title: Biodegradation of gasoline by gellan gum-encapsulated bacterial cells.
abstract: Encapsulated cell bioaugmentation is a novel alternative solution to in situ bioremediation of contaminated aquifers. This study was conducted to evaluate the feasibility of such a remediation strategy based on the performance of encapsulated cells in the biodegradation of gasoline, a major groundwater contaminant. An enriched bacterial consortium, isolated from a gasoline-polluted site, was encapsulated in gellan gum microbeads (16-53 microm diameter). The capacity of the encapsulated cells to degrade gasoline under aerobic conditions was evaluated in comparison with free (non-encapsulated) cells. Encapsulated cells (2.6 mg(cells) x g(-1) bead) degraded over 90% gasoline hydrocarbons (initial concentration 50-600 mg x L(-1)) within 5-10 days at 10 degrees C. Equivalent levels of free cells removed comparable amounts of gasoline (initial concentration 50-400 mg x L(-1)) within the same period but required up to 30 days to degrade the highest level of gasoline tested (600 mg x L(-1)). Free cells exhibited a lag phase in biodegradation, which increased from 1 to 5 days with an increase in gasoline concentration (200-600 x mg L(-1)). Encapsulation provided cells with a protective barrier against toxic hydrocarbons, eliminating the adaptation period required by free cells. The reduction of encapsulated cell mass loading from 2.6 to 1.0 mg(cells) x g(-1) bead caused a substantial decrease in the extent of biodegradation within a 30-day incubation period. Encapsulated cells dispersed within the porous soil matrix of saturated soil microcosms demonstrated a reduced performance in the removal of gasoline (initial concentrations of 400 and 600 mg x L(-1)), removing 30-50% gasoline hydrocarbons compared to 40-60% by free cells within 21 days of incubation. The results of this study suggest that gellan gum-encapsulated bacterial cells have the potential to be used for biodegradation of gasoline hydrocarbons in aqueous systems.
authors.affiliation: Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec H3A 2B2, Canada.
authors.forename: Peyman
authors.initials: P
authors.lastname: Moslemy
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Neufeld
authors.forename: Serge R
authors.initials: SR
authors.lastname: Guiot
mesh_terms: D001419:Bacteria / Q000145:classification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D018441:Biofilms; D020099:Coated Materials, Biocompatible; D005240:Feasibility Studies; D005742:Gasoline / Q000382:microbiology*; D006838:Hydrocarbons / Q000378:metabolism*; D008863:Microspheres; D011135:Polysaccharides, Bacterial; D012680:Sensitivity and Specificity; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism
chemical_list: D020099:Coated Materials, Biocompatible; D005742:Gasoline; D006838:Hydrocarbons; D011135:Polysaccharides, Bacterial; D012989:Soil Pollutants; C048288:gellan gum