Evaluation of Bacillus licheniformis Strain Ht3 as a Potential Probiotic

Abstract

The present study investigates the probiotic potential of \textit{Bacillus licheniformis} strain Ht3 (Bl-Ht3), which was isolated from thermal spring water. The isolate was taxonomically identified through 16S rDNA sequencing and subsequently subjected to a series of assays to characterize its probiotic attributes. Bl-Ht3 exhibited tolerance to a broad range of gastrointestinal conditions; however, it showed limited survivability at highly acidic pH levels (pH 1.0 and 2.0), which represents a critical constraint in terms of gastric passage. Despite this limitation, the strain demonstrated γ-hemolytic activity, and was highly susceptible to all tested antibiotics, fulfilling key safety requirements for probiotic application. In terms of functional properties, the strain exhibited relatively weak autoaggregation capacity (13.04%), which may affect its ability to colonize the intestinal mucosa. Conversely, the coaggregation ability exceeded 35%, suggesting potential for interaction with other microbial species within the gastrointestinal tract, possibly contributing to competitive exclusion of pathogens. Collectively, the findings of this study delineate both the beneficial and limiting characteristics of Bl-Ht3 as a probiotic candidate. Future optimization efforts, particularly the application of spore-based formulations, are recommended to enhance acid resistance and improve survivability through the gastric environment. These improvements may further strengthen the strain's utility as a safe and stable probiotic for functional food or pharmaceutical applications.