Acute Toxicity Assessment of Rhamnolipid Biosurfactant Produced by Pseudomonas aeruginosa BM02 Using Andiroba (Carapa guianensis Aubl.) Waste in Pithecopus hypochondrialis (Anura: Hylidae) Tadpoles

Rhamnolipid biosurfactants are amphiphilic molecules able to reduce surface and interfacial tension, primarily produced by the bacterium Pseudomonas aeruginosa, which utilizes numerous substrates for its growth, including agro-industrial waste. This study aimed to evaluate the toxicity of biosurfactants synthesized by P. aeruginosa BM02, utilizing andiroba (Carapa guianensis Aubl.) (Sapindales: Meliaceae) waste as the sole nutrient source, on Pithecopus hypochondrialis (Daudin, 1800) (Anura: Hylidae) tadpoles. The biosurfactant was produced in a vegetable saline medium and exhibited maximum emulsifying activity of 72%, with a yield of 2.5 g L⁻¹ achieved on the eleventh day of fermentation. Chemical characterization confirmed its identity as rhamnolipid. Tadpoles exposed to the biosurfactant (0.5 mg L-1) showed a slight reduction in morphological parameters compared to the control group. The control cohort exhibited measurements of total length, and head and tail lengths of 17.87 mm, 3.17 mm and 12.84 mm, whereas tadpoles exposed to the biosurfactant measured 15.30 mm, 2.81 mm, and 10.62 mm respectively. These reductions could reflect adaptive responses to environmental conditions or intrinsic alterations in growth rates or metabolism. Notably, the absence of significant behavioral modifications, including impairments in foraging or swimming behavior, suggests that biosurfactant exposure does not adversely affect the overall well-being of the tadpoles. Furthermore, histological examination revealed healthy epithelial and muscular tissues, indicating that the structural integrity of the tadpoles remained intact post-exposure. The absence of hyperplasia in intestinal columnar cells suggests preserved digestive functionality and no acute inflammatory response in the gut environment. Collectively, these results indicate that exposure to 0.5 mg L-1 of the biosurfactant does not induce significant adverse effects on tadpole survival, suggesting a favorable safety profile for rhamnolipid biosurfactants within the context of this study.