Publication

Abstract : One of the major technological challenges in developing a microalgal biorefinery is to minimize the fossil energy inputs, particularly in two important downstream unit operations, cell harvesting and disruption. Hence, this study involved synthesizing and applying biopolymer nanocomposite to achieve concomitant biomass harvesting, cell disruption, and nanocomposite recovery by exploiting its cationic, photocatalytic, and magnetic properties respectively, in an integrated and optimized process chain. Accordingly, dual-functionalized chitosan-TiO2 conjugated particles (CTC) and trifunctionalized magnetic nanocomposites (MNCs) namely, chitosan coated core–shell structures of Fe3O4–TiO2, were prepared and characterized. The harvesting efficiency of >98% was achieved at the optimal dosages of chitosan, CTC and MNCs of 0.11, 0.09, and 0.07 g g–1Chlorella minutissima biomass, respectively. TiO2 driven photocatalysis could effectively disrupt harvested wet-biomass, when exposed to UV irradiation in the presence of either CTC or MNCs for 2 h, and when subjected to visible light with only MNCs for 3 h. Photocatalytic cell disruption helped recover 96–97% of the intracellular lutein and lipid, when compared to ultrasonication as control. Subsequently, the MNCs were separated from residual biomass by physicochemical treatment, resulting in over 98% detachment efficiency for reuse in the downstream process chain. To the best of our knowledge, this integrated green process is novel, in terms of meeting a contemporary technological challenge in downstream processing of microalgal biomass, and this research outcome may inspire the development of sustainable microalgal biorefinery for the production of lutein and biodiesel.