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PubMed2005

Identification using versatile sampling and analytical methods of volatile compounds from Streptomyces albidoflavus grown on four humid building materials and one synthetic medium.

UNLABELLED: The Streptomyces spp. form a common group of bacteria found in the indoor air of water-damaged buildings. They are known for their capability to produce compounds, like geosmin, with low odor thresholds. In this study, two strains of Streptomyces albidoflavus were cultivated on pinewood, gypsum board, particle-board, sand and tryptone glucose extract agar (TGEA). Air samples from the cultures were collected on six different adsorbents and chemosorbents to sample a wide range of compounds such as VOCs, aldehydes, amines and lightweight organic acids. The samples were analyzed with gas chromatography, high-pressure liquid chromatography and ion chromatography. Mass spectrometry was used for identification of the compounds. Metabolites were found and identified in air samples from cultures on all materials except sand. Alcohols and ketones were the dominating compound groups produced by cultures grown on pinewood and gypsum board. Few metabolites were produced on particle-board. The culture growing on TGEA produced mainly sulfur compounds and sesquiterpenes. Ammonia, methylamine, diethylamine, ethylamine and one unidentifiable amine were also found from cultivation on TGEA. The growth medium was of crucial importance to the production of potentially irritating metabolites. PRACTICAL IMPLICATIONS: Microbial growth and the production of volatile metabolites is one possible explanation for building-related health problems. Streptomyces spp. are frequently found in water-damaged buildings. This study shows that Streptomyces spp. are able to produce not only odorous compounds like geosmin, but also potentially irritating compounds. This finding should be of interest in indoor air investigations.

Agar↗
PubMed1990

Effect of humidity on calcium sulphate hemihydrate.

The conversion of calcium sulphate hemihydrate powders to dihydrate by reaction with atmospheric water vapour has been re-examined gravimetrically. Storage is usually said to be safe at less than '70 per cent RH', but this is shown to be an inadequate criterion (water vapour pressure being more useful in the context) and based on an inappropriate experiment. At 23 degrees C, greater than about 2.3 kPa water vapour pressure caused rapid reaction, and this may be taken as a more reliable critical value.

Calcium Sulfate↗
PubMed1996

Dietary fat affects heat production and other variables of equine performance, under hot and humid conditions.

Does dietary fat supplementation during conditioning improve athletic performance, especially in the heat? Fat adaptation has been used to increase energy density, decrease bowel bulk and faecal output and reduce health risks associated with hydrolysable carbohydrate overload. It may also reduce spontaneous activity and reactivity (excitability), increase fatty acid oxidation, reduce CO2 production and associated acidosis, enhance metabolic regulation of glycolysis, improve both aerobic and anaerobic performance and substantially reduce heat production. A thermochemical analysis of ATP generation showed the least heat release during the direct oxidation of long chain fatty acids, which have a 3% advantage over glucose and 20 to 30% over short chain fatty acids and amino acids. Indirect oxidation via storage as triglyceride increased heat loss during ATP generation by 3% for stearic acid, 65% for glucose and 174% for acetic acid. Meal feeding and nutrient storage, therefore, accentuates the advantage of dietary fat. A calorimetric model was based on initial estimates of net energy for competitive work (10.76 MJ for the Endurance Test of an Olympic level 3-day-event), other work (14.4 MJ/day) and maintenance (36 MJ), then applied estimates of efficiencies to derive associated heat productions for the utilisation of 3 diets, Diet A: hay (100), Diet B: hay and oats (50:50) and Diet C: hay, oats and vegetable oil (45:45:10), the difference between the last 2 diets representing fat adaptation. During a 90.5 min speed and stamina test, heat production was estimated as 37, 35.4 and 34.6 MJ for the 3 diets, respectively, an advantage 0.8 MJ less heat load for the fat adapted horse, which would reduce water needed for evaporation by 0.33 kg and reduce body temperature increase by about 0.07 degree C. Total estimated daily heat production was 105, 93 and 88 MJ for the 3 diets, respectively, suggesting a 5 MJ advantage for the fat adapted horse (Diet C vs. Diet B). Estimated intake energy was 348, 269 and 239 MJ for the 3 diets, respectively, and corresponding daily intakes as fed were 22.2, 16.6 and 12.9 kg, an advantage of 3.7 kg for the fat adapted horse. Water requirement was estimated to decrease by about 6 kg/day in the fat adapted horse: 4 kg less faecal water output and 2 kg less water for evaporation. This model indicated that the fat supplemented diet reduced daily heat load by 5%, feed intake by 22%, faecal output (and bowel ballast) by 31% and water requirement by 12%. The advantage of fat supplementation over hay and oats was in general about half that gained by hay and oats over hay alone.

Adenosine Triphosphate↗