Multi omics approach to unravel the potential of lactic acid bacteria nitrogen metabolism in shaping the sourdough aromatic profile.

Sourdough is a complex and dynamic ecosystem of interacting microbial players, whose metabolic pathways and functions are influenced by continuous environmental changes. Specifically, nitrogen metabolism of lactic acid bacteria (LAB) in sourdough is pivotal due to the positive effects on the nutritional, sensory, and shelf-life properties of leavened baked goods. Strains of Lactiplantibacillus plantarum, Fructilactobacillus sanfranciscensis and Limosilactobacillus fermentum were tested for sourdough production in a single species batch and in a comprehensive consortium including all the selected ones. A real time qPCR was used to detect and quantify selected strains within different thesis. The expression of peptidases (e.g., PepN, PepI, PepX, PepO, PepP), glutamate dehydrogenases (GDH), and aminotransferases (ilvE) was evaluated by real-time qPCR for mRNA quantification. Volatile organic compound (VOC) and free amino acid (FAA) were detected during different times of fermentation. From preliminary results, different expression of targeted genes was evaluated in sourdoughs relative to distinct strain combination. The levels of VOC and FAA varied during sourdough fermentation and a different concentration of compounds was detected by comparing the different sourdough. This study revealed that LAB proteolytic metabolism contributed to the aroma of sourdough by a different expression of key genes and these findings laid the groundwork to better understand the selection of potential starter to improve the organoleptic characteristics of leavened bakery goods.