MTU Cork Library Catalogue

Mass spectrometry investigation of antifungal compounds from lactic acid bacteria and their application as natural antimicrobials / Bríd Brosnan.

By: Brosnan, Bríd [author].
Material type: materialTypeLabelBookSeries: Ph.D - Physical Sciences.Publisher: Cork : Cork Institute of Technology, 2015Description: 339 pages : illustrations (some color), tables, graphs ; 30 cm.Content type: text Media type: unmediated Carrier type: volumeSubject(s): Fungicides | Lactic acid bacteria | Bacterial genetic engineering | Microbial biotechnology | Bioactive compounds | Mass spectrometryDDC classification: THESES PRESS Dissertation note: Thesis (Ph.D) - Cork Institute of Technology, 2015. Summary: Lactic acid bacteria (LAB) have become an important part of the food chain in recent years. The desire of consumers to use natural food preservatives has allowed for much research to be devoted to identifying strains providing such activity without the need for addition of chemical preservatives. Several species of LAB have been recognised to provide antifungal activity, which may facilitate inhibition of food spoilage fungi. LAB have GRAS-status (Generally Recognised as Safe) and QPS status (Qualified Presumption of Safety) allowing them to be safely integrated into food systems as natural food preservatives. LAB have been used as starter cultures in numerous food and feed products ranging from bread to silage to malting. The integration of these strains as starter cultures into products has been used to produce a reduction of fungal growth and prolong shelf life of goods without the use of chemical preservatives. Initially, it was throught that the organic acides produced (such as lactic and acetic acid) were the main mechanism of antifungal activity due to the lowering of the PH. Studies have shown that the MIC (minimal inhibitory concentration ) of these compounds alone is too low to be the main mechanism of activity. Other metabolites from these strains have been identified as the source of the antifungal activity, e.g. cyclic dipeptides, proteinaceous compounds, fatty acids and lower molecular weight compounds. Knowledge about the active metabolites producing the antifungal activity is relatively limited. The main objective of this Ph.D is to develop universal isolation and detection methods that are fast, robust and efficient. The development of such methods will allow for an increased number of compounds to be identified. Improvements in extraction methods will ensure the optimum extract of samples allowing for easier, more comprehensive identification and profiling of both targeted and unknown compounds. The further development of accurate and sensitive identification methods will provide further information and unambiguous confirmation of compounds present. The combination of the improved procedures will provide greater identification and quantitation of these compounds produced by LAB. This will provide further data and aid in the exaplanation of the antifungal activity occurring. Improvement in these methods will also make the discovery of new compounds, variants and metabolites possible. The proposed methodologies will provide quick, efficient, robust procedures for the analytical extraction and identification of antifungal compounds. In comparison with previous detection methods which required both GC-MS and LC-MS, it will allow for a broader range of compounds to be identified within the same analysis using a single analytical technique. Previous methods only identified a maximum of 15 compounds and required a combination of both Gas Chromatography- Mass Spectrometry (GC-MS) and Liquid Chromatography - Mass Spectrometry (LC-MS) complimentary methods to discern these compounds. The methods proposed here have the capability of identifying up to 25 compounds on a single LC-MS method. The combination of all these improvements willl greatly enhance knowledge within this field of research. - (Author's abstract)
List(s) this item appears in: PhD Theses
Holdings
Item type Current library Call number Copy number Status Date due Barcode Item holds
Reference MTU Bishopstown Library Thesis THESES PRESS (Browse shelf(Opens below)) 1 Reference 00160731
Total holds: 0

Thesis (Ph.D) - Cork Institute of Technology, 2015.

Includes bibliographical references.

Lactic acid bacteria (LAB) have become an important part of the food chain in recent years. The desire of consumers to use natural food preservatives has allowed for much research to be devoted to identifying strains providing such activity without the need for addition of chemical preservatives. Several species of LAB have been recognised to provide antifungal activity, which may facilitate inhibition of food spoilage fungi. LAB have GRAS-status (Generally Recognised as Safe) and QPS status (Qualified Presumption of Safety) allowing them to be safely integrated into food systems as natural food preservatives. LAB have been used as starter cultures in numerous food and feed products ranging from bread to silage to malting. The integration of these strains as starter cultures into products has been used to produce a reduction of fungal growth and prolong shelf life of goods without the use of chemical preservatives. Initially, it was throught that the organic acides produced (such as lactic and acetic acid) were the main mechanism of antifungal activity due to the lowering of the PH. Studies have shown that the MIC (minimal inhibitory concentration ) of these compounds alone is too low to be the main mechanism of activity. Other metabolites from these strains have been identified as the source of the antifungal activity, e.g. cyclic dipeptides, proteinaceous compounds, fatty acids and lower molecular weight compounds. Knowledge about the active metabolites producing the antifungal activity is relatively limited. The main objective of this Ph.D is to develop universal isolation and detection methods that are fast, robust and efficient. The development of such methods will allow for an increased number of compounds to be identified. Improvements in extraction methods will ensure the optimum extract of samples allowing for easier, more comprehensive identification and profiling of both targeted and unknown compounds. The further development of accurate and sensitive identification methods will provide further information and unambiguous confirmation of compounds present. The combination of the improved procedures will provide greater identification and quantitation of these compounds produced by LAB. This will provide further data and aid in the exaplanation of the antifungal activity occurring. Improvement in these methods will also make the discovery of new compounds, variants and metabolites possible. The proposed methodologies will provide quick, efficient, robust procedures for the analytical extraction and identification of antifungal compounds. In comparison with previous detection methods which required both GC-MS and LC-MS, it will allow for a broader range of compounds to be identified within the same analysis using a single analytical technique. Previous methods only identified a maximum of 15 compounds and required a combination of both Gas Chromatography- Mass Spectrometry (GC-MS) and Liquid Chromatography - Mass Spectrometry (LC-MS) complimentary methods to discern these compounds. The methods proposed here have the capability of identifying up to 25 compounds on a single LC-MS method. The combination of all these improvements willl greatly enhance knowledge within this field of research. - (Author's abstract)

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