Genetic engineering of lactic acid bacteria to produce optically pure lactic acid and to develop a novel cell immobilization method suitable for industrial fermentations
Year: 2016
Type: dissertation
Abstract: Mankind has exploited lactic acid bacteria for thousands of years. For most of this time, the use of these bacteria was based on tradition without deeper knowledge of the nature of these organisms. Nowadays, we have learned to know lactic acid bacteria and we are capable to genetically modify these organisms. In this thesis, methods to modify Lactobacillus helveticus bacterium to produce optically pure L(+)-lactic acid are introduced. Also, a method to immobilize lactic acid bacteria on unmodified cellulosic material is described. Lactic acid has two optical isomers: D(-)-lactic acid and L(+)-lactic acid. Most typically lactic acid is produced by microbial fermentation process. When using strains belonging to genus Lactobacillus in these fermentations, the produced lactic acid is most typically mixture of D(-)- and L(+)-lactic acid. In certain industrial applications, like that of the production of biodegradable plastic, pure L(+)-lactic acid is the preferred choice to be used as a raw material. In this work, two novel Lactobacillus helveticus strains were constructed for this purpose. As demonstrated by experiments, both these strains are potential producers of plastic grade L(+)-lactic acid. In many industrial-scale fermentation processes, it is beneficial to immobilize production strain on a solid carrier, whenever possible. From economical point of view, this kind of approach is very attractive especially if the immobilization is possible to carry out with minimal use of chemicals and processing steps. In this work Lactococcus lactis was genetically engineered to provide binding to chemically unmodified cellulosic carrier material. Putatively, by applying this method in an industrial-scale setup, it is possible to develop novel continuous fermentation processes.
Source: Työväentutkimus Vuosikirja
Author: Kari Kylä-Nikkilä
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2388969001