Mechanistic insights into soy sauce flavor enhancement via Co-culture of Limosilactobacillus fermentum and Zygosaccharomyces rouxii

Abstract

For years, the intricate interactions between microorganisms in fermented food have played a key role in enhancing flavor. Our previous study highlighted that co-culture of Limosilactobacillus fermentum (L. fermentum) and Zygosaccharomyces rouxii (Z. rouxii) could enhance the flavor improvement capability of Z. rouxii in soy sauce fermentation, but the mechanism has been understudied. In this study, gas chromatography-mass spectrometry (GC-MS), GC-MS combined with derivatization (Der-GC-MS) and metabolite addition experiments were employed to elucidate their interaction. The first reason for the enhanced flavor of co-culture was that L. fermentum itself could produce the caramel-like compounds, such as HDMF and 2-furanmethanol. Another important reason was the commensality interaction between L. fermentum and Z. rouxii, where L. fermentum not only grew vigorously, but also significantly promoted the growth of Z. rouxii, mitigating the inhibitory effects of acetic acid on Z. rouxii. Further validation revealed that the metabolites of L. fermentum could stimulate the reproduction of Z. rouxii and increase the synthesis of aroma compounds such as phenylethyl acetate and ethyl acetate. Notably, glycerin and lactic acid emerged as pivotal metabolites facilitating enhanced aroma production. This study offers valuable insights for advancing flavor regulation techniques in soy sauce production.