Microalgal synthesis of metal nanoparticles - towards a circular economy

Heavy metals, such as cadmium, essential components of various dyes or other industrial processes, are listed among the ten chemicals of major public concern by the WHO for their potential to be carcinogenic and inflict acute organ damage. Algal systems for bioremediation (phycoremediation) are highly attractive as they are autotrophic - relying on sunlight and carbon dioxide as inputs. This project aims to address sustainable development goals by creating scalable methodologies for wastewater treatment using microalgae to extract and upgrade heavy metals into valuable metal nanoparticles.

Using a model system, this project seeks to understand how photobioreactor technologies suitable for in-situ remediation might be developed. Under heavy metal exposure, plants and algae produce phytochelatins (PC) - glutathione-derived compounds. These peptides form stable complexes with metal, protecting the cells. The diatom alga Phaeodactylum tricornutum has been selected as a model organism for this project as it is known to bioaccumulate cadmium (Cd) and can tolerate a wide range of salinities. The aim of this project is to characterise the interactions between upstream cultivation parameters and cadmium nanoparticle formation and how these might relate to process scale up. Through the design of novel experimental systems for studying heavy metal uptake and engineering characterisation of the microenvironment, this project will seek to understand how the form of metal nanoparticles can be manipulated.

The objectives identified:

OBJECTIVES
O1: To quantify the impact of cultivation conditions on cell growth and Cd uptake through growth experiments, cell viability testing and analysis. The nanoparticles formed will undergo morphological characterisation of size, shape and distribution.

O2: To examine the impact of reactor design and operation on retention times, to identify strategies for maximising throughput by understanding geometries and fluid flow conditions for improved mass transfer characteristics.

O3: To investigate the primary mode in which the bioreactor may operate, and how this may influence subsequent processing of cadmium by characterising the benefits/drawbacks of two mechanisms: bind and elute for recovery of metal bound to the cell surface vs recovery of cells and separation of cadmium from biomass. Green chemistry techniques will be evaluated for nanoparticle recovery.

IMPACT: Our goal is to develop a phycoremediation system for application in the field. Following on from a Knowledge Exchange workshop supported by SfAM we propose to work with NGO partners to identify case study sites in India in order to apply a user-centered design approach to a future water treatment process and evaluate technoeconomic feasibility. Findings from this project will inform future design efforts and will provide an evidence base for a pilot remediation system.

The CDT has a proven track record of delivering impact from its research and training activities and this will continue in the new Centre. The main types of impact relate to: (i) provision of highly skilled EngD and sPhD graduates; (ii) generation of intellectual property (IP) in support of collaborating companies or for spin-out company creation; (iii) knowledge exchange to the wider bioprocess-using industries; (iv) benefits to patients in terms of new and more cost effective medicines, and (v) benefits to the wider society via involvement in public engagement activities and impacts on policy.

With regard to training, provision of future bioindustry leaders is the primary output of the CDT and some 96% of previous EngD graduates have progressed to relevant bioindustry careers. These highly skilled individuals help catalyse private sector innovation and biomanufacturing activity. This is of enormous importance to capitalise on emerging markets, such as Advanced Therapy Medicinal Products (ATMPs), and to create new jobs and a skilled labour force to underpin economic growth. The CDT will deliver new, flexible on-line training modules on complex biological products manufacture that will be made available to the wider bioprocessing community. It will also provide researchers with opportunities for international company placements and cross-cohort training between UCL and SSPC via a new annual Summer School and Conference.

In terms of IP generation, each industry-collaborative EngD project will have direct impact on the industry sponsor in terms of new technology generation and improvements to existing processes or procedures. Where substantial IP is generated in EngD or sPhD programmes, this has the potential to lead to spin-out company creation and job creation with wider economic benefit. CDT research has already led to creation of a number of successful spin-out companies and licensing agreements. Once arising IP is protected the existing UCL and NIBRT post-experience training programmes provide opportunities for wider industrial dissemination and impact of CDT research and training materials.

CDT projects will address production of new ATMPs or improvements to the manufacture of the next generation of complex biological products that will directly benefit healthcare providers and patients. Examples arising from previous EngD projects have included engineered enzymes for greener pharmaceutical synthesis, novel bioprocess operations to reduce biopharmaceutical manufacturing costs and the translation of early stem cell therapies into clinical trials. In each case the individual researchers have been important champions of knowledge exchange to their collaborating companies.

Finally, in terms of wider public engagement and society, the CDT has achieved substantial impact via involvement of staff and researchers in activities with schools (e.g. STEMnet), presentations at science fairs (Big Bang, Cheltenham), delivery of high profile public lectures (Wellcome Trust, Royal Institution) as well as TV and radio presentations. The next generation of CDT researchers will receive new training on the principles of Responsible Innovation (RI) that will be embedded in their research and help inform their public engagement activities and impact on policy.