Enhanced protein recovery from Chlorella vulgaris using micro-nanobubble-assisted liquid biphasic flotation

Abstract

Microalgae hold great promise as a source of bioactive compounds due to their rapid growth and low resource requirements. This study evaluates the micro-nanobubble-assisted liquid biphasic flotation (MNBLBF) system for extracting protein from Chlorella vulgaris. Leveraging nanobubbles with high surface area-to-volume ratio, the system enhances protein adsorption and flotation transport. Nanobubble characterization, including zeta potential measurements, confirmed their high surface charge and stability, particularly in sodium carbonate solution, supporting their role in improving protein extraction. Subsequent optimization of key parameters for MNBLBF protein extraction including salt type and concentration, ethanol concentration, air flow, flotation duration, and biomass loading, yielded optimal conditions: 200 g L⁻¹ Na₂CO₃, 90% (v/v) ethanol, 300 cc min⁻¹ air flow rate, 12 min flotation duration, and 0.5% (w/v) biomass loading. Under these conditions, the MNBLBF system achieved maximum protein recovery of 99% with a partitioning efficiency of 85%. Scale-up to a 10× system resulted in a slight decrease in recovery (88%). This study underscores the potential of micro-nanotechnology-enhanced bioseparation for sustainable bioproduct recovery.