Metabolite profiling of Cheonggukjang, a fermented soybean paste, inoculated with various Bacillus strains during fermentation.

Metabolite profiling of Cheonggukjang inoculated with different Bacillus strains including Bacillus amyloliqueciens CH86-1, Bacillus licheniformis 58, and Bacillus licheniformis 67 during fermentation, was performed using gas chromatography-time of flight-mass spectrometry after derivatization, combined with multivariate statistical analysis. A total of 20 amino acids, 10 sugars, five sugar alcohols, and seven organic acids were identified in three Cheonggukjang samples. With fermentation time, most of the amino acids showed increasing amounts. On the other hand, most of the sugars including sucrose, fructose, and glucose decreasing patterns, and the amounts of organic acids varied. In order to observe differences in metabolites with fermentation time and inoculated Bacillus strains, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were carried out, respectively. On PCA plots, some sugars and organic acids including sucrose, fructose, glucose, mannose, succinic acid, and malonic acid, as well as most of the amino acids, contributed mainly to differentiation of the Cheonggukjang samples fermentation time. On the other hand, on PLS-DA, mannose, xylose, glutamic acid, and proline were mainly responsible for differentiating the Cheonggukjang among into various inoculated strains.