Factors And Mechanism Affecting The Capacity Of Bifidobacterial Strains To Bind Benzo[a]Pyrene

Benzo[a]pyrene (B[a]P), as potent carcinogens, is a member of polycyclic aromatic hydrocarbons (PAHs). It occurs widespread in the environments, including unburnt coal, oil and natural gas caused exhaust in industrial production and daily life, vehicle exhaust, rubber production and cigarette smoke. Uncorrect preparations, like smudging, barbecue and fry, also cause B[a]P to accumulate largely in food. B[a]P poses very risk to human body. Therefore, how to remove B[a]P inexpensively, safely, conveniently and fast from its surroundings has gained more attention. The objectives of this present study were:(1) to evulate the binding of 9 bifidobacterial strains to B[a]P; (2) to use 3 selected strains, i.e., Bifidobacterium lactis BI-04, HN019 and Bifidobacterium irfantis BY12 to deal with B[a]P-binding; (3) to detect factors affecting adsorption of B[a]P; and (4) to investigate possible mechanisms of 3 bifidobacterial strains to bind B[a]P by infrared detection. All bacterial cells and B(a)P were co-incubated at 37℃ for 4 h. The ability of each strain to binding B[a]P was expressed by the B[a]P-bound percentage quantitated by HPLC. The following are main results.1. The percentages of B[a]P-binding were75.95% for BI-04,74.42% for HN019 and 72.12% for BY12, respectively.2. Factors which include acidic condition, alkali condition, calcium salt, magnesium salt, sodium dodecyl sulfate(SDS), sodium periodate(NaIO4), lysozyme and neutral proteinase would have a certain impact on binding ability. Most of them reduced the binding ability, but acidic condition and alkali treatment in a short time could increase absorbent effect3. Extract the cellular structures respectively, then determinate of the binding ability solely. The result shows that exopolysaccharide, S-layer protein and spheroplast has quite low binding ability, even it was pretreated by different factors. The pure peptidoglycan of cell wall plays the most important role in binding.4. By the same pretreatment of peptidoglycan, the combination of B[a]P had the same trend with the original bacteria in adsorbing B[a]P. It means that peptidoglycan is the main binding site on the cell wall to B[a]P.5. The reason why B[a]P bound with pure peptidoglycan was the formation of C-O covalent bond, and it made binding much stable. In addition, the completeness of peptidoglycan structure determined the ability of binding. When it was destroyed, the percentage of B[a]P binding with peptidoglycan would abate significantly.