Effects of fermentation process on levels of Aflatoxin B1 in Cereals

Abstract

Aflatoxin contamination of cereals is of serious economic and health concern because of their toxigenic and carcinogenic effects.  Biological detoxification and biodegradation of aflatoxin by microorganisms (bacteria and fungi) or their enzymes have been reported. In  this study, a local fermentation strategy employed by farmers was mimicked using a native microflora, Saccharomyces cerevisiae, and  Lactic Acid Bacteria (LAB) on different cereals contaminated with aflatoxin B1. In the experiment, cereal flours were fermented without  any inoculum (chance fermentation), with Saccharomyces cerevisiae and with LAB separately. The setups were incubated at room  temperature for three days. The aflatoxin B1 levels were analysed quantitatively before and after fermentation using Enzyme Link  Immunoassay (ELISA). The results of the effects of fermentation types on the levels of AFB1 in the cereals revealed that the aflatoxin B1  levels in flour of millet obtained from the open market was reduced from 8.1±0.2ppb to 0.0±0.0ppb (100%) by chance and LAB  fermentation while it was reduced from 8.1±0.2ppb to 0.2±0.01 by the action of Saccharomyces cerevisiae. Also, reduction in aflatoxin B1  levels was noticed in flour of stored millet after fermentation; native microflora and LAB reduced the aflatoxin B1 level from 7.5±0.0 to  0.0±0.0 while the level was reduced to 0.1±0.0 by Saccharomyces cerevisiae. Relatively low aflatoxin B1 reduction was observed in flour of  stored wheat from 1.1±0.1ppb to 0.4±0.0 and 0.7±0.0 by native microflora and S. cerevisiae respectively, while total removal (from  1.1±0.1ppb to 0.0±0.0ppb) was noticed for LAB. Aflatoxin B1 bio-detoxification using the three types of fermentation showed that LAB had  a 100% reduction in almost all the sampled stored market cereal flours with the exception of sorghum (from 7.9±0.1 to 0.6±0.1 ppb),  rice (7.5±0.0 to 0.7±0.1 ppb) and sesame (1.2±0.0 to 0.1±0.1 ppb). These results showed that chance fermentation was as effective as  fermentation with Saccharomyces cerevisiae but, relatively low compared to LAB fermentation only. Pronounced reduction in aflatoxin B1  levels in flours of cereals in this study after fermentation by LAB, suggests that it is a better bio-detoxifier and should be added during  local fermentation by farmers.