Impact of Phytochemicals on Viability and Cereulide Toxin Synthesis in Bacillus cereus Revealed by a Novel High-Throughput Method, Coupling an AlamarBlue-Based Assay with UPLC-MS/MS

The potential of lactose to inhibit cereulide biosynthesis of emetic Bacillus cereus in milk

This study aims to investigate the potential role of lactose on cereulide biosynthesis by emetic Bacillus cereus in dairy matrices. The cereulide yields in whole milk and lactose-free milk were investigated using the emetic reference strain F4810/72. To eliminate the influence of complex food substrates, the LB medium model was further used to characterize the effect of lactose on cereulide produced by F4810/72 and five other emetic B. cereus strains. Results showed that the lactose-free milk displayed a 13-fold higher amount of cereulide than whole milk, but the cereulide level could be reduced by 91 % when the lactose content was restored. The significant inhibition of lactose on cereulide yields of all tested B. cereus strains was observed in LB medium, showing a dose-dependent manner with inhibition rates ranging of 89-98 %. The growth curves and lactose utilization patterns of all strains demonstrated that B. cereus cannot utilize lactose as a carbon source and lactose might act as a signal molecule to regulate cereulide production. Moreover, lactose strongly repressed the expression of cereulide synthetase genes (ces), possibly by inhibiting the key regulator Spo0A at the transcriptional level. Our findings highlight the potential of lactose as an effective strategy to control cereulide production in food.

Novel 3D Bioglass Scaffolds for Bone Tissue Regeneration

The design of scaffolds with optimal biomechanical properties for load-bearing applications is an important topic of research. Most studies have addressed this problem by focusing on the material composition and not on the coupled effect between the material composition and the scaffold architecture. Polymer–bioglass scaffolds have been investigated due to the excellent bioactivity properties of bioglass, which release ions that activate osteogenesis. However, material preparation methods usually require the use of organic solvents that induce surface modifications on the bioglass particles, compromising the adhesion with the polymeric material thus compromising mechanical properties. In this paper, we used a simple melt blending approach to produce polycaprolactone/bioglass pellets to construct scaffolds with pore size gradient. The results show that the addition of bioglass particles improved the mechanical properties of the scaffolds and, due to the selected architecture, all scaffolds presented mechanical properties in the cortical bone region. Moreover, the addition of bioglass indicated a positive long-term effect on the biological performance of the scaffolds. The pore size gradient also induced a cell spreading gradient.