D.M. Schaefer

Methane production from municipal refuse: A review of enhancement techniques and microbial dynamics

Methane is recovered from about 100 municipal solid waste landfills in the U.S. in saleable volumes, although yields are 1 to 50% of the methane potential of refuse based on biodegradability data. Studies on the microbiology of refuse decomposition and efforts to enhance refuse methanogenesis are reviewed here. Results of studies on the effects of leachate recycle and neutralization, a reduction in refuse particle size, the addition of anaerobic sewage sludge or old refuse as a seed, nutrient addition, calcium carbonate addition, and moisture on methane production are examined in consideration of new findings on landfill microbiology. A four‐phase description of refuse decomposition with leachate recycle, including an aerobic phase, an anaerobic acid phase, an accelerated methane production phase, and a decelerated methane production phase, is proposed. Mass balances and pumping tests may be used to estimate the methane potential of a sanitary landfill. The use of empirical, zero, and first‐order models t...

Dietary vitamin E supplementation and discoloration of pork bone and muscle following modified atmosphere packaging

The effects of modified atmosphere (80% O(2): 20% CO(2)) and illumination on the discoloration rate of pork bone (lumbar vertebrae) and muscle (longissimus lumborum), and on muscle lipid stability were studied in vitamin E-supplemented and unsupplemented pigs. Bone-in pork chops were placed in 80% O(2): 20% CO(2) at 0 °C and stored for 5 days in the dark. The chops were then displayed under (a) fluorescent light in air or modified atmosphere or (b) in air with or without illumination. Lipid oxidation was increased by the modified atmosphere packaging but this detrimental effect was offset by vitamin E supplementation. Higher supplementation levels (198 and 207mg/kg) improved bone color stability regardless of the packaging atmosphere or the lighting conditions. Although vitamin E supplementation improved muscle color stability during display in air or modified atmosphere, the benefit of supplementation on muscle color was detectable only for illuminated storage.

Supranutritional Administration of Vitamins E and C Improves Oxidative Stability of Beef

Vitamins E and C are important antioxidants in animals. Their antemortem activity continues to function in postmortem muscle (meat), where they have a critical role in maintaining quality in the food product. Dietary supplementation of vitamin E, and intravenous infusion of vitamin C immediately before harvest, are efficacious techniques for increasing the concentration of these vitamins in beef skeletal muscle. Meat with elevated levels of either and probably both of these antioxidant vitamins possesses greater stability of oxymyoglobin and lipid, which results in less discoloration and rancidity, respectively. A model is proposed for the redox relationships between myoglobin and phospholipid in beef with emphasis on vitamins E and C. Antemortem nutritional intervention appears to be a promising approach for improving the quality of fresh meat products subsequently obtained from livestock.

Microbial chemical and methane production characteristics of anaerobically decomposed refuse with and without leachate recycling

Abstract Microbial and chemical characteristics of refuse in an active state of methane production, incubated in the laboratory with and without leachate recycle, were compared. There were no significant differences in the total anaerobic population or the sub-populations of cellulolytic, hemicellulolytic, acetogenic or methanogenic (based on acetate or H 2 CO 2 utilization) bacteria in refuse incubated with or without leachate recycle. Therefore, leachate recycle may be used to accelerate refuse decomposition in laboratory-scale test lysimeters without changing the microbial composition of the aforementioned trophic groups. Differences in soluble constituent concentrations and methane production patterns between leachate recycle and non-leachate recycle containers were attributed to the mixing associated with leachate recycle. Under certain circumstances, leachate recycle is a useful technique for acceleration of refuse decomposition in the laboratory, thus reducing the period of time required to study the effect of an addition to the refuse ecosystem on methane production.

Growth inhibition of the rumen bacterium Selenomonas ruminantium by ammonium salts

SummaryThe objective of this study was to determine the maximum ammonium source concentration tolerated by Selenomonas ruminantium and its metabolic response to high ammonium source concentrations. The ammonia-nitrogen half-inhibition constant (Ki) in defined basal medium was 239 mabetm for NH4Cl, 173 mabetm for NH4OH, 153 mabetm for (NH4)2SO4 and 110 mabetm for NH4HCO3. Reduction in continuous culture maximal growth rate was similar to the reduction in the batch culture logarithmic growth rate for the respective NH4Cl concentrations. Cell yield when expressed as YATP decreased for 150 and 200 mabetm NH4C1. the NH3-N Ki estimates are in line with inhibiting concentrations observed for other bacteria and suggest that energy efficiency is reduced when the NH3-N concentration is increased.

Effect of dietary vitamin E on pigment and lipid stability of frozen beef: A kinetic analysis.

The effect of vitamin E supplementation on pigment and lipid stability was evaluated with beef wrapped in high or low oxygen permeability films and stored in the dark or under constant illumination at -20°C. Dietary vitamin E supplementation improved pigment and lipid stability in both cases. Illumination increased metmyoglobin accumulation but did not affect lipid oxidation rate in both control and supplemented beef. A predisplay dark storage period of 30 days delayed metmyoglobin accumulation during subsequent display. Kinetic analysis showed that vitamin E supplementation stabilized the oxymyoglobin complex by enhancing the deoxymyoglobin oxygenation rate and by decreasing oxymyoglobin autoxidation rate.

δ-Tocotrienol and quercetin reduce serum levels of nitric oxide and lipid parameters in female chickens.

BackgroundChronic, low-grade inflammation provides a link between normal ageing and the pathogenesis of age-related diseases. A series of in vitro tests confirmed the strong anti-inflammatory activities of known inhibitors of NF-κB activation (δ-tocotrienol, quercetin, riboflavin, (-) Corey lactone, amiloride, and dexamethasone). δ-Tocotrienol also suppresses β-hydroxy-β-methylglutaryl coenzyme A (HMG-CoA) reductase activity (the rate-limiting step in de novo cholesterol synthesis), and concomitantly lowers serum total and LDL cholesterol levels. We evaluated these compounds in an avian model anticipating that a dietary additive combining δ-tocotrienol with quercetin, riboflavin, (-) Corey lactone, amiloride, or dexamethasone would yield greater reductions in serum levels of total cholesterol, LDL-cholesterol and inflammatory markers (tumor necrosis factor-α [TNF-α], and nitric oxide [NO]), than that attained with the individual compounds.ResultsThe present results showed that supplementation of control diets with all compounds tested except riboflavin, (-) Corey lactone, and dexamethasone produced small but significant reductions in body weight gains as compared to control. (-) Corey lactone and riboflavin did not significantly impact body weight gains. Dexamethasone significantly and markedly reduced weight gain (>75%) compared to control. The serum levels of TNF-α and NO were decreased 61% - 84% (P < 0.001), and 14% - 67%, respectively, in chickens fed diets supplemented with δ-tocotrienol, quercetin, riboflavin, (-) Corey lactone, amiloride, or dexamethasone as compared to controls. Significant decreases in the levels of serum total and LDL-cholesterol were attained with δ-tocotrienol, quercetin, riboflavin and (-) Corey lactone (13% - 57%; P < 0.05), whereas, these levels were 2-fold higher in dexamethasone treated chickens as compared to controls. Parallel responses on hepatic lipid infiltration were confirmed by histological analyses. Treatments combining δ-tocotrienol with the other compounds yielded values that were lower than individual values attained with either δ-tocotrienol or the second compound. Exceptions were the significantly lower total and LDL cholesterol and triglyceride values attained with the δ-tocotrienol/(-) Corey lactone treatment and the significantly lower triglyceride value attained with the δ-tocotrienol/riboflavin treatment. δ-Tocotrienol attenuated the lipid-elevating impact of dexamethasone and potentiated the triglyceride lowering impact of riboflavin. Microarray analyses of liver samples identified 62 genes whose expressions were either up-regulated or down-regulated by all compounds suggesting common impact on serum TNF-α and NO levels. The microarray analyses further identified 41 genes whose expression was differentially impacted by the compounds shown to lower serum lipid levels and dexamethasone, associated with markedly elevated serum lipids.ConclusionsThis is the first report describing the anti-inflammatory effects of δ-tocotrienol, quercetin, riboflavin, (-) Corey lactone, amiloride, and dexamethasone on serum TNF-δ and NO levels. Serum TNF-δ levels were decreased by >60% by each of the experimental compounds. Additionally, all the treatments except with dexamethasone, resulted in lower serum total cholesterol, LDL-cholesterol and triglyceride levels. The impact of above mentioned compounds on the factors evaluated herein was increased when combined with δ-tocotrienol.

Atmosphere and blooming time affect color and lipid stability of frozen beef from steers supplemented with Vitamin E

The influence of blooming time (1, 6 or 48 h) and atmosphere (air or 100% oxygen) on color and lipid stability of frozen Longissimus lumborum (LL) from control and vitamin E supplemented steers was studied. Samples were stored at -20°C with or without illumination. Blooming control LL for 48 h in air followed by dark storage increased discoloration. Supplementation and blooming in oxygen, separately or combined, increased color display life. Illumination increased discoloration. Supplementation coupled with blooming for 6 or 48 h in 100% oxygen provided the highest color stability in both dark and illuminated storage. Color display lives for supplemented LL bloomed for 6 and 48 h in oxygen were 182 and 212 days for dark storage, and 21 and 73 days for illuminated display. Supplementation decreased lipid oxidation in illuminated LL, but blooming for 48 h in oxygen minimized this effect.

Inhibition of methane formation from municipal refuse in laboratory scale lysimeters

Changes in chemical composition and population development of key groups of bacteria (hydrolytic, acetogenic, and methanogenic) were measured in a laboratory scale simulation of refuse decomposition from the time of initial incubation through the methane production phase. Inhibition of methane production appeared to be characteristic of refuse decomposition. It was observed in 20 of 32 leachate recycle containers and all 19 control containers. Inhibition was not owing to an absence of indigenous microorganisms, toxic concentrations of carboxylic acids or cations, or insufficient ammonia. Characteristics of inhibited and successful containers are compared.

The relative effect of dietary energy density on repleted and resting muscle glycogen concentrations

The aim of this study was to assess the effect of dietary energy density on the glycogen concentration of bovine gluteus medius (GM) and longissimus thoracis et lumborum (LTL) muscles in castrated and intact males. Cattle received diet C (90% whole corn and supplement: 10% alfalfa haylage) or diet AH (100% alfalfa haylage) in three experiments involving a 2×2 factorial cross-over design. Cattle fed an AH diet for 70 days prior to the first experiment had high glycogen concentrations in the GM (129±9.9 mmol/kg) and LTL (108±7.6 mmol/kg) at the first biopsy session. These concentrations are similar to GM (133±6.2 mmol/kg) and LTL (105±5.8 mmol/kg) glycogen concentrations when these cattle subsequently received diet C for 30 or 37 days. Diet C increased muscle glycogen concentration, but the consistency of the increase in glycogen was dependent on the initial concentration. When the initial glycogen concentration was depleted to 50 μmol/g with one subcutaneous injection of adrenaline, repleted glycogen concentration was higher for diet C than AH (P<0.01) in all comparisons involving GM and LTL muscles of both steers and bulls. For resting muscle glycogen, the GM of bulls was more sensitive to the effect of diet C than the bull LTL or either muscle in steers. Diet was not a major determinant of resting muscle glycogen concentration. The ultimate pHs of GM, LTL and semimembranosus (SM) were not affected by diet and residual glycogen was lower in LTL of bulls fed either diet than for LTL of steers fed AH. Diet and male status did not affect residual glycogen in GM or SM.