No description available.

No description available.

Pseudomonas fragi CRDA 037 was used to produce both intracellular and extracellular lipases. The crude lipase fractions were fractionated using ammonium sulfate to obtain partially purified intracellular and extracellular lipases; the fraction precipitated at 20-60% of saturation of the intracellular proteins was retained as the source of the endolipase, whereas the culture medium precipitated at 20-40% of saturation, was used as the source of exolipase. Native gel electrophoresis (PAGE) suggested that the partially purified extracellular lipase has a molecular weight of 25,500 Da. Three major electrophoretic bands were present in the intracellular lipase fraction at 70,000, 49,000, and 35,500 Da. The partially purified lipases were characterized with respect to their optimum pH and temperature for lipase activity, and well as for their kinetics, specificities, and reactions toward inhibitors. The optimum pH for the activity of the endolipase was found to be 9.0 whereas that of the exolipase was 8.75. With respect to optimum temperature, 30$ sp circ$C was determined to be the best for the endolipase while 35$ sp circ$C was the optimal value for the exolipase. Enzyme specificity was carried out using triacetin, tributyrin, trimyristin, and triolein as substrates. The results for the exolipase indicated that the lowest K$ sb{m}$ was obtained with trimyristin and the highest K$ sb{m}$ was obtained with triolein whereas for the endolipase, the highest K$ sb{m}$ was obtained with tributyrin and the lowest was with trimyristin. Experiments carried out with inhibitors indicated that both lipases are serine lipases, sulfydryl enzymes, and that tryptophan is essential for maintaining the conformation of the proteins. The most potent inhibitor was ferrous chloride, and sodium deoxycholate was a weak inhibitor for both lipases, however, it was an activator at low concentrations for the exolipase.

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A new process was developed for the filtration of hydrophobic colloids without the assistance of chemical coagulants. The process consists of passing the suspension through a bed of electrically conducting granules which are fluidized by the upward flow of the suspension and simultaneously exposed to a D.C. electric field. The process was demonstrated on an aqueous polystyrene latex of mean particle size 0.34 (mu)m. At optimum conditions a bed of iron granules retained 98% of the entering particles. / Experiments showed that the following variables increased the retention: increasing electric field strength, increasing static bed height, decreasing electrical conductivity of the feed, and decreasing the superficial velocity. Retention was independent of inlet particle concentration. / A model of the process was formulated including various mechanisms of deposition and surface forces. It contained no empirical factors from filtration experiments except the mean particle size in the effluent when electric field is applied. / Electrocoagulation of the polystyrene latex was observed under the microscope and the mechanisms involved were elucidated.

Transglutaminases (EC 2.3.2.13) are a group of thiol enzymes that catalyse acyl-transfer reaction in which the gamma-carboxyamide groups of peptide-bound glutaminyl residues are the acyl donors. They cause post-translational modification of proteins mainly by protein to protein cross-linking, but also through acyl transfer reaction and deamidation of glutamine residues. / Crude liver and flesh extracts of bluefish (Pomatomus saltatrix ) were investigated to ascertain the effects of storage time and temperature on the stability and activity of transglutaminase (TGase). TGase activity was measured and the enzyme was subsequently characterized using CBZ-L-glutaminylglycine and hydroxylamine as substrates. Frozen bluefish liver and flesh extracts had higher specific activities (0.321 Units and 0.230 Units respectively) in comparison to refrigerated liver and flesh extracts (0.124 Units and 0.071 Units respectively) at the end of a 30 day storage period with the frozen liver extract retaining the highest stability. The optimum temperature for the crude bluefish liver TGase reaction with CBZ-L-glutaminylglycine and hydroxylamine was between 40°C and 45°C. The enzyme was stable at temperatures below 55°C, beyond which it lost activity progressively. The crude enzyme extract was active within the pH range of 6.0-7.5, with an optimum pH of 7.0, and was stable from pH 6.5-8.0. / TGase was partially purified from the frozen liver extract of bluefish by gel filtration on 8ephacryl S-200 HR. The partially purified extract was further characterized with respect to its response to temperature and pH. The effects of sodium as well as calcium chloride and other divalent cations, and the inhibitory effects of various chemicals on the activity of the partially purified TGase were also investigated. The partially purified bluefish TGase had an optimum temperature of 40°C via the reaction with CBZ-L-glutaminylglycine and hydroxylamine. The enzyme was observed to be stable at temperatures below 50°C and approximately 90% of the initial TGase activity was retained at the end of a 30 min incubation period. The partially purified bluefish TGase had a pH optimum of pH 7.5 and was stable within a narrow pH range of 7.0 - 8.0. / The partially purified enzyme showed requirement for calcium (Ca 2+) ions for activity and no activity was observed in the absence of Ca2+. The replacement of Ca2+ by other divalent cations such as Mg2+, Mn2+, Ba2+, Zn2+ and Fe2+ produced various levels of activity with the enzyme, albeit less than that achieved with Ca2+. Increasing NaCl concentrations, 0 - 15mM, did not seem to have an enhancing effect on the activity of partially purified bluefish TGase. TGase was inhibited by sulfhydryl alkylating agents (monoiodoacetic acid (IAA) and N'-ethylmaleimide (NEM)).

No description available.

No description available.

No description available.

No description available.