Optimizations of microwave-assisted extraction and transesterification of bio-crude oil from spirulina (Arthrospira platensis)

Optimizations of microwave-assisted extraction (MAE) and transesterification of bio-crude oil from spirulina (Arthrospira platensis) were conducted. The bio-crude oil from A. platensis was initially extracted using water as a solvent, centrifugation, dissolved with n-hexane, separation, and continued to evaporation. The optimization for the extraction was conducted with varieties of biomass-to-solvent ratio, extraction temperature, extraction time, and n-hexane contact time, yielding the optimum condition with biomass/solvent 1 : 7, extraction temperature 70 °C, extraction time 15 minutes, and contact time 25 minutes (D70/15-25) 5.56%. The average yield of the bio-crude oil obtained was 4.87%, variation 0.32, standard deviation 0.57, and standard error 0.14. The optimization for transesterification was carried out with variations of bio-crude oil-to-methanol ratio, reaction temperature, and reaction time, yielding the optimum condition with bio-crude oil/methanol 1 : 6, reaction temperature 65 °C, and reaction time 50 minutes (G65/50) 98%. The average yield of the bio-diesel obtained was 88%, variation 50.29, standard deviation 7.09, and standard error 2.68. The cell damage before and after extraction and also conventional heating observed using SEM showed massive damage by this method.