Enzymatic Regeneration of Spent Bleaching Earth for Sustainable Reuse in Edible Oil Processing

Spent bleaching earths (SBEs) resulting from the refining of soybean oil contain significant amounts of residual oil and phosphorus, which pose an environmental and disposal problem. In this study, a sustainable biotechnological approach to reactivate SBEs through enzymatic hydrolysis with a commercial lipase under moderate conditions was investigated. In an initial 23 factorial experimental design, the effects of temperature (40–60 °C), enzyme amount (50–200 mg), and reaction time (4–8 h) were evaluated, with reaction time identified as statistically significant (p < 0.05). A second experimental design with lower enzyme concentrations (5–25 mg) validated a positive effect of enzyme dosage on phosphorus removal. This result was validated by a presence/absence test in which no phosphorus removal occurred in the absence of the biocatalyst. The best conditions (60 °C, 4 h, 5 mg enzyme) reduced the oil content from 10% to 5% and achieved 97% phosphorus removal. However, pigment removal efficiency was limited to approximately 34%, indicating partial restoration of the bleaching capacity compared to virgin earth. The enzymatic process also produced a nutrient-rich liquid hydrolysate containing Mg (16 mg/L), P (750 μg/L), and S (980 μg/L), suggesting potential use as a biofertilizer. Regenerated SBE demonstrated suitability for reuse in oil bleaching systems and potential applications in filtration and soil conditioning, providing a cost-effective and environmentally friendly alternative to conventional regeneration methods.