PhD study trip

Biofilms of the thermophilic sporeformers geobacillus species and anoxybacillus flavithermus

The manufacture of milk powders and liquid concentrates requires production facilities operating at 40 – 65°C, which may lead to incidental contamination of the final product with thermo-resistant spores derived from the thermophilic species Geobacillus and Anoxybacillus, which are also observed as biofilm formers (Scott et al., 2007)

Their biofilm forming capacity facilitate the stay in the factory and in the end products.


The aim of the research is to acquire more insight in lifecycle of the thermophilc sporeformers isolated from dairy concentrate industry


We have made an inventory of the microbial diversity in a number of casein and (cheese)whey processing environments, by employing cultivation independent analysis of the full bacterial population based on mass-sequence 16S-genotyping as described previously (Keijser et al., 2008). We have identified bacterial species of ~ 20 different genera within ~ 10 different samples taken from ~ 6 processing environments and show selection for mesophiles and thermophilic sporeformers in niches at intermediate (~ 55°C) and  elevated temperatures (~ 65°C), respectively. Notably, Geobacillus and Anoxybacillus species were found at elevated temperatures. Phenotypic and genotypic characterization of a set of 70 industrial isolates revealed a large number of these mesophiles and thermophilic spore formers to be efficient biofilm formers at elevated temperatures. In the end, three model strains which have strong biofilm forming capacity in static system were chosen for further understanding of their biofilm formation mechanism.

Future research

We will use the obtained thermophilic model strains in a flow cell based lab-scale system to study the environmental factors affecting biofilm development.


1.    Scott, S.A. et al., The formation of thermophilic spores during the manufacture of whole milk powder (2007) Int. J. of Dairy Techn. 60, p109-117 (2007).

2.    Keijser B.J.F. et al., Pyrosequencing analysis of the Oral Microflora of healthy adults. J. of Dental Research, 87, p1016-1020 (2008).