Inhibition of biofilm formation of Geobacillus stearothermophilus in calcium-reduced milk protein formulation is associated with calcium, sodium and bacteria growth history: A preliminary study

Abstract

The effect of total calcium, sodium concentration and bacteria growth history was investigated on biofilm formation of Geobacillus stearothermophilus in milk formulations. Biofilm cell numbers of three G. stearothermophilus strains were compared in two milk formulations (MF1 and MF2) over 18 h. MF1 and MF2 had similar compositions but MF2 had relatively high sodium and low calcium concentrations. Biofilm formation of all three strains was lower (P < 0.05) in MF2 than in MF1, but the inhibition of MF2 was dependent on the growth history of bacterial inocula. Supplementation of MF1 with sodium decreased (P < 0.05) biofilm formation at 18 h for dairy isolates A1 and P3. Supplementation of MF2 with 26 mm calcium increased (P < 0.05) biofilm formation of A1 at 18 h, and P3 at 10 h. The cationic profile of MF2 seemed to be important in reducing biofilms of G. stearothermophilus.