Heat-Inactivated Lactiplantibacillus plantarum (RSB11) as a Multifunctional Postbiotic: Anti-Inflammatory Effects Compared with Live RSB11 Across Multiple Human Cell Models

The clinical potential of probiotics is increasingly recognized; however, dependence on microbial viability, formulation and storage constraints, and safety considerations in vulnerable populations can limit their broader application. Postbiotics offer an alternative by providing inanimate microbial preparations with retained biological activity, yet whether heat inactivation preserves the functional effects of probiotic-derived candidates remains an important question. Here, we compare Lactiplantibacillus plantarum RSB11 in its live (RSB11 life) and heat-inactivated (RSB11-HI) forms across human cell models representing the gut, lung, ovary, bone, kidney, and liver. Following inflammatory challenge with lipopolysaccharide or Escherichia coli, we assessed MMP-9 expression and the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β. Both RSB11 life and RSB11-HI broadly suppressed inflammatory responses, with RSB11-HI maintaining effects comparable to the live preparation across the MMP-9 and cytokine endpoints, where the two forms were tested side by side, and demonstrating greater suppression in selected experimental contexts. Additionally, RSB11-HI increased β-glucuronidase and estradiol levels relative to untreated controls in a gut–ovarian conditioned-medium model, suggesting effects extending beyond inflammatory modulation; a live comparator was not included in the β-glucuronidase measurements, so this effect is not established as specific to the inactivated form. Collectively, these findings demonstrate that heat inactivation preserves key biological functions of RSB11 and support RSB11-HI as a multifunctional candidate postbiotic with potential for expanded formulation and application.