Physicochemical characterization of Chlorella vulgaris starch for potential bioplastic applications

Abstract

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 high starch accumulation capacity. This first characterization of starch from the Ethiopian Lake Dendi Chlorella vulgaris isolate reveals superior granule size (1.12 \(\mu\) m), rheology, and amylose/amylopectin balance for high-resolution bioplastic applications, enabled by optimized two-phase N-starvation cultivation and DMSO-ultrasonic extraction. The approach yielded biomass productivity of 2310 mg/L and 46.39% starch content (463.92 ± 5.62 mg/g dry weight). Ultrasonic homogenization in DMSO followed by ethanol precipitation achieved 89.0% recovery (95.75 ± 0.313 g). Colorimetric analysis showed 20.74% amylose and 79.26% amylopectin, supporting good retrogradation, viscoelasticity, and shape retention. Sessile drop water contact angle measurements on the starch film yielded 57.63 ± 0.7°(after 3 s equilibration), indicating moderate hydrophilicity relevant for hydration-dependent processing behaviors. XRD indicated an A-type semi-crystalline structure favoring extrudability and stability, while thermal and rheological data confirmed broad gelatinization and strong shear-thinning. These properties position Chlorella vulgaris starch as a promising feedstock for future development of bioplastics with potential applicability in advanced fabrication techniques. Future efforts should optimize formulation, processing parameters, and biodegradability assessments to unlock its full industrial potential.