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Dye effluents released from various industries, notably the textile sector, are hazardous, and can cause significant damage to the environment. Thus, treatment and detoxification of these toxic dyes are of major concern for compliance with environmental legislations. So far, a number of physicochemical dye-removal methods have been proposed. However, despite their effectiveness in dye decolorization, by-products of chemical degradation methods may be more toxic than their parent dye molecules. The cost of these processes is also very high, thereby limiting their large-scale application. The use of yeast cells for the removal of toxic dyes is a comparatively effective, eco-friendly and cost-effective method. In this review, we describe the adverse effects of synthetic dyes on living organisms and enzymatic biodegradation mechanisms involved in mycoremediation processes of synthetic dyes. In addition, the influence of various physico-chemical factors on the decolorization performance of yeast cells, the analytical techniques used to identify the intermediates of dye biodegradation, the assessment of their toxicity and the molecular aspects of their biodegradation are also highlighted. This study may provide a basis for the development of dye bio-removal methods using yeast cells. Graphical abstract

Effect of polyamines on the reduction of hexavalent chromium by bacterial strains and their resistance. Polyamines are involved in several functions in bacteria. In this study, we examined the role of polyamines in hexavalent chromium (Cr[VI]) reduction by three bacterial strains isolated from sites contaminated by tannery effluents. The strains were identified as Serratia proteamaculans, Leucobacter chromiireducens and Brevibacterium frigoritolerans. The inhibition of polyamine synthesis by α-difluoromethylornithine (DFMO) caused a decrease in Cr(VI) tolerance in the bacterial isolates, indicating the role of endogenous polyamines in resistance to Cr(VI). The exogenous application of polyamines (putrescine, spermidine, cadaverine) was found to stimulate growth and Cr(VI) reduction by the bacterial strains in Luria-Bertani medium. The results show the importance of polyamines in response to heavy metal stresses, especially Cr(VI) toxicity.

Les polyamines sont impliquées dans plusieurs fonctions chez les bactéries. Dans ce travail, on a étudié le rôle de ces composés dans la réduction du chrome hexavalent (Cr[VI]) par trois souches bactériennes isolées à partir des sites contaminés par les effluents des tanneries. Les souches sont identifiées comme étant Serratia proteamaculans, Leucobacter chromiireducens et Brevibacterium frigoritolerans. L’inhibition de la synthèse des polyamines par l’α-difluorométhylornitine (DFMO) a provoqué une diminution de la tolérance des souches bactériennes au Cr(VI), ce qui montre le rôle des polyamines endogènes dans la résistance au Cr(VI). L’application exogène des polyamines (putrescine, spermidine, cadavérine) a permis de stimuler la croissance bactérienne et la réduction du Cr(VI) par les souches bactériennes, en milieu Luria-Bertani. Les résultats montrent l’importance des polyamines dans la réponse bactérienne au stress métallique causé par le Cr(VI). Effect of polyamines on the reduction of hexavalent chromium by bacterial strains and their resistance. Polyamines are involved in several functions in bacteria. In this study, we examined the role of polyamines in hexavalent chromium (Cr[VI]) reduction by three bacterial strains isolated from sites contaminated by tannery effluents. The strains were identified as Serratia proteamaculans, Leucobacter chromiireducens and Brevibacterium frigoritolerans. The inhibition of polyamine synthesis by α-difluoromethylornithine (DFMO) caused a decrease in Cr(VI) tolerance in the bacterial isolates, indicating the role of endogenous polyamines in resistance to Cr(VI). The exogenous application of polyamines (putrescine, spermidine, cadaverine) was found to stimulate growth and Cr(VI) reduction by the bacterial strains in Luria-Bertani medium. The results show the importance of polyamines in response to heavy metal stresses, especially Cr(VI) toxicity.

Effect of polyamines on the reduction of hexavalent chromium by bacterial strains and their resistance. Polyamines are involved in several functions in bacteria. In this study, we examined the role of polyamines in hexavalent chromium (Cr[VI]) reduction by three bacterial strains isolated from sites contaminated by tannery effluents. The strains were identified as Serratia proteamaculans, Leucobacter chromiireducens and Brevibacterium frigoritolerans. The inhibition of polyamine synthesis by α-difluoromethylornithine (DFMO) caused a decrease in Cr(VI) tolerance in the bacterial isolates, indicating the role of endogenous polyamines in resistance to Cr(VI). The exogenous application of polyamines (putrescine, spermidine, cadaverine) was found to stimulate growth and Cr(VI) reduction by the bacterial strains in Luria-Bertani medium. The results show the importance of polyamines in response to heavy metal stresses, especially Cr(VI) toxicity.

Acacias are spectacular angiosperms grouping single canopy species to those of tropical forests. Easy growth, hardiness and drought resistance of these Australian Wattle trees give them variable and great economic importance. Indeed, among other they produce, wood, edible seeds, gums and provide a valuable source of high quality fodder, rich in protein for subsistence and commercial production of livestock because they provide foliage during dry periods in the absence of herbaceous species. In addition, they contribute to the warmer climate of arid and semi-arid areas by reducing evaporation and creating a shadow that slows the soil drying and provide the setting and coastal sand dunes with their lateral root system that promotes better maintenance of the sand particles cohesion. These factors make it an economic resource of a great environmental and social importance, especially in arid and semi-arid areas, and an excellent candidate for reforestation of Mediterranean areas.