The ability of Lactiplantibacillus plantarum PK 1.1 to synthesize odd-chain and cyclic fatty acids in oat-based beverages

This study aims to optimize the composition of a model oat beverage to enhance the production of minor fatty acids, including odd-chain and cyclic fatty acids. The oat beverage composition was optimized in the Box-Behnken design, varying by the ratio of oat protein hydrolysate (0, 1, 2%), coconut oil (0, 1.5, 3.0%), and added sucrose (0, 2, 4%), while maintaining a constant ratio of oat β-glucan (2%) and oat protein (2%). In the first stage of the study, fermentation was conducted at 22 °C for 48 h using the Lactiplantibacillus plantarum PK 1.1 strain. The four best variants that promoted the biosynthesis of rare fatty acids were tested in a refined experiment. In this stage, the effects of low-temperature stress (15 °C) and osmotic stress induced by the addition of NaCl (up to 5%) were assessed. The prepared formulations were analysed for lactic acid bacteria (LAB) counts, titratable acidity, pH, apparent viscosity, and fatty acid composition. In the first experiment, the highest combined share of odd-chain and cyclic fatty acids (up to 0.353%) was observed in beverages prepared without coconut oil. This low concentration prompted a second experimental stage in which microbial stress was intensified by fermentation at 15 °C and by osmotic stress induced through NaCl addition (0%, 2.5%, or 5%). In this stage, the total share of these fatty acids increased to 1.51%, with cyclic fatty acids predominating. In both experiments LAB counts, titratable acidity, pH, and apparent viscosity were comparable to those of commercially available fermented plant-based beverages. We recommend further research to elucidate the metabolic and technological factors that influence the odd-chain and cyclic fatty acids ratio under suboptimal fermentation temperatures.