Augmented biosynthesis of cadmium sulfide nanoparticles by genetically engineered Escherichia coli

Abstract

Microorganisms can complex and sequester heavy metals, rendering them promising living factories for nanoparticle production. Glutathione (GSH) is pivotal in cadmium sulfide (CdS) nanoparticle formation in yeasts and its synthesis necessitates two enzymes: gamma-glutamylcysteine synthetase (gamma-GCS) and glutathione synthetase (GS). Hereby, we constructed two recombinant E. coli ABLE C strains to over-express either gamma-GCS or GS and found that gamma-GCS over-expression resulted in inclusion body formation and impaired cell physiology, whereas GS over-expression yielded abundant soluble proteins and barely impeded cell growth. Upon exposure of the recombinant cells to cadmium chloride and sodium sulfide, GS over-expression augmented GSH synthesis and ameliorated CdS nanoparticles formation. The resultant CdS nanoparticles resembled those from the wild-type cells in size (2-5 nm) and wurtzite structures, yet differed in dispersibility and elemental composition. The maximum particle yield attained in the recombinant E. coli was approximately 2.5 times that attained in the wild-type cells and considerably exceeded that achieved in yeasts. These data implicated the potential of genetic engineering approach to enhancing CdS nanoparticle biosynthesis in bacteria. Additionally, E. coli-based biosynthesis offers a more energy-efficient and eco-friendly method as opposed to chemical processes requiring high temperature and toxic solvents.

Biosynthesis of CdS Quantum Dots Mediated by Volatile Sulfur Compounds Released by Antarctic Pseudomonas fragi

“…CdS nanoparticles produced by this Antarctic strain showed a zeta potential value (lower than −20 mV) indicative of high stability in aqueous solutions, with nanocrystals produced with Met being the most stable (Kuznetsova and Rempel, 2015). The average size of the nanoparticles produced with Cys (∼2 nm) and Met (∼16 nm), determined from TEM images, were consistent with the size of QDs biosynthesized by other microorganisms (Chen et al, 2009; Khachatryan et al, 2009; Syed and Ahmad, 2013; Wu et al, 2015; Al-Shalabi and Doran, 2016; Tandon and Vats, 2016; Wang et al, 2018; Bruna et al, 2019). TEM as a technique for characterizing nanomaterials enables the visualization of the shape and size of the nanoparticles by providing direct images of nanomaterials at a spatial resolution (Lina et al, 2014).…”

‘Green’ synthesis of metals and their oxide nanoparticles: applications for environmental remediation

“…Fungi-mediated biosynthesis of metal/metal oxide nanoparticles is also a very efficient process for the generation of monodispersed nanoparticles with well-defined morphologies. They act as better biological agents for the preparation of metal and metal oxide nanoparticles, due to the presence of a variety of intracellular enzyme [ 23 ]. Competent fungi can synthesize larger amounts of nanoparticles compared to bacteria [ 24 ].…”

Bacteria in Nanoparticle Synthesis: Current Status and Future Prospects

“…After promoted PC synthesis, CdS nanocrystals were produced with a size distribution of 2–6 nm. Moreover, it was proven that glutathione synthetase overexpression in ABLEC E. coli strains, in conjunction with metal stress, simultaneously enhanced the biosynthesis of intracellular glutathione and CdS NPs [ 142 ]. In another study, stable NPs were recently achieved using the engineering of the Desulfovibrio desulfuricans flagellar FliC protein.…”