Browsing by Subject "entsyymit"

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  • Chung, Min-Sup (Suomen metsätieteellinen seura, 1981)
  • Vepsäläinen, Milja (Finnish Environment Institute, 2012)
    Monographs of the Boreal Environment Research 41
    Soil microorganisms mediate central reactions of element cycles in a heterogenic environment characterized by discontinuity of energy, nutrients, and water together with sharp pH gradients. They are diverse in species, numerous in quantity and possess a multitude of functions. One gram of soil may contain 10x109 microbial cells; for comparison, the Earth has only 7x109 human inhabitants. Species richness, evenness and composition in soils is impossible to measure, and therefore a convenient means of characterising soil microorganisms is to measure the type and rate of reactions occurring.The aim of this work was to develop a rapid, sensitive method to measure the activities of a set of soil enzymes simultaneously in a small scale. In the method, homogenized soil suspensions are investigated using fluorescent substrate analogues freeze-dried onto multiwall plates. It was shown that extraction of enzymes from soils produced inconsistent and unpredictable yields of the various activities and was therefore not applied as a pretreatment. Applicability of the method was evaluated by characterising soils treated with different agricultural practices, supporting a variety of crop plants and with fluctuating seasonal attributes. Bulk samples from experimental sites established both in agricultural and forest soils were utilized. Details of method development and of the effects of different treatments on enzyme activity pattern and on individual enzyme activities are discussed.The effects of eight crop plants, peat amendment and two consecutive sampling years yielded significant differences in soil extracellular enzyme activities. The effect of crop plants was most pronounced: eight of the measured ten activities yielded statistically significant differences in both years. The activities differed between years for six enzymes. The effect of peat was slight and was observed only two years after the addition. In another experiment, green or composted plant residues tended to enhance the activities of enzymes compared with chemical fertilizers, although the effect was not consistent. Forest soils usually yielded higher specific activities than field soils and the enzymes showed higher potential activities under alder than under pine. Temporal fluctuations of enzyme activities were also studied.Cluster analysis was utilized for data analysis in order to combine all measured attributes and to reveal the differences in the entire pattern, even though the differences in individual enzyme level were not statistically significant and the enzyme activities often correlated with each other.Due to the multitude of processes and functions, together with the wide taxonomic diversity in soils, method development in soil microbiology is still a major challenge. Interpretation of results usually requires a reference comparison. The method developed in the present study is proposed to be used as a sensitive measure of soil functional activity.
  • Hokkanen, Anu (Helsingin yliopisto, 2018)
    Tutkielman kirjallisuuskatsauksessa selvitettiin rukiin tärkeimpiä leivontaominaisuuksia, pakastuksen vaikutuksia leivän laatuun sekä keinoja parantaa pakasteleipien laatua ja säilyvyyttä. Pakkasvarastoinnin aikana pakasteleipien laatu heikkenee leivän sisuksessa tapahtuvan kosteuden siirtymisen takia ja siksi vedensidontakyvyn hallinta on pakasteruisleipien valmistuksessa tärkeää. Kokeellisessa osiossa tavoitteena oli kehittää lisäaineeton pakasteruisleipä, jonka pakkasvarastoinnin aiheuttamat laatuvauriot ja säilyvyyden huononeminen saataisiin mahdollisimman hyvin ehkäistyä. Käytännössä pakasteruisleivän kauppalaatua heikentää sisuksen kovenemisen ja tilavuuden pienenemisen lisäksi kosteuden siirtymisestä ja jään sublimoitumisesta johtuva valkea rengas ruisleivän kuoren alla. Tutkimuksessa ruisleivän vedensidontakykyä pyrittiin parantamaan kolmen tutkimukseen valitun apuaineen; entsyymi-, mallas- ja hydrokolloidituotteen, lisäyksillä. Leivonnoissa valmistettiin yksinkertaisen reseptin mukaan neljä ruistaikinaa, joista kolmeen lisättiin yhtä tutkimukseen valituista apuaineista. Ruisleiville suoritettiin sekä paiston että neljän viikon pakastuksen (-18 °C) jälkeen painojen, tilavuuksien ja kovuuksien mittaukset sekä aistinvaraiset arvioinnit. Tutkimuksen pohjalta pakasteruisleipien laatua ja säilyvyyttä paransi eniten entsyymilisäys, joka mm. kasvatti ruisleipien ominaistilavuutta, happamuutta ja pakastuksen jälkeistä pehmeyttä. Käytetty entsyymi lisäsi kuitenkin merkitsevästi ruisleipien painohäviötä kasvattamalla taikinan löysyyttä. Valitun mallastuotteen käytön ei havaittu parantavan pakasteruisleipien laatua tai säilyvyyttä. Hydrokolloidilisäys puolestaan pienensi painohäviötä, mutta kovetti ruisleipien rakennetta. Voimakkaasti vettä sitova hydrokolloidi oli ainoa, joka ehkäisi valkean renkaan syntymistä pakasteruisleivissä renkaan muodostumista nopeuttavissa olosuhteissa (2 vko, -10 °C).
  • Adamczyk, Sylwia (Finnish Society of Forest Science, 2016)
    Dissertationes Forestales
    Cycling of carbon (C) and nutrients plays pivotal role for functioning of every ecosystem. Biogeochemical cycles of carbon and nitrogen (N) are balanced by a network of inter-actions between plants, litter and soil chemistry, microbial communities, enzyme machinery and climate conditions. This thesis focuses on the role of terpenes in C and N transformations in boreal forest soils. Terpenes are abundant plant secondary compounds. The focus was on certain mono-, di-, and triterpenes. Soil incubation experiments revealed that terpenes increased the mineralization of carbon but decreased net nitrogen mineralization and net nitrification. Additionally they increased the amounts of carbon and nitrogen in the microbial biomass through enhancement of bacterial growth; however, they inhibited fungal growth. This study suggests that terpenes can act as a C source for some microbial communities. Moreover, terpenes showed inhibitory potential against enzymes, which are involved in C, N, P, S cycling. The mechanism of inhibition seems to be based at least partially on ability of terpenes to bind enzymes. The field experiment presented the effect of logging residues and wood ash on composition of terpenes and C and N cycling in soil five years after clear-cutting a Norway spruce stand. Logging residue treatment increased the concentrations of certain terpenes in the organic layer. Both, logging residue and wood ash treatments increased net N mineralization and net nitrification. Some changes in terpene concentrations correlated with C and N cycling processes, but the relationship between terpene concentration and C and N cycling processes remained still unclear in the field conditions. In conclusion, terpenes can affect C and N transformations in boreal forest soil. It is probable that terpenes change N cycling retaining more N in organic forms and potentially decrease nitrogen losses from forest ecosystem.