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Gopala Krishna Munianjinappa, Amulya (2018) SELECTION OF MICOBIAL CELLS WITH INCREASED PRODUCT YIELD FOR INDUSTRIAL FERMENTATIONS. Master's Thesis / Essay, Molecular Biology and Biotechnology (2016-2019).

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Lactic acid bacteria (LAB) are commonly used organisms in the fermentation of food to prevent its spoilage. Lactococcus lactis among the LAB are known to improve the organoleptic properties of the food products such as flavor, texture and aroma. Thus gaining much importance in food industry. L.lactis MG1363 has a relatively simple carbohydrate metabolic pathway that can be rerouted easily, thus used as a model of choice in metabolic engineering. This allows for the isolation of strains producing desired metabolite. Identification and isolation of the strain could be possible by usage of indicator strains responding to metabolites being produced by the desired strain. Engineering of Lactoccocal metabolism can result in the introduction of heterologous genes, derive energy from glycolysis metabolic pathway, and producvariety of compounds during the fermentation such as diacetyl, ethanol, acetoin, acetaldehyde etc. Diacetyl contributes to the buttery aroma of the dairy products such as butter, acid cream, cottage cheese, yogurt etc. Acetaldehyde contributes to a fruity flavor in yogurt and ethanol is present in alcoholic beverages. Few promoters that are capable of responding to organic compounds such as diacetyl, acetaldehyde, and ethanol were identified by transcriptomic analysis prior to this research study. In this study such promoters were introduced into the pSEUDO – gfp plasmid and later transformed in Escherichia coli DH5α bacterial cells to obtain multiple copies of the bacterial cells. Such copies were further transfrmed into Lactococcus lactis MG1363 thus allowing the plasmid to be integrated into the chromosomal genome of Lactococcus lactis MG1363. Thereby, constructing indicator cells for sensing the desired compounds. The indicator cells were there checked for the fluorescence intensity in the presence and absence of the desired compounds. Indicator cells with promoters ButA/B, llmg_1772 were found to show some fluorescence intensity in the presence of 2% acetaldehyde. Promoters llmg_0317, llmg_0941, llmg_1677, ButA/B also showed the presence of fluorescence signal in the presence of 4% ethanol and the promoters llmg_1019 and DhaM that were found to be responsive to diacetyl also showed the presence of fluorescence intensity. However, the results obtained with acetaldehyde is not promising as the bacterial cells showed negligible growth pattern even after 10 hours of incubation

Item Type: Thesis (Master's Thesis / Essay)
Supervisor name: Kuipers, O.P.
Degree programme: Molecular Biology and Biotechnology (2016-2019)
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 03 Apr 2018
Last Modified: 04 Apr 2018 09:13

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