Abstract: The biofilm-forming capabilities of Streptococcus thermophilus and Lactobacillus bulgaricus on different carriers (coconut, stainless steel mesh, plastic sheet, glass sheet or ceramic parts) was studied by using placed slice and plate culture count methods. The results showed that stainless steel mesh and coconut were suitable carriers for biofilm formation. During 7 days, the CFU (colony-forming units) of the single-species biofilm on coconut and stainless steel mesh initially reached 1 × 107 CFU/cm2 and then was kept at 3.2 × 106 CFU/cm2. The mixed-species biofilm was stable at approximately 1 × 107 CFU/cm2 in continuous seven days. In addition, scanning electron microscope was used to observe mixed-species biofilm formed by S. thermophilus and L. bulgaricus, and a typical mixed-species biofilm was observed on coconut and stainless steel mesh.

Key words: lactic acid bacteria, biofilm, carrier, stability