Expanding the bio-capabilities of Lactococcus lactis through efficient genome modification

Abstract

Lactic acid bacteria play an important role in a variety of biochemical and biomedical applications. This thesis focuses on methods to improve the use of lactic acid bacteria for use in a variety of different applications. The thesis starts by discussing techniques in improving gut health and treating gut dysbiosis related disorders. The primary focus of these techniques is the use of prebiotic substrates and the use of livebiotherapeutics and probiotics. Lactic acid bacteria are reasonable candidates for creating genetically modified live-biotherapeutics or probiotics. Focusing further, the thesis indicates the numerous live-biotherapeutic applications of Lactococcus lactis (L. lactis), the primary organism of interest throughout the rest of the thesis.After describing previous applications of modified L. lactis, the thesis shifts to improving the organism's ease of use and opens up further applications of modified L. lactis. The first research task was to improve the capability of L. lactis to metabolize biorenewable sugars and produce valuable biorenewable chemicals. This research endeavor focused on enabling levoglucosan metabolism in L. lactis. The sugar, levoglucosan, is a primary component of the carbohydrate profile in pyrolysized biomass. Introducing levoglucosan metabolism in L. lactis enabled the organism to consume more of the available carbohydrates in bio-oil, a component of pyrolysized biomass. Furthermore, this levoglucosan consuming L. lactis was modified to convert it's primary fermentation product, lactic acid, to a more valuable biorenewable chemical, 1,2-propanediol. This research endeavor enabled the metabolism of bio-oil carbohydrates and subsequent conversion to lactic acid and 1,2-propanediol in L. lactis.