Biofilm formation of hydrocarbon-degrading microbial community on porous media fixed bed bioreactors

SEPULVEDA M.A.; POLIFRONI R.; REVUELTA F.; NELDA L. OLIVERA; NIEVAS EL MAKTE M.L.

Río de Janeiro

Simposio; 9th Latin American Biodeterioration and Biodegradation Symposium; 2016

National Institute of Technology

Microbialbiofilms are natural conglomerates of microorganisms that group togethergetting competitive and survival advantages in comparison with planktoniccells. Hydrocarbon-degrading microbial communities in biofilms have widetechnological application for bioremediation of impacted sites and wastewatertreatment. The aim of this work was to evaluate the biofilm time courseformation of a marine microbial community able to mineralize hydrocarbons inpacked bioreactors. A microbial suspension of hydrocarbon polluted intertidalsediments from the Puerto Madryn´s port (Patagonia Argentina) was used as inoculum.The microbial suspension with crude oil as the only carbon source wasrecirculated 14 days through four fixed bed reactors (45 mm id, 500 mm length, 0.3 voidfraction) filled with gravel particles (1000 - 2000 mm).Then an aerated marine mineral medium with 1000 ppm crude oil was recirculatedthrough the reactor at 1.8 10-4 m/s superficial velocity. Samples ofgravel particles were withdrawn periodically and the biofilm formation wasevaluated by the crystal violet technique.  Microbial count of petroleum and naphthalenedegrading bacteria were assessed and the potential of hydrocarbonmineralization was determined by respirometric method Microresp? using crudeoil, n-hexadecane and phenanthrene assubstrates. The profile of the taxonomic dominant members of the community wasassessed by extracting DNA and analyzing by PCR-DGGE. The abundance of petroleum-and naphthalene-degrading microorganisms attached to gravel reached theirhighest values after 7 days of incubation (1.5 x 10 8 MPN g-dw-1and 5.9 x 107 MPN g-dw-1, respectively), then decreasingup to 5.6 x 106 MPN g-dw-1 and 3.5 x 105 MPNg-dw-1 at day 14 respectively, and since then they remained constantup to the end of the experiment. The adhesion of microorganisms to gravel occurredsince day 7 as determine by MPN count, but biofilm detection started after 20days. The microorganisms immobilized in gravel were able to mineralize n-hexadecane since day 7 days, whereas mineralizationof crude oil and phenanthrene were detected after the fifth week. The fourreactors?s microbial communities had reproducible DGGE profiles, showing lessdiversity than the sediment community used as inoculum. Finally, the resultsdemonstrated that a biofilm of marine microbial community was formed in 35 dayswith the capability to mineralize a wide range of hydrocarbons, with highermetabolic capability associated with biofilm development. These results are relevantfor treatment processes of hydrocarbon-containing wastewater.