Energy efficient bead milling of microalgae: Effect of bead size on disintegration and release of proteins and carbohydrates

•Bead milling is an energy efficient and mild microalgae disintegration method.•A smaller bead size results in a lower specific energy consumption.•The specific energy consumption was decreased from >1.7 to <0.5 kWh kgDW−1.•Product yields were unaffected using smaller bead sizes.

The disintegration of three industry relevant algae (Chlorella vulgaris, Neochloris oleoabundans and Tetraselmis suecica) was studied in a lab scale bead mill at different bead sizes (0.3-1 mm). Cell disintegration, proteins and carbohydrates released into the water phase followed a first order kinetics. The process is selective towards proteins over carbohydrates during early stages of milling. In general, smaller beads led to higher kinetic rates, with a minimum specific energy consumption of ⩽0.47 kWh kgDW−1 for 0.3 mm beads. After analysis of the stress parameters (stress number and stress intensity), it appears that optimal disintegration and energy usage for all strains occurs in the 0.3-0.4 mm range. During the course of bead milling, the native structure of the marker protein Rubisco was retained, confirming the mildness of the disruption process.