Modelling the resistance of Fructobacillus spp. to technological stress conditions

Fructobacillus tropaeoli H-Sp-0-4, F. pseudoficulneus H-Sp-0-1, and F. pseudoficulneus H-Pj-0-2, previously isolated from stingless bee honey ( Scaptotrigona pectoralis and Plebeia jatiformis ) and identified by 16S rRNA gene sequencing and phylogeny, were evaluated for their resistance to technological processing stresses relevant to food applications. Ionic osmotic (NaCl), non-ionic osmotic (glucose: fructose 1:1), ethanol, and acid stresses were assessed using Hill's logistic equation to determine the inhibitory concentration for 50 % of the population ( IC 50 ). Then, sublethal stress conditions (8 % NaCl, 30 % sugars, 8 % ethanol, pH 4) were selected for kinetic modelling using the modified Gompertz and Baranyi models, which yielded growth parameters including maximum specific growth rate ( μ ), adaptation time ( λ ), and maximum growth ( A ). Ionicionally, cell surface properties (autoaggregation, coaggregation with different pathogenic strains, and hydrophobicity) were evaluated under ionic osmotic stress (6 % NaCl). All three strains tolerated the tested stress conditions, with processing stress generally reducing μ and A while increasing λ . F. pseudoficulneus strains, particularly H-Sp-0-1, exhibited greater versatility in growth, adaptation, and coaggregation with Staphylococcus aureus . Under saline stress, all strains reduced autoaggregation and coaggregation but increased hydrophobicity, indicating changes in their cell surface. These results provide quantitative, population-level descriptors of stress tolerance that identify these Fructobacillus strains, particularly F. pseudoficulneus , as candidates for further evaluation as starter cultures, pending validation in real food matrices.