Spore Survival Research Articles

Lipid droplet dynamics during Schizosaccharomyces pombe sporulation and their role in spore survival.

ABSTRACTUpon nitrogen starvation, the fission yeast Schizosaccharomyces pombe forms dormant spores; however, the mechanisms by which a spore sustains life without access to exogenous nutrients remain unclear. Lipid droplets are reservoirs of neutral lipids that act as important cellular energy resources. Using live-cell imaging analysis, we found that the lipid droplets of mother cells redistribute to their nascent spores. Notably, this process was actin polymerization-dependent and facilitated by the leading edge proteins of the forespore membrane. Spores lacking triacylglycerol synthesis, which is essential for lipid droplet formation, failed to germinate. Our results suggest that the lipid droplets are important for the sustenance of life in spores.

Implications of Decreased Nitrite Concentrations on Clostridium perfringens Outgrowth during Cooling of Ready-to-Eat Meats

Increased popularity of natural and organic processed meats can be attributed to the growing consumer demand for preservative-free foods, including processed meats. To meet this consumer demand, meat processors have begun using celery juice concentrate in place of sodium nitrite to create products labeled as no-nitrate or no-nitrite-added meat products while maintaining the characteristics unique to conventionally cured processed meats. Because of flavor limitations, natural cures with celery concentrate typically provide lower ingoing nitrite concentrations for ready-to-eat processed meats than do conventional cures, which could allow for increased growth of pathogens, such as Clostridium perfringens, during cooked product cooling such as that required by the U.S. Department of Agriculture. The objective of this study was to investigate the implications associated with reduced nitrite concentrations for preventing C. perfringens outgrowth during a typical cooling cycle used for cooked products. Nitrite treatments of 0, 50, and 100 ppm were tested in a broth system inoculated with a three-strain C. perfringens cocktail and heated with a simulated product thermal process followed by a typical cooling-stabilization process. The nitrite concentration of 50 ppm was more effective for preventing C. perfringens outgrowth than was 0 ppm but was not as effective as 100 ppm. The interaction between nitrite and temperature significantly affected (P < 0.05) C. perfringens outgrowth in both total population and number of vegetative cells. Both temperature and nitrite concentration significantly affected (P < 0.05) C. perfringens spore survival, but the interaction between nitrite and temperature did not have a significant effect (P > 0.05) on spore outgrowth. Results indicate that decreased nitrite concentrations (50 ppm) have increased potential for total C. perfringens population outgrowth during cooling and may require additional protective measures, such as faster chilling rates.

Mapping as a tool for predicting the risk of anthrax outbreaks in Northern Region of Ghana.

IntroductionAnthrax is a febrile soil-born infectious disease that can affect all warm-blooded animals including man. Outbreaks of anthrax have been reported in northern region of Ghana but no concerted effort has been made to implement risk-based surveillance systems to document outbreaks so as to implement policies to address the disease. We generated predictive maps using soil pH, temperature and rainfall as predictor variables to identify hotspot areas for the outbreaks.MethodsA 10-year secondary data records on soil pH, temperature and rainfall were used to create climate-based risk maps using ArcGIS 10.2. The monthly mean values of rainfall and temperature for ten years were calculated and anthrax related evidence based constant raster values were created as weights for the three factors. All maps were generated using the Kriging interpolation method.ResultsThere were 43 confirmed outbreaks. The deaths involved were 131 cattle, 44 sheep, 15 goats, 562 pigs with 6 human deaths and 22 developed cutaneous anthrax. We found three strata of well delineated distribution pattern indicating levels of risk due to suitability of area for anthrax spore survival. The likelihood of outbreaks occurrence and reoccurrence was higher in Strata I, Strata II and strata III respectively in descending order, due to the suitability of soil pH, temperature and rainfall for the survival and dispersal of B. anthracis spore.ConclusionThe eastern corridor of Northern region is a Hots spot area. Policy makers can develop risk based surveillance system and focus on this area to mitigate anthrax outbreaks and reoccurrence.

Die another day: Fate of heat-treated Geobacillus stearothermophilus ATCC 12980 spores during storage under growth-preventing conditions

Geobacillus stearothermophilus spores are recognized as one of the most wet-heat resistant among aerobic spore-forming bacteria and are responsible for 35% of canned food spoilage after incubation at 55 °C. The purpose of this study was to investigate and model the fate of heat-treated survivor spores of G. stearothermophilus ATCC 12980 in growth-preventing environment. G. stearothermophilus spores were heat-treated at four different conditions to reach one or two decimal reductions. Heat-treated spores were stored in nutrient broth at different temperatures and pH under growth-preventing conditions. Spore survival during storage was evaluated by count plating over a period of months. Results reveal that G. stearothermophilus spores surviving heat treatment lose their viability during storage under growth-preventing conditions. Two different subpopulations were observed during non-thermal inactivation. They differed according to the level of their resistance to storage stress, and the proportion of each subpopulation can be modulated by heat treatment conditions. Finally, tolerance to storage stress under growth-preventing conditions increases at refrigerated temperature and neutral pH regardless of heat treatment conditions. Such results suggest that spore inactivation due to heat treatment could be completed by storage under growth-preventing conditions.

Effect of chilling, freezing and cooking on survivability of clostridium difficile spores in ground beef

Effect of chilling, freezing and cooking on survivability of clostridium difficile spores in ground beef

Effect of Nisin and Thermal Treatments on the Heat Resistance of Clostridium sporogenes Spores

The aim of this research was to evaluate the effect of thermal treatments (isothermal or nonisothermal) combined with nisin, a natural antimicrobial, on the survival and recovery of Clostridium sporogenes spores. The addition of nisin to the heating medium at concentrations up to 0.1 mg liter-1 did not reduce the heat resistance of C. sporogenes. Without a thermal treatment, nisin added at concentrations up to 0.1 mg liter-1 did not reduce the viable counts of C. sporogenes when added to the recovery medium, but inactivation of more than 4 log cycles was achieved after only 3 s at 100°C. At 100°C, the time needed to reduce viable counts by more than 3 log cycles was nine times shorter when 0.01 mg liter-1 nisin was added to the recovery medium than without it. The heat resistance values calculated under isothermal conditions were used to predict the survival in the nonisothermal experiments, and the predicted values accurately fit the experimental data. The combination of nisin with a thermal treatment can help control C. sporogenes.

Bacillus thermoamylovorans Spores with Very-High-Level Heat Resistance Germinate Poorly in Rich Medium despite the Presence of ger Clusters but Efficiently upon Exposure to Calcium-Dipicolinic Acid.

High-level heat resistance of spores of Bacillus thermoamylovorans poses challenges to the food industry, as industrial sterilization processes may not inactivate such spores, resulting in food spoilage upon germination and outgrowth. In this study, the germination and heat resistance properties of spores of four food-spoiling isolates were determined. Flow cytometry counts of spores were much higher than their counts on rich medium (maximum, 5%). Microscopic analysis revealed inefficient nutrient-induced germination of spores of all four isolates despite the presence of most known germination-related genes, including two operons encoding nutrient germinant receptors (GRs), in their genomes. In contrast, exposure to nonnutrient germinant calcium-dipicolinic acid (Ca-DPA) resulted in efficient (50 to 98%) spore germination. All four strains harbored cwlJ and gerQ genes, which are known to be essential for Ca-DPA-induced germination in Bacillus subtilis. When determining spore survival upon heating, low viable counts can be due to spore inactivation and an inability to germinate. To dissect these two phenomena, the recoveries of spores upon heat treatment were determined on plates with and without preexposure to Ca-DPA. The high-level heat resistance of spores as observed in this study (D120°C, 1.9 ± 0.2 and 1.3 ± 0.1 min; z value, 12.2 ± 1.8°C) is in line with survival of sterilization processes in the food industry. The recovery of B. thermoamylovorans spores can be improved via nonnutrient germination, thereby avoiding gross underestimation of their levels in food ingredients.

The differential effects of heat‐shocking on the viability of spores from Bacillus anthracis, Bacillus subtilis, and Clostridium sporogenes after treatment with peracetic acid‐ and glutaraldehyde‐based disinfectants

This study investigated (1) the susceptibility of Bacillus anthracis (Ames strain), Bacillus subtilis (ATCC 19659), and Clostridium sporogenes (ATCC 3584) spores to commercially available peracetic acid (PAA)- and glutaraldehyde (GA)-based disinfectants, (2) the effects that heat-shocking spores after treatment with these disinfectants has on spore recovery, and (3) the timing of heat-shocking after disinfectant treatment that promotes the optimal recovery of spores deposited on carriers. Suspension tests were used to obtain inactivation kinetics for the disinfectants against three spore types. The effects of heat-shocking spores after disinfectant treatment were also determined. Generalized linear mixed models were used to estimate 6-log reduction times for each spore type, disinfectant, and heat treatment combination. Reduction times were compared statistically using the delta method. Carrier tests were performed according to AOAC Official Method 966.04 and a modified version that employed immediate heat-shocking after disinfectant treatment. Carrier test results were analyzed using Fisher's exact test. PAA-based disinfectants had significantly shorter 6-log reduction times than the GA-based disinfectant. Heat-shocking B. anthracis spores after PAA treatment resulted in significantly shorter 6-log reduction times. Conversely, heat-shocking B. subtilis spores after PAA treatment resulted in significantly longer 6-log reduction times. Significant interactions were also observed between spore type, disinfectant, and heat treatment combinations. Immediately heat-shocking spore carriers after disinfectant treatment produced greater spore recovery. Sporicidal activities of disinfectants were not consistent across spore species. The effects of heat-shocking spores after disinfectant treatment were dependent on both disinfectant and spore species. Caution must be used when extrapolating sporicidal data of disinfectants from one spore species to another. Heat-shocking provides a more accurate picture of spore survival for only some disinfectant/spore combinations. Collaborative studies should be conducted to further examine a revision of AOAC Official Method 966.04 relative to heat-shocking.

Microbiological efficacy of pressure assisted thermal processing and natural extracts against Bacillus amyloliquefaciens spores suspended in deionized water and beef broth

Effect of aqueous extracts of pomegranate peel (PPE) and tamarind pulp (TPE) on lethality of pressure assisted thermal processing (PATP) against Bacillus amyloliquefaciens Fad 82 spores was investigated. B. amyloliquefaciens spores (≈108CFUml−1) were suspended in deionized water (DIW), 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer PPE, and TPE (1% w/v in DIW, pH-6) and beef broth with or without PPE and TPE (0.45% w/v). Samples were subjected to pressure assisted thermal processing (PATP, 600MPa, 105°C), and thermal processing (TP; 0.1MPa, 105°C) for 0 (come-up time), 0.5, 1, 3, and 5min. Beef broth samples were also pressure treated (HPP; 600MPa, 35°C) for 3 and 5min. Dormant spore survivors were enumerated by spread-plate technique. Heat shock (80°C for 15min) was used to enumerate the heat sensitive spores. A 5-min PATP reduced spore survivors counts to below 1-logCFUml−1 (≈6.5–7.0log reduction) in PPE and TPE as compared to 2.5-log and 3.1-log in DIW and HEPES buffer, respectively. 3min PATP treatment reduced the spore survival to 3.58 and 2.1logCFUml−1 in beef broth and beef broth+natural extract, respectively. TP and HPP processing could inactivate the spores only by 0.5–1.2logCFUml−1. PPE and TPE are found to enhance the efficacy of PATP.

ATP and related purines stimulate motility, spatial congregation, and coalescence in red algal spores.

Adenosine 5'-triphosphate (ATP) is a versatile extracellular signal along the tree of life, whereas cAMP plays a major role in vertebrates as an intracellular messenger for hormones, transmitters, tastants, and odorants. Since red algal spore coalescence may be considered analogous to the congregation process of social amoeba, which is stimulated by cAMP, we ascertained whether exogenous applications of ATP, cAMP, adenine, or adenosine modified spore survival and motility, spore settlement and coalescence. Concentration-response studies were performed with carpospores of Mazzaella laminarioides (Gigartinales), incubated with and without added purines. Stirring of algal blades released ADP/ATP to the cell media in a time-dependent manner. 10-300 μM ATP significantly increased spore survival; however, 1,500 μM ATP, cAMP or adenine induced 100% mortality within less than 24 h; the exception was adenosine, which up to 3,000 μM, did not alter spore survival. ATP exposure elicited spore movement with speeds of 2.2-2.5 μm · s(-1) . 14 d after 1,000 μM ATP addition, spore abundance in the central zone of the plaques was increased 2.7-fold as compared with parallel controls. Likewise, 1-10 μM cAMP or 30-100 μM adenine also increased central zone spore abundance, albeit these purines were less efficacious than ATP; adenosine up to 3,000 μM did not influence settlement. Moreover, 1,000 μM ATP markedly accelerated coalescence, the other purines caused a variable effect. We conclude that exogenous cAMP, adenine, but particularly ATP, markedly influence red algal spore physiology; effects are compatible with the expression of one or more membrane purinoceptor(s), discarding adenosine receptor participation.

Impacts of sporulation temperature, exposure to compost matrix and temperature on survival of Bacillus cereus spores during livestock mortality composting

To investigate impact of sporulation and compost temperatures on feasibility of composting for disposal of carcasses contaminated with Bacillus anthracis. Two strains of B. cereus, 805 and 1391, were sporulated at either 20 or 37°C (Sporulation temperature, ST) and 7 Log10 CFU g(-1) spores added to autoclaved manure in nylon bags (pore size 50 μm) or in sealed vials. Vials and nylon bags were embedded into compost in either a sawdust or manure matrix each containing 16 bovine mortalities (average weight 617 ± 33 kg), retrieved from compost at intervals over 217 days and survival of B. cereus spores assessed. A ST of 20°C decreased spore survival by 1·4 log10 CFU g(-1) (P < 0·05) compared to a 37°C ST. Spore survival was strain dependent. Compost temperatures >55°C reduced spore survival (P < 0·05) and more frequently occurred in the sawdust matrix. Sporulation and compost temperatures were key factors influencing survival of B. cereus spores in mortality compost. Composting may be most appropriate for the disposal of carcasses infected with B. anthracis at ambient temperatures ≤20°C under thermophillic composting conditions (>55°C).

Fast and effective inactivation of Bacillus atrophaeus endospores using light-activated derivatives of vitamin B2.

Highly resistant endospores may cause severe problems in medicine as well as in the food and packaging industries. We found that bacterial endospores can be inactivated quickly with reactive oxygen species (ROS) that were generated by a new generation of flavin photosensitizers. Flavins like the natural compound vitamin B2 are already known to produce ROS but they show a poor antimicrobial photodynamic killing efficacy due to the lack of positive charges. Therefore we synthesized new flavin photosensitizers that have one (FLASH-01a) or eight (FLASH-07a) positive charges and can hence attach to the negatively charged surface of endospores. In this study we used standardized Bacillus atrophaeus endospores (ATCC 9372) as a biological surrogate model for a proof-of-concept study of photodynamic inactivation experiments using FLASH-01a and FLASH-07a. After incubation of spores with different flavin concentrations, the flavin derivatives were excited with blue light at a light dose of 70 J cm(-2). The inactivation of spores was investigated either in suspension or after attachment to polyethylene terephthalate (PET) surfaces. Incubation of spores suspended in Millipore water with 4 mM FLASH-01a for 10 seconds and irradiation with blue light for 10 seconds caused a biologically relevant decrease of spore survival of 3.5 log10 orders. Using FLASH-07a under the same conditions we achieved a decrease of 4.4 log10 orders. Immobilized spores on PET surfaces were efficiently killed with 7.0 log10 orders using 8 mM FLASH-07a. The total treatment time (incubation + irradiation) was as short as 20 seconds. The results of this study show evidence that endospores can be fastly and effectively inactivated with new generations of flavin photosensitizers that may be useful for industrial or medical applications in the future.

The Effect of Resin and Monoterpenes on Spore Germination and Growth in Fusarium circinatum.

Resin obtained from Pinus radiata and five monoterpene components of resin (limonene, α-pinene, β-pinene, camphene, and myrcene) were tested to determine their effects on mycelial growth and germination and survival of spores of Fusarium circinatum, the cause of pitch canker in pine, and F. temperatum, which is interfertile with F. circinatum but not pathogenic to pine. Averaged across all treatments, F. temperatum sustained the greatest reduction in radial growth (16.9±0.02% of control). The greatest reduction in dry weight also occurred in F. temperatum (11.7±0.01% of control), and all isolates of F. circinatum were significantly less affected (P<0.05). Spore germination rates in a saturated atmosphere of monoterpenes were relatively high for all tested isolates but, when placed in direct contact with resin, spore survival was significantly greater for F. circinatum than for F. temperatum. Our results are consistent with the hypothesis that greater tolerance of resin is one factor distinguishing F. circinatum from the nonpathogenic F. temperatum. However, differential tolerance of monoterpene components of resin is not sufficient to explain the observed variation in virulence to pine in F. circinatum.

Spectroscopy and viability of Bacillus subtilis spores after ultraviolet irradiation: implications for the detection of potential bacterial life on Europa.

One of the most habitable environments in the Solar System outside of Earth may exist underneath the ice on Europa. In the near future, our best chance to look for chemical signatures of a habitable environment (or life itself) will likely be at the inhospitable icy surface. Therefore, it is important to understand the ability of organic signatures of life and life itself to persist under simulated europan surface conditions. Toward that end, this work examined the UV photolysis of Bacillus subtilis spores and their chemical marker dipicolinic acid (DPA) at temperatures and pressures relevant to Europa. In addition, inactivation curves for the spores at 100 K, 100 K covered in one micron of ice, and 298 K were measured to determine the probability for spore survival at the surface. Fourier transform infrared spectra of irradiated DPA showed a loss of carboxyl groups to CO2 as expected but unexpectedly showed significant opening of the heterocyclic ring, even for wavelengths>200 nm. Both DPA and B. subtilis spores showed identical unknown spectral bands of photoproducts after irradiation, further highlighting the importance of DPA in the photochemistry of spores. Spore survival was enhanced at 100 K by ∼5× relative to 298 K, but 99.9% of spores were still inactivated after the equivalent of ∼25 h of exposure on the europan surface.

Effects of Hot Water, UV-C and Modified Coconut Oil Treatments on Suppression of Anthracnose Disease and Maintenance of Quality in Harvested Mango cv. ‘Chok-Anan’

Anthracnose disease caused by Colletotrichum gloeosporioides Penz. is the major problem of harvested mango for domestic markets and for export. Control of anthracnose disease is currently based on the application of fungicides. However, it was reported that there are some chemical residues of chemical in mango and in the environment. Therefore, safe alternative methods for controlling anthracnose disease were studied. The aim of this experiment was to evaluate the antifungal properties of modified coconut oil (MCO) in vitro test and to investigate the combined effects of ethanolic shellac - modified coconut oil solution (ES-MCO), hot water (HW) and UV-C treatments on controlling anthracnose disease and maintaining postharvest quality of mango fruit cv. Chok-Anan (in vivo test). The antifungal activity of the MCO was determined by a paper disc method and tested the survival of MCO treated-fungal spores on PDA. The results revealed that 2% MCO significantly inhibited the mycelail growth of C. gloeosporioides on paper disc and completely killed fungal spore on PDA. In vivo test, harvested mangoes were cleaned with a solution of 100 ppm sodium hypochlorite and air dried. The fruit were treated with HW, UV-C followed by ES-MCO coating (HW + UV-C + ES-MCO), HW followed by UV-C (HW + UV-C), or ES-MCO alone. Untreated fruit served as the control. All fruit samples were then kept at 13°C for 15 days. HW + UV-C + ES-MCO treatments showed the most effective in reducing anthracnose disease, followed by HW + UV-C treatments, and ES-MCO treatment, while the control fruit showed the greatest symptoms of anthracnose disease. In addition, both the ES-MCO alone and the combined treatments of HW + UV-C + ES-MCO significantly delayed ripening of fruit by retarding firmness, weight loss, total soluble solids (TSS), titratable acidity (TA), ethylene production and respiration rate, while the peel and pulp color of mango fruit were maintained throughout the storage period. This founding shows that HW + UV-C + ES-MCO treatments may act as the safe alternative methods to suppress anthracnose disease and delayed the senescence of mango fruit during cold storage.

Survival of Desulfotomaculum spores from estuarine sediments after serial autoclaving and high-temperature exposure.

Bacterial spores are widespread in marine sediments, including those of thermophilic, sulphate-reducing bacteria, which have a high minimum growth temperature making it unlikely that they grow in situ. These Desulfotomaculum spp. are thought to be from hot environments and are distributed by ocean currents. Their cells and spores upper temperature limit for survival is unknown, as is whether they can survive repeated high-temperature exposure that might occur in hydrothermal systems. This was investigated by incubating estuarine sediments significantly above (40–80 °C) maximum in situ temperatures (∼23 °C), and with and without prior triple autoclaving. Sulphate reduction occurred at 40–60 °C and at 60 °C was unaffected by autoclaving. Desulfotomaculum sp. C1A60 was isolated and was most closely related to the thermophilic D. kuznetsoviiT (∼96% 16S rRNA gene sequence identity). Cultures of Desulfotomaculum sp. C1A60, D. kuznetsoviiTand D. geothermicum B2T survived triple autoclaving while other related Desulfotomaculum spp. did not, although they did survive pasteurisation. Desulfotomaculum sp. C1A60 and D. kuznetsovii cultures also survived more extreme autoclaving (C1A60, 130 °C for 15 min; D. kuznetsovii, 135 °C for 15 min, maximum of 154 °C reached) and high-temperature conditions in an oil bath (C1A60, 130° for 30 min, D. kuznetsovii 140 °C for 15 min). Desulfotomaculum sp. C1A60 with either spores or predominantly vegetative cells demonstrated that surviving triple autoclaving was due to spores. Spores also had very high culturability compared with vegetative cells (∼30 × higher). Combined extreme temperature survival and high culturability of some thermophilic Desulfotomaculum spp. make them very effective colonisers of hot environments, which is consistent with their presence in subsurface geothermal waters and petroleum reservoirs.

Life cycle and spore resistance of spore-forming Bacillus atrophaeus

Bacillus endospores have a wide variety of important medical and industrial applications. This is an overview of the fundamental aspects of the life cycle, spore structure and factors that influence the spore resistance of spore-forming Bacillus. Bacillus atrophaeus was used as reference microorganism for this review because their spores are widely used to study spore resistance and morphology. Understanding the mechanisms involved in the cell cycle and spore survival is important for developing strategies for spore killing; producing highly resistant spores for biodefense, food and pharmaceutical applications; and developing new bioactive molecules and methods for spore surface display.

Two distinct groups within the Bacillus subtilis group display significantly different spore heat resistance properties

The survival of bacterial spores after heat treatment and the subsequent germination and outgrowth in a food product can lead to spoilage of the food product and economical losses. Prediction of time-temperature conditions that lead to sufficient inactivation requires access to detailed spore thermal inactivation kinetics of relevant model strains. In this study, the thermal inactivation kinetics of spores of fourteen strains belonging to the Bacillus subtilis group were determined in detail, using both batch heating in capillary tubes and continuous flow heating in a micro heater. The inactivation data were fitted using a log linear model. Based on the spore heat resistance data, two distinct groups (p < 0.001) within the B. subtilis group could be identified. One group of strains had spores with an average D120 °C of 0.33 s, while the spores of the other group displayed significantly higher heat resistances, with an average D120 °C of 45.7 s. When comparing spore inactivation data obtained using batch- and continuous flow heating, the z-values were significantly different, hence extrapolation from one system to the other was not justified. This study clearly shows that heat resistances of spores from different strains in the B. subtilis group can vary greatly. Strains can be separated into two groups, to which different spore heat inactivation kinetics apply.

The combined effect of pasteurization intensity, water activity, pH and incubation temperature on the survival and outgrowth of spores of Bacillus cereus and Bacillus pumilus in artificial media and food products

The objective of the study was to evaluate the combined effects of pasteurization intensity (no heat treatment and 10min at 70, 80 and 90°C), water activity (aw) (0.960–0.990), pH (5.5–7.0) and storage temperature (7 and 10°C) on the survival and outgrowth of psychrotolerant spores of Bacillus cereus FF119b and Bacillus pumilus FF128a. The experiments were performed in both artificial media and a validation was performed on real food products (cream, béchamel sauce and mixed vegetable soup). It was determined that in general, heat treatments of 10min at 70°C or 80°C activated the spores of both B. cereus FF119b and B. pumilus FF128a, resulting in faster outgrowth compared to native (non-heat treated) spores. A pasteurization treatment of 10min at 90°C generally resulted in the longest lag periods before outgrowth of both isolates. Some of the spores were inactivated by this heat treatment, with more inactivation being observed the lower the pH value of the heating medium. Despite this, it was also observed that under some conditions the remaining (surviving) spores were actually activated as their outgrowth took place after a shorter period of time compared to native non-heated spores. While the response of B. cereus FF119b to the pasteurization intensity in cream and béchamel sauce was similar to the trends observed in the artificial media at 10°C, in difference, outgrowth was only observed at 7°C in both products when the spores had been heated for 10min at 80°C. Moreover, no inactivation was observed in cream or béchamel sauce when the spores were heated for 10min at 90°C in these two products. This was attributed to the protective effect of fat in the cream and the ingredients in the béchamel sauce. The study provides some insight into the potential microbial (stability and safety) consequences of the current trend towards milder heat treatments which is being pursued in the food industry.

Optimization of the spray drying of a Paenibacillus polymyxa-based biopesticide on pilot plant and production scales

Spore survival and moisture content are two important properties of biopesticides, and both are related to field biocontrol efficacy and storage shelf life. In this study, Paenibacillus polymyxa (HY96-2) was spray-dried on both pilot plant and production scales, and the effects of inlet and outlet temperatures on spore survival and moisture content were investigated. The results showed that inlet temperatures ranging from 170 to 230 °C (at an outlet temperature of 80 °C) had no obvious effect on the two properties during pilot scale processing, although an inlet temperature of 230 °C resulted in higher feed speed. When the outlet temperature on the pilot scale was reduced from 100 to 80 °C, no obvious variations in spore survival and moisture content were found, while a further reduction from 80 to 65 °C resulted in a decline in spore survival from 81.0 to 67.0% and an increase in moisture content from 2.3 to 31.7%. These results indicate that both outlet temperature and moisture content have an effect on spore survival. Optimum inlet and outlet temperatures for P. polymyxa processing were 230 °C and 85–90 °C on a production scale. Under these conditions, spore survival and moisture content were 83.5–86.6% and 2.73––4.12%, respectively.