

Detecting single Bacillus spores by surface enhanced Raman spectroscopy

Detection of Bacillus spores is of considerable importance to the food industry since they can survive standard processing procedures and sanitation treatments. Surface enhanced Raman spectroscopy (SERS) coupled with gold SERS-active substrates was used to detect and discriminate among five Bacillus spores (B. cereus ATCC 13061, B. cereus ATCC 10876, B. cereus sp., B. subtilis sp., and B. stearothermophilus sp.). Tremendously enhanced Raman signals of Bacillus spores deposited onto the gold substrates were detected, allowing the limit of detection (LOD) of SERS to reach the level of a single spore. Distinct spectral differences were observed between different Bacillus spores. Hierarchical cluster analysis (HCA) and principle component analysis (PCA) show clear data segregations at the species level between five Bacillus spores. Principle component (PC) values indicate that the Raman shift range between 900 and 1200 cm⁻¹ contributed significantly to the total data variance in the PCA results. In particular, a prominent band of dipicolinic acid (DPA) was observed at 998 cm⁻¹ and served as a biomarker for bacterial spores. This study demonstrates that SERS coupled with gold nanosubstrates is able to detect and discriminate single Bacillus spores non-destructively and with minimum sample preparation. SERS method is a promising tool for rapid, ultra-sensitive, and selective detection of bacterial spores, potentially in foods and other complex biological matrices.     

Research on factors allowing a risk assessment of spore-forming pathogenic bacteria in cooked chilled foods containing vegetables: a FAIR collaborative project

Vegetables are frequent ingredients of cooked chilled foods and are frequently contaminated with spore-forming bacteria (SFB). Therefore, risk assessment studies have been carried out, including the following: hazard identification and characterisation — from an extensive literature review and expertise of the participants, B. cereus and C. botulinum were identified as the main hazards; exposure assessment — consisting of determination of the prevalence of hazardous SFB in cooked chilled foods containing vegetables and in unprocessed vegetables, and identification of SFB representative of the bacterial community in cooked chilled foods containing vegetables, determination of heat-resistance parameters and factors affecting heat resistance of SFB, determination of the growth kinetics of SFB in vegetable substrate and of the influence of controlling factors, validation of previous work in complex food systems and by challenge testing and information about process and storage conditions of cooked chilled foods containing vegetables. The paper illustrates some original results obtained in the course of the project. The results and information collected from scientific literature or from the expertise of the participants are integrated into the microbial risk assessment, using both a Bayesian belief network approach and a process risk model approach, previously applied to other foodborne hazards.     

米曲霉孢子对同步辐射C、N、O元素K吸收边附近软X射线的吸收剂量分布研究

以C、N、O元素的K吸收边附近能量的软X射线为辐射光源,通过模型分析,比较了米曲霉孢子不同部位对不同能量软X射线吸收剂量分布.同时利用合肥同步辐射软X射线显微术光束线准单色的软X射线对孢子进行辐照实验,对不同能量辐照存活率结果进行了比较.理论分析表明,由于C、N、O元素K吸收边效应以及孢子不同部位元素组成的不同,受照时孢子不同部位对软X射线的吸收剂量分布随能量变化存在差异.实验结果显示,3种元素K吸收边附近软X射线对米曲霉孢子均有很强的辐射失活效应,其中2.3nm波长的软X射线对孢子的辐射损伤效应要高于3.2nm和4.4nm波长的软X射线.