Screening of Fruit and Vegetable Waste Extracts as an Eco-Friendly Strategy to Control the Proliferation of the Toxic Cyanobacterium Microcystis aeruginosa

Fruits and vegetables are among the most widely consumed products; however, their processing by both industry and households generates substantial peel waste, leading to significant environmental concerns. This study aimed to assess fruit and vegetable peels as an eco-friendly source of natural cyanbactericidal compounds for controlling toxic algal blooms. Aqueous Extract (AE), Ethyl Acetate Extract (EAE), and Ethanol Extract (EE) of five fruit and vegetable peels (Avocado, tomato, mango, eggplant, and potato) were screened for their inhibitory effects on Microcystis aeruginosa using both paper disc diffusion and microdilution techniques. Therefore, the extracts of avocado peel, the most bioactive of the five peels, were selected for further testing in a batch bioassay. The inhibitory effect appeared to be dose-dependent. The maximum inhibition rate (98%) was recorded following an 8-day exposure period at the dose (MIC = 0.8 mg/mL) for both the AE and EAE. Thus, the EE showed significant potential, particularly at the highest concentration (MIC = 0.2 mg/mL), where inhibition peaked at 92% on day 8. Accordingly, all treated groups demonstrated a significant decrease in primary photosynthetic pigments and phycobiliproteins in comparison to the control groups. In conclusion, avocado peel extracts show the most potent inhibition in batch bioassay. These extracts could constitute a promising strategy to valorize avocado peel waste as a sustainable cyanobactericidal agent to suppress the proliferation of M. aeruginosa blooms in eutrophic aquatic ecosystems.