The effect of carbon source and temperature on the formation and growth of Bacillus licheniformis and Bacillus cereus biofilms

Abstract

This study focused on biofilm characteristics of Bacillus licheniformis and Bacillus cereus which were the residual dominant strains in milk powder production system. The effects of different carbon sources (glucose, maltose, lactose and skimmed milk) and temperatures (37 and 55 °C) on biofilm formation and metabolic activity were investigated by crystal violet staining and CCK-8 method. The results showed that the biofilm formation enhanced with the increase of the concentration of carbon source in nutrient broth. The images of the scan electron microscope and light microscope showed that glucose and maltose could significantly increase（p < 0.05） the biomass and metabolic activity of biofilm. Skimmed milk can significantly improve（p < 0.05） the biomass of Bacillus licheniformis and Bacillus cereus biofilm and the metabolic activity of Bacillus licheniformis biofilm. While lactose can only significantly improve （p < 0.05） the metabolic activity of Bacillus licheniformis biofilm, which meant that lactose was not the main component in skimmed milk that affected the biofilm forming ability of Bacillus licheniformis and Bacillus cereus. This study estimated the effect of carbon source and temperature on the formation characteristics of biofilms, and was conductive to the prevention and control of Bacillus pollution in food industry.