A Review of Effects of Carbon Dioxide on Microbial Growth and Food Quality

References

In the preceding paper (Valley and McAlpine)1 it was shown that carbon dioxide exerts a very definite preserving action on serum alexin.2 It was further demonstrated that a displacement of atmospheric (molecular) oxygen by hydrogen, nitrogen and carbon monoxide exercised no greater preservative action than the mechanical removal of atmospheric air by evacuation, or by limiting the volume of enclosed air in an hermetically sealed tube. It is apparent, therefore, that aside from a mere mechanical displacement of molecular oxygen by carbon dioxide, this gas brought about other influences which favored alexin preservation. Hence the explanation of the phenomenon should be sought in the nature of carbon dioxide action on a serum complex. Displacement of oxygen may be more efficiently effected by carbon dioxide than by other gases, due to the chemical nature of the former.

Deaths from gaseous substances can occur from exposure to toxic gases or from accumulation of nontoxic gases that displace oxygen. We present a 38-year-old man with no known medical history, who was found deceased in a small bathroom with blankets and towels shoved under the door from the inside.At autopsy, the decedent was found to be in a moderate state of decomposition. There was mild pulmonary congestion, with no other significant findings. Standard postmortem toxicology on femoral blood was noncontributory.A search of the decedent's cell phone revealed statements and internet searches regarding carbon dioxide (CO 2 ) and asphyxia using dry ice. A journal entry also outlined a suicide plan using large amounts of dry ice, which was enacted by placing a laundry basket of dry ice into a bathtub containing water. Based on the investigation, the cause of death was determined to be asphyxia from displacement of oxygen with CO 2 .Dry ice sublimates into gaseous CO 2 , which quickly accumulates, with concentrations of 10% or more, rapidly becoming life-threatening. There are no pathognomonic autopsy findings seen in CO 2 -related asphyxia. In these circumstances, scene investigation is the most important factor in determining cause of death.

Between Scylla and Charybdis: energy, carbon dioxide, and indoor environmental quality

Organic acids play an important role in the acidification of our atmosphere. These weak acids can contribute up to 60 % of the free airborne acidity. By far the most abundant organic acids are the C1 and C2 monocarboxylic acids, formic acid (HCOOH) and acetic acid (CH3COOH), which show mixing ratios in the gas phase ranging up to 20 ppb over land1,2 and down to 0.2 ppb in the remote oceanic boundary layer or troposphere.3,4 These acids are partitioned between the gas phase and the particulate phase, where roughly one half to two thirds can be found in particulate matter (PM2.5).2 The most important removal mechanism is dry deposition, which accounts for more than 90 % of the total organic acid deposition budget. The remaining fraction is removed by rain as particulate-phase acids, whereas removal by chemical reactions is negligible.1,5 In addition to the two most important organic acids, C3–C10 aliphatic monocarboxylic acids1 and C2–C11 aliphatic dicarboxylic acids1,2,6–11 as well as aromatic carboxylic acids1 have also been observed in air. The water-soluble fraction of organic carbon can on average consist of 35 % mono- and dicarboxylic acids.12 While the C2-dicarboxylic acid, oxalic acid (COOH)2, is commonly observed in all field studies, the C1-dicarboxylic acid, carbonic acid (H2CO3), has barely received any attention, mainly because it is thought that it immediately decomposes to water and carbon dioxide. However, it has previously been shown that gaseous, water-free carbonic acid is surprisingly stable,13 that amorphous and crystalline solids of pure carbonic acid can be produced and stored without decomposition at temperatures up to 230 K even in the presence of water14 and that this solid can be sublimed at, for example, 220 K and recondensed in vacuo at surfaces of lower temperature.15

The conversion between carbonic acid and carbon dioxide plus water is of special significance in many biological and geochemical systems. In this work, we give a theoretical comparison study between H2CO3 and H2SO3 for the dissociation reaction in the environment of microsolvation with the size of the water cluster up to three water molecules,H2XO3 + (n‐1)H2O ⇌ XO2 +nH2O n = 1, 2, 3 X=C, SFrom the calculation of B3LYP/6‐31+G, we conclude that H2SO3 is more unstable than H2CO3 kinetically due to a smaller bond angle change of ∠OXO. It is also more unstable thermodynamically due to better solvation for the product XO2.

Chemical Controls on the Dissolution Kinetics of Calcite in Seawater

The knowledge requirements of the food microbiologist working with thermally processed products are very challenging; particularly in relation to minimally processed foods. In the past, the minimum criteria for sterilized canned foods was very well-defined, however, the diversity of food products, packages and related heat processes are now very difficult to summarize in terms of minimum requirements. The overall heating characteristics of these products can be complex, particularly for mixed particulate products or multicompartment packages. Similarly, the death kinetics of the contaminating micro-organisms can be markedly different dependent on the composition of the food product. These factors combined with the consumer demands for 'fresher' foods has resulted in product, process and package development and innovation progressing at a much faster rate than in the past. While food safety is the most important factor, there are also other issues such as shelf-life and visual quality that have strong market influences and must therefore also be considered by the microbiologist.

The apparent permeability coefficient for proton flux through phosphatidylcholine vesicles is dependent on the direction of flux

Microbially induced Ca-carbonate precipitation (MICP) in general, refers to a process in which the urease secreted by microbes hydrolyzes urea to ammonium and carbon dioxide. The main objectives of this study were to identify the environmental factors (e.g., microbial growth, cell/metabolite presences, and calcium sources) that control Ca-carbonate formation and to investigate the mineralogical characteristics of the Ca-carbonate precipitated using ureolytic microorganisms cultured in marine environments. The two types of carbonate-forming microorganisms (CFMs), mixed cultures hydrolyzing urea, were enriched from calcareous materials in marine environments. The experiments using a CFM, Sporosarcina pasteurii, was also used for comparison. All the microbes were cultured aerobically in D-1 growth media that included urea. To investigate the effect of microbial growth states on Ca-carbonate precipitation, Ca-acetate was injected into the media before (i.e., lag phase) and after (i.e., stationary phase) microbial growth, and into the soluble microbial products (SMP) solution, respectively. XRD, FT-IR, and SEM-EDS analyses were used for mineralogical characterization of the precipitated Ca-carbonates. Results indicated that the Ca-carbonates, vaterite and/or calcite, precipitated under all the experimental conditions. The fastest precipitation of Ca-carbonates occurred in the SMP solution and formed calcite (size = 5–15 μm). When the concentrations of added Ca-acetate were varied from 0 to 0.5 M, the highest amounts of calcite, 22.8 g/L, were produced when 0.3 M Ca-acetate was injected. Therefore, the environmental factors (e.g., microbial growth, cell/metabolite presences, and calcium sources) could have an effect the rate of formation of Ca-carbonate and the types of carbonate minerals formed. Moreover, the use of cell-free SMP solution is expected to be applicable to Ca-carbonate precipitation in an environment where microbial growth is unfavorable.

In the preceding communication evidence was brought forward in favour of the photosynthesis of carbohydrates when pure carbonic acid, adsorbed on a surface suspended in water, is exposed to ultra-violet light. Although possibly the results described may seem to mark a step forward towards the explanation of the phenomenon of natural photosynthesis of carbohydrates from carbonic dioxide and water, there still remains unexplained the greatest difficulty of all, namely, the utilisation by the living plant of visible light only. Furthermore, as we were the first to recognise at this stage, the evidence of the photosynthesis of carbohydrates given by the previous experiments is somewhat slender. In all the experiments described in the preceding paper carbonic acid adsorbed on a white surface was exposed to ultra-violet light, it being assumed that in the case of aluminium powder there is formed a layer of hydroxide which is effective. The possibility occurred to one of us (W. E. S.) that if a visibly coloured powder, capable of adsorbing carbonic acid, be employed, the photosynthesis may be brought about by visible light. Two powders which satisfy the conditions are the basic carbonates of nickel and cobalt in that they are visibly coloured and undoubtedly adsorb carbonic acid on their surface when suspended in water through which carbon dioxide is passed. Preliminary experiments were carried out in which suspensions of each of these powders in water were placed in vessels of ordinary German soda glass with walls from 1·5 to 2 mm. in thickness. Carbon dioxide was passed continuously through each vessel, and the results were illuminated by the light from an ordinary tungsten filament lamp. After filtration and evaporation the exposed solutions in each yielded a gummy residue which was undoubtedly organic in nature, since it readily charred with strong sulphuric acid. This experiment was repeated several times with the same results, and these convinced us that it is possible by the use of coloured powders to photosynthesise organic compounds from carbonic acid with the help of visible light.

Besides intrinsic and extrinsic factors such as antagonism for organic substrates or temperature, the storage atmosphere of meat has a high influence on the development of its initial microbiota. Specific modified atmospheres (MAs) selectively suppress growth of aerobic and anaerobic bacteria, thus reshaping the initial microbiota. As some microorganisms are more tolerant to MA, they overgrow competitors and produce metabolites that cause rejection of the product. In order to elucidate responses to different MA by means of metabolic adaptation and competition for organic substrates on meat, the typical representative meat spoilage bacteria Brochothrix (B.) thermosphacta TMW2.2101 and four lactic acid bacteria Carnobacterium (C.) divergens TMW2.1577, C. maltaromaticum TMW2.1581, Leuconostoc (L.) gelidum subsp. gelidum TMW2.1618 and L. gelidum subsp. gasicomitatum TMW2.1619 were chosen. Bacteria were grown in sterile glass bottles filled with a meat simulation medium, which was aerated constantly with either air, 100%_N2, 30%_CO2/70%_O2 or 30%_CO2/70%_N2. Growth of bacteria during incubation at 25°C and stirring at 120 rpm was monitored over 48 h and a label-free quantitative mass spectrometric approach was employed to determine changes within the bacterial proteomes in response to oxygen and carbon dioxide. Both Leuconostoc subsp. were intrinsically tolerant to MA, exhibiting no proteomic regulation of enzymes, whereas the other species provide a set of metabolic adaptation mechanism, enabling higher resistance to the detrimental effects of MA. Those mechanisms comprise: enhanced oxidative stress reduction, adjustment of the pyruvate metabolism and catabolic oxygen consumption in response to oxygen and intracellular pH homeostasis, maintenance of osmotic balance and alteration of the fatty acid composition in response to carbon dioxide. We further evaluated the potential of industrial used MA to inhibit specific bacterial spoilage. No bacterial inhibition is predicted for 30%_CO2/70%_O2 for the analyzed species, whereas 30%_CO2/70%_N2 predictively inhibits C. divergens TMW21577 and B. thermosphacta TMW2.2101. Furthermore, species-specific metabolic pathways enabling different and preferential carbon source utilization were identified, which enable non-competitive coexistence of respective bacteria on meat, resulting in synergistic spoilage. In conclusion, this study gives mechanistically explanations of their acknowledged status as typical spoilage organisms on MAP meats.

Exsheathed infective larvae of Haemonchus contortus developed to the fourth stage in a salt solution under carbon dioxide. The changes in morphology were similar to those seen in worms from sheep, but development was slower. Greatest numbers of fourth-stage larvae were obtained from solutions gassed with 40% carbon dioxide. Small numbers of fourth-stage worms were present after 48 hr, and as many as 90% were in the fourth stage after 72 hr. Once larvae had commenced to develop carbon dioxide could be withdrawn, and development proceeded readily under air. Serum labeled with a fluorochrome was not detected in the intestine of third-stage worms cultivated in vitro, but was present in fourth-stage worms. It is concluded that under these conditions third-stage larvae of H. contortus were unable to ingest the medium. Stoll (1940) and Sommerville (1964) have shown that exsheathed infective larvae, i.e., third-stage larvae, of Haemonchus contortus will develop to the fourth stage after incubation in salt solutions at 38 to 39 C. Stoll's experiments demonstrated that more fourthstage larvae developed when an aqueous extract of liver was added to the salt solution and when the supply of oxygen was restricted. Silverman (British Patent 894603) has shown that development of H. contortus to the fourth stage can take place in Earle's salt solution together with hydrolysates of liver and casein. Sommerville (1964) suggested that either dissolved gaseous carbon dioxide or carbonic acid, or both, provided a stimulus which induced development. He failed to demonstrate any effect from the addition of liver extract. This paper reports the results of further experiments on the development of the thirdstage larva to the fourth stage in vitro. MATERIALS AND METHODS Infective larvae of H. contortus were harvested from cultures of sheep feces 7 to 14 days old, and stored in tap water at 5 C for about 1 week before use. They were prepared for culture by passage through three layers of lens tissue in a sterile Baermann apparatus which contained 0.4% sterile sodium chloride at 38 C. Larvae were subsequently washed twice by suspension in 0.4% sterile sodium chloride and centrifuged at 350 g. They were exsheathed by rinsing for 10 min in 20 ml of 0.4% sterile sodium chloride to which had been added 1 ml of "Milton" (1% sodium hypochlorlite: Received for publication 20 April 1965. * Present address: Department of Zoology, University of Adelaide, Adelaide, South Australia. Milton Pharmaceuticals Ltd., London). They were then washed six times in sterile 0.4% sodium chloride and counted. These procedures were essentially those followed by Weinstein and Jones (1956). In some experiments, exsheathment was achieved by gassing with 100% carbon dioxide. The larvae were suspended for 21/ hr at 40 C in a sterile solution of sodium bicarbonate, the concentration of which was adjusted to give pH 6 when gassed with 100% carbon dioxide (Umbreit, Burris, and Stauffer, 1957). Larvae were incubated in screw-capped roller tubes which contained either 2 or 3 ml of the medium and 1,000 larvae, i.e., either 500 or approximately 330 larvae per ml of medium. The roller drum was kept in an incubator in the dark and rotated 12 times each hour. The temperature was 40 ? 0.5 C unless otherwise indicated. The temperature inside the tubes was checked periodically with thermocouples inserted in the tube and connected to an automatic recorder. The medium contained the following components in grams per liter: NaCl, 8.23; KCI, 0.42; CaC12, 0.33; MgS04-7H20, 0.34. Sodium bicarbonate was added to give the required pH with the particular gas mixture used, usually pH 6. The amount of bicarbonate required was calculated from data supplied by Umbreit, Burris, and Stauffer (1957). All components were sterilized by filtration before use, and the final medium contained 500 mg streptomycin and 500 units penicillin G (sodium salt) per ml. Commercially prepared gas mixtures were used. These contained either 5, 20, 40, 60, or 80% carbon dioxide, 10% oxygen, and the balance nitrogen. In some experiments, 100% carbon dioxide or 50% carbon dioxide in air was used. Each gas mixture was passed through sterile cotton wool, a d cultures were gassed for 2 min in a water bath at the same temperature as for subsequent incubation. Tubes were sealed with a screw top containing a silicone rubber lining. Unless otherwise stated, larvae were incubated under the gas mixtures for 72 hr. At the termination of each experiment, sterility tests were made

CO2 Capture via Crystalline Hydrogen-Bonded Bicarbonate Dimers

The effect of ratio of carbon dioxide and oxygen on the growth of 16 strains of food-borne pathogens and spoilage bacteria was investigated using the smear plate method. The results were as follows.1) Growth of facultative anaerobic bacteria (A. hydrophila, B. cereus, E. coli, E. cloacae, L. monocytogenes, S. liquefaciens, S. typhimurium, S. aureus) was not completely inhibited by carbon dioxide, oxygen and their mixtures. However, the growth rate of those bacteria was reduced in proportion to the increase in the ratio of carbon dioxide in the gas mixtures.2) Growth of microaerophilic bacteria (L. viridescens) was not affected by carbon dioxide, oxygen or their mixtures.3) Growth of the five species (A. calcoaceticus, F. lutescens, P. aeruginosa, P. fluorescens, P. fragi) of aerobic bacteria was not recognized in the presence of 100% carbon dioxide, while M. luteus grew to some extent under the same conditions. Growth of P. fragi was inhibited in the presence of 30% or more carbon dioxide. The growth of F. lutescens was observed only in the case of 10% carbon dioxide and 90% oxygen. The susceptibility of aerobic bacteria to carbon dioxide was higher than that of facultative anaerobic bacteria and microaerophilic bacteria.4) Growth of anaerobic bacteria (C. perfringens) was inhibited in the presence of oxygen regardless of its concentration.From these results, it is clear that carbon dioxide, oxygen and their gas mixtures can be used effectively to inhibit or delay bacterial growth.