Enhancing biomass productivity and parabens degradation in microalgae using organic carbon sources: Co-metabolism mechanisms and transcriptomic insights

The accumulation of endocrine disruptor compounds in aquatic environments raises environmental pollution concerns. Parabens are widely used as preservatives, and their environmental contamination poses serious threats to ecosystems and human health. Microalgae-based bioremediation techniques can effectively degrade organic contaminants. However, the low activity of microalgae toward parabens hinders the practical application of paraben removal. In this study, we investigated the mechanism of co-metabolism of methylparaben (MetP) by Chlorella sorokiniana by adding the addition of four different organic carbons. The results showed that acetate significantly increased the biomass production of the microalgae. Microalgal biomass increased by 48 %, chlorophyll a, b and carotenoids contents increased to 23.12 mg L⁻¹, 8.1 mg L⁻¹ and 5.7 mg L⁻¹, respectively. Meanwhile, acetate effectively alleviated the oxidative stress in the microalgae, enhanced the activity of antioxidant enzyme, and promoted the secretion of polysaccharides by extracellular polymeric substances (EPS). The ability to co-metabolize MetP was accelerated, and the degradation rate reached 65 %. In addition, nine major metabolites resulting from demethylation, dihydroxylation, dehydroxylation and oxidation reactions were identified. Transcriptomic analysis studies showed that acetate significantly enhanced biosynthetic processes and mediated photosynthesis, oxidative stress, tricarboxylic acid (TCA) cycle and glycolysis-related genes expression. The study demonstrates that adding carbon sources promotes microalgal biomass production and enhances the remediation of aquatic environments.