Biosurfactants, Polyhydroxyalkanoates, and Other Added-Value Products from Wastewater Electro-bioremediation: A New Biorefinery Concept.

Abstract

Electro-bioremediation of wastewater is a novel, nature-based solution towards clean water, based on microbial electrochemical technologies (METs). Electro-bioremediation technologies for wastewater treatment, except enhanced bioremediation results and renewable energy generation, offer an unlocked opportunity for harvesting by-products and using them in other applications. This concept contributes to circularity, sustainability, and environmental compatibility, mitigating the impact of climate change. In addition, wastewater valorization and, thus, water resilience are possible thereby leading to protection of water resources. Compounds and metabolites naturally synthesized by the microorganisms involved in the wastewater electro-assisted biodegradation, can result in the enhancement of both extracellular electron transfer (EET) and bioremediation. Such microbial products are added-value, natural, non-toxic and biodegradable such as biosurfactants (BSFs) and polyhydroxyalkanoates (PHAs). In this chapter, the effect of the presence of BSFs and PHAs in MET during electro-bioremediation, as well as when fed with conventional substrates, are exhaustively evaluated. The significance of BSFs even when they are added exogenously is also examined. The major categories of by-products biosynthesis including organic acids, biopolymers, recovered heavy metals and phenazines such as pyocyanin during electro-bioremediation processes are also discussed. Consequently, a future direction in wastewater electro-bioremediation is proposed.