Dynamics of microbial communities and metabolites in ganjang, a traditional Korean fermented soy sauce, during fermentation.

Six different ganjang batches were prepared and the microbial communities in the ganjang samples and raw materials (meju and solar salts), as well as the metabolites generated during fermentation were analyzed. The varying amounts of raw materials used differentially affected the microbial communities. Halophilic or halotolerant microbes derived from solar salts were abundant during middle or late fermentation. By contrast, non-halophilic microbes derived from meju were abundant mainly during early fermentation. Debaryomyces, Tetragenococcus, and Staphylococcus were abundant in all ganjang batches, which suggested that these may be the most common microbes involved in ganjang fermentation. The salt concentrations did not affect the abundance of Debaryomyces, which was abundant in all ganjang batches. Tetragenococcus was abundant in low salt ganjang, whereas Staphylococcus was abundant in high salt ganjang. Metabolite analysis revealed that carbohydrate concentrations were high in ganjang prepared using high amounts of meju. The level of lactate, which may be largely produced by Tetragenococcus, in low salt ganjang was high because of high microbial activity. The amino acid concentrations of the ganjang batches were mainly associated with meju quantity, but not salt concentration. These results indicated that the production of amino acids may be associated with indigenous proteases in meju, but not microbial activities during ganjang fermentation.