Biodegradation of aflatoxin by bacterial species isolated from poultry farms

Aflatoxins are carcinogenic compounds produced by certain Aspergillus spp and naturally contaminate poultry rations. Exposure to low levels of Aflatoxin B1 (AFB1) in poultry feeds is the second most threatening issue facing the poultry industry in Egypt; it can cause a reduction in growth, egg production, and compromised immune functions, resulting in significant economic loss. Hence, a safe, effective and eco-friendly detoxification method is strongly required. Biological decontamination is a promising approach to reduce aflatoxin levels within threshold limits. This study explores the biodegradation capacity of bacteria isolated from the moldy feed, soil and poultry feces in various poultry farms against AFB1 (100 ppb), G1 (100 ppb), B2 (30 ppb), G2 (30 ppb). Sixty-five bacterial isolates were initially screened using coumarin media with a concentration of (0.01%-0.5%) coumarin. Only one soil isolate (SZ1) grew at the highest concentration (0.5%). Coumarin and Aflatoxin degradation rates of ten promising isolates were measured using spectrophotometry and HPLC. Six isolates reduced AFG1 by more than 90% in the liquid medium, five reduced AFB2 while only four did the same with AFB1& AFG2. Impressively, isolate SZ1 (identified as Pseudomonas fluorescens) exhibited the best degradation capacity to both coumarin and aflatoxin with 100% degradation of AFG1 and 99% degradation of AFB1, AFB2 and AFG2. Biochemical and molecular identification of the ten isolates revealed that they belong to four genera; Bacillus (6), Pseudomonas (2), Enterococcus (1) and Stenotrophomonas (1). Factors affecting Pseudomonas fluorescens SZ1 degradation activity was further investigated. Optimum temperature, time and pH for maximum aflatoxin degradation were at 37 °C, 72 h and 7, respectively. Treatment with proteinase K reduced the degradation activity of G1 (31% ± 1.438), B1 (42% ± 1.438), G2 (19% ± 1.097), and B2 (25% ± 1.732), suggesting that the effective component in aflatoxin degradation may be protein in nature. Our study suggests the biocontrol potential of several different species isolated from poultry farms; B. haynesii, B. licheniformis, B. tequilensis, B. subtilis, B. amyloliquefaciens, Pseudomonas fluorescens, Enterococcus casseliflavus, and Stenotrophomonas maltophilia. The results proposed Pseudomonas fluorescens SZ1 as an excellent candidate for bioremediation and decontamination of aflatoxin in feed matrices. To the best of our knowledge, this is the first report identifying B. haynesii, Enterococcus casseliflavus, B. tequilensis and B. amyloliquefaciens with aflatoxin degradation activity.