Metabolomics of the Bio-Degradation Process of Aflatoxin B1 by Actinomycetes at an Initial pH of 6.0

Abstract

Contamination of food and feed by Aflatoxin B1 (AFB1) is a cause of serious economic and health problems. Different processes have been used to degrade AFB1. In this study, biological degradation of AFB1 was carried out using three Actinomycete species, Rhodococcus erythropolis ATCC 4277, Streptomyces lividans TK 24, and S. aureofaciens ATCC 10762, in liquid cultures. Biodegradation of AFB1 was optimised under a range of temperatures from 25 to 40 °C and pH values of 4.0 to 8.0. An initial concentration of 20 µg/mL of AFB1 was used in this study. The amount of AFB1 remaining was measured against time by thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC), coupled with UV and mass spectrometry (LC-MS). All species were able to degrade the AFB1, and no significant difference was found between them. AFB1 remained in the liquid culture for R. erythropolis, S. lividans and S. aureofaciens were 0.81 µg/mL, 2.41 µg/mL and 2.78 µg/mL respectively, at the end of the first 24 h. Degradation occurred at all incubation temperatures and the pH with the optimal conditions for R. erythropolis was achieved at 30 °C and pH 6, whereas for S. lividans and S. aureofaciens the optimum conditions for degradation were 30 °C and pH 5. Analysis of the degradative route indicated that each microorganism has a different way of degrading AFB1. The metabolites produced by R. erythropolis were significantly different from the other two microorganisms. Products of degradation were identified through metabolomic studies by utilizing high-resolution mass spectral data. Mass spectrometric analysis indicated that the degradation of AFB1 was associated with the appearance of a range of lower molecular weight compounds. The pathway of degradation or chemical alteration of AFB1 was followed by means of high resolution Fourier transform mass spectrometry (HR-FTMS) analysis as well as through the MS2 fragmentation to unravel the degradative pathway for AFB1. AFB1 bio-degradation was coupled with the accumulation of intermediates of fatty acid metabolism and glycolysis. A plausible mechanism of degradation of AFB1 by Rhodococcus was hypothesized.

Aflatoxin B 1 degradation by liquid cultures and lysates of three bacterial strains

“…2). Comparable results previously obtained in other similar studies also suggest that such degradation is a constitutive activity of the tested bacteria (Eshelli et al, 2015;Farzaneh et al, 2012;Guan et al, 2008;Samuel et al, 2014;Teniola et al, 2005).…”

“…Microsoft Excel, 2013 (Microsoft Corp., USA) was used to plot various graphs. A multivariate analysis, principal component analysis (PCA) was performed using JMP 12.1.0 statistical software (SAS Institute, Cary, North Carolina) to further summarize and describe the variations in the descriptive experimental factors (Eshelli et al, 2015). The results represent the average of triplicate determinations and are expressed as mean ± standard error of mean (SEM).…”

“…Additionally, lengthy degradation time and the possibility of fungal strains producing toxins under certain conditions limit their application (Eshelli et al, 2015). Although bacteria are more desirable for AF degradation, the use of whole cultures has less potential for large scale utilization in the industry (Kolosova and Stroka, 2011).…”

Biodegradation of aflatoxin-B1 and zearalenone by Streptomyces sp. collection

“…Several Actinomycetes strains were revealed to be able to degrade directly mycotoxins. AFB1 (Cserh ati , 2013;Eshelli et al, 2015;Krifaton et al, 2011) andZON (Cserh ati et al, 2013;Krifaton et al, 2013) were reported to be degraded effectively by Streptomyces and Rhodococcus strains also. In the present study, elimination of genotoxicity was detected in the case of AFB1 by SOS Chromotest and in the case of ZON estrogenic effect was measured by BLYES.…”

Detoxification of Groundnut Cake Naturally Contaminated with Aflatoxin B1 Using Rhodococcus erythropolis in Shake Flask Bioreactors

“…Pseudomonas aeruginosa is another good degrader, providing 90 % reduction, however, its high optimal growth temperature (55°C) may be economically problematic [17]. Eshelli et al [22] investigated degradation products of AFB 1 and reported a degradation product with 236 amu molecular mass, which lacks the mutagenic lactone ring property and later this product participated in the citrate cycle.…”