engleski

Laboratory X-Ray Microtomography as a tool for 3D visualization of biofilm in porous media made up of zeolite

The mesoscale 3D visualization and quantification of biofilms are essential for better understanding of the development of biofilm in porous media, such as biofilters. Laboratory X-ray microtomography is an imaging technique based on the absorption of X-ray by matter, and with the use of suitable contrast agent (1-chloronaphtalen) it is possible to differentiate three phases of a biofilter with developed biofilm: support media, biofilm and bulk liquid. During the experiment, biofilm was grown in duplicate in a mini biofilter (10 mm diameter, 200 mm length) for 9 days and then imaged with laboratory microtomograph. As a support media natural zeolite grains of 1-1.25 mm size fraction were used and as a model organism Bacillus cereus was chosen. After 9 days it was possible to visualize biofilm of >40 µm thickness as it encompasses zeolite grains. Image analysis allowed for biofilm 3D reconstruction and volume fraction quantification. In two “day 9” replicas the biofilm occupied respectively 55.3% and 57.9% of empty pore space, and 8.1% in “day 0”. The certain proportion of biofilm at “day 0” was an artifact ascribed to nutrient media trapped at grain/grain interface during the filling of contrast agent. To best of our knowledge this experiment is the first successful attempt to visualize 3D structure of biofilm inside a porous media filled with natural material by using laboratory X-Ray Microtomograph. From results obtained by two replicas compared to starting conditions it was concluded that biofilm could be visualized and quantified with satisfactory reproducibility and accuracy.

X-Ray Microtomography ; zeolite ; biofilm ; Bacillus cereus

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