Comparison between surface hydrophobicity of heated and thermosonicated cells to detoxify aflatoxin B1 by co-culture Lactobacillus plantarum and Lactobacillus rhamnosus in sourdough: Modeling studies

The capacity and stability binding of aflatoxin B1 under various temperature and time conditions of dough proofing were evaluated. Single and co-culture Lactobacillus plantarum ATCC 8014 and Lactobacillus rhamnosus ATCC 7469 were inoculated in various modes, mainly viable, heat-, and ultrasound-inactivated along with the combination of viable + heat- or ultrasound-inactivated cells. The highest AFB1 adsorption in order was thermosonication- treated Lb. plantarum + Lb. rhamnosus (8.042 μg kg−1) > heat treated Lb. plantarum + Lb. rhamnosus (6.90 μg kg−1) > live Lb. plantarum + Lb. rhamnosus (5.533 μg kg−1) after 24 h incubation at 37 °C. Regarding to circular dichroism spectra results, α-helix and β-turn of LAB cells showed highly increasing pattern in thermosonicated LAB (22.1% and 25.8%) compared to live (16.8% and 23.7%) and heated (21.3% and 24.2%) cells, respectively. The surface hydrophobicity (%) increased from 37.7 to 45.1% for viable LAB to 67.2–80.5% and 54.5–65.9% following inactivation by thermosonication and heating, respectively. The results obtained by AFB1 binding stability on cell surfaces displayed that in ultrasound-treated bacteria, 18.3–33.3% of the bounded AFB1 was released from the cells, which is significantly lower than heat-treated cells (31.1–46.5%) and viable cells (49.9–64.8%).