Effects of Substrate, pH and Yeast Extract on Bacterial Growth in Citrullus lanatus Peel–Based Media

Abstract

The search for cost-effective and sustainable microbial growth media has prompted interest in fruit peel–based substrates. This study investigated the growth of Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus on Citrullus lanatus (watermelon) peel–derived media, by examining the effects of substrate concentration, pH and yeast extract supplementation. Bacterial cultures were grown across a range of substrate concentrations (1–6%), pH values (6.5–7.2), and yeast extract levels (0–0.5%), and growth was measured in log CFU/ml. Optimal growth occurred at 5% substrate, near-neutral pH, and 0.2–0.4% yeast extract, with B. subtilis showing the highest proliferation. Growth declined slightly at 6% substrate concentration, and species-specific responses to yeast extract were observed. These findings indicate that Citrullus lanatus (watermelon) peel–derived media can effectively support robust bacterial growth hence, providing a sustainable and cost-effective alternative for industrial fermentation, probiotic production, bioremediation, and the valorization of agricultural waste.