Vi Pham | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Vi Pham. This seminar is open to the general public to attend.

PhD with Dr. Michael Gaenzle.

Zoom Link: https://ualberta-ca.zoom.us/j/96894399335
Meeting ID: 968 9439 9335

Thesis Topic: Exploration and utilization of novel organisms or metabolic pathways for fermenting unconventional substrates

Abstract: 

Current scientific knowledge provides a framework for fermentation of traditional substrates, e.g., starter culture and fermentation conditions are available for cheese, yogurt, sourdough. Interest in fermenting unconventional substrates such as byproducts or plant-based dairy products is increasing, but applying traditional starter culture or fermentation conditions to fermentation of unconventional substrates faces challenges as the performance of the microbes is not predictable. This PhD dissertation aimed to suggest a concept and tool to improve fermentation control and investigate the use of novel organisms or organisms with underexplored and novel metabolic pathways to ferment unconventional substrates.

Performance of starter culture or the microbial impact on fermentation quality is often strain specific. Current literature lacks a method and concept for strain identification. This study suggested that identification of strains or persistence of isolates using single-nucleotide polymorphisms (SNP) and guided the applications of this method to food fermentations.

Canola meal, a byproduct that is high in hydroxycinnamic acids and widely used as feedstuff, was fermented with Lactiplantibacillus plantarum and Furfurilactobacillus milii that metabolize phenolics. Hydroxycinnamic acids exhibit antimicrobial activity. Our result showed that the organisms metabolized hydroxycinnamic acids and fermented canola meal inhibits growth of Salmonella and Campylobacter. Hydroxycinnamic acids metabolism is a desirable trait when selecting starter culture for canola meal and fermented canola meal has a practical application as a poultry feed.

Microbial analysis of a back-slopped sourdough propagated at a novel condition revealed two novel species, Levilactobacillus sp. and Fructilactobacillus sp., with insufficiently studied metabolic pathways. Fructilactobacillus sp. produces yellow C30 carotenoid that when used to ferment sourdough for pasta production, enhanced the color of pasta. Twelve genera of Lactobacillaceae carry enzymes synthesizing C30 carotenoid, which linked to the ecology of lactobacilli and presented opportunities for use as starter culture to improve color of fermented foods. Another identified organism was Levilactobacillus parabrevis that converts lactate to 1,2-propanediol and acetate. This conversion contributed to rapid acidification upon revival during refrigerated storage. This finding addressed the challenges of extended lag phase when reactivating stored sourdough for production.

To determine the persistence of back-slopped sourdough isolates sampled at different times, this study developed a SNP bioinformatic pipeline that detected high-quality SNPs from high-quality Nanopore-sequenced genomes. Strains differed than 19 SNPs were identical. Strains that differed between 29 – 30 SNPs would require more samplings to conclude. Investigating train persistence in fermented foods provided insights into domestication of fermentation microbes.