Extraction and Characterization of Starch from Chlorella vulgaris Microalgae for 3D-Printable Bioplastic Materials

Microalgae are increasingly recognized as a promising source of starch for bioplastic production, with Chlorella vulgaris emerging as a particularly strong candidate due to its notable starch accumulation capacity. This study examined the chemical composition, structure, thermal properties, and flow behavior of starch extracted from Chlorella vulgaris to evaluate its suitability for 3D-printable bioplastic production. A two-phase nitrogen management cultivation strategy resulted in a biomass productivity of 2310 mg/L and a starch content of approximately 46.39% of dry weight (463.92 ± 5.62 mg/g). Starch extraction was performed using ultrasonic homogenization in dimethyl sulphoxide (DMSO), followed by ethanol precipitation, yielding an 89.0% recovery rate (95.75 ± 0.313 g). Characterization of the extracted starch using attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR) confirmed acceptable purity. A colorimetric assessment of amylose and amylopectin content revealed a composition of 20.74% amylose and 79.26% amylopectin, indicating favorable characteristics for retrogradation and viscoelasticity. Particle size analysis showed starch granules with an average diameter of 1.12~μm, which enhances flowability and printability. X-ray diffraction (XRD) analysis revealed broad peaks at 15.4º, 17.76º, 18.34º, 20.14º, and 23.14º, characteristic of an A-type semi-crystalline structure, along with an additional peak at 11.22º attributed to minor impurities. This semi-crystalline nature supports excellent extrudability and structural stability during 3D printing. Thermal and rheological analyses likewise confirmed properties favorable for melt extrusion, including clear shear-thinning behavior. Taken together, these findings position starch derived from Chlorella vulgaris as a promising alternative material for 3D-printable bioplastic applications. Future work should focus on optimizing filament formulations, refining printing parameters, and evaluating biodegradability to fully harness its industrial potential.