Postgraduate Seminar Presentation : Comparative systems biology approach to evaluate probiotic capabilities in lactic acid bacteria

Speaker Lokanand Koduru (Supervisors: Dr Lee Dong-Yup)

Host Department of Chemical and Biomolecular Engineering

Date/Time 18 Sep - 18 Sep, 2.00PM

Venue E5-03-19 , Faculty of Engineering, National University of Singapore

Synopsis

Lactic acid bacteria (LAB) are divided into homo-, facultative hetero- and obligate heterolactic groups, depending on the nature of fermentative metabolism used by them. Although the production of lactic acid as the major fermentative by-product is a common feature of LAB, the central metabolic variations of the three groups have significant physiological implications, which can lead to differential performance in their applications as probiotics. However, despite their widespread use, the mechanisms underlying such differences and the extent to which they are genus-, species- or strain-specific remain to be elucidated. The experimental methods, which currently involve the usage of animal models to deduce such basis, are time-consuming, expensive, and complicated by unforeseen environmental variables. In this regard, systems biology approaches involving genome-scale metabolic reconstructions and constraint-based flux analysis can greatly facilitate better understanding of their physiology and provide directions toward strain-selection for specific probiotic applications.

In this work, genome-scale metabolic models of six different LAB, Lactococcus lactis, Lactobacillus salivarius, Lactobacillus plantarum, Lactobacillus casei, Leuconostoc mesenteroides, and Lactobacillus fermentum, two from each of the three fermentative groups were developed. Culture data obtained from the LAB grown in a common chemically defined medium was used to validate all the models quantitatively. While the classical flux balance analysis (FBA) could sufficiently capture the obligate heterofermentative behaviour, FBA with additional constraints based on macromolecular crowding was required to describe the behaviour of homo- and facultative-heterofermentative LAB. These methods in combination with comparative genomic analysis were then employed to investigate the probiotic capabilities of each LAB. Overall, this study revealed the relationship between such capabilities and the metabolic signatures of different LAB.

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