Microorganisms with a taste for vanilla: Microbial ecology of traditional Indonesian vanilla curing

The microbial ecology of traditional postharvesting processing of vanilla b eans (curing) was examined using a polyphasic approach consisting of conven tional cultivation, substrate utilization-based and molecular identificatio n of isolates, and cultivation-independent community profiling by 16S ribos omal DNA based PCR-denaturing gradient gel electrophoresis. At two differen t locations, a batch of curing beans was monitored, In both batches a major shift in microbial communities occurred after short-term scalding of the b eans in hot mater. Fungi and yeast disappeared, although regrowth of fungi occurred in one batch during a period in which process conditions were temp orarily not optimal. Conventional plating showed that microbial communities consisting of thermophilic and thermotolerant bacilli (mainly closely rela ted to Bacillus subtilis, B. licheniformis,, and B. smithii) developed unde r the high temperatures (up to 65 degreesC) that mere maintained for over a week after scalding. Only small changes in the communities of culturable b acteria occurred after this period. Molecular analysis revealed that a prop ortion of the microbial communities could not be cultured on conventional a gar medium, especially during the high-temperature period. Large difference s between both batches were observed in the numbers of microorganisms, in s pecies composition, and in the enzymatic abilities of isolated bacteria, Th ese large differences indicate that the effects of microbial activities on the development of vanilla flavor could be different for each batch of cure d vanilla beans.