Vitamin B12 is essential for human life. It is common belief that it cannot be provided with a vegan diet, because it cannot be found in food of plant origin. Plants cannot synthesize it by themselves, but there are theories that support the possibility to add vitamin B12 to plants under certain environmental circumstances. In this BSc thesis different pathways of incorporation of vitamin B12 in plants with proper soil fertilization procedures, hydroponics agricultural practices, lactic fermentation of plant food and production of algae are reviewed. Advantages and disadvantages of the various qualitative and quantitative methods of determination of vitamin B12 will be discussed. For the purpose of determining the quantity of vitamin B12 in different samples of food of plant origin, the quantitative microbiological method with Lactobacillus delbrueckii subsp. lactis (leichmannii) was tested. With a vitamin B12 standard we have determined the linear range of the curve in which the method shows the right concentration ranges of vitamin B12 in samples. In the course of the research we found out that the method may have some drawbacks that need to be further explored. These are how does cyanide affect the extraction process of vitamin B12 from food samples and if the Lactobacillus micro-organism can grow only in the presence of cyanocobalamin or also in the presence of its analogues.
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