Influence Of Initial pH Research Articles

Effects of culture and medium conditions on hydrogen production from starch using anaerobic bacteria

The influences of initial pH (4.0–9.0), iron concentration (1.2–100 mg/ l), nitrogen concentration (NH 4HCO 3, 0.56–11.28 g/ l) and starch concentration (2–32 g/ l) on hydrogen production and volatile fatty acid (VFA) production were studied. Batch experiments using starch as a substrate and mixed bacteria were conducted at 35°C. The optimum pH, iron concentration and nitrogen concentration for hydrogen production at a starch concentration of 15 g/ l were 7.0–8.0, Fe 2+ 10 mg/ l and NH 4HCO 3 5.64 g/ l, respectively. The typical VFAs were acetate, propionate and butyrate, with acetate as the major component. The maximum specific hydrogen production rate of 146 ml/g-VSS·d (volatile suspended solids, VSS) and the hydrogen yield of 178 ml/g-starch were obtained at a starch concentration of 15 g/ l under optimum environmental conditions. The maximum hydrogen yield of 194 ml/g-starch was obtained at a starch concentration of 2 g/ l. The maximum specific hydrogen production rate of 237 ml/g-VSS·d was found at a starch concentration of 24 g/ l.

Influence of initial pH on the particle size and fluorescence properties of the nano scale Eu(III) doped yttria

Europium doped ytrrium oxide (Eu:Y 2O 3) was synthesized by a chemical wet method in the presence of tween-80 and ϵ-caprolactam in pH range 4–10. It has been observed that the variation in surface area, pore size, and pore volume of the final product, was strongly dependent on the initial pH of the solution. The powder with a large surface area (∼230 m 2/g) and low pore diameter (∼16 nm) was obtained when the powder was processed at pH ∼4. The crystallite sizes of the powders processed at pH ∼4 and 10, were found to be 35 and 198 nm, respectively. The structural, chemical and thermal studies of the powders were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectrophotometer (FTIR), Carbon analyzer and Thermogravimetry (TGA). High resolution transmission electron microscopic (HRTEM) study of heat treated powders showed a polygonal morphology with particle size of 40 nm when powder was derived at pH ∼4. Observations of fluorescence suggested that the 5D 0→ 7F 2 transition within europium was found to be highly dependent on the initial pH.

Optimization of some variables that affect the synthesis of laccase by Pleurotus ostreatus

The influence of initial pH, concentration of yeast extract, inducer, type of enzyme releaser and buffer system on the composition of a medium for laccase production by Pleurotus ostreatus DM-1513 was investigated. A 25 full factorial experimental design was initially employed to evaluate the effects of these variables on the enzyme synthesis. Data analysis showed that low pH and high yeast extract concentration values, as well as the absence of both an inducer and a buffer system, had positive effects on the secreted enzyme levels, whereas the type of enzyme releaser did not have a significant effect. The highest levels of laccase activity (489–540 U/l) were obtained in optimization experiments using media with initial pH between 6.0 and 6.5 and yeast extract concentrations of 0–0.25%

LITERATURE ABSTRACTS GENERAL PRINCIPLES

Fracture Stress of Fish Meat and the Glass Transition. H. Watanabe (corresponding author), C.Q. Tang, T. Suzuki and T. Mihori (Dept. of Food Sci. & Technol., Tokyo Univ. of Fisheries, Konan 4, Minato, Tokyo 108, Japan). J. Food Eng. 29, 317–327 (1996). Influence of Initial pH on Gelation Kinetics of Texturized Passion Fruit Pulp. C. Mouquet, C. Aymard, S. Guilbert, G. Cuvelier and B. Launay (corresponding author, ENSIA, avenue des Olympiades, 91305 Massy, France). Lebens.‐Wiss. u.‐Technol. 30, 129–134 (1997). Viscoelastic Characterization of Surmimi Gel: Effects of Setting and Starch. L. Ma, A. Grove and G.V. Barbosa‐Cánovas (Dept. of Biological Systems Eng., Washington State Univ., Pullman, WA 99164–6120, USA). J. Food Sci. 61, 881–883, 889 (1996). Influence of Temperature, Fibre Diameter and Conditioning on the Mechanical Properties of Single Muscle Fibres Extended to Fracture. G. Mutungi (corresponding author, Dept. of Physiology, School of Medical Sci., Univ. of Bristol, Bristol, BS8 ITD, United Kingdom), P. Purslow (The Royal Veterinary and Agric. Univ., Fredriksberg C, Denmark) and C. Warkup (Meat & Livestock Commission, Milton Keynes, MK6 1 AX, UK). J. Sci. Food Agric. 72, 359–366 (1996). Comparison of the Acoustic and Mechanical Signatures of Two Cellular Crunchy Cereal Foods at Various Water Activity Levels. R. Tesch, M.D. Normand and M. Peleg (corresponding author, Dept. of Food Sci., Univ. of Massachusetts, Amherst, MA 01003, USA). J. Sc. Food Agric. 70, 347–354 (1996). Multivariate Analysis as a Tool to Predict Bread Volume from Mixogram Parameters. K. Wikström (Dept. of Food Eng., Univ. of Lund, P.O. Box 124, S‐221 000 Lund, Sweden) and L. Bohlin (Bohlin Reologi AB, Oved 19, S‐275 94 Sjöbo, Sweden). Cereal Chem. 73, 686–690 (1996). Changes in Texture and Microstructure of Pressure‐Treated Fish Muscle Tissue During Chilled Storage. I.N.A. Ashe, B.K. Simpson (corresponding author) and H.S. Ramaswamy (Dept. of Food Sci. & Agric. Chemistry, McGill University, Macdonald Campus, 21, 111 Lakeshore Rd., Ste Anne de Bellevue, PQ, Canada H9X 3V9). J. Muscle Foods 8, 13–32 (1997). Collagen Characteristics and Meat Texture of Pigs Exposed to Different Levels of Physical Activity. J.S. Petersen (corresponding author), P. Berge, P. Henckel and M.T. Soerensen (Danish Inst. of Animal Science, Res. Centre Foulum, P.O. Box 39, DK—8830 Tjele, Denmark). J. Muscle Foods 8, 47–61 (1997). Peach Texture During Ripening After Extended Storage. J.A. Murillo, G.H. Brusewitz (corresponding author, Biosystems & Agric. Eng. Dept., Oklahoma State University, Stillwater, OK 74078) and N.O. Maness (Dept. of Hort. & Landscape Architecture). J. Food Quality 20, 61–72 (1997).

Biological processes: The effects of initial pH, percentage inoculum and nutrient enrichment on the solubilization of sediment bound metals

Biological solubilization of metals in highly contaminated sediments (Lachine Canal, Montreal, P.Q., Canada) was tested in 500 mL batches. The biological process uses the leaching capacity of Thiobacilli. Batch experiments were performed to determine the influence of initial pH, the percentage of inoculum, and the addition of nitrogen and phosphate on the efficiency of the process. Similar metal recoveries were obtained at either of the initial pH values (pH 4.0 and pH 4.5). The addition of 20% inoculum (v/v) appears to result in acceptable yields over a short time period (24–48 hours). Solubilization of Cu is strongly correlated with the presence of bacteria (r2 increase with time up to 0.90 after 53h). In the case of Zn (within first 6 hours) and Pb (at the beginning), the chemical environment appears to be the main factor controlling solubilization of these elements (r2 up to 0.99). The addition of nutrients had no affect on the production of Thiobacilli, but the addition of NH4 reduced the solubilization of Zn, Pb (r2 up to 0.90) and at the beginning, the solubilization of Cu (r2=0.67). While the addition of PO43- diminished the solubilization of Zn, Pb and Cu (r2 up to 0.96). Upon addition of substrate (FeSO 4.7H2), the growth of Thiobacilli already present in the sediments is favored. The application of this process to sediments appears feasible, as Zn and Cu levels were at acceptable levels following treatment. Further studies are necessary to improve the removal of Pb.

Influence of Initial pH on Gelation Kinetics of Texturized Passion Fruit Pulp

Homogeneous texturized fruit was prepared by internal setting with alginate, insoluble calcium salt at neutral pH and with glucono-δ-lactone. Hydrolysis of the latter gradually lowered pH, thus inducing calcium release and gel setting. Gelation kinetics of blends at different initial pH levels were determined by following the evolution of the compressive force of gels with a Texture Analyser. Biexponential and Avrami models provided good overall descriptions of the different S-shaped setting-curves in relation to initial pH. The biexponential model could provide a good basis for a physico-chemical interpretation of the gelation phenomenon.

Automatic determination of dissolved organic carbon in seawater in the sub-ppm range

The improvement of a dissolved organic carbon (DOC) analysis technique is described. This continuous flow system, based on both persulfate and UV oxidations, allows the automatic determination of DOC in sea and estuarine waters. The use of FID detection gives a very high sensitivity, permitting the detection of small variations in carbon content. The efficiency of the method and its sensitivity are tested, together with the influence of initial pH and duration of nitrogen bubbling. The system can also be used to determine total or inorganic carbon.