title: Rate-limiting step analysis of the microbial desulfurization of dibenzothiophene in a model oil system.
abstract: A mechanistic analysis of the various mass transport and kinetic steps in the microbial desulfurization of dibenzothiophene (DBT) by Rhodococcus erythropolis IGTS8 in a model biphasic (oil-water), small-scale system was performed. The biocatalyst was distributed into three populations, free cells in the aqueous phase, cell aggregates and oil-adhered cells, and the fraction of cells in each population was measured. The power input per volume (P/V) and the impeller tip speed (vtip ) were identified as key operating parameters in determining whether the system is mass transport controlled or kinetically controlled. Oil-water DBT mass transport was found to not be limiting under the conditions tested. Experimental results at both the 100 mL and 4 L (bioreactor) scales suggest that agitation leading to P/V greater than 10,000 W/ m(3) and/or vtip greater than 0.67 m/s is sufficient to overcome the major mass transport limitation in the system, which was the diffusion of DBT within the biocatalyst aggregates.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139.
authors.forename: Andres
authors.initials: A
authors.lastname: Abin-Fuentes
authors.forename: James C
authors.initials: JC
authors.lastname: Leung
authors.forename: Magdy El-Said
authors.initials: Mel-S
authors.lastname: Mohamed
authors.forename: Daniel I C
authors.initials: DI
authors.lastname: Wang
authors.forename: Kristala L J
authors.initials: KL
authors.lastname: Prather
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D008954:Models, Biological; D012240:Rhodococcus / Q000378:metabolism*; D013455:Sulfur / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013876:Thiophenes / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D013876:Thiophenes; D013455:Sulfur; C016366:dibenzothiophene
keywords: Rhodococcus erythropolis IGTS8; aggregation; biodesulfurization; dibenzothiophene; power input per volume; rate-limiting step