Koji Molds for Japanese Soy Sauce Brewing: Characteristics and Key Enzymes

Soy sauce is a traditional Japanese condiment produced from the fermentation of soybeans, wheat, and salt by three types of microorganisms, namely koji molds, halophilic lactic acid bacteria, and salt-tolerant yeast. The delicate balance between taste, aroma, and color contributes to the characteristic delicious flavor imparted by soy sauce. In soy sauce brewing, protein and starch of the raw materials are hydrolyzed into amino acids and sugars by enzymes derived from koji molds. These enzymatically hydrolyzed products not only directly contribute to the taste but are further metabolized by lactic acid bacteria and yeasts to most of organic acids and aromatic compounds, resulting in its distinctive flavor and aroma. The color of the soy sauce is also due to the chemical reactions between amino acids and sugars during fermentation. Therefore, koji mold, which produces various enzymes for the breakdown of raw materials, is an essential microorganism in soy sauce production and plays an essential role in fermenting the ingredients. In this review, we describe the manufacturing process of Japanese soy sauce, the characteristics of koji molds that are suitable for soy sauce brewing, and the key enzymes produced by koji molds and their roles in the degradation of materials during soy sauce fermentation, focusing on the production of umami taste in soy sauce brewing.

CHARACTERIZATION OF TETRAGENOCOCCUS HALOPHILUS FROM VIETNAMESE FISH SAUCE

The intracellular aminopeptidase activities and volatile compound profile of isolated halophilic lactic acid bacteria Tetragenococcus halophilus was investigated. Tetragenococcus halophilus CH2-4 and CH6-2 exhibited highest aminopeptidase activities 2.2 U/mL toward Glutamic-pNA. Meanwhile T. halophilus CH6-1 and V7-2 showed highest aminopeptidase activities 1.4 U/mL toward Leucine-pNA. The total 19 volatile compounds, including esters, alcohols, ketones, phenols, hydrocarbons and sulfur containing compounds were detected in fish broth inoculated with T. halophilus.T. halophilus CH6-2 produced most volatile compounds, 10/19 detected ones in this study.

Draft Genome Sequences of Tetragenococcus muriaticus Strains 3MR10-3 and PMC-11-5 Isolated from Thai Fish Sauce during Natural Fermentation

ABSTRACT Tetragenococcus muriaticus strains 3MR10-3 and PMC-11-5 are homofermentative halophilic lactic acid bacteria isolated from Thai fish sauce during natural fermentation. Their draft genomes were sequenced. Our interest in these organisms is related to their impact on fish sauce flavor and their high osmotolerance.