Comparative study on metabolic changes of Aspergillus oryzae isolated from fermented foods according to culture conditions

Aspergillus oryzae is an important microbial starter for making diverse fermented foods due to its high hydrolytic enzyme activities. In this study, two strains of A. oryzae (AOB/AOK) with different activities of hydrolytic enzymes, such as α-amylase, protease and lipase, were cultured under various conditions of temperature, fermentation time, and initial pH. Comparative mass spectrometry (MS) based metabolomic analysis was performed to obtain primary metabolites and secondary volatile metabolite data sets. In the results of partial least square-discriminant analysis (PLS-DA), fatty acids and volatile metabolites derived from fatty acids and amino acids mainly contributed to AOK with higher protease and lipase activities, whereas carbohydrate-derived volatiles, sugars and sugar alcohols were related to main metabolites of AOB with higher α-amylase activity. The temperature and initial pH were critical factors for the generation of primary metabolites and secondary volatile metabolites, such as organic acids, fatty acids-derived volatiles, and some amino acids, in both A. oryzae strains. This study demonstrated that the specific culture conditions were closely linked to the formation of primary metabolites and secondary volatile metabolites of A. oryzae.