Hydrocarbon degrading microorganism interaction in the formation of biofilm on solid surfaces

MARCELA SEPÚLVEDA; EDUARDO HARRIS; NELDA LILA OLIVERA; A. ORMAZABAL; VERÓNICA BUCALÁ; MARINA NIEVAS

Mar del Plata

Congreso; VIII Congreso SAMIGE 2012; 2012

SAMIGE

A biofilm is a structure that results from the association between one or more microbial populations which bind to a surface by extracellular substances. Biofilm systems have gained relevance in the last 20 years to enhance effluent bioremediation because they show higher xenobiotic biodegradation rates than free cells. Alcanivorax sp. (PA2) and Pseudomonas putida (PA1) form cell aggregates when they grow in liquid medium as mixed culture (Olivera et al., 2009). We studied the individual capability of these strains to form a biofilm on surfaces of different hydrophobicity and their interaction regarding the adhesion to granular activated carbon, (GAC) with the aim to apply PA1-PA2 consortium in effluent treatment. The strains were cultured individually with hydrocarbons as carbon source (Olivera et al., 2009) using 10 ml glass and 50 ml polypropylene tubes, as hydrophilic and hydrophobic materials, respectively. After 28 days of incubation, microbial growth and biofilm formation (violet crystal technique) were assessed. Both strains grew in the two tested materials, PA2 was the only one that produced biofilm on glass (DO595=0,58 U.A., p<0,05). None of them formed biofilm on polypropylene. In addition, the presence of PA2 on the PA1 binding capability on hydrophilic surface (GAC) was assessed. A 48-h-old culture (2 ml with 1.8 x 108 FCU/ml) was added to 30 ml-glass flasks containing 200 mg of sterile GAC. After 48 h, the liquid medium was withdrawn and the GAC washed to eliminate free cells. Then, 2 ml of a PA1 suspension were added to each flask and incubated again for 48 h. The concentration of the adhered cells of each strain was quantified by counting in solid plates at the end of the incubations (Olivera et al., 2009). PA1 and PA2 were detected adhered to GAC at 1.5 x 108 FCU/g and 8.7 x 107 FCU/g, respectively in the individual cultures, as well as in the sequential cultures. No significantly differences were found between the individual and the sequential cultures. This fact indicates that PA2 does not affect the binding behavior of PA1 on GAC, which lacked the capability to form biofilm on glass. These results suggest that the adhesion of both strains on GAC, is more likely due to the sorption characteristic of the support than to an intrinsic capability of the strains to form biofilm. In summary, results indicate that GAC is an adequate support for cell adhesion of the studied strains, showing a high potential to be used in bioreactors for effluent treatments.