Integrated Microbiomic and Metabolomic Dynamics of Fermented Corn and Soybean By-Product Mixed Substrate.

Cheng Wang,Min Yue,Siyu Wei,Mingliang Jin,Bojing Liu,Yizhen Wang

doi:10.3389/fnut.2022.831243

Abstract

Microbes and their metabolites produced in fermented food have been considered as critical contributors to the quality of the final products, but the comprehensive understanding of the microbiomic and metabolomic dynamics in plant-based food during solid-state fermentation remains unclear. Here, the probiotics of Bacillus subtilis and Enterococcus faecalis were inoculated into corn and defatted soybean to achieve the two-stage solid-state fermentation. A 16S sequencing and liquid chromatography–tandem mass spectrometry were applied to investigate the dynamics of microbiota, metabolites, and their integrated correlations during fermentation. The results showed that the predominant bacteria changed from Streptophyta and Rickettsiales at 0 h to Bacillus and Pseudomonas in aerobic stage and then to Bacillus, Enterococcus, and Pseudomonas in anaerobic stage. In total, 229 notably different metabolites were identified at different fermentation times, and protein degradation, amino acid synthesis, and carbohydrate metabolism were the main metabolic pathways during the fermentation. Notably, phenylalanine metabolism was the most important metabolic pathway in the fermentation process. Further analysis of the correlations among the microbiota, metabolites, and physicochemical characteristics indicated that Bacillus spp. was significantly correlated with amino acids and carbohydrate metabolism in aerobic stage, and Enterococcus spp. was remarkably associated with amino acids metabolism and lactic acid production in the anaerobic stage. The present study provides new insights into the dynamic changes in the metabolism underlying the metabolic and microbial profiles at different fermentation stages, and are expected to be useful for future studies on the quality of fermented plant-based food.

Highlights

Corn is one of the main grains produced worldwide, providing 30% of food calories for more than 4.5 billion people worldwide, and is considered to be the main staple food in most countries [1, 2]
The rank-curve generated by OTU ranks and their relative abundance illustrated that α-diversity reduced during the initial 24 h after B. subtilis treatment, whereas increased at the anaerobic fermentation stage (Figure 1A). β-Diversity represents the explicit comparison of microbial communities based on their composition and provides a measure of the distance or dissimilarity between each sample pair
The result showed that microbial β-diversity based on Nonmetric Multidimensional Scaling (NMDS) and Jaccard index distance method was distinct at different time points since the structures of microbial communities were separated into four clusters (Figure 1B)

Summary

Introduction

Corn is one of the main grains produced worldwide, providing 30% of food calories for more than 4.5 billion people worldwide, and is considered to be the main staple food in most countries [1, 2]. Whereas, compared with other cereal crops, the nutritional value of corn is low, lacking essential amino acids and lysine [3]. Soy-derived foods have been consumed for centuries, especially in Asian diets. Soy products contain isoflavones, antigen proteins, and fiber substances that are not easy to be absorbed, which affect their bioavailability [4, 5]. Many processing technologies like physical and chemical methods have been applied to corn and soybean-based foods to enhance the nutritional value of the final products. These processing tools are un-environmental friendly and lose nutrients [6]

Methods

Results

Discussion

Conclusion