ABSTRACT
Kinetics of phenol biodegradation using suspended biomass of Comamonas testosteroni Pb50 (monoculture) was measured under conditions of nutrient abundance, limitation, and prolonged cell starvation in a fed-batch reactor, with phenol being the sole carbon and energy source. The pre-washed cells were applied for measurement of the phenol and oxygen uptake rates at varied starting phenol concentrations with the kinetic parameters calculated using the Haldane model. The results revealed that nutrient limitation significantly suppressed the maximum value of exogenous respiration rate while the endogenous respiration rate, affinity and tolerance to phenol increased. By contrast, cell starvation resulted in a drop of both the exogenous and endogenous respiration rates by an order of magnitude.
ABSTRACT
Precursor-directed biogenetic approach was used to produce a range of nonactin homologues in a 50 l fermentor cultivation of strain Streptomyces griseus 34/249 obtained by UV mutagenesis. The production medium contained sodium propionate, isobutyrate and isovalerate as individual precursors, and 10 g l(-1) Diaion HP20 styrene-divinylbenzene resin that maintains suitable precursor concentration by reversibly adsorbing and releasing it. The produced nonactin homologues were separated on two C18 reversed-phase liquid chromatography columns in series and analyzed by MS with ESI source in the positive ion mode. Formation of doubly charged ions was suppressed by an excess of Na(+) ions throughout the process. The production of the homologues increased up to day 5 and then it leveled off. Cultivations with individual precursors yielded a total of 18 nonactin homologues whose spectrum depended on the precursor used. The total production of the homologues was lowered but their spectrum was shifted to higher-molecular-weight compounds.
