An aliquot (300 μL) of 108 CFU/mL from Lactobacillus strains and E. coli (positive biofilm-forming bacteria) was transferred to a 96-well polystyrene microtiter plate containing the corresponding growth medium added with OL or HT. Wells containing only growth medium were also included as control. Plates were incubated for 24 h at 37 °C; supernatants comprising unattached bacteria cells and nutrient were then withdrawn, and the wells washed gently three times with PBS (300 μL). The remaining attached bacteria were fixed with 250 μL ethanol (96%, v/v); after 15 min, plates were emptied and left to dry. Biofilm was then stained using 200 μL of crystal violet (2%, w/v) for 15 min. Excess stain was rinsed off by placing the plates under running tap water. After complete drying of the stained plates, biofilms were visible as purple rings formed on the sides of each well.