Biotransformation of 1-naphthalenesulfonic acid by the green alga Scenedesmus obliquus.

Under sulfate limitation, axenic batch cultures of the green alga Scenedesmus obliquus metabolized 1-naphthalenesulfonic acid and partially used the sulfonate as a source of sulfur. The main metabolite, 1-hydroxy-2-naphthalenesulfonic acid, which was not metabolized further in the algal culture, was formed by hydroxylation of the substrate in position 1 and by migration of the sulfonic acid group to position 2 of the naphthalene ring (NIH shift). A smaller amount of 1-naphthalenesulfonic acid was desulfonated. The resulting 1-naphthol was mostly transformed into 1-naphthyl beta-d-glucopyranoside.

Deterministic interpretation of the temperature response of microbial growth.

A deterministic approximation of the thermal deactivation process is undertaken by structuring growth kinetics of cell populations on the activity level. Growth data of the green microalga Scenedesmus obliquus under forced periodic conditions of light intensity have been used for model verification. The model considers a straightforward extension of normal growth kinetics in such a way that different growth activities can be adjusted in the context of a thermal damage and repair mechanism. The nonlinear fitting of the measured response renders parameter values as a function of the light availability per unit biomass.

Kinetics of growth and substrate consumption of Escherichia coli ML 30 on two carbon sources.

When E. coli ML 30 is grown in batch culture on a mineral salt medium containing a mixed carbon source of glucose and pyruvate, there is no sequential utilization of the carbon sources. The consumption of glucose and pyruvate takes place simultaneously with reciprocal influence (inhibition) on rates of substrate uptake. The specific growth rate is greater than mupmax for pyruvate but smaller than musmax for glucose. In the paper three cases of kinetics of growth and of substrate consumption at several combinations of initial substrate concentrations are considered. A mathematical model is proposed and investigated. The model allows to describe the growth on glucose or on pyruvate not only as singular carbon sources, but also as a mixed carbon source with reciprocal inhibition on rates of substrate uptake. By data fitting parameters of growth and substrate consumption were found.