In this paper, we discuss the influence of different factors on the measured values of dehydrogenase activity. We focus on the incubation time of the sample and optimal 2,3,5-triphenyl-tetrazolium chloride concentration. We provide a comparison between results obtained from three methods: Casida method, standard method, and optimization method. Some disadvantages of traditional methods were critically discussed. We showed that the results of dehydrogenase activity determination strongly depend on the method used. To minimize these discrepancies, the increase in TPF concentration should be described with the kinetic model which allows determining tangent activity. Michaelis–Menten kinetics can be used to describe the relationship between TTC concentration and tangent activities. We suggest using the value of 4 km as the optimal TTC concentration.

The presence of polystyrene (PS) waste increases constantly. Styrofoam, the most popular form of PS, is one of the major plastic pollutants in the environment. An efficient and environmentally friendly method of PS recycling is still needed. The biodegradation of PS by insects has been presented by researchers as a promising alternative to chemical, mechanical and thermal methods. The main aim of this study was to assess the survival, growth, and development of yellow mealworms (the larvae of Tenebrio molitor) fed with PS to determine if the insects are able to use PS as a source of mass and energy. The Dynamic Energy Budget (DEB) model was used to analyze the effects of food type on the growth trajectory and metabolism of tested organisms. We investigated five possible modes of influence of PS diet on DEB model parameters including a decrease of food availability, an increase in somatic maintenance power, an increase in costs for structure, allocation of energy, and a decrease in somatic maintenance power. Our results show that changes in the development of larvae fed with PS are mainly caused by a decrease in reserves density and reaction of the organism to the insufficient food supply. The inability or difficulty in completing the life cycle of T. molitor larvae fed with PS raises doubts about the use of mealworms as an effective technology for utilizing polystyrene.

A series of hydrazide-hydrazones 1–3, the imine derivatives of hydrazides and aldehydes bearing benzene rings, were screened as inhibitors of laccase from Trametes versicolor. Laccase is a copper-containing enzyme which inhibition might prevent or reduce the activity of the plant pathogens that produce it in various biochemical processes. The kinetic and molecular modeling studies were performed and for selected compounds, the docking results were discussed. Seven 4-hydroxybenzhydrazide (4-HBAH) derivatives exhibited micromolar activity K_i = 24–674 µM with the predicted and desirable competitive type of inhibition. The structure–activity relationship (SAR) analysis revealed that a slim salicylic aldehyde framework had a pivotal role in stabilization of the molecules near the substrate docking site. Furthermore, the presence of phenyl and bulky tert-butyl substituents in position 3 in salicylic aldehyde fragment favored strong interaction with the substrate-binding pocket in laccase. Both 3- and 4-HBAH derivatives containing larger 3-tert-butyl-5-methyl- or 3,5-di-tert-butyl-2-hydroxy-benzylidene unit, did not bind to the active site of laccase and, interestingly, acted as non-competitive (K_i = 32.0 µM) or uncompetitive (K_i = 17.9 µM) inhibitors, respectively. From the easily available laccase inhibitors only sodium azide, harmful to environment and non-specific, was over 6 times more active than the above compounds.

The presence of heavy metals in the environment can lead to ecological and health problems. The evolution of biological systems, such as activated sludge, exposed to heavy metals is still underexplored. Therefore, this study sought to develop a model of microorganism activity and growth in activated sludge and used it to investigate the toxicity of five metals: Cu, Cd, Ni, Zn, and Ag. Patterns in the evolution of the toxic effects caused by these metals were similar at the beginning of exposure. Differences in toxicity between metal ions were noted for longer exposure times. Changes in model parameters indicate the influence of metal ions on the mass and energy balance of living cells. Decreases in new enzyme units and biomass production yields in contaminated activated sludge indicate a shift from anabolic reactions to metal homeostasis and resistance.

The purpose of the investigation was to evaluate the effect of the selected bioflavonoids curcumin, resveratrol and baicalin on the wound healing process in an in vitro model. In the study, Balb3t3 and L929 cell lines were used. The first step was the evaluation of the cytotoxicity of the substances tested (MTT assay). Then, using the scratch test (ST), the influence of bioflavonoids on the healing process was evaluated in an in vitro model. The second stage of the work was a mathematical analysis of the results obtained. On the basis of experimental data, the parameters of the Brian and Cousens model were determined in order to determine the maximum value of the cellular and metabolic response that occurs for the examined range of concentrations of selected bioflavonoids. In the MTT assays, no cytotoxic effect of curcumin, resveratrol and baicalin was observed in selected concentrations, while in the ST tests for selected substances, a stimulatory effect was observed on the cell division rate regardless of the cell lines tested. The results obtained encourage further research on the use of substances of natural origin to support the wound healing process.