Biocontrol of aspergillus flavus and aflatoxin b1 production in corn
Aspergillus flavus and Aspergillus parasiticus are the most important aflatoxin-producing filamentous fungi. They can occur in several plant products, like spices, cereals and oily seeds (Jelinek 1998, Pittet, 1998 and Lewellyn, 1992). Aflatoxins (AF) are secondary metabolites with a high carcinogenic potential, especially in liver tissue. In addition the aflatoxins possess an acute toxicity at higher concentrations. The high health risk caused by aflatoxins leads to strict concentration limits in different countries. The USA Food and Drug Administration established 20 ppb as the minimum acceptable level of aflatoxin in all foods other than milk. The European Union has banned the import of peanut with >2 ppb of AFB1 content and with >4 ppb of total aflatoxins in nuts prepared for human consumption. To export tree nuts to the European market, aflatoxin levels should be <3 ppb (Schatzki, 2001). Several works were carried out on the removal and/or the detoxification of aflatoxin (D’souza, 2000) and some microorganisms were reported to be capable of degrading AFB1 such as Flavobacterium aurantiacum by enzymatic way (Ciegler, 1966). Some strains of lactic acid bacteria (LAB) were found to be active in removing AFB1 from contaminated media by the contact method without further incubation (El-Nezami, 1998). During the last century it was realized that the lactic acid bacteria are responsible for the fermentation, and through that the bio- preservative effect, utilized in many food and feed processes. Bio- preservation refers to extended shelf life and enhanced safety of foods using the natural or added micro-flora and their antimicrobial products. Besides lactic acid, several other antimicrobial compounds are produced during growth of LAB (Lindgren, 1990).