Evaluation of prebiotic utilisation and thermal tolerance of Bacillus clausii VTT and DP strains: Potential applications in the food industry

Abstract

Bacillus species are promising probiotic bacteria because of their spore-forming ability, which enables them to survive in harsh environments, giving them an advantage over genera such as Lactobacillus and Bifidobacterium. While the effects of fibres such as fructo-oligosaccharide, inulin, and psyllium on Lactobacillus have been extensively studied, data on Bacillus clausii are scarce. This study investigated (1) the effects of fructo-oligosaccharide (FOS), inulin, and psyllium on the growth of B. clausii (VTT and DP) using OD₆₀₀ measurements and (2) survival following heat treatment at 80°C for 10 min. The results showed that the B. clausii VTT strain exhibited enhanced growth with FOS and inulin at both 0.5 and 1%. In particular, 0.5% FOS resulted in the highest OD₆₀₀ value (0.598±0.025) after 42 hours, significantly higher than the control (0.270±0.030). In contrast, psyllium inhibited VTT growth. The DP strain showed inconsistent responses to the prebiotics, and 1% inulin significantly reduced OD₆₀₀ compared to the control. Both strains showed slight reductions in log colony-forming units (CFU)/ml after heat treatment, indicating high heat tolerance. These results demonstrate strainspecific differences in prebiotic responsiveness in B. clausii and identify FOS as an effective prebiotic for combination with B. clausii VTT, supporting the potential use of this combination in synbiotic formulations intended for high-temperature processing.