This research aims to study the simultaneous extraction and transesterification of Chlorella vulgaris (C. vulgaris) using microwave irradiation with methanol as solvent and potassium hydroxide (KOH) as catalyst. The microwave-assisted insitu transesterification of C. vulgaris is assessed at various ratios of biomass-to-methanol, reaction times, and catalyst concentrations during the centrifugation and evaporation process. Gas chromatography-mass spectrometry (GC-MS) analysis is performed to confirm fatty acid methyl ester (FAME) composition. Biodiesel preparation is carried out by simultaneous extraction and transesterification of microalgae from C. vulgaris. The product is then characterized using Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR); microalgae are observed using scanning electron microscopy (SEM). The highest amount of FAME is obtained at a biomass-to-methanol ratio of 1:12, reaction time of 40 min, and catalyst concentration of 2 wt%. Biodiesel shows conversion to about 77.64% of methyl ester (methyl myristate, methyl palmitoleate, methyl linoleate, methyl oleate, methyl arachidonate, and methyl 5,8,11,14,17-eicosapentanoate).

Abstract
1. Introduction
2. Experimental Procedures
3. Results and Discussion
    3.1 Microwave-assisted In-situ Transesterification
    3.2 Effect of Various Biomass-to-methanol Ratios
    3.3 Effect of Various Reaction Time
    3.4 Effect of Various Catalyst Concentration
    3.5 FTIR Characterization
    3.6 GC-MS Characterization
    3.7 1H-NMR Characterization
    3.8 SEM Characterization
4. Conclusions
References

• Randy Adhiputra(Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada)
• Maisari Utami(Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Islam Indonesia)
• Eko Agus Suyono(Department of Biology, Faculty of Biology, Universitas Gadjah Mada)
• Arief Budiman(Department of Chemical Engineering, Faculty of Engineering, Universitas Gadjah Mada)
• Poedji Loekitowati Hariani(Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Sriwijaya)
• Ani Setyo Pratiwi(Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada)
• Karna Wijaya(Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada) Corresponding author