The Interpretation of Dissolved Oxygen on Flavor Characteristics and Microorganism Community Succession between Soy Sauce Fermented in Tank and Soy Sauce Fermented in Pond

Traditional soy sauce fermentation modernization is crucial, yet soy sauce fermented in a tank (SSFT) exhibits a flavor difference compared to superior soy sauce fermented in a pond (SSFP). Dissolved oxygen (DO) was hypothesized as a key regulator of microbial dynamics and flavor variation. This study employed genomic and metabolomic analyses to investigate DO's role in synthetic microbial communities, aiming to clarify how DO drives flavor difference between SSFP and SSFT. Results showed that higher DO levels drive: (i) sensory shift favoring umami/kokumi over bitterness, (ii) metabolic reprogramming toward elevated levels of citric acid, glutaric acid, glycolic acid, tartaric acid, erythritol, and umami-enhancing N-acetyl/lactoyl amino acids, and (iii) preferential enrichment of certain bacteria and fungi; notably Staphylococcus saprophyticus, Wickerhamiella versatilis, and Candida etchellsii. These traits align with SSFP's advantages, confirming DO level differences as a reason for SSFT's flavor weakness and providing a theoretical basis for improving soy sauce flavor in large-scale fermentation.