Factors affecting the removal of aflatoxin M1 from food model by Lactobacillus and Bifidobacterium strains

This paper describes the ability of six dairy strains of Lactobacillus and Bifidobacterium to remove aflatoxin M₁ (AFM₁) from phosphate-buffered saline (PBS) and reconstituted milk. Bacteria were incubated in both PBS and reconstituted milk containing 5, 10 and 20 ng mL^?1 for 0, 4 and 24 h at 37°C. After centrifugation the concentration of AFM₁ was determined in the supernatant fraction using high-performance liquid chromatography. The binding abilities of AFM₁ by viable (10⁸ CFU mL^?1) and heat-killed Lactobacillus and Bifidobacterium strains in PBS ranged from 10.22 to 26.65% and 14.04 to 28.97%, respectively. Similarly, AFM₁-binding capacity in reconstituted milk was found to range from 7.85 to 25.94% and from 12.85 to 27.31% for viable and heat-killed bacteria, respectively within 4 h. While B. bifidum Bb 13 was the best binder, the poorest removal was achieved by L. acidophilus NCC 68. Binding was reversible, and a small proportion of AFM₁ was released back into the solution. The toxin concentration and incubation period had no effect on the removal of AFM₁ by bacteria both in PBS and reconstituted milk.     

Para-chlorophenol containing synthetic wastewater treatment in an activated sludge unit: effects of hydraulic residence time

Due to the toxic nature of chlorophenol compounds present in some chemical industry effluents, biological treatment of such wastewaters is usually realized with low treatment efficiencies. Para-chlorophenol (4-chlorophenol, 4-CP) containing synthetic wastewater was treated in an activated sludge unit at different hydraulic residence times (HRT) varying between 5 and 30 h while the feed COD (2500 mg l(-1)), 4-CP (500 mg l(-1)) and sludge age (SRT, 10 days) were constant. Effects of HRT variations on COD, 4-CP, toxicity removals and on settling characteristics of the sludge were investigated. Percent COD removals increased and the effluent COD concentrations decreased when HRT increased from 5 to 15 h and remained almost constant for larger HRT levels. Nearly, 91% COD and 99% 4-CP removals were obtained at HRT levels above 15 h. Because of the highly concentrated microbial population at HRT levels of above 15 h, low effluent (reactor) 4-CP concentrations and almost complete toxicity removals were obtained. High biomass concentrations obtained at HRT levels above 15 h were due to low 4-CP contents in the aeration tank yielding negligible inhibition effects and low maintenance requirements. The sludge volume index (SVI) decreased with increasing HRT up to 15 h due to high biomass concentrations at high HRT levels resulting in well settling sludge with low SVI values. Hydraulic residence times above 15 h resulted in more than 90% COD and complete 4-CP and toxicity removals along with well settling sludge.