Removal of cholesterol by lactobacilli via incorporation and conversion to coprostanol

Fifteen strains of Lactobacillus and Bifidobacterium were screened based on their ability to adhere to hydrocarbons via the determination of cellular hydrophobicity. Lactobacillus acidophilus ATCC 314, L. acidophilus FTCC 0291, Lactobacillus bulgaricus FTCC 0411, L. bulgaricus FTDC 1311, and L. casei ATCC 393 showed greater hydrophobicity and, thus, were selected for examination of cholesterol-removal properties. All selected strains showed changes in cellular fatty acid compositions, especially total fatty acids and saturated and unsaturated fatty acids in the presence of cholesterol compared with those grown in the absence of cholesterol. In addition, we found that cells grown in media containing cholesterol were more resistant to sonication and enzymatic lysis compared with those grown without cholesterol. We further evaluated the location of the incorporated cholesterol via the insertion of fluorescence probes into the cellular membrane. In general, enrichment of cholesterol was found in the regions of the phospholipid tails, upper phospholipids, and polar heads of the cellular membrane phospholipid bilayer. Our results also showed that lactobacilli were able to reduce cholesterol via conversion of cholesterol to coprostanol, aided by the ability of strains to produce cholesterol reductase. Our results provided experimental evidence to strengthen the hypothesis that probiotics could remove cholesterol via the incorporation of cholesterol into the cellular membrane and conversion of cholesterol to coprostanol. The strains studied may be potential health adjunct cultures in fermented dairy products with possible in vivo hypocholesterolemic effects.     

Sedimentary coprostanol and hydrocarbon distribution adjacent to a sewage outfall

The concentrations of coprostanol and hydrocarbons were measured in the effluent from the Chesapeake-Elizabeth sewage treatment plant (STP) and surface sediments from the area surrounding the effluent discharge site. Most of the coprostanol (> 84%) and hydrocarbons (> 91%) were associated with particulates in the effluent. The area was found to be dynamic where changes in the percentage and distribution of fine grained sediments occur over periods of months and the movement of these sediments is an important determinant of the distribution of sewage derived contaminants. The Chesapeake-Elizabeth STP was found to be responsible for only 7% of the hydrocarbon contamination of the sediments in the study area. The sediment hydrocarbon distribution also indicates that the Bay Bridge tunnel may be a unique source of hydrocarbons to the lower Chesapeake Bay. This study shows the usefulness of coprostanol in providing a better understanding of the fate and importance of sewage derived contaminants in areas around sewage outfalls.     

Using faecal sterols from humans and animals to distinguish faecal pollution in receiving waters

The sterol content of faeces from humans and 14 species of animals common to rural or urban environments were examined. The major human faecal sterol was the 5β-stanol, coprostanol which constituted ≈ 60% of the total sterols found in human faeces. The sterol profiles of herbivores were dominated by C₂₉ sterols and 5β-stanols were generally in equal or greater abundance than 5-stanols. The principal faecal biomarker of herbivores was 24-ethylcoprostanol. The sterol content of bird faeces was extremely variable and largely dependent on the animals diet. Both 5β and 5 stanols were in very low abundance in birds and dogs faeces from this study presumably due to the absence or low activity of the necessary anaerobic biota required to reduce Δ⁵- or Δ^5,22-sterols to stanols. Cats and pigs were the only animals that had similar faecal sterol profiles to humans. However, the concentration of the principal human biomarker coprostanol was some 10 times more abundant on a dry weight basis in the faeces of humans than in those of cats and pigs. The source specificity of faecal sterol biomarkers is a combination of sterol intake, metabolic production of sterols and the biota resident within the animal's digestive tract. The “sterol fingerprints” of the faeces of humans and animals are sufficiently distinctive to be of diagnostic value in determining whether faecal pollution in water samples are of human or animal origin.     

Dispersal of Contaminants from Municipal Discharges as Evidenced from Sedimentary Records in a Great Lakes Coastal Wetland,Cootes Paradise,Ontario

Cootes Paradise is a coastal wetland, at the western end of Lake Ontario. The marsh, which is an important spawning ground for fish and a crucial habitat for other species, has been considerably degraded by excessive contaminant inputs from wastewater treatment plants (WTPs), marsh tributaries, and Combined Sewer Overflows (CSOs). These discharges are not only major sources of nutrients (e.g., phosphorus) to the marsh, but are also the main contributors of pharmaceuticals, hormones, and other wastewater contaminants. Studies have shown that many of these compounds are toxic and have estrogenic effects on organisms living in the vicinity of these sources. This study investigates dispersal of contaminants from nearby point sources, as determined from sediment contamination, both spatially and stratigraphically. This was accomplished by establishing the trends and utilizing the relationships between limiting nutrient phosphorus, estrogenic alkylphenols, and faecal sterols, specifically, coprostanol. High levels of phosphorus (1,655–1,987 mg TP kg⁻¹) and alkylphenolics (2.51–4.89 mg kg⁻¹) were measured in sediments near the discharge outlets. Statistical analysis revealed a close relationship between investigated pollutants and the molecular marker coprostanol, and provides evidence of significant sediment contamination near the discharge points, suggesting deposition of most contaminants within a short distance from the points of entry and limited dispersal of pollutants within the wetland. The stratigraphic distribution of pollutants, which reflects the historical trends, reveals major spikes in pollutant concentrations near point sources that could be attributed to episodic events of major significance and shows a long persistence of the investigated contaminants in sedimentary environments.     

水体受粪便污染的分子示踪物(粪醇)的研究

介绍了粪醇的形成、结构及性质,综述了粪醇的分析方法及其示踪作用,讨论了粪便细菌如大肠杆菌作为粪便污染指示物的限制条件,指出粪醇可作为粪便污染的一个度量指标,并为区分粪便污染源提供了一个新的工具．     

Concentrations of coprostanol that correspond to existing bacterial indicator guideline limits

Coprostanol is a faecal sterol that has been proposed as an alternative measure of faecal pollution. While the technique has been used successfully to trace sewage-derived organic matter in a range of environments, it has not been embraced for use as a water quality indicator. This is mostly because of a lack of epidemiological evidence relating coprostanol abundance to any health risk. However, there is a valuable reason why the concentration of coprostanol should be related as quantitatively as possible to the abundance of bacterial indicators currently used to measure faecal pollution. The measurement of coprostanol (and concurrently other faecal sterols) offers many diagnostic and quantitative advantages over traditional techniques for detecting human sewage pollution versus faecal contamination from animal sources. Knowing the amount of coprostanol expected given a certain amount of human sewage pollution would provide a measure against which water managers could quantitatively assess faecal pollution as a whole and relate that assessment to variables with which they are more familiar. This study determines the relationships between coprostanol concentrations and indicator bacterial counts and synthesises the results from several environments to propose coprostanol concentrations broadly equivalent to existing bacterial standards. Our data suggest that 60 and 400 ng L⁻¹ of coprostanol correspond to currently defined primary and secondary contact limits for bacteria measured as thermotolerant coliforms (commonly referred to as faecal coliforms) or enterococci.