Heavy metal (HM) contamination of water bodies is a serious global environmental problem. Because they are not biodegradable, they can accumulate in food chains, causing various signs of toxicity to exposed organisms, including humans. Due to its effectiveness, low cost, and ecological aspect, phycoremediation, or the use of microalgae's ecological functions in the treatment of HMs contaminated wastewater, is one of the most recommended processes. This study aims to examine in depth the mechanisms involved in the phycoremediation of HMs by microalgae, it also provides an overview of the prospects for improving the productivity, selectivity, and cost-effectiveness of this bioprocess through physicochemical and genetic engineering applications. Firstly, this review proposes a detailed examination of the biosorption interactions between cell wall functional groups and HMs, and their complexation with extracellular polymeric substances released by microalgae in the extracellular environment under stress conditions. Subsequently, the metal transporters involved in the intracellular bioaccumulation of HMs as well as the main intracellular mechanisms including compartmentalization in cell organelles, enzymatic biotransformation, or photoreduction of HMs were also extensively reviewed. In the last section, future perspectives of physicochemical and genetic approaches that could be used to improve the phytoremediation process in terms of removal efficiency, selectivity for a targeted metal, or reduction of treatment time and cost are discussed, which paves the way for large-scale application of phytoremediation processes.

Dye effluents are among the most polluted wastewaters that require adequate treatment before their discharge into the environment. They have multiple chemical properties that allow them great resistance to environmental conditions, such as the persistence of coloured fabric against washing, exposure to light, chemicals, and biological attacks. However, these same particularities make them hardly degradable, thereby complicating their disposal using traditional methods. The use of biosorption for the removal of dye from wastewater has emerged as a simple, effective, and ecologically technique. Diverse biomaterials are known to bind such pollutants, including natural residues, agricultural wastes and various microorganisms like bacteria, fungi, microalgae, and yeast. In recent decades, the use of yeast cells has received increasing attention, due to their advantages such as low-cost price, availability, and ability to remove various recalcitrant contaminants. On the other hand, their autoaggregation properties can facilitate their recuperation after treatment. The present paper explores the state of the art in the field of biosorption of dye using living, dead, and modified yeast cells. Kinetic, equilibrium models as well as the analytical methods employed in biosorption studies are also discussed. The effects of physicochemical conditions on the biosorption efficiency, including physical, chemical, and biotechnological techniques that can be utilized to increase yeast’s biosorption capacities are also highlighted. GRAPHICAL ABSTRACT