Partial nitritation treatment of underground brine waste with high ammonium and salt content

Underground brine waste containing high concentrations of ammonium and with a salinity of 3% is usually generated during the production of methane gas and iodine in the gas field of Chiba Prefecture, Japan. In this study, one swim-bed reactor, packed with a novel acrylic fiber biomass carrier (Biofringe), was applied to the partial nitritation treatment of this kind of underground brine waste. A stable nitrite production rate of 1.6 kg NO₂-N m^− 3 d^− 1 was obtained under a nitrogen loading rate of 3.0 kg-N m^− 3 d^− 1, at a pH of 7.5 and a temperature of 25 °C. Nitrate production was negligible and the effluent NO₂-N/NO_x-N ratio was above 98% due to the successful inhibition of nitrite-oxidizing bacterial activity. Free ammonia was considered to be the main factor for inhibiting the activity of nitrite-oxidizing bacteria. A microbial community shift was demonstrated by 16S rRNA analysis, and it was shown that the ammonium-oxidizing bacteria became the predominant species after successful nitrite accumulation was observed.     

Stable and high-rate nitrogen removal from reject water by partial nitrification and subsequent anammox

A combined process of partial nitrification (PN) and anaerobic ammonium oxidation (anammox) was carried out to treat reject water with a high concentration of ammonium and a low level of hardly biodegraded organic carbon. Stable treatment performance was obtained under high nitrogen loading rates of 5.7 kg-N/m³/day and 10.5 kg-N/m³/day for the PN and anammox reactors for more than 2 months, respectively. Successful nitrite accumulation was observed in the PN reactor, with an effluent NH₄-N/NO₂-N ratio of 1: 1.1 and marginal nitrate production, which is suitable for the subsequent anammox process. The strict control of DO concentration was adopted as the main manipulating strategy for the stable running of the PN reactor. And results indicated that the value of FA and FNA within a favorable range was essential for the successful operation of PN reactor. The anammox process was carried out in an up-flow fixed-bed reactor. The influent NH₄-N/NO₂-N ratio played a vital role in obtaining efficient nitrogen removal. The anammox reactor was successfully operated with a nitrogen removal rate of 9.1 kg-N/m³/day for 2 months, indicating high operational stability. Inorganic carbon was shown to have a positive impact on the high nitrogen removal rate during the combined process. In addition, the characteristics of the sludge in both reactors were investigated. The Stover–Kincannon model was used for kinetics studies. K_B and U_max were determined as 30.1 g/L/day and 13.9 g/L/day, respectively, for the PN reactor and 42.1 g/L/day and 31.2 g/L/day, respectively, for the anammox reactor.     

High rate partial nitrification treatment of reject wastewater

Partial nitrification (PN) treatments on reject wastewater were carried out. Dissolved oxygen concentration was limited by controlling air flowrate, which was the main operational strategy in this study. Stable PN performance was obtained during continuous operation for 80 days, with a maximum nitrogen loading rate (NLR) of 4.2 kg-N m⁻³ day⁻¹ and ammonium conversion rate of 2.1 kg-Nm⁻³ day⁻¹. The production of nitrite oxidizers was assumed to be responsible for the nitrogen loss in the reactor. The ratios of NO₂⁻–N/ (NO₂⁻–N + NO₃⁻–N) were always above 99.9%, and BOD removal efficiencies were also stable at around 70% even if a sharp increase in NLR was applied during the stable period. Additionally, bacterial consortia analysis showed ammonium-oxidizing bacteria were the dominant microorganisms, which provided evidence for the long-term stable performance of this PN reactor. During the experiment, sludge setting properties deteriorated due to the absence of a biomass carrier. The stable performance of partial nitrification from reject wastewater demonstrated the feasibility of the operation strategy in this study.     

Effects of timing of corn silage supplementation on digestion, fermentation pattern, and nutrient flow during continuous culture fermentation of a short and intensive orchardgrass meal

Using a dual-flow continuous culture fermenter system, this study evaluated the effect of timing of corn silage supplementation on ruminal digestion and nutrient flows following a short and intensive orchardgrass herbage meal. Treatments included 28 g dry matter (DM) of corn silage added either 9 h (9BH; 0700 h) or 1 h (1BH; 1500 h) before adding 42 g DM orchardgrass herbage or no corn silage (control; 70 g DM herbage). Herbage was fed as follows: 66% of the total herbage meal at 1600 h, 22% at 1720 h, and the remaining 12% at 1840 h. Effluent was analyzed for organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF). Purine concentrations in effluent and bacterial isolates were used to estimate the partition of effluent N flow into bacterial and nonbacterial fractions, and to calculate true OM digestibility. Fermenters were sampled for pH, volatile fatty acids (VFA), and NH₃-N at 0730, 1100, 1530, 1600, 1720, 1840, and 2000 h on d 10. Data were analyzed as a 3 × 4 Latin square experimental design. True digestibilities for OM (average of 78.5%) and CP (average of 84.6%), and apparent NDF digestibility (average of 82.7%) were not affected by treatment. Mean ruminal pH was lower for 9BH than for 1BH, averaging 5.6 and 6.5, respectively. Molar proportions of acetate were not affected by treatment. Propionate concentration was greater for 9BH than for 1BH, averaging 20.5 and 18.1 mM, respectively. Diurnal patterns of pH, NH₃-N, and acetate:propionate ratio were affected by treatment: 9BH had the lowest values for all measurements as the day progressed. The NH₃-N concentration and effluent NH₃-N flow were higher for 1BH (11.4 mg/100 mL and 0.26 g/d, respectively) than for 9BH (8.8 mg/100 mL and 0.20 g/d, respectively). Effluent NH₃-N flow (as a % of total N flow) was the lowest for 9BH. Bacterial efficiency was not affected by treatments, with a mean of 10.5 g of N/kg of OM truly digested. Under the same resource allocation (pasture plus supplement), a simple change in timing of corn silage feeding (9 rather than 1 h before an orchardgrass herbage meal) may alter ruminal fermentation pattern. These changes could increase the glucogenic nutrient supply and improve N utilization by reducing ammonia N losses.     

Influence of banded fertiliser on the chemical environment surrounding the band: I.—Effect on pH and solution nitrogen

The influence of several banded fertilizers on soil pH, soil solution pH, and concentration of NH₄-N, NO₂-N and NO₃-N at two distances from the band was studied. Treatments consisted of various combinations of monocalcium phosphate (MCP), KCl, NH₄-NO₃, (NH₄)₂HPO₄ and urea applied on a nutrient element basis of 22.4 or 67.2 kg/ha. Urea treatments produced the highest initial pH, and MCP treatments resulted in the lowest pH values. The greatest pH changes during a 32-day incubation period resulted from treatments that contained urea, (NH₄)₂ HPO₄ or NH₄NO₃. Changes in pH with time, for treatments containing the N sources, reflected the rate of nitrification of NH₄-N to NO₃-N which, in turn, controlled the solution concentrations of NH₄-N and NO₃-N. The NO₂-N content near 67.2 kg/ha urea applications increased with time to potentially toxic concentrations (over 500 ppm). Combination of MCP with urea markedly lowered pH and NO₂-N content compared to treatments in which MCP was not supplied. Application of (NH₄)₂HPO₄ or urea at 22.4 kg/ha resulted in a rapid increase in NO₃-N and decrease in pH with time. The pH decrease and accumulation of NO₃-N were much slower when (NH₄)₂HPO₄ or urea was applied at 67.2 kg/ha.     

Efficacy optimization of plasma-activated water for food sanitization through two reactor design configurations

The chemistry, antimicrobial efficacy and energy consumption of plasma-activated water (PAW) was optimized by altering the discharge frequency, ground-electrode configuration, gas flow rate and initial water conductivity for two reactor configurations, i.e., air pin-to-liquid discharge and air plasma-bubble discharge in water. The ratio of NO₂⁻ and NO₃⁻ formation was altered to optimise the antimicrobial effects of PAW, tested against two Gram-negative bacteria. An initial solution conductivity of 0.2 S·m⁻¹ and 2000-Hz discharge frequency with the ground electrode positioned inside the pin reactor showed the highest antimicrobial effect resulting in a 3.99 ± 0.13-log₁₀ reduction within 300 s against Escherichia coli and 5.90 ± 0.24-log₁₀ reduction within 240 s for Salmonella Typhimurium. An excellent energy efficiency of reactive oxygen and nitrogen species (RONS) generation of 10.1 ± 0.1 g·kW⁻¹·h⁻¹ was achieved.Industrial relevancePlasma-activated water (PAW) is deemed as an eco-friendly alternative to chemical disinfection because its bactericidal activity is temporary. Optimizing the design and operation of PAW reactors to achieve high inactivation rates of more than 5-log₁₀ reductions, as demonstrated in this work, will support the industrial application of this technology and the scaleup at industrial level.     

Fe3+存在下制浆中段废水好氧活性污泥的驯化

研究了Fe³⁺存在下处理制浆中段废水的好氧活性污泥的驯化过程。首先通过Fe³⁺对微生物生长曲线的影响确定Fe³⁺最佳用量为30 mg/L;然后在Fe³⁺用量为30 mg/L下,采用制浆中段废水对好氧活性污泥进行驯化,并设置不加Fe³⁺的空白组对照。结果表明,整个驯化过程中,加Fe³⁺组COD_Cr去除率和污染物去除率(以UV-254减少率表示)均高于空白组;驯化结束后,加Fe³⁺组和空白组COD_Cr去除率分别达78.2%和76.0%,污染物去除率分别为50.0%和37.7%。通过对脱氢酶活性的分析表明,加Fe³⁺组活性高于空白组。     

Enhanced treatment efficiency of an anaerobic sequencing batch reactor (ASBR) for cassava stillage with high solids content

Cassava stillage is a high strength organic wastewater with high suspended solids (SS) content. The efficiency of cassava stillage treatment using an anaerobic sequencing batch reactor (ASBR) was significantly enhanced by discharging settled sludge to maintain a lower sludge concentration (about 30 g/L) in the reactor. Three hydraulic retention times (HRTs), namely 10 d, 7.5 d, 5 d, were evaluated at this condition. The study demonstrated that at an HRT of 5 d and an organic loading rate (OLR) of 11.3 kg COD/(m³ d), the total chemical oxygen demand (TCOD) and soluble COD (SCOD) removal efficiency can still be maintained at above 80%. The settleability of digested cassava stillage was improved significantly, and thus only a small amount of settled sludge needed to be discharged to maintain the sludge concentration in the reactor. Furthermore, the performance of ASBR operated at low and high sludge concentration (about 79.5 g/L without sludge discharged) was evaluated at an HRT of 5 d. The TCOD removal efficiency and SS in the effluent were 61% and 21.9 g/L respectively at high sludge concentration, while the values were 85.1% and 2.4 g/L at low sludge concentration. Therefore, low sludge concentration is recommended for ASBR treating cassava stillage at an HRT 5 d due to lower TCOD and SS in the effluent, which could facilitate post-treatment.     

Leaching losses of nutrients and yield and nutrient uptake by container-grown begonia as affected by lime and fertiliser applications to a peat medium

The effect of increased lime applications and one rate of soluble basal fertiliser on leaching losses of NH₄-N, NO₃-N, P, Ca, Mg and K from peat in containers was studied in the presence or absence of Begonia semperflorens plants in a greenhouse pot experiment. Percentage recoveries (leached, plus extractable nutrient remaining in the peat, plus plant uptake) of mineral N and P were in the range of 60–80% while those for Ca, Mg and K ranged from 95 to 111%. Percentage leaching losses in the absence of plants were: mineral N, 75–76%; P, 59–74%; Ca, 5–7%; Mg, 14–19%; and K, 17–31%. In the presence of plants, the average decrease in the percentage loss of nutrients by leaching was: N, 9.3%; P, 4.4%; Ca, 0.5%; Mg, 0.3%; and K, 1.3% Liming tended to decrease leaching losses of NH₄-N, P, Ca and Mg but increase those of K and NO₃-N. The phosphate adsorption capacity of the peat was not measurable but significant ammonia fixation from added (NH₄)2SO₄ was demonstrated at high pH (>6.5) concomitant with high N rates (> 300 g N m^?3). Effective cation-exchange capacity (CEC) and CEC measured with unbuffered 1m NH₄CI were both more than doubled with increased lime additions as the pH of the peat increased from 4.3 to 5.6. The conventional CEC measurement (NH₄OAc, pH 7.0) and BaCl₂-TEA (pH 8.2) CEC both remained unaffected by the initial lime rates, and both greatly overestimated the CEC of the peat at its unbuffered pH.     

Novel partial nitritation treatment for anaerobic digestion liquor of swine wastewater using swim-bed technology

A swim-bed reactor using the biofringe acryl-fiber biomass carrier was used for partial nitritation treatment for anaerobic digestion liquor of swine wastewater. The sludge in the reactor demonstrated excellent settling properties, and the sludge volumetric index (SVI) was always about 50 ml g(-1). The mixed liquor suspended solids (MLSS) concentration was maintained above 10,000 mg l(-1) with a maximum of 16,800 mg l(-1). Satisfactory and stable partial nitritation was obtained at a nitrogen loading rate (NLR) of 1.9 kg-N m(-3) d(-1) without any operational control. Only a little nitrate was produced almost during the whole operational period and the nitrite to total oxidized nitrogen ratio (NO(2)-N/(NO(2)-N+NO(3)-N)) was always above 95%. In addition, the influence of temperature on partial nitritation efficiencies was also investigated and non-controlled efficiencies were maintained stably between 15 degrees C and 30 degrees C at an NLR of 1.9 kg-N m(-3) d(-1), but suddenly deteriorated when the temperature fell below 15 degrees C. Nitrite oxidizing bacteria were inhibited by free ammonia and free nitric acid, which prevented the conversion of nitrite to nitrate and the inhibition due to free nitric acid weaken with a decrease in temperature. It was apparent that these phenomena were crucial to the control of partial nitritation treatment.     

Substrate specificity of a recombinant d-lyxose isomerase from Providencia stuartii for monosaccharides

The specific activity and catalytic efficiency (k_cat/K_m) of the recombinant putative protein from Providencia stuartii was the highest for d-lyxose among the aldose substrates, indicating that it is a d-lyxose isomerase. Gel filtration analysis suggested that the native enzyme is a dimer with a molecular mass of 44 kDa. The maximal activity for d-lyxose isomerization was observed at pH 7.5 and 45 °C in the presence of 1 mM Mn²⁺. The enzyme exhibited high isomerization activity for aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration, such as d-lyxose, d-mannose, l-ribose, d-talose, and l-allose (listed in decreasing order of activity). The enzyme exhibited the highest activity for d-xylulose among all pentoses and hexoses. Thus, d-lyxose was produced at 288 g/l from 500 g/l d-xylulose by d-lyxose isomerase at pH 7.5 and 45 °C for 2 h, with a conversion yield of 58 % and a volumetric productivity of 144 g l^− 1 h^− 1. The observed k_cat/K_m (920 mM^− 1 s^− 1) of P. stuartiid-lyxose isomerase for d-xylulose is higher than any of the k_cat/K_m values previously reported for sugar and sugar phosphate isomerases with monosaccharide substrates. These results suggest that the enzyme will be useful as an industrial producer of d-lyxose.     

Influence of nitrogen form and concentration on the nitrate reductase activity of winter barley (Hordeum vulgare L cv Igri)

Winter barley (Hordeum vulgare L cv Igri) plants were grown for 5 weeks in a controlled environment room using a recirculating nutrient solution culture system at a root and shoot temperature of 10°C. When solution NO₃-N concentration was varied between 0 and 64 mg litre^?1, shoot endogenous and induced nitrate reductase activity (NRA_e and NRA_i respectively) increased asymptotically from zero in plants grown with O mg NO₃-N litre^?1 to a maximum activity in solutions containing ? 16 mg NO₃-N litre^?1. Shoot Nitrogen Response Index (NRI = NRA_i/NRA_e) showed an opposite trend decreasing from a maximum of 2.6 at 2 mg NO₃-N litre^?1 to a minimum approaching unity when ? 32 mg N litre^?1 was supplied. In a separate experiment, nitrogen form (NO₃-N, NH₄-N or a 1:1 mixture) had a marked influence on shoot NRA. Enzyme activity was negligible in tissue from plants absorbing NH₄-N, highest in NO₃-fed plants and intermediate in those supplied with both N forms. NRI, however, approached unity in all treatments. The results provide evidence to suggest that NRI may be used as an indicator of the N status of barley plants grown with varied N nutrition.     

Comparison of chemical modifiers for direct determination of Cd, Cu and Zn in food stuffs by solid-sampling-ETAAS

In this work, the capability of different chemical modifiers (Pd, Pd/Mg(NO₃)₂, Pd/NH₄NO₃, NH₄H₂PO₄, NH₄H₂PO₄/Mg(NO₃)₂) to eliminate the matrix effects in the direct determination of Cd, Cu and Zn in food-stuffs by solid sampling-electrothermal atomic absorption spectrometry was compared. The alternative analytical lines were used for determination of Cu (327.4 nm) and Zn (307.6 nm) in order to allow the introduction of reasonably high sample mass into the furnace. Mixed modifiers containing palladium were useful to eliminate the matrix effect in Cd determination. For Cu and Zn determination the application of Pd shows satisfactory analytical performance. In the determinations of Cd and Zn the phosphate containing modifiers shows elimination of matrix effects only when applying them to a partially pyrolysed sample (at 400 °C). The achievable limits of detection for Cd, Cu and Zn in solid samples were 0.279 ng g⁻¹; 0.020 μg g⁻¹ and 2.04 μg g⁻¹, respectively.     

Efficacy of ozone against Rhyzopertha dominica adults in wheat

Adults of a laboratory strain of the lesser grain borer, Rhyzopertha dominica (F.), were exposed to ozone concentrations of 0.42 and 0.84 g/m³ for up to 36 and 30 h, respectively, to estimate lethal time (LT) and lethal dose (LD) to kill 99% of insects at 28 °C and 65% r.h. After exposure, adult mortality was counted daily for 5 d. Adult progeny production data from ozone-exposed adults was used to estimate effective time (ET) and effective dose (ED) for 99% reduction in adult progeny production. At 0.42 and 0.84 g/m³, LT₉₉ values for adult mortality on day 1 were 67 and 42 h, respectively. Corresponding LD₉₉ values for adult mortality on day 1 were 28 and 36 g-h/m³, respectively. On day 5, LT₉₉ and LD₉₉ values decreased by 52–54% of day 1 values. The LT₉₉ or LD₉₉ values over days 1 through 5 decreased in a nonlinear fashion, suggesting delayed toxic effects of ozone. The ET₉₉ value for reduction in adult progeny production was 22 h at an ozone concentration of 0.84 g/m³, whereas it was 39 h at 0.42 g/m³. Like LD₉₉ values, ED₉₉ value for adult progeny reduction at 0.42 g/m³ of ozone was lower than at an ozone concentration of 0.84 g/m³. Doubling the ozone concentration from 0.42 to 0.84 g/m³ did not reduce the LT₉₉ or ET₉₉ values by 50%. In general, the LD₉₉ values on days 1 through 5 at an ozone concentration of 0.84 g/m³ were significantly greater than similar values at an ozone concentration of 0.42 g/m³, suggesting that R. dominica adults tend to be more susceptible when exposed to a low ozone concentration for extended time periods.     

Treatment capability of an up-flow anammox column reactor using polyethylene sponge strips as biomass carrier

The feasibility of applying a polyethylene (PE) sponge as a biomass carrier in an anaerobic ammonium oxidation (anammox) reactor and its nitrogen removal performance were also investigated. Experiments were carried out in an up-flow column reactor with synthetic inorganic wastewater. Experimental results indicate that reactor containing PE sponge biomass carriers showed a high nitrogen removal capability and exhibited stable performance. In addition, the reactor with 8 strips PE sponge as biomass carrier exhibited greater adaptation capacity compared to that with 6 strips and could achieve a high TN removal rate within a very short period. The ratio of NO₂-N removal and NO₃-N production to NH₄-N removal for the reactor was 1.26:0.21. Furthermore, to investigate the bacterial composition of the mature community, 16S rRNA sequences were amplified by PCR and analyses were conducted using DNA databases. Results showed that a new kind of anammox microorganism (Kumadai-1) was the dominant species in the reactor when using PE sponge as a biomass carrier.     

Effect of modifiers on thermal behaviour of Se in acid digestates and slurries of vegetables by graphite furnace atomic absorption spectrometry

The influence of sample preparation strategy of vegetables on the electrothermal behaviour of Se without and with chemical modifiers such as Pd(NO₃)₂, Pd(NO₃)₂ + Mg(NO₃)₂, Pd(NO₃)₂ + Cd(NO₃)₂, pre-reduced Pd, Mg(NO₃)₂, and Ni(NO₃)₂ was investigated. Acid digestates and slurries of vegetables (0.1% m/v in 1% v/v HNO₃ + 0.005% v/v of Triton X-100) were used to prepare reference solutions or slurries. For 10 μl of each modifier tested, pyrolysis and atomization temperatures were evaluated using pyrolysis and atomization curves, respectively. Best conditions, such as thermal stability, signal profile, repeatability and sensitivity were attained using Pd(NO₃)₂ as chemical modifier. The following heating program (temperature, ramp/hold time) of the graphite tube of the Varian SpectrAA-800Z atomic absorption spectrometer was used: dry step (85 °C, 5/0 s; 95 °C, 40/0 s; 120 °C, 10/5 s); pyrolysis step (1400 °C, 10/3s); atomization step (2200 °C, 1/2 s); clean step (2600 °C, 2/0 s). This pyrolysis temperature is 800 °C higher than when measuring without any modifier. For 20 μL sample volume and 10 μg Pd(NO₃)₂, analytical curves in the 3.0–30 μg Se l⁻¹ range were obtained. The method was applied for Se determination in acid digestates and slurries of 10 vegetable samples and one standard reference material (rice flower) and results were in agreement at 95% confidence level. Recoveries varied from 89 to 95% for spiked samples. The lifetime of the graphite tube was ca. 250 firings and the relative standard deviations (n=12) for a typical acid digestate and slurry containing 20 μg Se l⁻¹ were 3.8% and 8.3%, respectively. The limits of detection were 2.0 μg Se l⁻¹ and 0.6 μg Se l⁻¹ Se for digestates and slurries, respectively.     

Nitrogen fractions and soluble carbohydrates in Italian ryegrass II.—Effects of light intensity,form and level of nitrogen

S.22 Italian ryegrass grown in a glasshouse during June on clay loam soil at three light intensities (100, 68 and 44% of daylight), was given 6 amounts of N (0–500 ppm) as NH₄⁺-N or NO₃^?-N. Grass grew best in 100% daylight, and with NH₄⁺-N yields were most at 500 ppm and with NO₃^?-N at 200 ppm. Total-N, total soluble-N and nitrate-N, were much more, and protein-N, amide-N (psrticularly asparagine-N) and α-amino-N much less in grass given NO₃^?-N than in grass given NH₄⁺-N. These differences increased with increasing amounts of applied N. Shading, or increasing the amount of N increased total-N, total soluble-N, soluble organic-N and nitrate-N, and decreased protein-N and soluble carbohydrates. Light intensity had most effect on the amount of solyble carbohydrates in grass given 100 ppm of N and the effect decreased with increasing amounts of N. ‘N-Serve’ indirectly influenced the chemical composition of grass by maintaining N in the soil in the NH₄⁺-N form.     

Inhibition of Chymosin and the Coagulation of Para-Casein Micelles by Anions

The effect of monovalent anions on the coagulation of para-casein micelles was determined by monitoring light transmission after adding different Ca salts (40 mM) to partially hydrolyzed casein micelles. The release of macro-peptide by chymosin was quantified using fluorescamine. The average rate of the chymosin-initiated coagulation of casein micelles, approximated by the reciprocal of clotting time, was determined as a function of anion type and concentration to determine the simultaneous effects of anions on chymosin velocity and para-casein micelle aggregability.Chymosin velocity and the coagulation of para-casein micelles were progressively inhibited by anions; the larger the anion, the greater the inhibition (SCN⁻ > NO₃⁻ > Br⁻ > Cl⁻). This is attributed to the binding of anions to cationic binding sites on kappa-casein and para-kappa-casein. The relative effect of the larger anions compared with that of Cl⁻ on the average rate of the chymosin-initiated coagulation of casein micelles increased with anion concentration (6 to 120 mM) but became limited at 120 mM. In the presence of 120 mM SCN⁻, NO₃⁻ and Br⁻, the average rate of coagulation was 26, 59, and 78% of that obtained with 120 mM Cl⁻.The marked sensitivity of the interactions between chymosin and kappa-casein and between para-casein micelles to anion type support conclusions that cationic sites on kappa-casein are important in the mechanism of the chymosin-initiated coagulation of casein micelles. Thus, monovalent anions may be useful to elucidate the mechanism of protein-protein interactions in food systems.     

Helvellisin,a novel alkaline protease from the wild ascomycete mushroom Helvella lacunosa

A 33.5-kDa serine protease designated as helvellisin was isolated from dried fruiting bodies of the wild ascomycete mushroom Helvella lacunosa. It was purified by using a procedure which entailed ion exchange chromatography on DEAE-cellulose, CM-Sepharose, Q-Sepharose, and FPLC-gel filtration on Superdex 75. The protease was characterized by unique N-terminal amino acid sequence, thermostability and pH stability. The protease exhibited a pH optimum of 11.0 and a temperature optimum of 65 °C, with about 40% activity remaining at 87 °C and pH 5 and 13. Helvellisin demonstrated a protease activity of 14 600 U/mg toward casein. The K_m of the purified protease for casein was 3.81 mg/ml at pH 11.0 and 37 °C. The V_max was 5.35 × 10^− 2 mg ml^− 1 min^− 1. It was adversely affected by phenylmethylsulfonyl fluoride, suggesting that it is serine protease. The activity of the protease was enhanced by Mg²⁺, Fe²⁺ and Mn²⁺, but was curtailed by Cu²⁺, Hg²⁺ and Fe³⁺. It was devoid of antifungal and ribonuclease activities.     

Identification of optimal membrane morphological parameters during microfiltration of mosambi juice using low cost ceramic membranes

In this work, experimental investigations were carried out for the identification of optimal membrane morphological parameters (pore size distribution, average pore size and porosity) during microfiltration (MF) of mosambi juice using low cost ceramic membranes. Four different low cost ceramic membranes with different pore diameters (d_m) and porosities (?) were subjected to MF studies to evaluate the effect of d_m and ? on permeation characteristics (permeate flux and juice quality) of centrifuged mosambi juice (CJ) and enzyme treated centrifuged mosambi juice (ETCJ). Subsequently, a convenient factor namely effective permeable area factor (?_md_m²) was evaluated to provide greater insights in the fouling phenomena. Various physio-chemical properties such as colour, clarity, pH, citric acid content, density, total soluble solid (TSS) and alcohol insoluble solids (AIS) were measured for both feed and permeate juice samples to evaluate the effect of ?_md_m² on juice quality. Typical permeate fluxes were observed to vary from 5.78 × 10⁻⁶ to 13.45 × 10⁻⁶ m³/m² s for CJ and 14.07 × 10⁻⁶ to 60.64 × 10⁻⁶ m³/m² s for ETCJ at 82.7 kPa (ΔP) for different membranes whose ?_md_m² varied from 0.249 to 0.783 μm². Among different membrane pore blocking models, flux decline by cake filtration was found to be the best fitted model. The cake filtration model constant (k_c) was found to vary with ΔP and ?_md_m² and was empirically correlated. Phenomenological models were proposed to illustrate the dependency of total hydraulic resistance of membrane on ?_md_m², ΔP and time (t). Based on experimental as well as theoretical investigations, membranes with ?_md_m² up to 0.443 μm² for CJ and 0.294 μm² for ETCJ and a ΔP of 82.7 kPa were recommended for MF of mosambi juice.