53 research outputs found
Ultrastructure of Biofilms Formed by Bacteria from Industrial Processes
No full textMicroorganisms exist predominantly as sessile multispecies communities in natural habitats. Most bacterial species can form these matrix-enclosed microbial communities called biofilms. Biofilms occur in a wide range of environments, on every surface with sufficient moisture and nutrients, also on surfaces in industrial settings and engineered water systems. This unwanted biofilm formation on equipment surfaces is called biofouling. Biofouling can significantly decrease equipment performance and lifetime and cause contamination and impaired quality of the industrial product.
In this thesis we studied bacterial adherence to abiotic surfaces by using coupons of stainless steel coated or not coated with fluoropolymer or diamond like carbon (DLC). As model organisms we used bacterial isolates from paper machines (Meiothermus silvanus, Pseudoxanthomonas taiwanensis and Deinococcus geothermalis) and also well characterised species isolated from medical implants (Staphylococcus epidermidis). We found that coating of steel surface with these materials reduced its tendency towards biofouling: Fluoropolymer and DLC coatings repelled all four biofilm formers on steel. We found great differences between bacterial species in their preference of surfaces to adhere as well as their ultrastructural details, like number and thickness of adhesion organelles they expressed. These details responded differently towards the different surfaces they adhered to.
We further found that biofilms of D. geothermalis formed on titanium dioxide coated coupons of glass, steel and titanium, were effectively removed by photocatalytic action in response to irradiation at 360 nm. However, on non-coated glass or steel surfaces irradiation had no detectable effect on the amount of bacterial biomass. We showed that the adhesion organelles of bacteria on illuminated TiO2 coated coupons were complety destroyed whereas on non-coated coupons they looked intact when observed by microscope.
Stainless steel is the most widely used material for industrial process equipments and surfaces. The results in this thesis showed that stainless steel is prone to biofouling by phylogenetically distant bacterial species and that coating of the steel may offer a tool for reduced biofouling of industrial equipment. Photocatalysis, on the other hand, is a potential technique for biofilm removal from surfaces in locations where high level of hygiene is required.
Our study of natural biofilms on barley kernel surfaces showed that also there the microbes possessed adhesion organelles visible with electronmicroscope both before and after steeping. The microbial community of dry barley kernels turned into a dense biofilm covered with slimy extracellular polymeric substance (EPS) in the kernels after steeping in water. Steeping is the first step in malting. We also presented evidence showing that certain strains of Lactobacillus plantarum and Wickerhamomyces anomalus, when used as starter cultures in the steeping water, could enter the barley kernel and colonise the tissues of the barley kernel. By use of a starter culture it was possible to reduce the extensive production of EPS, which resulted in a faster filtration of the mash.Mikrobit esiintyvät luonnossa etupäässä pintoihin kiinnittyneinä, useiden lajien muodostamina yhdyskuntina. Näitä liman verhoamia mikrobiyhteisöjä kutsutaan biofilmeiksi. Suurin osa mikrobilajeista pystyy muodostamaan biofilmejä. Biofilmejä esiintyy kaikilla pinnoilla, joilla on tarjolla tarpeeksi kosteutta ja ravinteita. Tällaisia pintoja on kaikkialla missä käsitellään vettä tai vesipitoisia nesteitä, kuten teollisuudessa ja vesijohtoverkossa. Biofilmin muodostus teollisuusprosesseissa voi heikentää laitteiden toimintakykyä ja lyhentää niiden käyttöikää, sekä aiheuttaa kontaminaatioita ja laadun heikenemistä tuotteisiin. Tästä syystä biofilmejä pyritään häätämään prosessilaitteista.
Tutkin väitöskirjassani bakteerien tarttumista pinnoitetuille ja pinnoittamattomille teräspinnoille. Käytin koe-eliöinä paperikoneiden biofilmeistä eristettyjä bakteerilajeja, Meiothermus silvanus, Pseudoxanthomonas taiwanensis ja Deinococcus geothermalis, sekä lajia, joka tekee biofilmejä ihmisen elimistöön sijoitetuille esineille (implantit), Staphylococcus epidermidis. Löysin bakteerilajien väliltä suuria eroja sekä niiden kyvyssä tarttua eri pinnoille, että itse bakteerien pinnan rakenteissa. Turtkimani bakteerit osasivat myös sopeuttaa solurakenteensa eri pinnoilla, mm. tarttumaelimien paksuus ja lukumäärät olivat erilaisia.
Käytin työssäni D. geothermalis -bakteerin muodostamia biofilmejä tutkiakseni, voidaanko ne irrottaa lasi- tai teräspinnoilta, jos pinnat pinnoitetaan titaanidioksidilla joka aktivoidaan 360 nm valolla. Tulokseni osoittivat, että näin saatiin aikaan biofilmiä tuhoava fotokatalyysi. Pinnoittamattomalla lasilla ja teräksellä biofilmin määrä pysyi muuttumattomana valaisusta riippumatta. Kun tutkin kenttäemissiopyyhkäisy-elektronimikroskoopilla biofilmejä TiO2 pinnoitetuilla pinnoilla, havaitsin että valokäsitellyillä pinnoilla bakteerien tarttumaelimet olivat tuhoutuneet, mutta pinnoittamattomilla pinnoilla ne näyttivät ehjiltä. Teräs on yleisin koneiden ja laitteiden materiaali monilla teollisuuden aloilla. Väitöskirjan tulokset kuitenkin näyttävät, että bakteerit tarttuvat hyvin juuri teräkseen. Samat tulokset saatiin hyvin erilaisilla, fylogeneettisesti kaukaisilla, bakteerilajeilla. Tulokset osoittivat myös, että teräksen alttiutta kerätä biofilmejä voidaan vähentää pinnoittamalla ja jos käytetään fotokatalyyttisesti aktiivista pinnoitetta, jo muodostuneetkin biofilmit voidaan poistaa valokäsittelyn avulla.
Tutkin myös eläviin solukkoihin tarttuvia mikrobibiofilmejä. Tutkimuskohteena oli ohran jyvän luonnollinen biofilmi. Havaitsin että myös nämä biofilmit rakentuivat mikrobeista, joilla oli tarttumaelimiä. Ulkonäöltään tarttumaelimet muistuttivat niitä, joita olin löytänyt teräs- ja lasipinnoilta. Ohraa mallastettaessa kuivat jyvät liotetaan vedessä. Kun ohran jyvän biofilmiä tarkasteltiin elektronimikroskoopilla, havaittiin että likovaiheen aikana kuivien jyvien mikrobisto muuttui tiheäksi liman peittämäksi biofilmiksi. Tutkimukseni osoitti, että tätä limanmuodostusta voi vähentää lisäämällä likoveteen tiettyjä maitohappobakteereja (Lactobacillus plantarum) ja hiivoja (Wickerhamomyces anomalus). Nämä mikrobit pystyivät tunkeutumaan jyvän kuorikerroksen alle ja täyttämään pinnan, joka muuten olisi täyttynyt limaista biofilmiä tuottavilla mikrobeilla. Kun liman määrä väheni, niin mäskin suodatettavuus parani.ei saavutettav
Cereal Grain Structure by Microscopic Analysis
No full textMicroscopy techniques can be utilized in studying the structure of cereal grains, their processing or end products. By stereomicroscope, the appearance of cereal samples can be recorded. For light microscopy, samples are usually fixed, embedded and cut into sections for staining with different dyes in order to visualize various components present in cereals. Less sample preparation is needed for confocal laser scanning microscopy (CLSM), which enables optical sectioning of the sample. Scanning electron microscopy (SEM) gives information on the structure with higher magnification, when high resolution is required. Depending on which structural level is of interest, these techniques can be used in revealing the structural differences between processes, enzymatic treatments, etc. Several examples are presented on the visualization of grain structures and components and their changes due to processing
Manufacture and characterization of pasta made with wheat flour rendered gluten-free using fungal proteases and selected sourdough lactic acid bacteria
No full textWheat flour, which was rendered gluten-free by sourdough lactic acid bacteria fermentation and fungal proteases, was used for manufacturing experimental gluten-free pasta (E-GFp), according to a traditional process with low temperature drying cycle. Chemical, technological, structural, nutritional and sensory features were characterized and compared with those of commercial gluten-free (C-GFp) and durum wheat pasta (C-DWp). As shown through immunological analyses, the residual concentration of gluten of the hydrolyzed wheat flour was below 10 ppm. E-GFp showed rapid water uptake and shorter optimal cooking time compared to the other pastas. Despite the absence of the gluten network, the supplementation with pre-gelatinized rice flour allowed structural properties of E-GFp, which were comparable to those of C-GFp. The in vitro protein digestibility of E-GFp resulted the highest. Probably due to proteolysis during sourdough fermentation; chemical scores, essential amino acid profile, biological value and nutritional index of E-GFp were higher than those of C-DWp. The hydrolysis index (HI) of E-GFp was ca. 30% lower than that found for C-GFp. As shown by sensory analysis, the characteristic of E-GFp were acceptable. The manufacture of E-GFp should be promising to expand the choice of gluten-free foods, which combine sensory and nutritional propertie
Asiakastyytyväisyys henkilöstöravintoloissa : Case: Atria Suomi Oy
No full textLämmintä lounasta syö kodin ulkopuolella päivittäin noin kaksi miljoonaa kansalaista. Vuonna 2008 henkilöstöravintolat tuottivat 61 miljoonaa ateriaa vuodessa. (Joukkoruokailun kehittäminen 2010, 23.) Päivän ainut lämmin ateria saattaa tulla syödyksi henkilöstöravintolassa, joten lounaan ja lounastauon merkitys on suuri. Lounastauko tarjoaa ruoan lisäksi sosiaalisen irrottautumishetken päivän töistä. Ravitsemuksellisesti oikea ravinto auttaa jaksamaan ja keskittymään, jolloin työtehtävätkin tulevat hoidetuksi todennäköisemmin ilman työtapaturmia. (Raulio 2007, [viitattu 2.12.2012].)
Tämä työ on pitkittäistutkimus, joka seuraa Nikulan ja Riihimäen syksyn 2007 ja Vuorelan kevään 2009 tutkimuksia Atria Suomi Oy:n henkilöstöravintoloiden asiakastyytyväisyydestä. Työn tavoitteena oli selvittää asiakkaiden tyytyväisyyttä ruoka- ja välipalatarjontaan, antaa Atria Suomi Oy:lle tietoa asiakastyytyväisyyden kehityksestä heidän henkilöstöravintoloissaan edellisiin kyselyihin verrattuna sekä tarkastella, ovatko asiakkaat huomanneet kehitystä henkilöstöravintolan toiminnassa edellisten kyselyiden jälkeen.
Tähän tutkimukseen suoritettiin kvalitatiivisella haastattelumenetelmällä esitutkimus, jolla haluttiin saada tietoa eri henkilöstöryhmien tyytyväisyydestä ravintoloiden toimintaan. Haastatteluissa ilmenneitä tyytyväisyystekijöitä lisättiin kysymysten muodossa kvantitatiiviseen kyselylomakkeeseen. Kvantitatiivinen kysely tehtiin kaikissa seitsemässä Atria Suomen henkilöstöravintolassa marraskuussa 2012, joissa kaikilla asiakkailla oli mahdollisuus vastata kyselyyn kokonaisotantana. Vastauksia tuli yhteensä 1120.Hot lunch is eaten outside the home on a daily basis by about two million Finnish citizens. In 2008 personnel restaurants produced 61 million meals per year. (Joukkoruokailun kehittäminen 2010, 23.) The only hot meal of the day might be eaten in a personnel restaurant, so the meaning of the lunch-break, and the meal that goes along with it, is significant. In addition to food, the lunch break offers a social moment from the day’s work. Nutritionally balanced food helps workers to cope and focus on the job tasks which will then most likely get done without work-related accidents. (Raulio 2007, [viitattu 2.12.2012].)
This work is a longitudinal study that follows customer satisfaction studies by Nikula and Riihimäki, in the autumn of 2007 and Vuorela in the spring of 2009 for Atria Finland Ltd's personnel restaurants. The aim was to examine the customers' satisfaction with meals and snack supply. The goal was also to give Atria Finland Ltd information on development of the customer satisfaction in their personnel restaurants compared to the previous surveys, as well as to examine whether the customers had noticed any development in the service or products after the previous surveys.
For this research pre-qualitative interviews were conducted to get information about different categories of the staff satisfaction in the restaurants. The satisfac-tion factors, which emerged in the interviews, were added in a question form to the quantitative questionnaire. The quantitative research was conducted in November 2012 in all seven of Atria Finland's personnel restaurants where all the customers were given a chance to respond to the survey. 1120 answers were received
SRB and methanogens in corrosion of steel in anaerobic water
No full textDuring the operation, maintenance and decommissioning of nuclear power plants contaminated waste is produced. This waste is disposed of in underground repository 60-100 meters below the ground surface. The metallic waste consists mostly of carbon steel and stainless steel. A long-term field exposure show high corrosion rates, general corrosion up to 29 ?m a-1 and localized corrosion even higher. Corrosion rates this high are possible if microbes are present and produce corrosive products or alter the local microenvironment to corrosion favoring. The bacterial and archaeal composition of biofilm formed on the surface of carbon steel was studied using 16S rRNA gene targeting pyro-sequencing followed by phylogenetic analyses of microbial community. The functional potential of microbial communities in biofilm was studied by functional gene targeting quantitative PCR. The corrosion rate was analyzed with weigh loss measurements and the deposits on the surfaces were analyzed with SEM/EDS. Our results demonstrate that the bacterial diversity on the surface of carbon steel and their functionality is vast. Our results suggest that the role of methanogenic archaea in corrosive biofilm, in addition to sulphate reducing bacteria, could be greater than previously suspected in these nutrient poor conditions
Sulphate Reducing Bacteria and Methanogenic Archaea Driving Corrosion of Steel in Deep Anoxic Ground Water
No full textDuring the operation, maintenance and decommissioning of nuclear power plant radioactive contaminated waste is produced. This waste is stored in an underground repository 60-100 meters below the surface. The metallic portion of this waste comprises mostly carbon and stainless steel. A long-term field exposure showed high corrosion rates, general corrosion up to 29 μm a-1 and localized corrosion even higher. High corrosion rate is possible if microbes produce corrosive products, or alter the local microenvironment to favor corrosion. The bacterial and archaeal composition of biofilm formed on the surface of carbon steel was studied using 16S rRNA gene targeting sequencing, followed by phylogenetic analyses of the microbial community. The functional potential of the microbial communities in biofilm was studied by functional gene targeting quantitative PCR. The corrosion rate was calculated from weight loss measurements and the deposits on the surfaces were analyzed with SEM/EDS and XRD. Our results demonstrate that microbial diversity on the surface of carbon steel and their functionality is vast. Our results suggest that in these nutrient poor conditions the role of methanogenic archaea in corrosive biofilm, in addition to sulphate reducing bacteria, could be greater than previously suspected
Food Safety Assurance Systems: Management of Biofilm Risk
No full textBiofilms occur in a wide range of environments, on every surface when supplied with moisture and nutrients. The biofilms consist of microcolonies formed by multiple microbial species embedded in an extracellular matrix. Biofilms are utilized in water purification and bioremediation of hazardous substances in the environment. However, they cause inconvenience when formed on industrial surfaces. Quantification of the actual number of microbes from surfaces is challenging because detection methods for measuring microbes directly from the surface are unpractical and detachment of microbes completely without damaging the surface or the microbes is difficult due to strong microbial adherence of biofilm
Ultrastructure of biofilms formed on barley kernels during malting with and without starter culture
No full textMalted barley is a major raw material of beer, as well as distilled spirits and several food products. In the malting process, dry barley kernels are steeped in water which initiates germination and invigorates microbial growth on the kernels. In the present study, field emission scanning electron microscopy (FESEM) was used to visualize the microbial community within the tissues of barley kernels before and after the steeping, with and without Lactobacillus plantarum E76 added as a starter culture. The results show that the community of 108 cfu g−1 on dry, stored barley kernels increased 5–10 fold during the steeping forming a dense biofilm of bacteria and fungi with slimy exopolymeric matrix. FESEM revealed that crevices between the outer epidermis and the testa of sound barley kernels were heavily colonized with microbes, whereas there were only few microbes on the outer surface of the husks, in the aleurone layer or in the endosperm underneath an intact testa layer. The microbes frequently possessed appendages forming bridging them to the kernel and the individual microbial cells to each other. The L. plantarum added to the steeping water reduced the amount of exopolymeric matrix in the biofilm and improved the wort filterability
Mikrobien estäminen elintarvike- ja juomateollisuuden pinnoilla (Disconnecting projekti)
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