Analysis of phytotoxic compounds in residues from olein production

ESCALANTE, J.; GOTTIG, N.; JORGELINA OTTADO; GARAVAGLIA, B.S.

Congreso; XVIII Congreso Samige; 2023

Olein or acid oil is obtained through the acidification of soapstock, a byproduct resulting from the caustic refining of soybean oil and other seeds. Soapstock is primarily composed of fatty acid soaps (sodium salts of neutralized fatty acids), triglycerides, phosphatides, and degradation products, along with small amounts of sterols, tocopherols, pigments, proteins and carbohydrates. As a result of this process, a residue is generated, which has a high content of chemical oxygen demand (COD), soluble solids in ether (SSE) and low pH (2-3). However, to date, there are no studies reporting the toxicity of this residue on plants (phytotoxicity), a fact observed during our experiments working with both the total residue and the aqueous supernatant. Furthermore, our research group successfully identified a bacterial strain isolated from residual samples (Cytobacillus sp.) capable of significantly reducing this adverse effect as well as COD and SSE of these residues.Therefore, the objective of this study was to isolate and characterize the phytotoxic compounds present in the residue. Samples of non-treated and treated (after growing Cytobacillus sp.) residues were analyzed in order to study the mechanisms involved in bacterial elimination of these phytotoxic compounds.To accomplish this, separations using thin-layer chromatography (TLC) were conducted on the aqueous fraction of the residue to isolate and concentrate phytotoxic compounds present in the sample. Concurrently, a phytotoxicity assay, using lettuce seedlings as a biosensor, was carried out with different fractions recovered from the TLC experiments.The results showed that phytotoxic compounds were retained in specific regions on TLC plates and their activity was impacted by the bacterial treatment. A comparison between treated and untreated samples demonstrated significant alterations in root and hypocotyl elongation of the seedlings, indicating a reduction in phytotoxicity after bacterial treatment in the assessed regions. However, a more thorough study using techniques such as nuclear magnetic resonance spectroscopy (NMR) will be necessary to identify their nature.In summary, we were able to obtain a fraction enriched with phytotoxic compounds present in the treated and non-treated samples, which will facilitate a more comprehensive study using appropriate techniques for compound identification