Green energy from Coelastrella sp. M-60: Bio-nanoparticles mediated whole biomass transesterification for biodiesel production

Application of nanoparticles in microalgal biodiesel production comprise of nanoparticle usage for lipid accumulation, lipid extraction and transesterification process. Conventionally, microalgal biomass/oil are converted into fatty acid methyl esters (FAME) using methanol in the presence of homogeneous acid/base catalysis through transesterification. In this study, bio-nanoparticles were synthesized from bio-waste (seashell) and employed them as heterogeneous catalysts in the direct/whole-cell transesterification of wet microalgal biomass. Bio-nano CaO and bio-nano CaCO3 were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FT-IR) analyses. Specific surface areas of bio-nano CaCO3 and bio-nano CaO were found to be 73.519 and 19.810 m(2)/g with an average pore size diameter of 7.141 and 2.348 nm respectively through BET analysis. FT-IR analysis of the synthesized bio-nanoparticles showed similar absorption frequencies as that of bulk counterpart with noticeable differences in absorption at some frequencies. Thus, the present study employs the as-synthesized bio-nanoparticles from waste seashell as heterogeneous catalysts for whole-cell/direct transesterification of N starved Coelastrella sp. M-60 for FAME conversion and compared with (i) conventional acid catalyst and (ii) commercial TiO2 nanocatalyst. The above mentioned direct transesterification reactions had yielded C 16:0 (7.5-22.3%) and C 18:1 (63.2-78%) as the major FAME products. Bio-nano CaCO3 and bio-nano CaO had yielded an average of 1.29 and 1.02 folds increase in FAME proportions respectively than conventional acid catalysis. Hence, this study shows the potential of bio-nanocatalysts for direct transesterifcation of Coelastrella sp. M-60 as a greener approach for biodiesel production.