Inhibition of Aspergillus parasiticus Growth and Reduction of Aflatoxin by Yeast Isolated from Ragi, an lndonesian Traditional Culture Starter

Abstract

Aflatoxins are secondary metabolites of Aspergillus flavus and A. parasiticus frequently found to contaminate both food and feed. The toxins have been found to be carcinogenic and their presence in food or feed is strictly regulated. Indonesia's climate with high humidity, temperature and amount of rainfall are supportive of mold growth and hence aflatoxin production. Control of aflatoxin production can be achieved by using competitor microorganisms such as mold and yeast. The objective of this research was to isolate yeasts capable of reducing aflatoxin from ragi, an lndonesian traditional culture starter and to evaluate the yeast or its metabolite's activity in inhibiting A. parasiticus growth, aflatoxin synthesis and degradation of preformed aflatoxin. The research showed that all isolates reduced aflatoxin production by A. parasiticus. Saccharomyces sp. of rogi NKL gave the highest reduction of aflatoxin (AF) production, i.e. 95.9% for aflatoxin B1 (AFB1); 97.1% for aflatoxin B2 (AFB2); 89.4% for aflatoxin Gl(AFG1); 99.1% for AFG2 and 98.1% for total aflatoxin. The metabolites of the Saccharomyces sp. also decreased aflatoxin production by A. parasiticus. The yeast also showed ability to degrade preformed AFB1, AFB2, AFG1, AFG2 by 36.4 %; 55.6 %; 37.8 %; and 46.7 %, respectively.