Acclimation of microalgae to wastewater environments involves increased oxidative stress tolerance activity

Area of Science:

• Environmental microbiology
• Eukaryotic microalgae research
• Wastewater treatment technologies

Background:

• Wastewater environments pose toxicity challenges for eukaryotic microalgae.
• Mechanisms of microalgae adaptation and tolerance to wastewater are not fully understood.
• It remains unclear if wastewater tolerance is an innate or species-specific trait.

Purpose of the Study:

• To investigate the species-specific ability of microalgae to acclimate to secondary-treated municipal wastewater.
• To identify metabolic and physiological changes associated with wastewater acclimation in different microalgal strains.
• To determine if wastewater tolerance is an inherent characteristic or a learned response.

Main Methods:

• Acclimation of six microalgal species (Chlamydomonas debaryana, Chlorella luteoviridis, Chlorella vulgaris, Desmodesmus intermedius, Hindakia tetrachotoma, Parachlorella kessleri) over 8 weeks in municipal wastewater.
• Measurement of growth rate, biomass productivity, chlorophyll content, and photosynthetic activity.
• Metabolic fingerprinting using Fourier transform infrared spectroscopy (FTIR) to analyze metabolic responses.

Main Results:

• Most acclimated microalgae exhibited significantly higher growth rates and biomass productivity, except for C. debaryana.
• Total chlorophyll content and photosynthetic activity increased significantly in most acclimated strains (except C. vulgaris for chlorophyll).
• Species-specific acclimation efficiency was observed, with C. luteoviridis and P. kessleri showing greater tolerance than C. debaryana and D. intermedius. FTIR distinguished metabolic responses, including altered lipid and carbohydrate accumulation, correlated with carotenoid pigments and ascorbate peroxidase activity.

Conclusions:

• The capacity for microalgae to acclimate to wastewater is a species-specific trait.
• Wastewater acclimation enhances growth, productivity, and photosynthetic efficiency in tolerant microalgal strains.
• Metabolic fingerprinting is a valuable tool for assessing microalgal stress responses and identifying tolerance mechanisms.