A new biosensor was designed for the assessment of aquatic environment quality. Three microalgae were used as toxicity bioindicators: Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. These microalgae were immobilized in alginate and silica hydrogels in a two step procedure. After studying the growth rate of entrapped cells, chlorophyll fluorescence was measured after exposure to (3-(3,4-dichlorophenyl)-1,1-dimethylurea) (DCMU) and various concentrations of the common herbicide atrazine. Microalgae are very sensitive to herbicides and detection of fluorescence enhancement with very good efficiency was realized. The best detection limit was 0.1 µM, obtained with the strain C. reinhardtii after 40 minutes of exposure.

Here we introduce an assembly for bioremediation of polluted water based on the immobilization of alginate beads loaded with filamentous fungus Stereum hirsutum inside nanoporous silica hydrogels. The resulting hybrid device exhibits good physical, chemical and biological stability, being effective in the removal and degradation of malachite green (MG), even in solutions with a high concentration of the dye. This fact is a consequence of adsorption and regulated transport of the dye, as well as the retention of dye degradation enzymes inside the hydrogel. The optimal structure of the hydrogel for an efficient dye–enzyme encounter resulted from the fine adjustment of synthesis conditions in order to achieve a suitable porosity. The results presented here open the possibility of bioremediation without dissemination of exotic organisms to the environment, and can be extended to a vast variety of strains due to the inherent high biocompatibility of the present procedure.