title: Modeling of olive oil degradation and oleic acid inhibition during chemostat and batch cultivation of Bacillus thermoleovorans IHI-91.
abstract: Olive oil degradation by the thermophilic lipolytic strain Bacillus thermoleovorans IHI-91 in chemostat and batch culture was modeled to obtain a general understanding of the underlying principles and limitations of the process and to quantify its stoichiometry. Chemostat experiments with olive oil as the sole carbon source were successfully described using the Monod chemostat model extended by terms for maintenance requirements and wall growth. Maintenance requirements and biomass yield coefficients were in the range reported for mesophiles. For a chemostat experiment at D = 0.3 h(-1) the model was validated up to an olive oil feed concentration of about 3.0 g L(-1) above which an inhibitory effect occurred. Further analysis showed that the liberated oleic acid is the main cause for this inhibition. Using steady-state oleic acid concentrations measured in chemostat experiments with olive oil as substrate it was possible to derive a kinetic expression for oleic acid utilization, showing that a concentration of 430 mg L(-1) leads to a complete growth inhibition. Oleic acid accumulation observed during batch fermentations can be predicted using a model involving growth-associated lipase production and olive oil hydrolysis. Simulations confirmed that this accumulation is the cause for the sudden growth cessation occurring in batch fermentations with higher olive oil start concentrations. Further, an oscillatory behavior, as observed in some chemostat experiments, can also be predicted using the latter model. This work clearly demonstrates that thermophilic lipid degradation by Bacillus thermoleovorans IHI-91 is limited by long-chain fatty acid beta-oxidation rather than oil hydrolysis.
authors.affiliation: Department of Bioprocess and Biochemical Engineering, Technical University Hamburg-Harburg, Denickestr. 15, 21071 Hamburg, Germany. pbec@novo.dk
authors.forename: P
authors.initials: P
authors.lastname: Becker
authors.forename: H
authors.initials: H
authors.lastname: Märkl
mesh_terms: D001407:Bacillus / Q000502:physiology*; D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism; D018929:Cell Culture Techniques / Q000379:methods*; D003470:Culture Media / Q000378:metabolism; D004075:Diglycerides / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D005989:Glycerides / Q000032:analysis; D006868:Hydrolysis; D007700:Kinetics; D008049:Lipase / Q000378:metabolism; D008055:Lipids / Q000032:analysis; D008962:Models, Theoretical; D019301:Oleic Acid / Q000037:antagonists & inhibitors*; D000069463:Olive Oil; D010100:Oxygen / Q000378:metabolism; D010938:Plant Oils / Q000378:metabolism*; D014304:Triolein / Q000032:analysis
chemical_list: D003470:Culture Media; D004075:Diglycerides; D005989:Glycerides; D008055:Lipids; D000069463:Olive Oil; D010938:Plant Oils; D014304:Triolein; D002245:Carbon Dioxide; D019301:Oleic Acid; C005953:monoolein; D008049:Lipase; D010100:Oxygen; C013965:diolein