The subjects of the article are investigations concerning the ability of both Rhodococcus opacus 1CP and mixed bacterial cultures to use selected surfactants as sole carbon and energy source. In a comparative manner the biosurfactants rhamnolipid, sophorolipid and trehalose tetraester, and the synthetic surfactant Tween 80 were examined. Particular emphasis was put on a combinatorial approach to determine quantitatively the degree of surfactant degradation by applying calorimetry, thermodynamic calculations and mass spectrometry, HPLC as well as determination of biomass. The pure bacterial strain R. opacus was only able to metabolize a part of the synthetic surfactant Tween 80, whereas the mixed bacterial cultures degraded all of the applied surfactants. Exclusive for the biosurfactant rhamnolipid a complete microbial degradation could be demonstrated. In the case of the other surfactants only primary degradation was observed.

Kinetic methods for analytical applications can be divided into noncatalytic and catalytic methods. Enzyme kinetic determinations are a special type of catalytic methods. Enzymatic reactions are used analytically to determine enzyme activities – for instance, in the diagnosis of diseases, substrate concentrations in the food industry or medicine, and concentrations of effectors – for example, in trace analysis. Owing to the high selectivity of enzymatic analysis, the importance of this method in various fields is growing rapidly. The widest use is observed in clinical chemistry and food chemistry. This article gives only a general survey of the high potential of enzymatic analysis, with references to more detailed literature. Enzymatic reactions are characterized by some special features, explained after the introduction. The theoretical background for kinetic determination is the comprehension of the principles on enzymatic kinetics. In Section 3, the simplest mechanism, outlined by Michaelis and Menten, and several transformations of the equation are described. In this section, two kinetic parameters, enzyme activity and the Michaelis constant, are introduced. Section 4 deals with substances, the so‐called effectors , influencing the rate of an enzymatic reaction. Simple mechanisms of these effectors are shown. Different methods for determination of substrates, enzymes, and effectors, illustrated by many examples, are represented in Section 5. While substrate concentrations can be determined using both equilibrium or kinetic methods, the determination of enzymes and effectors can be performed only by kinetic approaches. In the last two sections, the application of enzymes in flow systems and biosensor development are shown.

Aims:  To investigate the stress response during nutrient deprivation, particularly with regard to the application of phenol as growth substrate of Pseudomonas putida with calorimetric measurements as a new method. Methods and Results:  The online and noninvasive measurement of the thermal power P0 permits the detection of microbial activity during the starvation period. While the results of the investigations with phenol reveal a significant loss of activity as a function of the temporal nutrient dosage, only a small loss of activity was detected by using glucose. Microbiological methods (colony forming units (CFU) and activity of catechol‐2,3‐dioxygenase) showed a loss of the enzyme activity at a constant CFU. The introduction of a simple decay parameter kD in the kinetic description of the growth process on phenol was sufficient for the successful kinetic modelling. Conclusions:  The combination of calorimetric measurements and the determination of the enzymatic activity proved the loss of activity of Ps. putida during the deprivation of the substrate phenol. Significance and Impact of the study:  The initial heat power (P0) proves to be a suitable parameter for the characterization of the physiological state of the culture and can be used for the regulation of nutrient supply in biotechnological process development.