Sand administration as an instrument for biofilm control ofPseudomonas putida ATCC 11172 in chemostat cultures

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Abstract
Pseudomonas putida ATCC 11172 was grown in chemostat on L‐asparagine or phenol as the sole, limiting carbon and energy source. The growth characteristics of a culture where a biofilm was present, were compared with one where the biofilm was strongly reduced by the grinding and shearing effect of sand suspended in the culture. In the presence of the intact biofilm, the curve of steady‐state biomass versus dilution rate diverged greatly from the theoretical pattern predicted by conventional chemostat models. The sand strongly retarded the biofilm formation and to a high degree restored the shape of the biomass versus dilution rate curve to a more conventional pattern. The maximum specific growth rate (μmax) could not be calculated from the biofilm cultures. However using the sand cultures, μmax was determined to 0.64 h−1 with L‐asparagine as the carbon source and 0.49 h−1 with phenol which compare favorably with the respective μmax values calculated from batch cultures. Incorporation of sand into strongly agitated cultures is recommended as an efficient and simple means of controlling biofilm formation in continuous cultures. The method may enable the gathering of basic kinetic data difficult to obtain in the presence of biofilm.