Low-Field Nuclear Magnetic Resonance Characteristics of Biofilm Development Process

To in situ and noninvasively monitor the biofilm development process by low-field nuclear magnetic resonance (NMR), experiments should be made to determine the mechanisms responsible for the T₂ signals of biofilm growth. In this paper, biofilms were cultivated in both fluid media and saturated porous media. T₂ relaxation for each sample was measured to investigate the contribution of the related processes to T₂ relaxation signals. In addition, OD values of bacterial cell suspensions were measured to provide the relative number of bacterial cells. We also obtained SEM photos of the biofilms after vacuum freeze-drying the pure sand and the sand with biofilm formation to confirm the space within the biofilm matrix and identify the existence of biofilm formation. The T₂ relaxation distribution is strongly dependent on the density of the bacterial cells suspended in the fluid and the stage of biofilm development. The peak time and the peak percentage can be used as indicators of the biofilm growth states.