High pressure homogenization inactivation of Escherichia coli and Staphylococcus aureus in phosphate buffered saline,milk and apple juice

High pressure homogenization (HPH) offers new opportunities for food pasteurization/sterilization. Escherichia coli and Staphylococcus aureus suspended in phosphate buffered saline (PBS) buffer, milk and apple juice at initial concentration of ~10⁶ log₁₀ CFU per ml were subjected to HPH treatments up to 200 MPa with inlet temperatures at 4–40°C. After HPH at 200 MPa with the inlet temperature at 40°C, the count of E. coli suspended in PBS, milk and apple juice reduced by 3·42, 3·67 and 3·19 log₁₀ CFU per ml respectively while the count of S. aureus decreased by 2·21, 1·02 and 2·33 log₁₀ CFU per ml respectively suggesting that S. aureus was more resistant. The inactivation data were well fitted by the polynomial equation. Milk could provide a protective effect for S. aureus against HPH. After HPH at 200 MPa with the inlet temperature at 20°C, the cell structure of E. coli was destroyed, while no obvious damages were found for S. aureus.     

Pressure induces interdigitation differently in DPPC and DPPG

The phase behaviours of chain-perdeuterated dipalmitoylphosphatidylcholine (DPPC-d ₆₂) and chain-perdeuterated dipalmitoylphosphatidylglycerol (DPPG-d ₆₂) bilayers were compared using ²H nuclear magnetic resonance spectroscopy and quadrupole echo decay measurements over pressures ranging from ambient to 196 MPa and temperatures ranging from 60 to −25°C. At ambient pressure, the phase behaviours of DPPC-d ₆₂ and DPPG-d ₆₂ were nearly identical. At 196 MPa, their behaviours were also very similar and both lipids appeared to pass from an interdigitated gel phase at high temperature, through a non-interdigitated gel phase at intermediate temperature, to a chain-immobilized ordered phase at low temperature. At 85 MPa, the behaviour of DPPC-d ₆₂ was similar to its ambient pressure behaviour with no evidence of interdigitation. For DPPG-d ₆₂, however, the behaviour at 85 MPa was similar to its higher pressure behaviour and spectra characteristic of an interdigitated gel phase were observed. Pressure-temperature phase diagrams for both lipids were compared. While the minimum pressure for DPPC-d ₆₂ interdigitation is about 150 MPa, DPPG-d ₆₂ was observed to interdigitate at pressures as low as 60 MPa. Given the similarity of their phase behaviours at both higher and lower pressures, this difference reflects the extent to which bilayer phase behaviour depends on the balance between interactions in the headgroup and hydrocarbon regions of the bilayer.     

Stomatal response to vapour pressure deficit and the effect of plant water stress

Abstract The dynamic response of stomata to changes in atmospheric humidity was investigated in Fragaria × ananassa Duch., Picea engelmannii Parry, and Pseudotsuga menziesii (Mirb.) Franco; and the effect of water stress on this response was determined in Pseudotsuga menziesii. The plants were rotated through three regimes of ambient temperature and vapour pressure deficit: 35°C–3. 5kPa, 35°C–0. 5 kPa, and 20°C–1. 5kPa. Branch and leaflet conductance were measured with a steady-state porometer, first at ambient vapour pressure deficit and then at one of four treatment conditions achieved by increasing or decreasing vapour pressure within the porometer cuvette. All three species showed similar stomatal response: enhanced conductance at low vapour pressure deficit and depressed conductance at high vapour pressure deficit. Engelmann spruce was more sensitive than Douglas fir and strawberry. Plant water status significantly altered stomatal response to vapour pressure deficit. The relationship of conductance of xylem water potential was linear under ambient conditions but became curvilinear when conductance was measured above and below ambient vapour pressure deficit. Between ?0. 5 MPa and ?2. 0 MPa xylem water potential, the stomata were sensitive to vapour pressure deficit, but below ? 2. 0 MPa, the sensitivity decreased.     

Thermoregulation in the primitively eusocial paper wasp, Polistes dominulus

Regulation of wing muscle temperature is important for sustaining flight in many insects, and has been well studied in honeybees. It has been much less well studied in wasps and has never been demonstrated in Polistes paper wasps. We measured thorax, head, and abdomen temperatures of inactive Polistes dominulus workers as they warmed after transfer from 8 to ~25°C ambient temperature, after removal from hibernacula, and after periods of flight in a variable temperature room. Thorax temperature (T _th) of non-flying live wasps increased more rapidly than that of dead wasps, and T _th of some live wasps reached more than 2°C above ambient temperature (T _a), indicating endothermy. Wasps removed from hibernacula had body region temperatures significantly above ambient. The T _th of flying wasps was 2.5°C above ambient at T _a = 21°C, and at or even below ambient at T _a = 40°C. At 40°C head and abdomen temperatures were both more than 2°C below T _a, indicating evaporative cooling. We conclude that P. dominulus individuals demonstrate clear, albeit limited, thermoregulatory capacity.     

Temperature response of carbon isotope discrimination and mesophyll conductance in tobacco

The partial pressure of CO₂ at the sites of carboxylation within chloroplasts depends on the conductance to CO₂ diffusion from intercellular airspace to the sites of carboxylation, termed mesophyll conductance (g_m). We investigated the temperature response of g_m in tobacco (Nicotiana tabacum) by combining gas exchange in high light, ambient CO₂ in either 2 or 21% O₂ with carbon isotope measurements using tuneable diode laser spectroscopy. The g_m increased linearly with temperature in 2 or 21% O₂. In 21% O₂, isotope discrimination associated with g_m decreased from 5.0 ± 0.2 to 1.8 ± 0.2‰ as temperature increased from 15 to 40 °C, but the photorespiratory contribution to the isotopic signal is significant. While the fractionation factor for photorespiration (f = 16.2 ± 0.7‰) was independent of temperature between 20 and 35 °C, discrimination associated with photorespiration increased from 1.1 ± 0.01 to 2.7 ± 0.02‰ from 15 to 40 °C. Other mitochondrial respiration contributed around 0.2 ± 0.03‰. The drawdown in CO₂ partial pressure from ambient air to intercellular airspaces was nearly independent of leaf temperature. By contrast, the increase in g_m with increasing leaf temperature resulted in the drawdown in CO₂ partial pressure between intercellular airspaces and the sites of carboxylation decreasing substantially at high temperature.     

Microorganism inactivation using high-pressure generation in sealed vessels under sub-zero temperature

In order to test the possibility of utilizing high pressure in bioscience and biotechnology, a simple method for high-pressure generation and its use for microbial inactivation have been studied. When a pressure vessel was filled with water, sealed tightly and cooled to sub-zero temperatures, high pressure was generated in the vessel. The pressure generation was 60 MPa at −5 °C, 103 MPa at −10 °C, and 140 MPa at −15 °C, −20 °C, and −22 °C. The high pressure generated inactivated microorganisms effectively: yeasts (Saccharomyces cerevisiae and Zygosaccharomyces rouxii), bacteria (Lactobacillus brevis and Eschericia coli), and fungi (Aspergillus niger and Aspergillus oryzae) were completely inactivated when stored in sealed vessels −20 °C for 24 h. However, Staphylococcus aureus was only partly inactivated under the same conditions. This method opens up a new application of high pressure for storing, transporting, and sterilizing of foods and biological materials. Received: 28 July 1997 / Received last revision: 12 June 1998 / Accepted: 19 June 1998     

Temperature regulation in the echidna (Tachyglossus aculeatus)

The echidna (Tachyglossus aculeatus) maintained a body temperature of 30.7°C ± 1.03 s.d. (N = 23) at ambient temperatures (T_A) between 0 and 25°C. It may, however, also become hypothermic at low T_A. At T_A = 30°C or above the echidna became hyperthermic. The thermoneutral range was about 20–30°C. At low T_A the metabolic rate might be increased several fold. The thermal conductance was at a minimum at T_A = 20°C, and was not further reduced at lower T_A. At higher T_A the thermal conductance increased up to five-fold. The evaporation showed little change with increasing T_A. At the highest T_A we used (33°C) the evaporation on the average accounted for the dissipation of only about one-third of the metabolic heat produced. These findings suggest that the echidna, although it can maintain its body temperature at low ambient temperature, cannot rely upon evaporation as the major avenue for heat loss at high ambient temperature.     

Kinetics of lipase catalyzed isoamyl acetate synthesis at high hydrostatic pressure in hexane

Lipase-catalyzed synthesis of isoamyl acetate in hexane at 10–250 MPa at 80°C and 1–100 MPa at 40°C resulted in activation volumes of −12.9 ± 1.7 and −21.6 ± 2.9 cm³ mol⁻¹, respectively. Increasing pressure from 10 to 200 MPa resulted in approximately 10-fold increase in V _max at both 40 and 80°C. Pressure increased the K _m from 2.4 ± 0.004 to 38 ± 0.78 mM at 40°C. In contrast, at 80°C the pressure did not affect the K _m.     

Effects of microwave exposure and temperature on survival of mice infected with Streptococcus pneumoniae

Female CD-1 mice were injected with an LD₅₀ dose of Streptococcus pneumoniae and then exposed to 2.45 GHz (CW) microwave radiation at an incident power density of 10 mW/cm² (SAR = 6.8 W/kg), 4 h/d for 5 d at ambient temperatures of 19 °C, 22 °C, 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C. Four groups of 25 animals were exposed at each temperature with an equal number of animals concurrently sham-exposed. Survival was observed for a 10-d period after infection. Survival of the sham-exposed animals increased as ambient temperature increased from 19 °C–34 °C. At ambient temperatures at or above 37 °C the heat induced in the body exceeded the thermoregulatory capacity of the animals and deaths from hyperthermia occurred. Survival of the microwave-exposed animals was significantly greater than the shams (～20%) at each ambient temperature below 34 °C. Based on an analysis of the data it appears that the hyperthermia induced by microwave exposure may be more effective in increasing survival in infected mice than hyperthermia produced by conventional methods (ie, high ambient temperature). Microwave radiation may be beneficial to infected animals at low and moderate ambient temperatures, but it is detrimental when combined with high ambient temperatures.     

Determining the disinfection of textiles in compressed carbon dioxide using various indicator microbes

Aims: This paper presents a research on the disinfection efficiency of inoculated textile swatches by compressed carbon dioxide, an environmental friendly way to disinfect textiles as opposed to the conventional laundering procedures using water. The disinfection efficiency was determined by using the following microbes inoculated on cotton test fabrics: Enterococcus faecium, Enterobacter aerogenes and Candida albicans. Methods and Results: The experiments were performed using the high pressure extraction device with a maximum pressure of 50 MPa and a small extraction vessel of 500 ml. Pure CO₂ and CO₂ with added disinfection agent or commercial detergent were used. The chosen disinfecting agent was hydrogen peroxide, a widespread disinfecting chemical. It was found that treatment with CO₂ for 25 min at 5 MPa and 40°C (313K) and the addition of 4 ml of specific detergent per litre of CO₂ assures at least a five log step reduction of Enterobacter aerogenes and C. albicans, whilst treatment at 50°C (323K) with CO₂ for 25 min at 5 MPa is sufficient for at least a five log step reduction for Enterococcus faecium. It was also found that a 15‐min CO₂ treatment at 7 MPa and 20°C (293K) was sufficient for the inactivation of the yeast C. albicans, whilst these conditions were not rigorous enough for the challenge bacteria. On the other hand, the labscale treatment with CO₂ for 25 min at pressure 4 and 6 MPa with the addition of detergent or hydrogen peroxide only yields a log step reduction of up to 4 log steps, thus proving the slightly disinfective properties of the CO₂ treatment with added agents, but not reaching efficient results as a 5 log step reduction was not reached. Conclusions: Addition of heat to the compressed CO₂ treatment of textiles inoculated with microorganisms proved more effective than the addition of detergent or disinfectant with compressed CO₂ treatment at temperature of 20°C. Significance and Impact of the Study: CO₂ treatment of textiles is a promising ecological alternative dry‐cleaning method for the disinfection of medical textiles.     

Optimization of Culture Medium for Sporulation and Biomass Production of a Nematophagous Fungus: Consideration of Nutritional and Environmental Conditions

This study reports the effects of various nutritional and environmental factors on sporulation and biomass of Paecilomyces lilacinus IPC‐P. These factors included carbon and nitrogen sources, carbon‐to‐nitrogen ratios, mineral elements and vitamins together with water potentials, temperatures, dark/light cycles and pH. On the basis of these results, together with a ‘two‐step’ cultivation and orthogonal method, the culture conditions for sporulation of this fungus were optimized. The spore suspension was inoculated on a basal medium (sucrose 19.00 g/l, soy peptone 4.06 g/l, K₂HPO₄ 1.00 g/l, KCl 0.50 g/l, MgSO₄ 0.50 g/l, FeSO₄ 0.01 g/l, agar 13.00 g/l) for 4 days, before being transferred to a sporulation medium (dextrin 2.27 g/l, urea 2.13 g/l, CaCl₂ 3.00 g/l, ZnSO₄·7H₂O 0.01 g/l, agar 13.00 g/l) for a further 4 days under the following environmental conditions: ?3.9 MPa/pH 7/light 24 h/temperature 29°C; these conditions were altered to ?0.3 MPa/pH 6/light 24 h/temperature 23°C in order to obtain better biomass yields. The data presented provide information on the nutrient and environmental requirements of this fungus, which will be essential for its commercial production.     

Mycelial growth of the snow mold fungus, Sclerotinia borealis, improved at low water potentials: an adaption to frozen environment

The snow mold fungus, Sclerotinia borealis, shows optimal growth at 4°C on potato dextrose agar (PDA) and can grow even at subzero temperature. Its mycelial growth was improved on frozen PDA at −1°C and on PDA containing potassium chloride (KCl) (water potential, −4.27 to −0.85 MPa) or d(−) sorbitol (−3.48 to −0.92 MPa). Its optimal growth temperature shifted from 4 to 10°C on PDA amended with KCl or sorbitol, indicating that inherent optimal growth occurs at high temperatures. These results suggest that S. borealis uses concentrated nutrients in the frozen environment and that such physiologic characteristics are critical for the fungus to prevail at subzero temperatures.     

Thermoregulatory responses to variations of photoperiod and ambient temperature in the male lesser mouse lemur: a primitive or an advanced adaptive character?

The lesser mouse lemur, a small Malagasy primate, is exposed to strong seasonal variations in ambient temperature and food availability in its natural habitat. To face these environmental constraints, this nocturnal primate exhibits biological seasonal rhythms that are photoperiodically driven. To determine the role of daylength on thermoregulatory responses to changes in ambient temperature, evaporative water loss (EWL), body temperature (T _b) and oxygen consumption, measured as resting metabolic rate (RMR), were measured in response to ambient temperatures ranging from 5 °C to 35 °C, in eight males exposed to either short (10L:14D) or long (14L:10D) daylengths in controlled captive conditions. In both photoperiods, EWL, T _b and RMR were significantly modified by ambient temperatures. Exposure to ambient temperatures below 25 °C was associated with a decrease in T _b and an increase in RMR, whereas EWL remained constant. Heat exposure caused an increase in T _b and heat loss through evaporative pathways. Thermoregulatory responses to changes in ambient temperature significantly differed according to daylength. Daily variations in T _b and EWL were characterized by high values during the night. During the diurnal rest, lower values were found and a phase of heterothermia occurred in the early morning followed by a spontaneous rewarming. The amplitude of T _b decrease with or without the occurrence of torpor (T _b < 33 °C) was dependent on both ambient temperature and photoperiod. This would support the hypothesis of advanced thermoregulatory processes in mouse lemurs in response to selective environmental pressure, the major external cue being photoperiodic variations. Accepted: 4 August 1998     

Effects of elevated pCO2 on the metabolism of a temperate rhodolith Lithothamnion corallioides grown under different temperatures

Coralline algae are considered among the most sensitive species to near future ocean acidification. We tested the effects of elevated pCO₂ on the metabolism of the free‐living coralline alga Lithothamnion corallioides (“maerl”) and the interactions with changes in temperature. Specimens were collected in North Brittany (France) and grown for 3 months at pCO₂ of 380 (ambient pCO₂), 550, 750, and 1000 μatm (elevated pCO₂) and at successive temperatures of 10°C (ambient temperature in winter), 16°C (ambient temperature in summer), and 19°C (ambient temperature in summer +3°C). At each temperature, gross primary production, respiration (oxygen flux), and calcification (alkalinity flux) rates were assessed in the light and dark. Pigments were determined by HPLC. Chl a, carotene, and zeaxanthin were the three major pigments found in L. corallioides thalli. Elevated pCO₂ did not affect pigment content while temperature slightly decreased zeaxanthin and carotene content at 10°C. Gross production was not affected by temperature but was significantly affected by pCO₂ with an increase between 380 and 550 μatm. Light, dark, and diel (24 h) calcification rates strongly decreased with increasing pCO₂ regardless of the temperature. Although elevated pCO₂ only slightly affected gross production in L. corallioides, diel net calcification was reduced by up to 80% under the 1,000 μatm treatment. Our findings suggested that near future levels of CO₂ will have profound consequences for carbon and carbonate budgets in rhodolith beds and for the sustainability of these habitats.     

Stability and activity of Dictyoglomus thermophilum GH11 xylanase and its disulphide mutant at high pressure and temperature

The functional properties of extremophilic Dictyoglomus thermophilum xylanase (XYNB) and the N-terminal disulphide-bridge mutant (XYNB-DS) were studied at high pressure and temperature. The enzymes were quite stable even at the pressure of 500 MPa at 80 °C. The half-life of inactivation in these conditions was over 30 h. The inactivation at 80 °C in atmospheric pressure was only 3-times slower. The increase of pressure up to 500 MPa at 80 °C decreased only slightly the enzyme's stability, whereas in 500 MPa the increase of temperature from 22 to 80 °C decreased significantly more the enzyme's stability. While the high temperature (80–100 °C) decreased the enzyme reaction with short xylooligosaccharides (xylotetraose and xylotriose), the high pressure (100–300 MPa) had an opposite effect. The temperature of 100 °C strongly increased the K_m but did not affect the k_cat to the same extent, thus indicating that the interaction of the substrate with the active site suffers before the catalytic reaction begins to decrease as the temperature rises. Circular dichroism spectroscopy showed the high structural stability of XYNB and XYNB-DS at 93 °C.     

Pressure and temperature effects on growth and viability of the hyperthermophilic archaeon Thermococcus peptonophilus

We studied the effects of high temperatures and elevated hydrostatic pressures on the physiological behavior and viability of the extremely thermophilic deep-sea archaeon Thermococcus peptonophilus. Maximal growth rates were observed at 30 and 45 MPa although no significant increases in cell yields were detected. Growth at 60 MPa was slower. The optimal growth temperature shifted from 85° C at 30 MPa to 90–95° C at 45 MPa. Cell viability during the stationary phase was also enhanced under high pressure. A trend towards barophily at pressures greater than those encountered in situ at the sea floor was demonstrated at increasing growth temperatures. The viability of cells during starvation, at high temperature (90, 95° C), and at low temperature (10° C) was enhanced at 30 and 45 MPa as compared to atmospheric pressure. These results show that the extremely thermophilic archaeon T. peptonophilus is a barophile. Received: 21 October 1996 / Accepted: 5 February 1997     

Increased temperature mitigates the effects of ocean acidification on the calcification of juvenile Pocillopora damicornis,but at a cost

This study tested the interactive effects of increased seawater temperature and CO₂ partial pressure (pCO₂) on the photochemistry, bleaching, and early growth of the reef coral Pocillopora damicornis. New recruits were maintained at ambient or high temperature (29 or 30.8 °C) and pCO₂ (~ 500 and ~ 1100 μatm) in a full-factorial experiment for 3 weeks. Neither a sharp decline in photochemical efficiency (Fv/Fm) nor evident bleaching was observed at high temperature and/or high pCO₂. Furthermore, elevated temperature greatly promoted lateral growth and calcification, while polyp budding exhibited temperature-dependent responses to pCO₂. High pCO₂ depressed calcification by 28% at ambient temperature, but did not impact calcification at 30.8 °C. Interestingly, elevated temperature in concert with high pCO₂ significantly retarded the budding process. These results suggest that increased temperature can mitigate the adverse effects of acidification on the calcification of juvenile P. damicornis, but at a substantial cost to asexual budding.

     

The effect of heat waves,elevated [CO2] and low soil water availability on northern red oak (Quercus rubra L.) seedlings

The frequency and intensity of heat waves are predicted to increase. This study investigates whether heat waves would have the same impact as a constant increase in temperature with the same heat sum, and whether there would be any interactive effects of elevated [CO₂] and soil moisture content. We grew Quercus rubra seedlings in treatment chambers maintained at either ambient or elevated [CO₂] (380 or 700 μmol CO₂ mol^?1) with temperature treatments of ambient, ambient +3 °C, moderate heat wave (+6 °C every other week) or severe heat wave (+12 °C every fourth week) temperatures. Averaged over a 4‐week period, and the entire growing season, the three elevated temperature treatments had the same average temperature and heat sum. Half the seedlings were watered to a soil water content near field capacity, half to about 50% of this value. Foliar gas exchange measurements were performed morning and afternoon (9:00 and 15:00 hours) before, during and after an applied heat wave in August 2010. Biomass accumulation was measured after five heat wave cycles. Under ambient [CO₂] and well‐watered conditions, biomass accumulation was highest in the +3 °C treatment, intermediate in the +6 °C heat wave and lowest in the +12 °C heat wave treatment. This response was mitigated by elevated [CO₂]. Low soil moisture significantly decreased net photosynthesis (A_net) and biomass in all [CO₂] and temperature treatments. The +12 °C heat wave reduced afternoon A_net by 23% in ambient [CO₂]. Although this reduction was relatively greater under elevated [CO₂], A_net values during this heat wave were still 34% higher than under ambient [CO₂]. We concluded that heat waves affected biomass growth differently than the same amount of heat applied uniformly over the growing season, and that the plant response to heat waves also depends on [CO₂] and soil moisture conditions.     

The role of the miR399-<Emphasis Type="Italic">PHO2</Emphasis> module in the regulation of flowering time in response to different ambient temperatures in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

A moderate change in ambient temperature significantly affects plant physiology including flowering time. MiR399 and its target gene PHOSPHATE 2 (PHO2) are known to play a role in the maintenance of phosphate homeostasis. However, the regulation of flowering time by the miR399-PHO2 module has not been investigated. As we have previously identified miR399 as an ambient temperature-responsive miRNA, we further investigated whether a change in expression of the miR399-PHO2 module affects flowering time in response to ambient temperature changes. Here, we showed that miR399b-overexpressing plants and a loss-of-function allele of PHO2 (pho2) exhibited an early flowering phenotype only at normal temperature (23°C). Interestingly, their flowering time at lower temperature (16°C) was similar to that of wild-type plants, suggesting that alteration in flowering time by miR399 and its target PHO2 was seen only at normal temperature (23°C). Flowering time ratio (16°C/23°C) revealed that miR399b-overexpressing plants and pho2 mutants showed increased sensitivity to ambient temperature changes. Expression analysis indicated that expression of TWIN SISTER OF FT (TSF) was increased in miR399b-overexpressing plants and pho2 mutants at 23°C, suggesting that their early flowering phenotype is associated with TSF upregulation. Taken together, our results suggest that miR399, an ambient temperature-responsive miRNA, plays a role in ambient temperature-responsive flowering in Arabidopsis.