Critical flux and fouling in ultrafiltration of proteins

In this thesis different parameters influencing critical flux in protein ultrafiltration and membrane foul-ing were studied. Short reviews of proteins, cross-flow ultrafiltration, flux decline and criticalflux and the basic theory of Partial Least Square analysis (PLS) are given at the beginning. The experiments were mainly performed using dilute solutions of globular proteins, commercial polymeric membranes and laboratory scale apparatuses. Fouling was studied by flux, streaming potential and FTIR-ATR measurements. Critical flux was evaluated by different kinds of stepwise procedures and by both con-stant pressure and constant flux methods. The critical flux was affected by transmembrane pressure, flow velocity, protein concentration, mem-brane hydrophobicity and protein and membrane charges. Generally, the lowest critical fluxes were obtained at the isoelectric points of the protein and the highest in the presence of electrostatic repulsion between the membrane surface and the protein molecules. In the laminar flow regime the critical flux increased with flow velocity, but not any more above this region. An increase in concentration de-creased the critical flux. Hydrophobic membranes showed fouling in all charge conditionsand, furthermore, especially at the beginning of the experiment even at very low transmembrane pressures. Fouling of these membranes was thought to be due to protein adsorption by hydrophobic interactions. The hydrophilic membranes used suffered more from reversible fouling and concentration polarisation than from irreversible foul-ing. They became fouled at higher transmembrane pressures becauseof pore blocking. In this thesis some new aspects on critical flux are presented that are important for ultrafiltration and fractionation of proteins.

Correlations of glycogen synthase and phosphorylase activities with glycogen concentration in human muscle biopsies. Evidence for a double-feedback mechanism regulating glycogen synthesis and breakdown.

The purpose of this study was to verify in man the relationships of muscle glycogen synthase and phosphorylase activities with glycogen concentration that were reported in animal studies. The upper level of glycogen concentration in muscle is known to be tightly controlled, and glycogen concentration was reported to have an inhibitory effect on synthase activity and a stimulatory effect on phosphorylase activity. Glycogen synthase and phosphorylase activity and glycogen concentration were measured in muscle biopsies in a group of nine normal subjects after stimulating an increase of their muscle glycogen concentration through either an intravenous glucose-insulin infusion to stimulate glycogen synthesis, or an Intralipid (Vitrum, Stockholm, Sweden) infusion in the basal state to inhibit glycogen mobilization by favoring lipid oxidation at the expense of glucose oxidation. Phosphorylase activity increased from 71.3 +/- 21.0 to 152.8 +/- 20.0 nmol/min/mg protein (P < .005) after the glucose-insulin infusion. Phosphorylase activity was positively correlated with glycogen concentration (P = .005 and P = .0001) after the glucose-insulin and Intralipid infusions, respectively. Insulin-stimulated glycogen synthase activity was significantly negatively correlated with glycogen concentration at the end of the Intralipid infusion (P < .005). In conclusion, by demonstrating a negative correlation of glycogen concentration with glycogen synthase and a positive correlation with phosphorylase, this study might confirm in man the double-feedback mechanism by which changes in glycogen concentration regulate glycogen synthase and phosphorylase activities. It suggests that this mechanism might play an important role in the regulation of glucose storage.

When cholesterol is not cholesterol: a note on the enzymatic determination of its concentration in model systems containing vegetable extracts

Background: Experimental evidences demonstrate that vegetable derived extracts inhibit cholesterol absorption in the gastrointestinal tract. To further explore the mechanisms behind, we modeled duodenal contents with several vegetable extracts. Results: By employing a widely used cholesterol quantification method based on a cholesterol oxidase-peroxidase coupled reaction we analyzed the effects on cholesterol partition. Evidenced interferences were analyzed by studying specific and unspecific inhibitors of cholesterol oxidase-peroxidase coupled reaction. Cholesterol was also quantified by LC/MS. We found a significant interference of diverse (cocoa and tea-derived) extracts over this method. The interference was strongly dependent on model matrix: while as in phosphate buffered saline, the development of unspecific fluorescence was inhibitable by catalase (but not by heat denaturation), suggesting vegetable extract derived H2O2 production, in bile-containing model systems, this interference also comprised cholesterol-oxidase inhibition. Several strategies, such as cholesterol standard addition and use of suitable blanks containing vegetable extracts were tested. When those failed, the use of a mass-spectrometry based chromatographic assay allowed quantification of cholesterol in models of duodenal contents in the presence of vegetable extracts. Conclusions: We propose that the use of cholesterol-oxidase and/or peroxidase based systems for cholesterol analyses in foodstuffs should be accurately monitored, as important interferences in all the components of the enzymatic chain were evident. The use of adequate controls, standard addition and finally, chromatographic analyses solve these issues.

How hard is a commercial puzzle: the eternity II challenge

Recently, edge matching puzzles, an NP-complete problem, have received, thanks to money-prized contests, considerable attention from wide audiences. We consider these competitions not only a challenge for SAT/CSP solving techniques but also as an opportunity to showcase the advances in the SAT/CSP community to a general audience. This paper studies the NP-complete problem of edge matching puzzles focusing on providing generation models of problem instances of variable hardness and on its resolution through the application of SAT and CSP techniques. From the generation side, we also identify the phase transition phenomena for each model. As solving methods, we employ both; SAT solvers through the translation to a SAT formula, and two ad-hoc CSP solvers we have developed, with different levels of consistency, employing several generic and specialized heuristics. Finally, we conducted an extensive experimental investigation to identify the hardest generation models and the best performing solving techniques.

Esterification of oleic acid catalayzed by an Aspergillus niger strain. Influence of water activity and alcohol concentration

Effects of water activity and 1-propanol concentration on synthesis of propyl oleate from oleic acid using Aspergillus niger cell-bound lipases in isooctane are described. A. niger produces lipases (EC 3.1.1.3) which partly bind to the mycelium during growth. Ester production was monitored for 72 hours at different 1-propanol concentrations and water activities. Aliquots were sequentially withdrawn and propyl esters were quantified using GC and methyl palmitate as an internal standard. In all assayed conditions A. niger cell-bound lipases catalysed propyl oleate synthesis, but at different degrees.

Soil nutrient availability and its impact on fruit quality of Tahiti acid lime

The Tahiti acid lime in Brazil is mostly grown in the São Paulo State. The value of this crop production ranks among the ten most important fruits in the country. The Brazilian exports of Tahiti limes have increased in the last years with a corresponding increased demand for superior quality of fresh fruits, which is affected by mineral nutrients. Therefore, this study evaluated nutrient soil availability and its influence on nutritional status of trees based on the determination of leaf and fruit nutrient concentrations, fruit characteristics, and post harvest quality. Eleven commercial groves with trees older than 4-yr and differently managed were studied. Plots with six trees in each grove were sampled for soil (0-20 cm depth layer), leaf and fruit analyses with three replicates. Correlation coefficients were pair wised established for all variables. The results showed that N leaf concentration was well correlated with green color of fruit peel as measured by a color index (r = -0.71**), and which was optimum with Leaf-N around 22 g kg-1. Leaf-Ca was inversely correlated with fruit water loss after 14-day interval from harvest (r = -0.54*) demonstrating that Ca plays an important role in Tahiti fruit shelf-life. Data also suggested that increased fruit K concentration correlated with increased fruit water losses during storage (r >0.58*).

The Saccharomyces cerevisiae Hot1p regulated gene YHR087W (HGI1) has a role in translation upon high glucose concentration stress.

Background While growing in natural environments yeasts can be affected by osmotic stress provoked by high glucose concentrations. The response to this adverse condition requires the HOG pathway and involves transcriptional and posttranscriptional mechanisms initiated by the phosphorylation of this protein, its translocation to the nucleus and activation of transcription factors. One of the genes induced to respond to this injury is YHR087W. It encodes for a protein structurally similar to the N-terminal region of human SBDS whose expression is also induced under other forms of stress and whose deletion determines growth defects at high glucose concentrations. Results In this work we show that YHR087W expression is regulated by several transcription factors depending on the particular stress condition, and Hot1p is particularly relevant for the induction at high glucose concentrations. In this situation, Hot1p, together to Sko1p, binds to YHR087W promoter in a Hog1p-dependent manner. Several evidences obtained indicate Yhr087wp"s role in translation. Firstly, and according to TAP purification experiments, it interacts with proteins involved in translation initiation. Besides, its deletion mutant shows growth defects in the presence of translation inhibitors and displays a slightly slower translation recovery after applying high glucose stress than the wild type strain. Analyses of the association of mRNAs to polysome fractions reveals a lower translation in the mutant strain of the mRNAs corresponding to genes GPD1, HSP78 and HSP104. Conclusions The data demonstrates that expression of Yhr087wp under high glucose concentration is controlled by Hot1p and Sko1p transcription factors, which bind to its promoter. Yhr087wp has a role in translation, maybe in the control of the synthesis of several stress response proteins, which could explain the lower levels of some of these proteins found in previous proteomic analyses and the growth defects of the deletion strain. Keywords: Saccharomyces cerevisiae; High glucose osmotic stress; Gene YHR087W; Gene expression; Translation; Hot1p; Hog1p; Polysomes

STYREENI-BUTADIEENILATEKSIN VALMISTUS EMULSIOPOLYMEROIN-NILLA JA LATEKSIN VISKOSITEETTIIN VAIKUTTAVAT TEKIJÄT.

Työn tavoitteina oli kirjallisuusosassa selvittää emulsiopolymeroinnin perusperiaatteet ja lateksien viskositeettiin vaikuttavat tekijät. Kokeellisessa osassa selvitettiin eräiden kaupallisten lateksien viskositeettiin vaikuttavia tekijöitä. Tutkittujen kaupallisten lateksien viskositeettien riippuvuudelle kuiva-ainepitoisuudesta saatiin tulokset, jotka ovat melko hyvin yhtäpitäviä kirjallisuudesta saatujen tulosten kanssa. Tutkitut lateksit erosivat lähinnä maksimaalisen polymeeripartikkelin tilavuusosuuden kohdalla kirjallisuudesta saaduista arvoista. Tämän todettiin johtuvan sähköisen kaksoiskerroksen ja partikkelin pintaan kiinnittyneiden ryhmien vaikutuksesta. Tämä tulos varmentui elektrolyyttipitoisuuden vaikutusta selvitettäessä. Elektrolyyttilisäys laski lateksien viskositeetteja ja pienensi lateksien välisiä viskositeettieroja. Lateksin pH:n nostolla oli selvästi viskositeettia kasvattava vaikutus. Tämä johtuu osaltaan myös sähköisen kaksoiskerroksen kasvamisesta happoryhmien ionisoituessa. Latekseja toisiinsa verrattaessa havaittiin selkeästi karboksyylihapon ja initiaattorista peräisin olevien happoryhmien määrän vaikutus lateksin viskositeetin muutokselle. Paljon karboksyylihappoa ja initiaattoria sisältävien lateksien viskositeetti muuttui selvästi voimakkaammin pH:n muuttuessa. Latekseissa havaittiin myös ero heikkojen karboksyylihapporyhmien ja vahvojen initiaattorista peräisin olevien happoryhmien ionisoitumisen välillä. Vahvat happoryhmät ionisoituivat matalammassa pH:ssa kuin vahvat ja nostavat näin myös viskositeettia matalammassa pH:ssa kuin karboksyylihapporyhmät. Anionisen emulgaattorin lisäyksellä ei havaittu olevan kovinkaan suurta vaikutusta viskositeettiin. Partikkelikoon vaikutusta voitiin tutkia ainoastaan prosessista saadun mittausaineiston avulla. Partikkelikoon vaikutukset peittyivät suurelta osin muiden tekijöiden alle. Ainoastaan yhdelle lateksityypille saatiin selkeä riippuvuus partikkelikoon ja viskositeetin välille. Riippuvuus noudattaa kirjallisuudesta saatuja tietoja eli partikkelikoon kasvaessa viskositeetti laskee. Myös lateksin viskositeetin riippuvuus käytetystä leikkaus-nopeudesta noudattaa hyvin kirjallisuudesta saatuja tuloksia. Lateksin viskositeetti laskee leikkausnopeuden kasvaessa.

Kalvojen vertailu heran nanosuodatuksessa

Työssä verrattiin kaupallisia nanosuodatuskalvoja heran konsentroinnissa. Tutkitut kalvot olivat Desal-5 DK, NF45 ja Koch SR1. NF45-kalvosta tutkittiin kahta eri sukupolven kalvoa. Konsentrointiajoja tehtiin sekä laboratoriomittakaavan levysuotimella että pilot-mittakaavan spiraalimoduulilaitteella. Lisäksi tutkittiin juoksute- ja happoheran konsentrointien eroja. Erityistä huomiota kiinnitettiin permeaattivuon arvoihin konsentroinnissa ja kalvojen suolojen ja laktoosin pidätyskykyyn. NF45-kalvon uuden sukupolven malli osoittautui mittauksissa samankaltaiseksi suolojen ja laktoosin pidätyskyvyltään kuin Desal-5 DK. Koch SR1-kalvo, jonka suolojen ja laktoosin pidätyskyky on Desal-5 DK-kalvoa heikompi, puolestaan vastaa ominaisuuksiltaan NF45 vanhan sukupolven kalvoa. Vanhan sukupolven NF45-kalvon valmistus on loppunut keväällä 2000. Vaihdettaessa vanhan sukupolven NF45-kalvot uuden sukupolven kalvoihin on odotettavissa pienemmät permeaattivuot ja suuremmat suolojen ja laktoosin retentiot kuin aiemmin NF45-kalvolla. Juoksuteheran konsentroinnissa suurimmat permeaattivuot saatiin Koch SR1-kalvolla. Levysuotimella ja spiraalimoduulilla saadaan koostumukseltaan samanlainen juoksuteheratiiviste. Levysuotimella permeaattivuot ovat samalla konsentrointikertoimella suuremmat kuin spiraalimoduulilla. Tämä johtuu spiraalimoduuliin jäävistä kuolleista alueista, joissa ei ole virtausta. Uutta prosessia suunniteltaessa voidaan käyttää laboratoriomittakaavan levysuodinkokokeita, kun halutaan tietoa saatavan tuotteen koostumuksesta. Prosessin tuotantokapasiteetin arvioimiseen tarvitaan pilot-mittakaavan spiraalimoduulikokeita. Happoheratiiviste sisältää enemmän suoloja kuin samalla kalvolla valmistettu juoksuteheratiiviste. Tämä johtuu happoheran juoksuteheraa suuremmasta suolapitoisuudesta. Lisäksi happoheran konsentroinnin permeaattivuo on pienempi kuin juoksuteheran permeaattivuo, sillä happoheran alhainen pH, noin 4,5, vaikuttaa kalvon permeabiliteettiin heikentävästi.

Potential of antioxidant extracts produced by aqueous processing ofrenewable resources for the formulation of cosmetics

The performance of natural extracts obtained from underutilized and residual vegetal and macroalgal biomass processed with food-grade green solvents was compared with that of commercial antioxidants. Selected extracts were obtained from two terrestrial sources: winery byproducts concentrate (WBC) and chestnut burs hydrothermally fractionated extract (CBAE), and from two underutilized seaweeds: Sargassum muticum extracts, either extracted with ethanol (SmEE) or after alginate extraction and hydrothermal fractionation (SmAE) and from Ulva lactuca processed by mild acid extraction and membrane concentration (UlAE). These extracts showed in vitro antioxidant properties comparable to commercial antioxidants and were safe for topical use based on the absence of skin-irritant effects at 0.1% on reconstructed human tissues. The stability of several cosmetic model emulsions was assessed during accelerated oxidation assays. The incorporation of natural extracts produced from renewable underutilized resources at 0.4-0.5% in an oil-in-water emulsions reduced lipid oxidation during storage.

Daily precipitation concentration across Europe 1971-2010

Daily Precipitation Concentration Index (CI) was used in this paper to investigate the statistical structure of daily precipitation across Europe based on 530 daily rainfall series for the period 1971-2010. Annual CI shows a North- West to South-East gradient (excluding Turkey and Greece). The same gradient is also observed in winter, spring and autumn, while in summer the gradient is North-South. Highest annual and seasonal daily concentrations of rainfall were detected in the western Mediterranean basin, mainly along Spanish and French coastlands. Latitude and distance from the sea seems to play a major role on spatial CI distribution; at subregional scale also relief plays an important role. The Mann-Kendall test did not identify uniform significant pattern in temporal trend across Europe for 1971-2010 period. The only broad areas with increasing annual and seasonal CI values are located in northern and south-western France and northern coastlands of the Iberian Peninsula. This findings suggest that daily precipitation distribution has not significantly changed during the 1971-2010 over Europe.