Biological degradation of aflatoxin B 1 by a Rhodococcus pyridinivorans strain in by-product of bioethanol

Dried distillers grain with solubles (DDGS), as a separated and dried solid part of bioethanol by-products, is often utilized as animal feed. Aflatoxin B1 contamination of corn kernels may affect corn-based bioethanol production due to regulatory issues. In scenarios where prevention was not effective, possible solutions for aflatoxin contamination may be the detoxification of raw material of bioethanol production or the by-product, intended to be used as animal feed. In this paper we investigated and compared the aflatoxin degradation efficiency of a Rhodococcus pyridinivorans strain as bacterial inoculum and as bacterial extract in both the liquid and solid phases of an aflatoxin B1 contaminated bioethanol by-product (i.e. whole stillage) during a three-day incubation period. Results show that three-day microbial treatment cannot cause aflatoxin B1 degradation due to its tight binding into the solid stillage. Therefore longer, namely a twelve-day degradation experiment was performed in which the degradation profile of this strain was determined. Our results demonstrated that the aflatoxin content of the stillage significantly decreased between the 3rd and 7th days of the microbial reaction. More than two-thirds of the aflatoxin B1 content reacted during this time. The growth of bacteria was also monitored and statistically analysed. The exponential stage of biomass growth changed to a stagnant state after seven days incubation time, in harmony with the mycotoxin degradation rate. This work gives an early-state insight of aflatoxin B1 detoxification of animal feed, sourcing from bioethanol production as a by-product, by Rhodococcus pyridinivorans K408 bacterium strain.