Transcriptional analysis of oxidative-tolerant and temperature-sensitive genes of Bifidobacterium animalis BF052 during freeze-drying process and development of its soymilk-synbiotic product containing banana and jicama powders

This study investigated the transcriptional stress responses, physicochemical stability, and functionality attributes of Bifidobacterium animalis subsp. lactis BF052 in freeze-dried synbiotic powder formulations containing soymilk with banana or jicama powder. Gene expression profile revealed that oxidative stress-related genes (mutT and rnr) and temperature stress-related genes (groES2, clp1, csp1 and csp2) were significantly upregulated during freeze-drying and early storage (p < 0.05), indicating their pivotal roles in cellular defense, DNA repair, and protein homeostasis. Physicochemical analysis of the synbiotic powders demonstrated that formulations containing soymilk with banana or jicama powder exhibited improved water solubility index up to 65.4 %, reduced particle size, and favorable moisture and water activity levels. Probiotic viability remained above 90 % following the freeze-drying process, with viable cell counts exceeding 10⁸ CFU/g. No statistically significant differences were observed between the banana- and jicama-based formulations (p > 0.05), indicating maintained functional stability. Antioxidant activity, as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), total phenolics, and flavonoids, was highest in formulations combining soymilk and 5 % (w/v) banana or jicama powder (p < 0.05), suggesting an additive effect. Storage at 25 °C enhanced flavonoid stability without compromising microbial integrity. These findings demonstrate that synbiotic powders formulated with B. animalis BF052, soymilk, and low concentrations of banana or jicama powder exhibit excellent functional and physicochemical properties, offering strong potential for commercial development as shelf-stable nutraceutical products.