Adaptive laboratory evolution empowers lipids and biomass overproduction in Chlorella vulgaris for environmental applications

Microalgal strain improvement with commercial features is needed to generate green biological feedstock to produce lipids for bioenergy. Hence, improving algal strain with enhanced lipid content without hindering cellular physiological parameters is pivotal for commercial applications of microalgae. In this report, we demonstrated the adaptive laboratory evolution (ALE) by hypersaline conditions to improve the algal strains for increasing the lipid overproduction capacity of Chlorella vulgaris for environmental applications. The evolved strains (namely E2 and E2.5) without notable impairment in general physiological parameters were scrutinized after 35 cycles. Conventional gravimetric lipid analysis showed that total lipid accumulation was hiked by 2.2 fold in the ALE strains compared to the parental strains. Confocal observation of algal cells stained with Nile-red showed that the abundance of lipid droplets was higher in the evolved strains without any apparent morphological aberrations. Furthermore, evolved strains displayed notable antioxidant potential than the control cells. Interestingly, carbohydrates and protein content were significantly decreased in the evolved cells, indicating that carbon flux was redirected into lipogenesis in the evolved cells. Altogether, our findings demonstrated a potential and feasible strategy for microalgal strain improvement for simultaneous lipids and biomass hyperaccumulation.