Synthetic Biology-Based Approaches for Microalgal Bio-Removal of Heavy Metals From Wastewater Effluents

Abstract

Heavy metal polluted wastewater from industries is currently one of the major environmental concerns leading to insufficient supply of clean water. Several strategies have been implemented to overcome this challenge including the use of microalgae as heavy metal bio-removers. However, there are still limitations that prevent microalgae to function optimally. Synthetic biology is a new biological discipline developed to solve challenging problems via bioengineering approaches. To date, synthetic biology has no universally affirmed definitions; however, it is uncontroversial that synthetic biology utilizes a constructive library of genetic standardized parts to create new biological systems or to redesign existing ones with improved characteristics. In this mini-review, we present state-of-the-art synthetic biology-based approaches that can be used to enhance heavy metal bio-removal from wastewater effluents by microalgae with a narrative synthetic biology workflow (Design-Build-Test-Learn cycle) to guide future developments of more advanced systems. We also provide insights into potent genes and proteins responsible for the bio-removal processes for stepwise developments of more advanced systems. A total of 49 unique genes and proteins are listed based on their eight heavy metals (Mn, Fe, Cu, Zn, As, Cd, Hg, and Pb) bio-removal functions in transport system, cellular tolerance, synthesis of key players in heavy metal bio-removal, biotransformation of heavy metals, and gene expression regulation. Thus, with our library, genetic parts are ready to be recruited for any synthetic biology-based designs. Thereby, this mini-review identifies potential avenues of future research and maps opportunities to unleash more potential of microalgae as heavy metal bio-removers with synthetic biology.

Putative Protein Discovery from Microalgal Genomes as a Synthetic Biology Protein Library for Heavy Metal Bio-Removal

“…Microalgae perform three main mechanisms that allow them to bio-remove heavy metals from wastewater effluents. Previously, we have compiled a list of genes with reported use for genetic engineering to enhance microalgal bio-removing capacity [ 7 ]. Thus, in this work, we utilize the list as a primary source for protein targets.…”

“… Microalgal heavy metal bio-removing mechanisms and the use of synthetic biology for system enhancement. ( A ) Mechanisms and cellular functions used by microalgae to bio-remove heavy metals (HMs) from wastewater, adapted from Sattayawat et al, 2021 [ 7 ]; ( i ) biosorption, ( ii ) bioaccumulation ( iii ) biotransformation and ( iv ) cellular uptake of heavy metals via transporters ( v ) cellular responses to heavy metal-induced stresses. ( B ) Synthetic biology Design-Build-Test-Learn (DBTL) cycle.…”

“…Microalgae are promising bio-removers of contaminated heavy metals from wastewater effluents [ 6 ]. In our latest review, we summarized three mechanisms used by microalgae to bio-remove heavy metals from wastewater: biosorption, bioaccumulation and biotransformation [ 7 ]. In brief, biosorption is a process by which microalgae absorb heavy metal ions onto their cell surface; the anionic composition plays a role in attracting positive heavy metal ions ( Figure 1 A).…”

“…We propose that microalgal native abilities to bio-remove heavy metals could be enhanced via synthetic biology-based approaches with the proposed strategies previously listed [ 7 ]. Generally, the study of synthetic biology follows a guideline called “Design-Build-Test-Learn” or DBTL cycle ( Figure 1 B), which allows systematic implementation of the new system.…”

A synthetic biology approach for the treatment of pollutants with microalgae

“…Most reviews in this field have focused on microalgal bioproduction, such as Naduthodi et al (Naduthodi et al, 2021), Rock et al (Rock et al, 2021), Ng et al (Ng et al, 2020), and Cao et al (Cao et al, 2023), which are centred around carbon metabolism, biofuel production, metabolic regulation, and natural pigment synthesis respectively. Fewer reviews have focused on synthetic biology for pollutant removal in microalgae, and these few have focused on wastewater bioremediation, such as the reviews by Sattayawat et al (Sattayawat et al, 2021) and Hassanien et al (Hassanien et al, 2023).…”