Amylasers enzymatiska aktivitet i saltvattensmiljö

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Examensarbete för kandidatexamen
Bachelor Thesis
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2011
Författare
Vimpari, Silvana
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Amylases are enzymes that digest starch by cleavage of glycosidic bonds, therby releasing glucose, maltose and/or malto-oligosaccharides. Amylase is used for biotechnological purposes such as the production of biofuels, in the food industry where starch is found naturally in cereals, but also in the paper industry and in the manufacture of detergents. The difference between α-amylase, β-amylase and glucoamylase is how they cleave starch into smaller glucose-containing units. α-amylase breaks down starch into oligosaccharides and dextrins, while β-amylase breaks down starch into maltose and amyloglucosidase to glucose. The aim of the project was to investigate how the enzyme activity of industrial purified amylases, that are commercially available, are affected by saline environments compared to freshwater conditions. Another part of the project was to isolate marine bacteria that use starch as a carbon source and thus produce amylases. This was performed by isolation and purification of the bacteria in starch medium, characterization in shake flask cultures and measurement of enzyme activity. Two strains were found that had better cell growth, released larger amounts of glucose from the starch, and showed a higher enzymatic activity than the other in seawater. The industrially produced amylases were tested for dependence on various parameters such as pH, temperature and enzyme activity. α-amylase Aspergillus oryzae, β-amylase and amyloglucosidases from Aspergillus niger were activated at pH 4.8. α-amylases Bacillus subtilis and porcine were activated at pH 6.9. Enzyme activity measurments for the industrially isolated amylases showed that a number of those tested had a higher amylase activity in seawater than in freshwater whereas the α-amylases from Bacillus licheniformis and Aspergillus oryzae did not exhibit any activity in seawater. This may be due to the substances found in seawater helps to facilitate the binding of and reaction with substrates and/or stabilizes the protein structure of a beneficial form. A possible reason for the differences observed between similar amylases may be that different types of treatment processes at the manufacturing companies can provide a finished product that has a different sensitivity to ions. To use algae as a future fuel source and cultivate them in saltwater you need to have a salt-tolerant amylase that can break down large amounts of starch. More analyses of existing purified amylases is recommended as these show that there is potential to find amylases that acutally are activated better in saltwater than freshwater.
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Energi, Industriell bioteknik, Energy, Industrial Biotechnology
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