Abstract

In the dairy industry, the biofilms formed by spore forming bacteria are not well characterized. Microscopic methods are crucial for the study of biofilm structural and architectural features. Here, a simple surface-associated non-submerged model combined to environmental scanning electron microscope (ESEM) imaging was used for the study of Bacillus cereus and Geobacillus spp. dairy biofilms. To evaluate the utility of this approach, non-submerged biofilms were compared to those developed in situ on stainless steel coupons introduced inside milk processing lines. Results reveal that both B. cereus and Geobacillus spp. are able to form specific biofilm characteristics on non-immersed surfaces, notably an original dispersion style not previously described. Non-submerged biofilms in vitro are elaborate three-dimensional or extensive complex structures well resolved in ESEM and comparable to dairy biofilms in situ. The non-submerged surface-associated biofilm combined to ESEM imaging revealed a relevant model for the study of dairy biofilms.

Key words: Biofilms, Geobacillus, Bacillus cereus, non-submerged surfaces, environmental scanning electron microscope (ESEM) imaging.