Postbiotic production from bifidobacterium animalis subsp. lactis by heat treatment and ultrasound methods

In this study, the viability and functional properties of postbiotics obtained after ultrasound and heat treatments applied to Bifidobacterium animalis subsp. lactis BB-12 strain were evaluated in detail. Sixteen different processing conditions were tested for both heat treatment (5–90 min, 65–95 °C) and ultrasound treatment (15–60 min, 98–320 µm). Complete inactivation was achieved under all heat treatment conditions, while inactivation was observed in 11 out of the 16 ultrasound conditions. As ultrasound amplitude increased, the time required for inactivation decreased, whereas lower amplitudes necessitated longer processing times. These results indicate that microbial resistance is higher at lower amplitudes and shorter ultrasound durations. Postbiotics were assessed for their antimicrobial activity, their probiotic-enhancing effect on Lacticaseibacillus casei 431 and Bifidobacterium cultures, and their ability to promote short-chain fatty acid (SCFA) production. Heat-treated postbiotics demonstrated significantly greater probiotic-enhancing activity, with growth increases of approximately 2.9-fold for L. casei 431 and 37.7-fold for Bifidobacterium cultures compared to control groups. Additionally, heat-treated postbiotics exhibited significantly higher antimicrobial activity against Enterococcus faecalis. Using ultrasound, the postbiotic produced at 320µm for 45 minutes provided the highest probiotic-enhancing activity for Lacticaceibacillus casei 431 (1.07-fold increase), while the postbiotic produced at 172µm for 60 minutes (11.7-fold increase) achieved the highest probiotic-enhancing activity for Bifidobacterium. Both inactivation methods resulted in significant increases in SCFA levels (p<0.05). Principal component analysis (PCA) showed significant clustering of samples according to processing methods, supporting the differentiation in the functional profiles of postbiotics depending on the inactivation technique used. Overall, heat treatment proved to be a more effective approach than ultrasound for producing biologically active postbiotics from B. lactis BB-12. The enhanced biological activity observed in heat-inactivated samples indicates that thermal processing is a suitable and robust method for postbiotic production. These findings highlight the potential of heat-derived postbiotics as effective bioactive ingredients in functional foods and dietary supplements, particularly those targeting the gut microbiota. However, to fully realize this potential and support regulatory approval, further in vivo validation studies and standardization of production processes are necessary.