Enhancing microalgae cell inactivation through hydrodynamic cavitation: Insights from flow cytometry analysis.

Area of Science:

• Biotechnology
• Bioprocess Engineering
• Microalgae Cultivation

Background:

• Hydrodynamic cavitation (HC) offers a low-energy alternative for microalgae cell disruption.
• HC efficiency varies with microalgae species and operating conditions.
• Quantifying cellular damage and optimizing HC parameters are critical for bioproduct harvesting.

Purpose of the Study:

• To investigate the time-dependent effects of HC on Dunaliella viridis.
• To quantify cell disruption and inactivation kinetics under HC.
• To identify key physiological endpoints for optimizing HC treatment.

Main Methods:

• A bench-top cavitation system was used for multiple HC passes.
• Cell concentration, size distribution, and counts were analyzed via cell counter and flow cytometry.
• Cell viability, metabolic activity, and reactive oxygen species (ROS) were assessed using fluorescent probes (FDA, EB, DCFDA).

Main Results:

• HC effectively disrupted and inactivated Dunaliella viridis cells, following pseudo-first-order kinetics.
• Inactivation rate and energy efficiency decreased with increasing cell debris, necessitating debris levels below 10-20%.
• Cell membrane rupture was the primary mechanism of inactivation, releasing intracellular contents.

Conclusions:

• Cell membrane integrity is a critical endpoint for optimizing HC protocols in microalgae bioproduct harvesting.
• A P-factor model improved prediction of cell inactivation kinetics compared to cavitation number alone.
• HC inactivates cells by rupturing membranes, with reduced ROS in viable cells.