Simultaneous Promotion of Microalgal CO₂ Assimilation, Biomass Accumulation, Lipid Production, and Wastewater Nutrient Removal by Adding 5-Aminolevulinic Acid

Abstract

Microalgae-based wastewater management has the potential to serve dual purposes, including biofuel production and wastewater bioremediation. The current study investigates the role of 5-aminolevulinic acid (5-ALA) in the regulation of photosynthesis, biomass accumulation, lipid production, and nutrient removal from wastewater by Chlorella pyrenoidosa. In wastewaters, a 3 μM concentration of 5-ALA was considered optimal, as it increased the photosynthetic light reaction and CO2 assimilation of C. pyrenoidosa cells, thereby facilitating cellular growth, metabolism, and biomass accumulation. The acceleration of algal cellular metabolism increased the substrate pool and enhanced the expression of lipogenic genes, thereby promoting lipid production. Meanwhile, the removal of nutrients from wastewater was accelerated after the addition of 5-ALA. The accelerated nutrient removal from wastewaters following 5-ALA treatment was related to C. pyrenoidosa cell growth. C. pyrenoidosa is capable of utilizing nitrogen and phosphorus from wastewater and accumulating biomass. The biomass from microalgae can be used as a feedstock to produce biofuels. Therefore, the current study provided a novel strategy for simultaneously promoting CO2 assimilation, biomass accumulation, lipid production, and wastewater nutrient removal with microalgae. It is possible to use microalgae for the management of wastewater if research and development on commercializing technologies based on microalgae, both upstream and downstream, are carried out continuously.