Microfiltration of microalgae biomolecules: Impact of pulsed electric fields and high-pressure homogenization on single-cell protein recovery and membrane fouling

This study investigated the separation of single-cell proteins from disrupted Auxenochlorella protothecoides microalgae using microfiltration. The microalgae were heterotrophically cultivated and subjected to two cell disruption methods, high-pressure homogenization (HPH) and pulsed electric field with incubation (PEF + inc), and stored at-20 degrees C. The impact of HPH and PEF + inc on the microfiltration performance of thawed samples was assessed. HPH treatment resulted in complete cell lysis, releasing a heterogeneous mixture of intracellular compounds. This, potentially combined with freezing effects, led to rapid membrane fouling and a 70 % decline in the permeate flux, finally stabilizing at 15 L m-2 h-1. In contrast, PEF + inc preserved cell integrity and particle size even after freezing, liberating mainly soluble compounds. This resulted in a more porous cake layer and a limited decline in the permeate flux, which stabilized at 24 L m-2 h-1. Additionally, higher protein transmission rates were achieved with PEF + inc (141.75 g m-2 h-1) than with HPH (54.53 g m-2 h-1) and it was 5.6 times more energy efficient. The cake layer formed by the HPH-treated samples had a higher resistance owing to smaller apparent pores and increased interaction with permeating proteins, which hindered protein transmission. These findings demonstrate that cell disruption methods can significantly influence downstream protein recovery efficiency and energy consumption. PEF + inc shows great potential as an energy-efficient bioprocessing method for microalgae biorefineries.