Intensification and characterization of biosorption of microalgal cells on filamentous fungal pellets as effective tools for harvesting of microalgal biomass

Microalgae are promising resources with a variety of advantages and applications. However, their harvesting cost in large-scale cultivation may account for 20-30 % and in some instances up to 50 % of the overall production cost. This study then aimed to apply biosorption of microalgal cells by using fungal pellets as an alternative lowcost and practical harvesting technique. Among the fungal strains screened, Aspergillus tubingensis TSIP9 formed spherical, mycelium packed and consistent in size. The biosorption of microalgal cells process was optimized through response surface methodology (RSM). The maximum harvesting efficiency of 98.3 +/- 1.2 % was achieved when using pellet loading of 60 % and pH 5.0. The biosorption process can be explained by Langmuir isotherm model with the maximum biosorption capacity (qmax) of 0.338 g/g and the Langmuir constant (K) of 0.999 L/g. Pseudo-first-order model is suitable for describing the biosorption kinetics of microalgal cells on fungal pellets. The application of fungal pellets in downstream process for microalgae cultivation was attempted. The fungal pellets could harvest microalgal cells as high as 3.70 x 1011 cells/g after 5 cycles of repeated harvesting process. FTIR analysis revealed the possible functional groups involved in fungi-microalgae interaction are C--O, C-O, C-N, and C-H. These results indicated that the potential of fungal pellets as effective tools for harvesting/ immobilizing microalgal cells and their practical applications in harvesting on a large scale and resource recycling.