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Multifunctional Cellulose Magnetic Hybrid (CMH) Nanomaterial for Integrating Downstream Processing of Microalgae

Periodic Reporting for period 1 - CMHAlgae (Multifunctional Cellulose Magnetic Hybrid (CMH) Nanomaterial for Integrating Downstream Processing of Microalgae)

Berichtszeitraum: 2017-08-02 bis 2019-08-01

Microalgae are promising biomass feedstock for valuable chemical production and biofuel. Now withstanding the extensive R&D efforts devoted to upscaling of microalgae production in the past decade, the cost and energy demand remain too high. In this connection, significant improvements are needed in multiple steps of downstream processing, particularly in harvesting, dewatering and cell disruption. Functionalized nanomaterials have numerous applications in fields ranging from catalysis, electrode materials, medical diagnosis, drug delivery, environmental remediation and biotechnology. In recent years, nanoparticles with multiple functionalities have emerged, which are capable of combining several unit operations into a single step, e.g. a multifunctional collagen based magnetic nanomaterial has been applied for selective absorption and recovery of oil from spills through external magnetic field. Nanomaterials are increasingly being used in microalgae downstream processing, e.g. for harvesting, lipid extraction or biodiesel conversion. This project aimed to achieve a significant cost reduction by using multifunctional nanomaterials to combine multiple unit operations in downstream processing (harvesting, dewatering and cell disruption) into a single technology. The overall objective of this project was to develop a bio-based and reusable cellulose magnetic hybrid (CMH) nanomaterial that can be used for combining flocculation, cell disruption and dewatering of microalgae. This project integrated several promising recent breakthroughs in nanotechnology for downstream processing of microalgae into a single technology with cellulose magnetic hybrid nanomaterial to decrease the downstream processing costs in a microalgal biorefinery.
Cellulose nanocrystals (CNCs) were functionalized with methylimidazolium (MIM) and pyridinium (PRY). These cationic CNCs were efficient in flocculating both fresh water (Chlorella) and marine (Nannochloropsis) microalgae. These highly charged cationic flocculants resulted in a maximum of 95% flocculation in Chlorella and about 90% flocculation in Nannochloropsis. MIM and PRY-CNCs have point charges and are pH independent. No significant differences were observed in flocculation efficiency from pH 4 to 10 at a given dose. Moreover, these flocculants were efficient in disrupting the cell wall, which would be helpful in later stages of biomass processing, especially during compound extraction.
Further, MIM and PRY-CNCs were hybridized with Fe3O4 nanoparticles to form uniformly dispersed nanomaterial. Thus developed CMH nanomaterials possessed surface charge of 42.4 mV for MIM-CMH and 36.9 mV for PRY-CMH. These CMH nanomaterials were efficient if flocculation of both Chlorella (flocculation efficiency >85%) and Nannochloropsis (flocculation efficiency >85%). Moreover, these CMH nanomaterials also retained the cell disruption efficiency of the MIM and PRY grafts.
Following the flocculation with CMH nanomaterials, the Chlorella cells were detached using SDS and further evaluated with lipid extraction for the effectiveness of cell disruption. The cells flocculated with MIM and PRY-CMH nanomaterials resulted increase lipid yield when compared to untreated control and unmodified CMH nanomaterial. Further, with mild pre-treatment of 5 min bead milling, lipid yield with MIM and PRY-CMH nanomaterial treated cells further increased as high as 85% of the total lipid. The cost-benefit analysis suggests that the process would be profitable compared to the existing industrially relevant methods if the CMH nanomaterial could be reused for five or more cycles. With successful development of recyclable cellulose magnetic hybrid nanomaterials and expected lowering of nanocellulose costs, it could be possible to develop cost-effective downstream processing of microalgae.
One manuscript is under revision in Algal Research. Three more manuscripts are under preparation. The findings were presented in several research meetings and conferences. Further, the technology was explained to the schoolchildren during Children’s University, 2017 at KU Leuven.
This project developed cellulose magnetic hybrid nanomaterial that could be used for harvesting, dewatering and disrupting the microalgal cell in a single step. Production of uniformly dispersed cationic cellulose magnetic hybrid nanomaterial is a crucial success of this project. These charged magnetic nanomaterial could have wide applications such as combating microalgal blooms, wastewater treatment etc.
This project allowed the researcher to broaden his scientific expertise and to acquire new knowledge in preparation, functionalization and characterization of nanocellulose. The researcher got training in supervision of researchers, writing of proposals, tenure track applications and project management. All these collective experiences helped the researcher in attaining assistant professor position in Roskilde University, Denmark.
The researcher’s contact in South Korea led to a Belgium-South Korea research cooperation funding from FWO-NRF. Through this project, a network established between KU Leuven, Belgium, Chungnam National University and Pusan National University in Korea. This allowed research exchange of students between these universities.