Optimization of benzo[α]pyrene degradation by Enterococcus faecium using response surface methodology

Benzo[α]pyrene (BaP) is a persistent organic pollutant that is notoriously difficult to remove. Here, we report the isolation of a novel BaP-degrading probiotic, Enterococcus faecium MA-4, from Kefir grains. Four factors for degradation of BaP by MA-4 were obtained through single factor test: pH 7, temperature 37°C, BaP concentration 10 mg L^-1, inoculum size 15%. Employing a Box-Behnken design within response surface methodology, the study investigated the impact of pH, temperature, BaP concentration, and inoculum size on the degradation rate of BaP by MA-4, aiming to enhance its degradation kinetics. The results revealed that the inoculum size was the predominant factor affecting degradation. Under optimal conditions, pH 6.5, an initial BaP concentration of 7 mg L^-1, a temperature of 35°C, and an inoculum size of 10%, the degradation rate of BaP by MA-4 was enhanced to 61.52%. Analysis of Variance confirmed the model's accuracy with a significant F-value of 12.03 at p < 0.0001 while the quadratic regression model showed a high R² value 0.9232. R²adj (0.8465) closely matches R²pred (0.6506). Adeq Precision(10.986) and Lack of Fit (F-value = 0.99) both demonstrate the reliability of the model. The probiotic MA-4 effectively degrades BaP, showing promise for food-grade applications in BaP mitigation. However, the application of Enterococcus faecium requires rigorous safety assessment due to their potential as opportunistic pathogens. This study provides key theoretical and practical guidance for the probiotic-based remediation of BaP in foodstuffs.