A liver metalloendopeptidase which degrades the circulating hypotensive peptide hormones bradykinin and atrial natriuretic peptide

A new metalloendopeptidase was purified to apparent homogeneity from a homogenate of normal human liver using successive steps of chromatography on DEAE-cellulose, hydroxyapatite and Sephacryl S-200. The purified enzyme hydrolyzed the Pro7-Phe8 bond of bradykinin and the Ser25-Tyr26 bond of atrial natriuretic peptide. No cleavage was produced in other peptide hormones such as vasopressin, oxytocin or Met- and Leu-enkephalin. This enzyme activity was inhibited by 1 mM divalent cation chelators such as EDTA, EGTA and o-phenanthroline and was insensitive to 1 µM phosphoramidon and captopril, specific inhibitors of neutral endopeptidase (EC 3.4.24.11) and angiotensin-converting enzyme (EC 3.4.15.1), respectively. With Mr 85 kDa, the enzyme exhibits optimal activity at pH 7.5. The high affinity of this endopeptidase for bradykinin (Km = 10 µM) and for atrial natriuretic peptide (Km = 5 µM) suggests that it may play a physiological role in the inactivation of these circulating hypotensive peptide hormones.

Purification and partial characterization of Phaseolus vulgaris seed aminopeptidase

The aminopeptidase activity of Phaseolus vulgaris seeds was measured using L-Leu-p-nitroanilide and the L-aminoacyl-ß-naphthylamides of Leu, Ala, Arg and Met. A single peak of aminopeptidase activity on Leu-ß-naphthylamide was eluted at 750 µS after gradient elution chromatography on DEAE-cellulose of the supernatant of a crude seed extract. The effluent containing enzyme activity was applied to a Superdex 200 column and only one peak of aminopeptidase activity was obtained. SDS-polyacrylamide gel electrophoresis (10%) presented only one protein band with molecular mass of 31 kDa under reducing and nonreducing conditions. The aminopeptidase has an optimum pH of 7.0 for activity on all substrates tested and the highest Vmax/KM ratio for L-Leu-ß-naphthylamide. The enzyme activity was increased 40% by 0.15 M NaCl, inhibited 94% by 2.0 mM Zn2+, inhibited 91% by sodium p-hydroxymercuribenzoate and inhibited 45% by 0.7 mM o-phenanthroline and 30 µM EDTA. Mercaptoethanol (3.3 mM), dithioerythritol (1.7 mM), Ala, Arg, Leu and Met (70 µM), p-nitroaniline (0.25 mM) and ß-naphthylamine (0.53 mM) had no effect on enzyme activity when assayed with 0.56 mM of substrate. Bestatin (20 µM) inhibited 18% the enzyme activity. The aminopeptidase activity in the seeds decayed 50% after two months when stored at 4oC and room temperature. The enzyme is leucyl aminopeptidase metal- and thiol group-dependent.

Mixing in rotating drums

Tämän diplomityön tarkoitus on parantaa meesauunin toiminnallista tehokkuutta tehostamalla lämmönsiirtoa. Lämmönsiirron parantamiseksi kehitetään erilaisia nostinratkaisuja. Kokeita suoritetaan käyttäen eri sekoitinratkaisuja ja erilaisia prosessiparametreja. Työn kirjallisuusosassa esitetään meesauuni sekä rumpumaisten uunien toiminta. Työssä selvitetään myös sekoituksen analysointiin käytettäviä tapoja ja laskukaavoja. Kirjallisuusosassa keskitytään myös rummussa tapahtuviin fysikaalisiin ilmiöihin sekä erilaisten fluidien reologiaan. Työn kokeellisessa osassa käytettiin LUT Kemiantekniikalla suunniteltua pilot -kokoluokan rumpu-uunia, jolla kokeitaan suoritettiin, käyttäen erilaisia sekoitinratkaisuja ja sekoitusprosessiparametreja. Kokeissa käytettiin myös eri viskositeetin omaavia materiaaleja. Valitut materiaalit olivat vesi, CMC (karboksimetyyliselluloosa) ja kiinteä meesa. Kokeiden tuloksena löydettiin nostinratkaisuja, joilla sekoittumista ja lämmönsiirtoa pystytään parantamaan sekä pidentämään viipymäaikaa.

Entsyymien talteenotto ja kierrätys selluloosaetanolin valmistuksessa

Bioetanolin valmistus selluloosapitoisista raaka-aineista vaatii selluloosapolymeerien pilkkomisen liukoisiksi sokereiksi. Tämä voidaan toteuttaa entsymaattisella hydrolyysillä. Selluloosan pilkkomiseen tarkoitetut entsyymit, sellulaasit, ovat entsymaattisen hydrolyysin jälkeen sitoutuneet joko kiintoainefaasiin tai ovat nestemäisessä faasissa ns. vapaina entsyymeinä. Prosessin taloudellisuuden kannalta on erityisen tärkeää minimoida siinä käytettävien entsyymien tarve, sillä tehokkaat entsyymivalmisteet ovat suhteellisen kalliita. Yksi varteenotettava vaihtoehto bioetanoliprosessin saamiseksi taloudellisemmaksi on käytettyjen entsyymien talteenotto ja kierrätys. Työn tarkoituksena oli selvittää kirjallisuudesta, millaisia menetelmiä on kehitetty entsyymien talteenottoon ja kierrätykseen lignoselluloosasta valmistettavan bioetanolin valmistuksessa. Työssä on keskitytty tuoreisiin tutkimuksiin ja menetelmien käyttökelpoisuuteen ja taloudellisuuteen. Viime vuosina sellulaasien talteenotto- ja kierrätysmenetelmiä koskevat tutkimukset ovat keskittyneet pääasiassa käsittelemään nanopartikkelien avulla tapahtuvaa entsyymien immobilisointia, ultrasuodatusta, erilaisia desorptiomenetelmiä, kiinteän hydrolyysijäännöksen kierrättämistä, tuoreen substraatin lisäämistä sekä myös tislausvaiheen jälkeistä entsyymien kierrättämistä. Jotta kierrätysmenetelmä olisi tehokas, tulisi sen pyrkiä säilyttämään entsyymien aktiivisuuksia, sokerisaantoa menettämättä ja sisältää sekä neste-, että kiintoainefaasista tapahtuva kierrätys. Jokaisella kierrätysmenetelmällä on hyvät ja huonot puolensa. Entsyymien talteenottoastetta saadaan kuitenkin parannettua yhdistämällä erilaisia menetelmiä. Useista tutkimuksista huolimatta, taloudellisinta ja käyttökelpoisinta entsyymien talteenotto- ja kierrätysmenetelmää ei ole vielä saavutettu.

Superkondensaattoreiden valmistus selluloosageeleistä ja hiilimustasta

Tässä työssä tavoitteena oli selvittää selluloosageelien soveltuvuutta superkondensaattorien elektrodimateriaaliksi. Superkondensaattoreiden elektrodit valmistetaan yleensä hyvin huokoisesta hiilimateriaalista. Näin ollen selluloosageeliin joukkoon sekoitettiin sähkönjohtavuutta parantamaan hiilimustaa. Kirjallisessa osassa keskityttiin superkondensaattorin toimintaperiaatteeseen, rakenteeseen ja yleisimmin käytössä oleviin elektrodimateriaaleihin. Yksityiskohtaisemmin paneuduttiin selluloosan käyttöön superkondensaattorien rakennemateriaalina. Kokeellisessa osassa valmistettiin erilaisia selluloosageelejä ja tämän jälkeen elektrodeja hiilimusta-selluloosageeli-seoksesta. Eri sekoitustapojen vaikutusta elektrodin sähköisiin ominaisuuksiin tarkasteltiin sekoittamalla hiilimustaa selluloosageeliin kahdella eri tavalla; korkeapainehajottajalla ja sekoittimella. Tämän lisäksi selvitettiin myös eri kuivaustapojen ja kuivauslämpötilojen vaikutusta elektrodiarkkien ominaisuuksiin. Arkkien sähköiset ominaisuudet määritettiin syklistä voltammetriaa (SV) käyttäen. Saavutetut tulokset osoittivat, että selluloosageelin valmistus on yksi kriittisimmistä kohdista elektrodimateriaalin valmistuksessa. Riittävä entsyymikäsittely vaaditaan, jotta saadaan muodostettua sopiva geeli, johon hiilimusta-partikkelit saadaan takertumaan. Hiilimustan sekoitustavalla sekä elektrodiarkin kuivauslämpötilalla ja – tavalla on myös suuresti vaikutusta elektrodin sähköisiin ominaisuuksiin.

Pressurized hot water flow-through extraction of birch wood

Effective processes to fractionate the main compounds in biomass, such as wood, are a prerequisite for an effective biorefinery. Water is environmentally friendly and widely used in industry, which makes it a potential solvent also for forest biomass. At elevated temperatures over 100 °C, water can readily hydrolyse and dissolve hemicelluloses from biomass. In this work, birch sawdust was extracted using pressurized hot water (PHWE) flow-through systems. The hypothesis of the work was that it is possible to obtain polymeric, water-soluble hemicelluloses from birch sawdust using flow-through PHW extractions at both laboratory and large scale. Different extraction temperatures in the range 140–200 °C were evaluated to see the effect of temperature to the xylan yield. The yields and extracted hemicelluloses were analysed to obtain sugar ratios, the amount of acetyl groups, furfurals and the xylan yields. Higher extraction temperatures increased the xylan yield, but decreased the molar mass of the dissolved xylan. As the extraction temperature increased, more acetic acid was released from the hemicelluloses, thus further decreasing the pH of the extract. There were only trace amounts of furfurals present after the extractions, indicating that the treatment was mild enough not to degrade the sugars further. The sawdust extraction density was increased by packing more sawdust in the laboratory scale extraction vessel. The aim was to obtain extracts with higher concentration than in typical extraction densities. The extraction times and water flow rates were kept constant during these extractions. The higher sawdust packing degree decreased the water use in the extractions and the extracts had higher hemicellulose concentrations than extractions with lower sawdust degrees of packing. The molar masses of the hemicelluloses were similar in higher packing degrees and in the degrees of packing that were used in typical PHWE flow-through extractions. The structure of extracted sawdust was investigated using small angle-(SAXS) and wide angle (WAXS) x-ray scattering. The cell wall topography of birch sawdust and extracted sawdust was compared using x-ray tomography. The results showed that the structure of the cell walls of extracted birch sawdust was preserved but the cell walls were thinner after the extractions. Larger pores were opened inside the fibres and cellulose microfibrils were more tightly packed after the extraction. Acetate buffers were used to control the pH of the extracts during the extractions. The pH control prevented excessive xylan hydrolysis and increased the molar masses of the extracted xylans. The yields of buffered extractions were lower than for plain water extractions at 160–170 °C, but at 180 °C yields were similar to those from plain water and pH buffers. The pH can thus be controlled during extraction with acetate buffer to obtain xylan with higher molar mass than those obtainable using plain water. Birch sawdust was extracted both in the laboratory and pilot scale. The performance of the PHWE flow-through system was evaluated in the laboratory and the pilot scale using vessels with the same shape but different volumes, with the same relative water flow through the sawdust bed, and in the same extraction temperature. Pre-steaming improved the extraction efficiency and the water flow through the sawdust bed. The extracted birch sawdust and the extracted xylan were similar in both laboratory and pilot scale. The PHWE system was successfully scaled up by a factor of 6000 from the laboratory to pilot scale and extractions performed equally well in both scales. The results show that a flow-through system can be further scaled up and used to extract water-soluble xylans from birch sawdust. Extracted xylans can be concentrated, purified, and then used in e.g. films and barriers, or as building blocks for novel material applications.

Intensification of hemicellulose hot-water extraction from spruce wood by parameter tuning

The growing population on earth along with diminishing fossil deposits and the climate change debate calls out for a better utilization of renewable, bio-based materials. In a biorefinery perspective, the renewable biomass is converted into many different products such as fuels, chemicals, and materials, quite similar to the petroleum refinery industry. Since forests cover about one third of the land surface on earth, ligno-cellulosic biomass is the most abundant renewable resource available. The natural first step in a biorefinery is separation and isolation of the different compounds the biomass is comprised of. The major components in wood are cellulose, hemicellulose, and lignin, all of which can be made into various end-products. Today, focus normally lies on utilizing only one component, e.g., the cellulose in the Kraft pulping process. It would be highly desirable to utilize all the different compounds, both from an economical and environmental point of view. The separation process should therefore be optimized. Hemicelluloses can partly be extracted with hot-water prior to pulping. Depending in the severity of the extraction, the hemicelluloses are degraded to various degrees. In order to be able to choose from a variety of different end-products, the hemicelluloses should be as intact as possible after the extraction. The main focus of this work has been on preserving the hemicellulose molar mass throughout the extraction at a high yield by actively controlling the extraction pH at the high temperatures used. Since it has not been possible to measure pH during an extraction due to the high temperatures, the extraction pH has remained a “black box”. Therefore, a high-temperature in-line pH measuring system was developed, validated, and tested for hot-water wood extractions. One crucial step in the measurements is calibration, therefore extensive efforts was put on developing a reliable calibration procedure. Initial extractions with wood showed that the actual extraction pH was ~0.35 pH units higher than previously believed. The measuring system was also equipped with a controller connected to a pump. With this addition it was possible to control the extraction to any desired pH set point. When the pH dropped below the set point, the controller started pumping in alkali and by that the desired set point was maintained very accurately. Analyses of the extracted hemicelluloses showed that less hemicelluloses were extracted at higher pH but with a higher molar-mass. Monomer formation could, at a certain pH level, be completely inhibited. Increasing the temperature, but maintaining a specific pH set point, would speed up the extraction without degrading the molar-mass of the hemicelluloses and thereby intensifying the extraction. The diffusion of the dissolved hemicelluloses from the wood particle is a major part of the extraction process. Therefore, a particle size study ranging from 0.5 mm wood particles to industrial size wood chips was conducted to investigate the internal mass transfer of the hemicelluloses. Unsurprisingly, it showed that hemicelluloses were extracted faster from smaller wood particles than larger although it did not seem to have a substantial effect on the average molar mass of the extracted hemicelluloses. However, smaller particle sizes require more energy to manufacture and thus increases the economic cost. Since bark comprises 10 – 15 % of a tree, it is important to also consider it in a biorefinery concept. Spruce inner and outer bark was hot-water extracted separately to investigate the possibility to isolate the bark hemicelluloses. It was showed that the bark hemicelluloses comprised mostly of pectic material and differed considerably from the wood hemicelluloses. The bark hemicelluloses, or pectins, could be extracted at lower temperatures than the wood hemicelluloses. A chemical characterization, done separately on inner and outer bark, showed that inner bark contained over 10 % stilbene glucosides that could be extracted already at 100 °C with aqueous acetone.

Sellulaasit ja niiden käyttö teollisuudessa

Kandidaatintyön kirjallisuuskatsauksessa esitellään selluloosan entsymaattisen hydrolyysin toimintamekanismi ja kerrotaan sellulaasien käytöstä aiheutuvista eduista ja haitoista eri teollisuussovelluksissa.

Selluloosapohjaisten superkondensaattorien valmistaminen hiilinanoputkista

Tämän työn tarkoitus on seuloa oleelliset prosessiparametrit superkondensaattoreiden elektrodikomposiittien valmistuksessa, jotka vaikuttavat kondensaattorin laatuun. Tarkoitus on tutkia parametreja, joiden avulla prosessia on mahdollista optimoida. Työn tarkoituksena on tutkia myös itse komponenttimateriaalien valmistusvaiheen sekoitusprosessia mitatulla ja laskennallisella seokseen siirtyvällä tehonkulutuksella. Työn kirjallisuusosassa esitetään superkondensaattoreiden rakennetta, toimintamekanismia ja ominaisuuksia sähköenergian varastoijana. Lisäksi tarkastellaan tavallisimpia kondensaattoreihin sisältyviä materiaaleja, erityisesti hiilinanoputkia ja selluloosakuituja. Sekoitusprosesseista tarkastellaan kokeellisessa osassa käytettävien sekoituslaitteita ja niiden toimintamekanismeja komponenttien sekoitusprosesseissa. Kokeellisessa osassa tutkimuskysymyksiksi asetettiin eri sekoitusparametrien (materiaalin määrä ja laatu sekä sekoitusajat) vaikutus superkondensaattorien elektrodiarkkien ominaiskapasitansseihin. Testit suoritettiin LUT Prosessien laboratoriossa, ja testeissä massojen sekoitukseen käytettiin roottoristaattoria ja ultraäänisekoitinta. Lisäksi tutkittiin prosessin skaalausta varten skaalatulla laitteistolla sekoitettuja massanäytteitä. Sekoitusprosessin riittävyyttä varten tutkittiin kokeellisesti käytettyjen sekoituslaitteiden tehonkulutusta. Lisäksi roottoristaattorille tehtiin laskentaohjelmalla virtaussimulaatio paikallisen tehonkulutuksen selvittämiseksi Testeissä todettiin tutkittujen parametrien vaikutus, mutta tulosten perusteella varsinaista optimointia ei kyetty tekemään. Tulokset kuitenkin antavat suunnan, johon prosessia voi optimointia varten kehittää. Myös sekoitukseen todettiin siirtyvän suuri määrä tehoa tutkituilla laitteilla, mitä voidaan pitää mahdollisesti riittävänä käytettyjen komponenttien sekoitukseen.

CPU0213, a novel endothelin type A and type B receptor antagonist, protects against myocardial ischemia/reperfusion injury in rats

The efficacy of endothelin receptor antagonists in protecting against myocardial ischemia/reperfusion (I/R) injury is controversial, and the mechanisms remain unclear. The aim of this study was to investigate the effects of CPU0123, a novel endothelin type A and type B receptor antagonist, on myocardial I/R injury and to explore the mechanisms involved. Male Sprague-Dawley rats weighing 200-250 g were randomized to three groups (6-7 per group): group 1, Sham; group 2, I/R + vehicle. Rats were subjected to in vivo myocardial I/R injury by ligation of the left anterior descending coronary artery and 0.5% sodium carboxymethyl cellulose (1 mL/kg) was injected intraperitoneally immediately prior to coronary occlusion. Group 3, I/R + CPU0213. Rats were subjected to identical surgical procedures and CPU0213 (30 mg/kg) was injected intraperitoneally immediately prior to coronary occlusion. Infarct size, cardiac function and biochemical changes were measured. CPU0213 pretreatment reduced infarct size as a percentage of the ischemic area by 44.5% (I/R + vehicle: 61.3 ± 3.2 vs I/R + CPU0213: 34.0 ± 5.5%, P < 0.05) and improved ejection fraction by 17.2% (I/R + vehicle: 58.4 ± 2.8 vs I/R + CPU0213: 68.5 ± 2.2%, P < 0.05) compared to vehicle-treated animals. This protection was associated with inhibition of myocardial inflammation and oxidative stress. Moreover, reduction in Akt (protein kinase B) and endothelial nitric oxide synthase (eNOS) phosphorylation induced by myocardial I/R injury was limited by CPU0213 (P < 0.05). These data suggest that CPU0123, a non-selective antagonist, has protective effects against myocardial I/R injury in rats, which may be related to the Akt/eNOS pathway.

Cell wall polysaccharides of common beans (Phaseolus vulgaris L.)

The soluble and insoluble cotyledon (SPF-Co and IPF-Co) and tegument (SPF-Te and IPF-Te) cell wall polymer fractions of common beans (Phaseolus vulgaris) were isolated using a chemical-enzymatic method. The sugar composition showed that SPF-Co was constituted of 38.6% arabinose, 23.4% uronic acids, 12.7% galactose, 11.2% xylose, 6.4% mannose and 6.1% glucose, probably derived from slightly branched and weakly bound polymers. The IPF-Co was fractionated with chelating agent (CDTA) and with increasing concentrations of NaOH. The bulk of the cell wall polymers (29.4%) were extracted with 4.0M NaOH and this fraction contained mainly arabinose (55.0%), uronic acid (18.9%), glucose (10.7%), xylose (10.3%) and galactose (3.4%). About 8.7% and 10.6% of the polymers were solubilised with CDTA and 0.01M NaOH respectively and were constituted of arabinose (52.0 and 45.9%), uronic acids (25.8 and 29.8%), xylose (9.6 and 10.2%), galactose (6.1 and 3.9%) and glucose (6.5 and 3.8%). The cell wall polymers were also constituted of small amounts (5.6 and 7.2%) of cellulose (CEL) and of non-extractable cell wall polymers (NECW). About 16.8% and 17.2% of the polymers were solubilised with 0.5 and 1.0M NaOH and contained, respectively, 92.1 and 90.7% of glucose derived from starch (IST). The neutral sugar and polymers solubilization profiles showed that weakly bound pectins are present mainly in SPF-Co (water-soluble), CDTA and 0.01-0.1M NaOH soluble fractions. Less soluble, highly cross-linked pectins were solubilised with 4.0M NaOH. This pectin is arabinose-rich, probably highly branched and has a higher molecular weight than the pectin present in SPF-Co, CDTA and 0.01-0.1M NaOH fractions.

Feasibility of industrial implementation of laser cutting into paper making machine

Laser cutting implementation possibilities into paper making machine was studied as the main objective of the work. Laser cutting technology application was considered as a replacement tool for conventional cutting methods used in paper making machines for longitudinal cutting such as edge trimming at different paper making process and tambour roll slitting. Laser cutting of paper was tested in 70’s for the first time. Since then, laser cutting and processing has been applied for paper materials with different level of success in industry. Laser cutting can be employed for longitudinal cutting of paper web in machine direction. The most common conventional cutting methods include water jet cutting and rotating slitting blades applied in paper making machines. Cutting with CO2 laser fulfils basic requirements for cutting quality, applicability to material and cutting speeds in all locations where longitudinal cutting is needed. Literature review provided description of advantages, disadvantages and challenges of laser technology when it was applied for cutting of paper material with particular attention to cutting of moving paper web. Based on studied laser cutting capabilities and problem definition of conventional cutting technologies, preliminary selection of the most promising application area was carried out. Laser cutting (trimming) of paper web edges in wet end was estimated to be the most promising area where it can be implemented. This assumption was made on the basis of rate of web breaks occurrence. It was found that up to 64 % of total number of web breaks occurred in wet end, particularly in location of so called open draws where paper web was transferred unsupported by wire or felt. Distribution of web breaks in machine cross direction revealed that defects of paper web edge was the main reason of tearing initiation and consequent web break. The assumption was made that laser cutting was capable of improvement of laser cut edge tensile strength due to high cutting quality and sealing effect of the edge after laser cutting. Studies of laser ablation of cellulose supported this claim. Linear energy needed for cutting was calculated with regard to paper web properties in intended laser cutting location. Calculated linear cutting energy was verified with series of laser cutting. Practically obtained laser energy needed for cutting deviated from calculated values. This could be explained by difference in heat transfer via radiation in laser cutting and different absorption characteristics of dry and moist paper material. Laser cut samples (both dry and moist (dry matter content about 25-40%)) were tested for strength properties. It was shown that tensile strength and strain break of laser cut samples are similar to corresponding values of non-laser cut samples. Chosen method, however, did not address tensile strength of laser cut edge in particular. Thus, the assumption of improving strength properties with laser cutting was not fully proved. Laser cutting effect on possible pollution of mill broke (recycling of trimmed edge) was carried out. Laser cut samples (both dry and moist) were tested on the content of dirt particles. The tests revealed that accumulation of dust particles on the surface of moist samples can take place. This has to be taken into account to prevent contamination of pulp suspension when trim waste is recycled. Material loss due to evaporation during laser cutting and amount of solid residues after cutting were evaluated. Edge trimming with laser would result in 0.25 kg/h of solid residues and 2.5 kg/h of lost material due to evaporation. Schemes of laser cutting implementation and needed laser equipment were discussed. Generally, laser cutting system would require two laser sources (one laser source for each cutting zone), set of beam transfer and focusing optics and cutting heads. In order to increase reliability of system, it was suggested that each laser source would have double capacity. That would allow to perform cutting employing one laser source working at full capacity for both cutting zones. Laser technology is in required level at the moment and do not require additional development. Moreover, capacity of speed increase is high due to availability high power laser sources what can support the tendency of speed increase of paper making machines. Laser cutting system would require special roll to maintain cutting. The scheme of such roll was proposed as well as roll integration into paper making machine. Laser cutting can be done in location of central roll in press section, before so-called open draw where many web breaks occur, where it has potential to improve runability of a paper making machine. Economic performance of laser cutting was done as comparison of laser cutting system and water jet cutting working in the same conditions. It was revealed that laser cutting would still be about two times more expensive compared to water jet cutting. This is mainly due to high investment cost of laser equipment and poor energy efficiency of CO2 lasers. Another factor is that laser cutting causes material loss due to evaporation whereas water jet cutting almost does not cause material loss. Despite difficulties of laser cutting implementation in paper making machine, its implementation can be beneficial. The crucial role in that is possibility to improve cut edge strength properties and consequently reduce number of web breaks. Capacity of laser cutting to maintain cutting speeds which exceed current speeds of paper making machines what is another argument to consider laser cutting technology in design of new high speed paper making machines.

Rheological characterization of polysaccharide gels

In this Master’s Thesis work the rheological properties of different polysaccharide gels have been studied. The results of this study are used as a starting point for further investigations of potential applications. In order to understand rheological behavior of studied materials, the commercial hydrocolloids such as sodium carboxymethyl cellulose, xanthan gum and guar gum were used as reference and comparison material for rheological studies. As a part the rheological research the development and implementation of proper measurement methods for studied materials were carried out. In the literature review, short introductions of studied materials and application areas of rheological modifiers are summarized. In addition, basic rheological concepts and key fundamentals are explained. In the experimental part the focus was on the rheological characterization of aqueous suspensions of studied materials. Especially, gel strength and solution stability were investigated. The rheological measurements included both rotational and oscillatory measurements in different conditions, where several chemical and physical properties were measured with Anton Paar MCR302 dynamic rotational rheometer. Studied polysaccharide gels can be clearly defined to be shear thinning and thixotropic materials. They have strong gel forming properties even at low concentrations, which explains the superior thickening behavior for some of the samples. Along with rheological characterization of selected materials the factors behind different phenomena were investigated. To reveal value and potential use of polysaccharide gels the influence of various factors such as concentration, temperature and ionic strength were determined. The measurements showed a clear difference between studied materials under investigated external parameters.

Development of an alternative technology for the oyster mushroom production using liquid inoculum

Pleurotus ostreatus, worldwide known as oyster mushroom, was cultivated in banana straw using inocula produced by two different processes - liquid inoculum and the traditionally used solid inoculum. Different ratios (5, 10, 15, and 20%) were tested. Biological efficiency, yield, productivity, organic matter loss, and moisture of fruiting bodies as well as physical-chemical characteristics of banana straw were studied. Significant differences were observed for cellulose, lignin, and hemicellulose content between one and two harvests for both solid and liquid inocula. It was observed that P. ostreatus growth promoted higher degradation of lignin (80.36%), followed by hemicellulose (78.64%) and cellulose (60.37%). Significant differences between one and two harvests were also observed for the production parameters (biological efficiency and yield) for both kinds of inocula, liquid and solid. However, significant differences in productivity between harvests were observed only for solid inoculum.

Effect of addition of different hydrocolloids on pasting, thermal, and rheological properties of cassava starch

Starches and gums are hydrocolloids frequently used in food systems to provide proper texture, moisture, and water mobility. Starch-gum interaction in food systems can change the starch granule swelling and its gelatinization and rheological properties. In this study, the effect of the addition of xanthan gum (XG), sodium carboxymethyl cellulose (SCMC), and carrageenan (CAR) at the concentrations of the 0.15, 0.25, 0.35 and 0.45% (w/v) on the pasting, thermal, and rheological properties of cassava starch was studied. The swelling power (SP) and the scanning electron microscopy (SEM) of the starch gels were also evaluated. The results obtained showed that xanthan gum (XG) had a strong interaction with the cassava starch penetrating between starch granules causing increase in pasting viscosities, SP, storage and loss (G', and G", respectively) modulus and reduction in the setback of the starch; sodium carboxymethyl cellulose (SCMC) greatly increased the pasting viscosities, the SP, and the storage and loss (G', and G", respectively) modulus of the starch-mixtures, mainly due to its greater capacity to hold water and not due to the interaction with cassava starch. Carrageenan (CAR) did not change any of the starch properties since there was no interaction between this gum and cassava starch at the concentrations used.