Performance of a sulfide-oxidizing, sulfur-producing membrane biofilm reactor treating sulfide-containing bioreactor effluent

Sulfide-containing waste streams are generated in mining, petrochemical plants, tanneries, viscose rayon manufacture, and the gasification of coal. Colorless sulfur bacteria can oxidize sulfide to elemental sulfur (S°), which can be recovered, when oxygen is their electron acceptor. This study evaluated sulfide oxidation and S° recovery in an oxygen-based membrane biofilm reactor (MBfR) treating the effluent from a sulfidogenic anaerobic baffled reactor. Sulfide oxidation efficiency (37-99%) and S° recovery (64-89% of oxidized sulfide) could be controlled by manipulating the sulfide loading, oxygen pressure to the fibers, and hydraulic retention time (HRT). For example, too-low oxygen pressure decreased S° recovery due to decreased sulfide oxidation, but too-high oxygen pressure lowered S° recovery due to its oxidation to sulfate. Most importantly, high sulfide oxidation (>98%) and conversion to S° (>75%) could be achieved together when the sulfide loading was less than 1.7 mol/m2·d and the O? pressure was sufficient to give an O? flux of at least 1.5 mol/m2·d. However, higher sulfide loading could be compensated by a higher O? pressure, and the best performance occurred when the sulfide loading was high (2 molS/m2·d), the O? pressure was high (～1 atm), and the HRT was short (1.9 h). Membrane fouling caused a low O? flux, which led to low sulfide-oxidation efficiency, but fouling could be reversed by mild acid washing.     

Pressure effects on acid-catalysed autoxidation of oxymyoglobin

 Two opposing factors have been found to affect the rate of autoxidation of the fresh meat pigment oxymyoglobin, MbFe(II)O₂, in air-saturated aqueous acetate buffer with increasing hydrostatic pressure to yield metmyoglobin, MbFe(III): (1) expansion in the transition state, corresponding to a volume of activation of ΔV# = +12.7±0.6 ml mol^–1 (25.0°C, 0.16 M NaCl), in effect decreasing the rate; and (2) an increased specific acid catalysis resulting from a decrease in solution pH and increasing the rate. In the pressure range investigated (up to 250 MPa) and at the pH relevant to traditionally deboned meat (pH = 5.65 at ambient pressure investigated, together with pH = 5.21 in order to obtain mechanistic information), the pressure/pH effect was found almost to negate the kinetic effect of expansion in the transition state. Red-to-brown discoloration during pressure treatment of meat is accordingly expected to be less significant for hot-deboned and other high-pH meats. Received: 7 April 1997 / Revised version: 2 June 1997     

Pressure effects on acid-catalysed autoxidation of oxymyoglobin

 Two opposing factors have been found to affect the rate of autoxidation of the fresh meat pigment oxymyoglobin, MbFe(II)O₂, in air-saturated aqueous acetate buffer with increasing hydrostatic pressure to yield metmyoglobin, MbFe(III): (1) expansion in the transition state, corresponding to a volume of activation of ΔV# = +12.7±0.6 ml mol^–1 (25.0°C, 0.16 M NaCl), in effect decreasing the rate; and (2) an increased specific acid catalysis resulting from a decrease in solution pH and increasing the rate. In the pressure range investigated (up to 250 MPa) and at the pH relevant to traditionally deboned meat (pH = 5.65 at ambient pressure investigated, together with pH = 5.21 in order to obtain mechanistic information), the pressure/pH effect was found almost to negate the kinetic effect of expansion in the transition state. Red-to-brown discoloration during pressure treatment of meat is accordingly expected to be less significant for hot-deboned and other high-pH meats. Received: 7 April 1997 / Revised version: 2 June 1997     

Mechanism of perchlorate formation on boron-doped diamond film anodes

This research investigated the mechanism of perchlorate (ClO(4)(-)) formation from chlorate (ClO(3)(-)) on boron-doped diamond (BDD) film anodes by use of a rotating disk electrode reactor. Rates of ClO(4)(-) formation were determined as functions of the electrode potential (2.29-2.70 V/standard hydrogen electrode, SHE) and temperature (10-40 °C). At all applied potentials and a ClO(3)(-) concentration of 1 mM, ClO(4)(-) production rates were zeroth-order with respect to ClO(4)(-) concentration. Experimental and density functional theory (DFT) results indicate that ClO(3)(-) oxidation proceeds via a combination of direct electron transfer and hydroxyl radical oxidation with a measured apparent activation energy of 6.9 ± 1.8 kJ·mol(-1) at a potential of 2.60 V/SHE. DFT simulations indicate that the ClO(4)(-) formation mechanism involves direct oxidation of ClO(3)(-) at the BDD surface to form ClO(3)(?), which becomes activationless at potentials > 0.76 V/SHE. Perchloric acid is then formed via the activationless homogeneous reaction between ClO(3)(?) and OH(?) in the diffuse layer next to the BDD surface. DFT simulations also indicate that the reduction of ClO(3)(?) can occur at radical sites on the BDD surface to form ClO(3)(-) and ClO(2), which limits the overall rate of ClO(4)(-) formation.     

Surface properties of muscle protein extracts

The interfacial properties of proteins extracted from muscle using salt solutions of different concentration and for different extraction times were determined by the drop volume method. At a bulk phase concentration of 10(-2) wt%, it appears that the sarcoplasmic-rich fraction of muscle is more surface active than the salt-soluble fraction. The average equilibrium surface pressure at the air-liquid interface was 21·5 mN m(-1) for an aqueous extract and 20·1 mN m(-1) for a 1m KCl-extract. The equilibrium surface pressure decreased from 21·7 mN m(-1) to 19·50mN m(-1) as the extraction time with Weber-Edsall solution increased from 15 min to 48 h.     

High pressure thermal denaturation kinetics of whey proteins

Pressure processing of foodstuff has been applied to produce or modify proteinaceous gel structures. In real pressure processing the treatment is non-isothermal, due to the adiabatic nature of the process and the heat loss from the product to the vessel. In order to estimate the effect of pressurization on milk constituents pressure and temperature dependent kinetics were determined separately from each other. In a detailed kinetic study whey protein isolate was treated under isobaric (200 to 800 MPa) and isothermal conditions (-2 to 70 degrees C), and the resulting degree of denaturation of beta-lactoglobulin A and B and alpha-lactalbumin was analysed. Kinetic parameters of denaturation were estimated using a one step non-linear regression method which allowed a global fit of the whole data set. The isobaric isothermal denaturation of beta-lactoglobulin and alpha-lactalbumin was found to follow third and second order kinetics, respectively. Isothermal pressure denaturation of both beta-lactoglobulin fractions do not differ significantly and were characterized by an activation volume decreasing with increasing temperature from -10 to about -30 ml mol(-1), which demonstrates that the denaturation rate is accelerated with increasing temperature. The activation energy of about 70 to 100 kJ mol(-1) obtained for beta-lactoglobulin A and B is not dependent to a great extent on the pressure which indicates that above 200 MPa denaturation rate is limited by the aggregation rate while pressure forces unfolding of the molecule.     

(31)P NMR study of post mortem changes in pig muscle

The rate and the extent of post mortem pH changes in pig muscle largely determine pork quality. Fast pH fall combined with low ultimate pH leads to pale soft exudative (PSE) meat; high ultimate pH leads to dark firm dry (DFD) meat. Post mortem metabolism was studied in pig muscle using(31)P NMR. Fifteen pigs, i.e. 7 Large White pigs and 8 Pietrain pigs, were used. Five pigs of each breed were slaughtered, taking care to minimize preslaughter stress. The other pigs (3 Large Whites and 2 Pietrains) were injected with 0·1 mg adrenaline per kg liveweight before slaughter, in order to increase meat ultimate pH. All the animals were killed by electronarcosis and exsanguination. Three of the adrenaline-treated pigs (1 Large White and 2 Pietrains) gave meat with ultimate pH above 6 (DFD meat). The pigs with normal muscle ultimate pH, i.e. 6 Large Whites and 6 Pietrains, had very variable rates of post mortem muscle metabolism (pH at 30 min after slaughter: 6·17-6·85 in Large Whites; 6·04-6·23 in Pietrains). The relationships between pH and ATP changes were similar in all pigs showing normal muscle ultimate pH, whereas ATP disappeared at a high pH value (on average pH 6·4) in pigs with high ultimate pH. The course of post mortem biochemical changes in a given animal could be predicted rather well by examination of a single(31)P NMR spectrum obtained around 30 min after death. At this time, muscle with a low rate of metabolism simultaneously showed medium to high pH, high ATP content (4-6·8 μmol/g) and rather low Pi content (6-14 μmol/g); muscle with a fast rate of metabolism (PSE-prone muscle) had low pH, low to medium ATP content (1·1-4 μmol/g) and generally high phosphomonoester (PME) content (9-23 μmol/g); muscle with high ultimate pH (DFD-prone muscle) had high pH, low PME content (4-8 μmol/g) and high Pi content (22-27 μmol/g).     

Mass transfer and chemical oxidation of naphthalene particles with zerovalent iron activated persulfate

The usage of zerovalent iron (ZVI) activated persulfate to induce sulfate radical (SO(4)(-)·) oxidation of both aqueous and solid phase naphthalene (Nap) was investigated. It was determined that the removal of Nap particles occurred through an indirect route. Specifically, Nap released through dissolution from the pure Nap particles was subsequently oxidized in the aqueous phase by SO(4)(-)·. Rapid destruction of dissolved Nap created a greater concentration gradient between the solid and aqueous phases. This caused more Nap particles to be dissolved which were then available for the subsequent oxidative destruction of dissolved Nap. The rate constant (k(obs,Nap)) of ZVI activated persulfate degradation of dissolved Nap was determined to be 3.74 min(-1). The overall dissolution mass transfer coefficients (k(L)a) for the Nap particles were determined, 3.0 × 10(-2) min(-1) with initial 10 mg Nap in 40 mL water, and found to be proportional to the quantities of the Nap particles present. The results indicate that the k(obs,Nap) is much greater than the k(L)a. The net result of the dissolution of Nap particles and the destruction of dissolved Nap by oxidation was the removal of Nap particles. Sequential additions of ZVI at a lower concentration to slow down the formation of SO(4)(-)· can prevent the scavenging of SO(4)(-)· by ZVI and enhance the removal of Nap particles. The results of the mass balance analysis during the oxidized, aqueous and solid phases of Nap were consistent with experimental observations.     

白蜡多年卧孔菌多糖提取工艺优化及其抗氧化活性

采用超声辅助水提醇沉法提取白蜡多年卧孔菌（Perenniporia fraxinea）子实体与菌丝体多糖,利用单因素试验结合Box-Behnken响应面法优化子实体与菌丝体多糖提取工艺参数,并测定其DPPH·、ABTS+·清除能力。结果表明,子实体多糖的最佳提取工艺条件为：料液比1∶60（g∶mL）、提取时间76 min和超声时间16 min,在此优化条件下,子实体多糖提取率为4.39%;菌丝体多糖的最佳提取工艺条件为：料液比1∶30（g∶mL）、提取时间101 min和超声时间16 min,在此优化条件下,菌丝体多糖提取率为6.33%。当子实体和菌丝体多糖质量浓度为2.0 mg/mL时,子实体对DPPH·、ABTS+·清除率分别为45.67%和72.89%,菌丝体多糖对DPPH·、ABTS+·的清除率分别为51.67%和75.83%。子实体和菌丝体多糖能降低植物油过氧化值（POV）,表明白蜡多年卧孔菌多糖具有一定的抗油脂氧化的能力。     

Fatty acid profiles of the total lipids and lipid oxidation in pork muscles as affected by canola oil in the animal diet and muscle location

Twelve pigs at about 35 days of age were fed a control diet or test diets containing either 10% or 20% canola oil (CO) for 100 days. Four different muscles were excised from each carcass at 24 h post-mortem for analyses. Inclusion of 10% and 20% CO in the animal diet increased (P < 0·05) the relative amount (weight per cent) of unsaturated fatty acids in the total lipids (lipids extracted by 2:1 chloroform-methanol) by 6·7 and 15·8 percentage points, respectively, from 57·8% for the control and also increased (P < 0·05) that of polyunsaturated fatty acids by 5·5 and 9·7 percentage points, respectively, from 19·4% for the control. The 20% CO treatment increased (P < 0·05) the relative amount of monounsaturated fatty acids (primarily C18:1) by 6·1 percentage points from 38·4% for the control, while the 10% CO treatment had no significant effect. The 10% or 20% CO treatment had no significant effect on microsomal enzymic lipid peroxidation activity, heme pigment content, nonheme iron content and total lipid concentration. Overall lipid oxidation in ground muscle samples stored at 4°C tended to be higher for the 10% and 20% CO treatment groups than for the control. The tendency of increased lipid oxidation by the CO treatments apparently resulted from the increased percentages of polyunsaturated fatty acids, rather than from changes in catalytic constituents.     

Oxygen and superoxide-mediated redox kinetics of iron complexed by humic substances in coastal seawater

Complexes with terrestrially derived humic substances represent one of the most reactive pools of dissolved Fe in natural waters. In this work, redox kinetics of Fe-humic substance complexes (FeL) in simulated coastal seawater were investigated using chemiluminescence techniques with particular attention given to interactions with dioxygen (O2) and superoxide (O2?-). Although rate constants of FeIIL oxidation by O2 (5.6-52 M-1 · s-1) were 4-5 orders of magnitude less than those for O2?- (6.9-23 × 105 M-1 · s-1),O2 is likely to outcompete O2?- for FeIIL oxidation in coastal seawaters where steady-state O2?- concentrations are generally subnanomolar. Rate constants for FeIIIL reduction by O2?- of 1.8-5.6 × 104 M-1 · s-1 were also determined. From the balance of FeIIL oxidation rates and O2?- -mediated FeIIIL reduction rates, steady-state FeIIL concentrations were estimated to be in the subpicomolar to picomolar range, which is generally lower than measured in situ Fe(II) concentrations under relevant conditions. This suggests that (i) processes other than O2?- -mediated reduction (such as photochemical ligand-to-metal charge transfer) may be responsible for Fe(II) formation, (ii) the in situ ligands differ significantly from the humic substances used in this work, and/ or (iii) the influence of other environmental factors such as pH and temperature on Fe redox kinetics may have to be considered.     

草浆造纸中段废水处理的组合工艺研究

采用ABPb-生物接触氧化-混凝组合工艺处理草浆中段废水。试验结果表明：ABE适宜的停留时间为8h,适宜的容积负荷为2．5kgCOD／（m^3d）以下,COD去除率可达38．8％～41．6％;生物接触氧化池的适宜水力停留时间为10h,适宜的容积负荷为0．75～1．2kgCOD／（m^3·d）,适宜的气水比为20：1,COD去除率为62．7％～65．5％;混凝剂聚合氯化铝铁（PAFC）最佳用量为0．5g／L。经组合工艺处理后,中段废水生物接触氧化处理效率有较大提高,系统COD去除率保持在91．3％～92．4％,出水COD基本达到DB57／336-2005的要求。     

Survival of Escherichia coli O157:H7 during storage in pressure-treated orange juice.

The effect of a high-pressure treatment on the survival of a pressure-resistant strain of Escherichia coli O157:H7 (NCTC 12079) in orange juice during storage at 3 degrees C was investigated over the pH range of 3.4 to 5.0. The pH of shelf-stable orange juice was adjusted to 3.4, 3.6, 3.9, 4.5, and 5.0 and inoculated with 10(8) CFU ml(-1) of E. coli O157:H7. The orange juice was then pressure treated at 400 MPa for 1 min at 10 degrees C or was held at ambient pressure (as a control). Surviving E. coli O157:H7 cells were enumerated at 1-day intervals during a storage period of 25 days at 3 degrees C. Survival of E. coli O157:H7 during storage was dependent on the pH of the orange juice. The application of high pressure prior to storage significantly increased the susceptibility of E. coli O157:H7 to high acidity. For example, after pressure treatment, the time required for a 5-log decrease in cell numbers was reduced from 13 to 3 days at pH 3.4, from 16 to 6 days at pH 3.6, and from >25 to 8 days at pH 3.9. It is evident that the use of high-pressure processing of orange juice in order to increase the juice's shelf-life and to inactivate pathogens has the added advantage that it sensitizes E. coli O157:H7 to the high acid conditions found in orange juice, which results in the survival of significantly fewer E. coli O157:H7 during subsequent refrigerated storage.     

Variability in rates of pH fall and of lactate production in the muscles on cooling beef carcasses

The rate of pH fall in four major muscles on cooling beef carcasses varied by about twofold. Thus the time taken to reach pH 6·0 from initial pH values of about 7·1 varied between 8 and 16h, and in one extreme case of an LD muscle was as low as 3·5 h. Some of this variability was due to different rates of cooling between muscles in the same animal, but even after correction of the rates to a constant temperature of 38°C the variability was still about twofold in the higher range of pH (7·0-6·7) and slightly lower in the lower range (6·6-5·8). Similar variability was shown in excised TB muscles, kept at a constant temperature of 38°C. Damage to muscles during excision can lead to much higher variability than this (in rabbit LD muscles, to about sixfold). The rate of pH fall is determined by the rate of ATP-turnover, and so the variability in the former rate is likely to be due to varying intracellular free Ca(2+) levels exerting a stimulating effect on the actomyosin ATP-ase. Some of this extra Ca(2+) may arise from calcium release from mitochondria as they become anaerobic after death.     

Hydroxyl radical generation mechanism during the redox cycling process of 1,4-naphthoquinone

Airborne quinones contribute to adverse health effects of ambient particles probably because of their ability to generate hydroxyl radicals (·OH) via redox cycling, but the mechanisms remain unclear. We examined the chemical mechanisms through which 1,4-naphthoquinone (1,4-NQ) induced ·OH, and the redox interactions between 1,4-NQ and ascorbate acid (AscH(2)). First, ·OH formation by 1,4-NQ was observed in cellular and acellular systems, and was enhanced by AscH(2). AscH(2) also exacerbated the cytotoxicity of 1,4-NQ in Ana-1 macrophages, at least partially due to enhanced ·OH generation. The detailed mechanism was studied in an AscH(2)/H(2)O(2) physiological system. The existence of a cyclic 1,4-NQ process was shown by detecting the corresponding semiquinone radical (NSQ·-) and hydroquinone (NQH(2)). 1,4-NQ was reduced primarily to NSQ·- by O2·- (which was from AscH(2) reacting with H(2)O(2)), not by AscH(2) as normally thought. At lower doses, 1,4-NQ consumed O2·- to suppress ·OH; however, at higher doses, 1,4-NQ presented a positive association with ·OH. The reaction of NSQ·- with H(2)O(2) to release ·OH was another important channel for OH radical formation except for Haber-Weiss reaction. As a reaction precursor for O2·-, the enhanced ·OH response to 1,4-NQ by AscH(2) was indirect. Reducing substrates were necessary to sustain the redox cycling of 1,4-NQ, leading to more ·OH and a deleterious end point.     

Ultrasonication and the quality of human milk: variation of power and time of exposure

Donor human milk is pasteurized to prevent the potential risk of the transmission of pathogens to preterm infants. Currently, Holder pasteurization (human milk held at 62·5°C for 30 min) is used in most human milk banks, but has the disadvantage that it results in excessive inactivation of important bioactive components. Power-ultrasound (20-100 kHz) is an emerging technology for the preservation of foods and could be an alternative method for the treatment of human milk. The aim of this study was to investigate the effect of different ultrasound settings on the elimination of Escherichia coli and the retention of bile salt stimulated lipase (BSSL) activity. Ultrasonication with a constant power decreased Esch. coli viability exponentially over time until the processing temperature increased to sub-pasteurization level to between 51·4 and 58·5°C, then a log10 1·3 decrease was observed (P<0·05). BSSL activity decreased to 91% until a temperature of 51·4°C and then it decreased to 8% between 51·4 and 64·9°C. Ultrasonication with a constant energy and various power and exposure times showed the highest temperature (53·7°C) when treated with the longest exposure time and lowest ultrasound-power (276 s at 3·62 W) compared with 37·6°C for 39 s at 25·64 W. The findings predict that the viability of Esch. coli could be reduced by log10 5 with a minimal loss of activity of BSSL by applying 13·8 kJ of energy in 12 ml of human milk using high ultrasound power over a short exposure time to ensure that the temperature remains below the critical level for protein denaturation. Alternatively, the use of lower power settings such as the 26 W used in the present studies would require a cooling system to ensure the human milk BSSL was protected against temperature denaturation.     

Heat-induced gelation of actomyosin

Rheological properties of actomyosin gels were markedly affected by protein concentration, pH and heating temperature. Gel strength increased with increasing protein concentration (30-60 mg ml(-1)) and heating temperature (55-75°C), but decreased with increasing pH (5·5-9·0). Low heating temperatures (50-55°C) favoured the formation of more cohesive actomyosin gels than the higher heating temperatures (60-75°C). Gels formed at low pH (5·5 and 6·0) were less cohesive than those formed at high pH (7·5-9·0). Addition of ATP and pyrophosphate (10 mm) prior to heating decreased gel strength and cohesiveness, whereas EDTA (1-5 mM) reduced gel strength but did not affect gel cohesiveness.     

Oxidation of chlorinated ethenes by heat-activated persulfate: kinetics and products

In situ chemical oxidation (ISCO) and in situ thermal remediation (ISTR) are applicable to treatment of groundwater contaminated with chlorinated ethenes. ISCO with persulfate (S2O8(2-)) requires activation, and this can be achieved with the heat from ISTR, so there may be advantages to combining these technologies. To explore this possibility, we determined the kinetics and products of chlorinated ethene oxidation with heat-activated persulfate and compared them to the temperature dependence of other degradation pathways. The kinetics of chlorinated ethene disappearance were pseudo-first-order for 1-2 half-lives, and the resulting rate constants-measured from 30 to 70 degrees C--fit the Arrhenius equation, yielding apparent activation energies of 101 +/- 4 kJ mol(-1) for tetrachloroethene (PCE), 108 +/- 3 kJ mol(-1) for trichloroethene (TCE), 144 +/- 5 kJ mol(-1) for cis-1,2-dichloroethene (cis-DCE), and 141 +/- 2 kJ mol(-1) for trans-1,2-dichloroethene (trans-DCE). Chlorinated byproducts were observed, but most of the parent material was completely dechlorinated. Arrhenius parameters for hydrolysis and oxidation by persulfate or permanganate were used to calculate rates of chlorinated ethene degradation by these processes over the range of temperatures relevant to ISTR and the range of oxidant concentrations and pH relevant to ISCO.     

The ultra-rapid chilling of lamb carcasses

Experiments were carried out on the effects of chilling lamb carcasses very rapidly in a pre-rigor condition. The chilling regime which was finally used was to cool the carcasses at an ambient temperature of -20°C and an air speed of 1·5 m/s for 3·5 h. Examination of striploins from carcasses subjected to this chilling regime showed that, after 7 day's storage, the meat was as tender as that from carcasses which had been conventionally chilled at 4°C for 24 h There were significant reductions in weight loss as a result of ultra rapid chilling, compared to conventionally chilled carcasses. The reductions obtained after 24 h varied between 0·8 and 0·9%, depending on whether the carcasses were washed or unwashed.     

Thyroid hormones in milk and blood of lactating donkeys as affected by stage of lactation and dietary supplementation with trace elements

The traditional utilization of donkeys (Equus asinus) as dairy animals has recently attracted substantial scientific interest with regard to human nutrition. Donkey milk is well tolerated by infants with cows' milk allergy, useful in the treatment of human immune-related diseases, in the prevention of atherosclerosis, and in-vitro studies showed an anti-proliferative effect. Active 3-3'-5-triiodothyronine (T3) in colostrum and milk could play different physiological roles, systemic and paracrine, for both the mother and the suckling offspring. The aim was to evaluate whether thyroid hormones (TH) concentrations in milk and blood of lactating donkeys change with the advancing lactation and whether they can be affected by dietary supplementation with several trace elements, some of them directly involved with TH synthesis (I), metabolism (Se) and action (Zn). Sixteen lactating jennies were divided into two groups (CTL and TE). Mixed feed for TE was added with Zn, Fe, Cu, Mn, I, Se and Co. Every 2 weeks milk and blood samples were collected at 11·00. Total concentrations of T3 in milk (T3M) and T3 and T4 in plasma (T3P and T4P) were assayed using ELISA kits, validated for the donkey species. T3M was not correlated with TH concentrations in blood, did not change with the stage of lactation, and was significantly higher in TE (4·09 ± 0·07 ng/ml, mean ± SE) than in CTL group (3·89 ± 0·08 ng/ml). T4P (81·8 ± 5·2 ng/ml) and T3P (15·2 ± 1 ng/ml) significantly changed with time, but were not significantly affected by dietary treatment. T3P/T4P ratio was significantly lower in TE group. This study indicates that in donkey milk the concentration of T3, a human-like bioactive compound, can be affected by trace elements intake.