ARS | Publication request: Diversity of Aspergillus oryzae genotypes (RFLP) isolated from traditional soy sauce production within Malaysia and Southeast Asia

Submitted to: Mycoscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 19, 2007
Publication Date: December 31, 2007
Citation: Wicklow, D.T., Mcalpin, C.E., Yeoh, Q. 2007. Diversity of Aspergillus oryzae genotypes (RFLP) isolated from traditional soy sauce production within Malaysia and Southeast Asia. Mycoscience. 48(6):373-380.

Interpretive Summary: Aspergillus oryzae and Aspergillus sojae, used in the production of traditional Oriental fermented beverages or foods, are identified in a recent U.S. Patent as 'biocompetitive agents' for controlling aflatoxin in susceptible grains and oil seeds. DNA fingerprinting was performed on 64 strains of A. oryzae and one strain of A. sojae isolated from soysauce factories within Malaysia and Southeast Asia that use primitive traditional methods in producing soy sauce. None of these Aspergillus strains produced aflatoxin in broth culture. Strains of A. oryzae were distributed among 30 genotypes. Only two fingerprint matches were produced with the 43 fingerprints in our data base representing NRRL strains of A. oryzae from Japan, China, and Taiwan. This information will enable scientists to combine cultures with unique physiological or biochemical adaptations to produce a superior 'biocompetitive' inoculum, and determine the common ancestry of industrial starter molds used in food fermentations and as sources of industrial enzymes.

Technical Abstract: DNA fingerprinting was performed on 64 strains of Aspergillus oryzae and one strain of A. sojae isolated from soysauce factories within Malaysia and Southeast Asia that use primitive traditional methods in producing 'tamari type' Cantonese soy sauce. PstI digests of total genomic DNA from each isolate were probed using the pAF28 repetitive sequence. Strains of A. oryzae were distributed among 30 genotypes (DNA fingerprint groups). Ten genotypes were recorded among 17 A. oryzae isolates from a single soysauce factory. Genotype Ao-46 and GTAo-47, represented by eight strains and six strains respectively, were isolated from factories in three cities. Four strains of GTAo-49, isolated from soy sauce factories in three Malaysian cities, each produced sclerotia. Two strains were found to be naturally occurring color mutants of GTAo-49 and GTAo-52. Only two fingerprint matches were produced with the 41 fingerprints in our data base representing A. oryzae genotypes from Japan, China, and Taiwan. A single strain of A. sojae NRRL 32650, isolated from a factory in Penang, Malaysia, produced a fingerprint matching GTAo-9, the only known genotype representing koji strains of A. sojae. No aflatoxin was detected in broth cultures of these koji strains as determined by TLC.