Co-Cultivation of Chlorella vulgaris Enhances Growth and Bioactive Compounds in Hydroponically Grown Lettuce

Cultivation knowledge deficiencies limit the appreciation of microalgae-based nutrient solutions on hydroponic plants. This study compared Chlorella vulgaris implications for lettuce growth and the production of high-value components through the use of four different co-cultivation hydroponic scenarios. The results of 30-day co-cultivation of Chlorella vulgaris and lettuce demonstrated the significance of controls of pH (7.0–7.75) and green microalgal cell density (107 cells/mL) to improve the qualities in lettuce leaf growth, root vigor, and nutrient yield from days 15 to 30 during the co-cultivation. Plant height increased by 19%, leaf area by 4%, root cortex thickness by 14% (p < 0.05), total chlorophyll content by 49%, soluble sugar content by 12%, and protein content by 6% through the adoption of 1.0 × 107~1.6 × 107 cells/mL of microalgal solution during hydroponic cultivation. Furthermore, the aerated hydroponic device benefits of co-cultivating high-concentration Chlorella vulgaris and lettuce resulted in a 1.0-time increase in vitamin C compared to the cultivation of low-concentration Chlorella vulgaris. This study highlights the benefits of the sustainable strategy of the microalgal cultivation technique used in the hydroponic systems for nutritious and healthy leafy vegetable growers, which is also emphasized for eco-friendly bioactive compound production.