In situ MTBE biodegradation supported by diffusive oxygen release

Microcosm studies with sediments from Vandenberg Air Force Base, CA, suggest that native aerobic methyl tert-butyl ether (MTBE)-degrading microorganisms can be stimulated to degrade MTBE. In a series of field experiments, dissolved oxygen has been released into the anaerobic MTBE plume by diffusion through the walls of oxygen-pressurized polymeric tubing placed in contact with the flowing groundwater. MTBE concentrations were decreased from several hundred to less than 10 microg/L during passage through the induced aerobic zone, due apparently to in situ biodegradation: abiotic MTBE loss mechanisms were insignificant. Lag time for initiation of degradation was less than 2 months, and the apparent pseudo-first-order degradation rate was 5.3 day(-1). Additional MTBE was added in steps to raise the influent concentration to a maximum of 2.1 mg/L. With each step, MTBE was degraded within the preestablished aerobic treatment zone at rates ranging from 4.4 to 8.6 day(-1). Excess dissolved oxygen suggested that even higher MTBE concentrations could have been treated. Continued flow through the treatment zone was repeatedly confirmed through tracer and other tests. These and others' results suggest that it is possible to create permeable in situ treatment zones solely by releasing oxygen to support native microbial degradation of MTBE.     

Assessment of the risk of solar ultraviolet radiation to amphibians. I. Dose-dependent induction of hindlimb malformations in the northern leopard frog (Rana pipiens)

A number of environmental stressors have been hypothesized as responsible for recent increases in limb malformations in several species of North American amphibians. The purpose of this study was to generate dose-response data suitable for assessing the potential role of solar ultraviolet (UV) radiation in causing limb malformations in a species in which this phenomenon seemingly is particularly prevalent, the northern leopard frog (Rana pipiens). Frogs were exposed from early embryonic stages through complete metamorphosis to varying natural sunlight regimes, including unaltered (100%) sunlight, sunlight subjected to neutral density filtration to achieve relative intensities of 85%, 75%, 65%, 50%, and 25% of unaltered sunlight, and sunlight filtered with glass or acrylamide to attenuate, respectively, the UVB (290-320 nm) and UVB plus UVA (290-380 nm) portions of the spectrum. The experiments were conducted in a controlled setting, with continual monitoring of UVB, UVA, and visible light to support a robust exposure assessment. Full sunlight caused approximately 50% mortality of the frogs during early larval development; no significant treatment-related mortality occurred under any of the other exposure regimes, including 100% sunlight with glass or acrylamide filtration. There was a dose-dependent (p < 0.0001) induction of hindlimb malformations in the frogs, with the percentage of affected animals ranging from about 97% under unaltered sunlight to 0% in the 25% neutral density treatment. Malformations were comprised mostly of missing or truncated digits, and generally were bilateral as well as symmetrical. Filtration of sunlight with either glass or acrylamide both significantly reduced the incidence of malformed limbs. The estimated sunlight dose resulting in a 50% limb malformation rate (ED50) was 63.5%. The limb ED50 values based on measured sunlight intensities corresponded to average daily doses of 4.5 and 100 Wh x m(-2) for UVB and UVA, respectively. Exposure to sunlight also resulted in increased eye malformations in R. pipiens, however, the dose-response relationship for this endpoint was not monotonic. The results of this study, in conjunction with measured or predicted exposure data from natural settings, provide a basis for quantitative prediction of the risk of solar UV radiation to amphibians.     

Transport of Cryptosporidium oocysts in porous media: role of straining and physicochemical filtration

The transport and filtration behavior of Cryptosporidium parvum oocysts in columns packed with quartz sand was systematically examined under repulsive electrostatic conditions. An increase in solution ionic strength resulted in greater oocyst deposition rates despite theoretical predictions of a significant electrostatic energy barrier to deposition. Relatively high deposition rates obtained with both oocysts and polystyrene latex particles of comparable size at low ionic strength (1 mM) suggest that a physical mechanism may play a key role in oocyst removal. Supporting experiments conducted with latex particles of varying sizes, under very low ionic strength conditions where physicochemical filtration is negligible, clearly indicated that physical straining is an important capture mechanism. The results of this study indicate that irregularity of sand grain shape (verified by SEM imaging) contributes considerably to the straining potential of the porous medium. Hence, both straining and physicochemical filtration are expected to control the removal of C. parvum oocysts in settings typical of riverbank filtration, soil infiltration, and slow sand filtration. Because classic colloid filtration theory does not account for removal by straining, these observations have important implications with respect to predictions of oocyst transport.     

The use of sourdough fermented by antifungal LAB to reduce the amount of calcium propionate in bread

Addition of sourdough is a common practice in the bakery industry to improve, among other quality parameters, the shelf life of bread. In this study, sourdough fermented by antifungal Lactobacillus plantarum strains was investigated for the ability to inhibit growth of common bread spoilage fungi. In both in vitro and sourdough wheat bread system, the antifungal sourdoughs significantly affected the outgrowth of Aspergillus niger, Fusarium culmorum, or Penicillium expansum spores, however on wheat bread outgrowth of Penicillium roqueforti spores was not affected. In an attempt to reduce the amounts of chemical additives in bread, the antifungal sourdoughs were used in combination with calcium propionate (CAP) and possible synergistic effects were evaluated. Presence of 3000 ppm CAP in the bread did not affect the outgrowth of P. roqueforti, whereas outgrowth of the other fungi was retarded. A strong synergistic effect was observed when CAP and antifungal sourdoughs were combined into the bread formulation, and outgrowth of P. roqueforti was affected. The use of reduced CAP amount (1000 ppm) showed significant inhibition only when antifungal sourdough was added. Remarkably, the increase in shelf life achieved was higher than that obtained using 3000 ppm of CAP alone. In conclusion, the results of this study clearly show that the addition of antifungal sourdough has the potential to reduce the levels of chemical additives needed in the bakery industry to ensure the microbiological safety of bread.     

Thermal stability of soy protein isolate and hydrolysate ingredients

The objective of this study was to characterize the effects of pH, protein concentration and calcium supplementation on thermal stability, at 140 °C, of soy protein isolate (SPI) and soy protein hydrolysate (SPH) ingredients. Increasing pH between 6.4 and 7.5 led to significantly (p < 0.05) higher mean heat coagulation times (HCTs) at 140 °C, for all soy protein ingredients at 1.8, and 3.6% (w/v) protein. Increasing protein concentration from 1.8 to 7.2% (w/v) led to shorter HCTs for protein dispersions. Calcium supplementation up to 850 mg/L, except in the case of supplementation of SPI 1 with calcium citrate (CaCit), decreased HCT for soy protein ingredient dispersions, at pH 6.4 – 7.5. No significant differences (p < 0.05) were found in mean HCT for dispersions supplemented with calcium chloride (CaCl₂) and those supplemented with CaCit at 450, 650 and 850 mg/L Ca²⁺, in the pH range 6.4–7.5.     

Experimental study on the effect of SO2 on PCDD/F emissions: determination of the importance of gas-phase versus solid-phase reactions in PCDD/F formation

Cofiring coal in municipal solid waste incinerators (MSWls) has previously been reported to reduce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) emissions due to increasing the flue gas SO2 concentration. The present study was focused on understanding the primary mechanism responsible for the suppressant effect of SO2 on total PCDD/F formation and toxic equivalent (TEQ) emissions. The addition of SO2, simulating the effect of coal addition on the flue gas composition, resulted in significant reductions in the TEQ emissions due to reactions involving SO2 in the postcombustion zone. However, emissions of total PCDDs/Fs, unlike the TEQ value, were dependent upon the Cl2 and SO2 injection temperatures due to increases in non-TEQ correlated isomers. The conversion of metal chlorides in the fly ash to sulfates, thus reducing the sites responsible for chlorination/oxidation reactions, was concluded to be the main suppressant mechanism; proposed reactions for copper and iron are presented. This mechanism was found to be independent of combustion conditions and could have prolonged effects on PCDD/F emissions from deposits formed with high flue gas S/Cl ratios.     

A beetroot juice shot is a significant and convenient source of bioaccessible antioxidants

The total antioxidant capacity (TAC) and total polyphenol (TP) content of a beetroot juice shot (70 mL) was examined following in vitro digestion. TAC was assessed using the ferric reducing antioxidant power (FRAP) assay and TP content was measured using the Folin Ciocalteu (FC) method (measured as gallic acid equivalents (GAE) before and after an in vitro digestion procedure with simulated gastric (GAS) and duodenal (DUO) phases. The beetroot shot had a high TAC (697.9 ± 1.6 μmol/70 mL) and TP content (68.4 ± 0.3 mg GAE/70 mL). FRAP values increased approximately 3-fold after GAS (2361.2 ± 20.9 μmol/70 mL) and remained high following DUO (1740.3 ± 21.1 μmol/70 mL). TP content increased 5-fold following GAS (341.6 ± 4.8 mg GAE/70 mL) and remained 3.3-fold higher following DUO (223.2 ± 5.4 mg GAE/70 mL). The beetroot shot delivers a high amount of bioaccessible antioxidants and may be a cost effective and convenient method of increasing antioxidant status.     

Comparison of calcium lactate with chlorine as a washing treatment for fresh‐cut lettuce and carrots: quality and nutritional parameters

The efficacies of calcium lactate and chlorine washing treatments of fresh‐cut lettuce and carrots were compared during storage at 4 °C over 10 days. The gas composition of packages, colour, enzyme activity, texture, sensory attributes, microflora and levels of ascorbic acid and carotenoids were evaluated at 1, 3, 7 and 10 days. Calcium lactate treatment was not significantly different to chlorine treatment (p < 0.05) in terms of maintaining colour, texture and acceptability of fresh‐cut lettuce and carrots during the entire storage period. The washing treatments did not affect levels of ascorbic acid of fresh‐cut lettuce or carrots. Carotenoid levels were higher in calcium lactate‐treated carrots than chlorine‐treated samples at the end of storage. Mesophilic, psychrotrophic and lactic acid bacteria counts were not significantly different between treatments for both vegetables. Copyright © 2005 Society of Chemical Industry