Comprehensive Metabolite Profiling of Four Different Beans Fermented by Aspergillus oryzae

Abstract

Fermented bean products are used worldwide; most of the products are made using only a few kinds of beans. However, the metabolite changes and contents in the beans generally used during fermentation are unrevealed. Therefore, we selected four different beans (soybean, Glycine max, GM; wild soybean, Glycine soja, GS; common bean, Phaseolus vulgaris, PV; and hyacinth bean, Lablab purpureus, LP) that are the most widely consumed and fermented with Aspergillus oryzae. Then, metabolome and multivariate statistical analysis were performed to figure out metabolite changes during fermentation. In the four beans, carbohydrates were decreased, but amino acids and fatty acids were increased in the four beans as they fermented. The relative amounts of amino acids were relatively abundant in fermented PV and LP as compared to other beans. In contrast, isoflavone aglycones (e.g., daidzein, glycitein, and genistein) and DDMP-conjugated soyasaponins (e.g., soyasaponins βa and γg) were increased in GM and GS during fermentation. Notably, these metabolite changes were more significant in GS than GM. In addition, the increase of antioxidant activity in fermented GS was significant compared to other beans. We expect our research provides a basis to extend choice for bean fermentation for consumers and food producers.

Keywords: Aspergillus oryzae; antioxidant activity; beans; fermentation; metabolite profiling.

Figure 1

Photographs of the four types of beans (A), and a principal component analysis of the metabolites in the four beans before fermenting. The methods included gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) (B) and liquid chromatography-linear trap quadrupole-orbitrap-tandem mass spectrometry (UHPLC-LTQ-Orbitrap-MS/MS) (C). ( (GM): G. max, (GS): G. soja, (PV): P. vulgaris, (LP): L. purpureus).

Figure 2

Heatmap analysis of four beans based on GC-TOF-MS (A) and UHPLC-LTQ-Orbitrap-MS/MS (B) analyses. The heatmap represents the relative content of significantly different metabolites determined by the partial least squares discriminant analysis (PLS-DA) model (VIP > 0.7, p-value < 0.05). The colored blocks represent the fold changes (blue to red) normalized by the average of all values for each metabolite. The colors indicate the relative abundances of each metabolite. Blue color: lower content relative to the mean, red color: higher content relative to the mean. GM: G. max, GS: G. soja, PV: P. vulgaris, LP: L. purpureus.

Figure 3

PCA analyses and heatmap analyses of the metabolites in the four beans that were fermented with A. oryzae. The methods included GC-TOF-MS (A,C) and UHPLC-LTQ-Orbitrap-MS/MS (B,D). The heatmap represents the relative content of significantly different metabolites determined by the partial least squares discriminant analysis (PLS-DA) model (VIP > 0.7, p-value < 0.05). The colored blocks represent the fold changes (blue to red) normalized by the average of all values for each metabolite. The colors indicate the relative abundances of each metabolite. Blue color: lower content relative to the mean, red color: higher content relative to the mean. GM: G. max, GS: G. soja, PV: P. vulgaris, LP: L. purpureus, 0D: 0 day of fermentation, 1D: 1 day after fermentation, 2D: 2 days after fermentation, 3D: 3 days after fermentation.

Figure 4

The pathway and heatmap analysis for the metabolites in the four beans that were fermented with A. oryzae 0 d and 3 d after fermentation. The metabolite pathways were adopted from the KEGG database. The colors symbolize relative abundance. GM: G. max, GS: G. soja, PV: P. vulgaris, LP: L. purpureus, 0D: 0 day of fermentation, 3D: 3 days after fermentation.

Figure 5

The antioxidant activity test, total flavonoids, and phenolic contents. (A) 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt [ABTS], (B) ferric reducing antioxidant power [FRAP], (C) total flavonoid contents [TFC], and (D) total phenolic contents [TPC]. The significance was determined using Duncan’s multiple range test, and different letters indicate significant differences (p-value < 0.05). (GM): G. max, (GS): G. soja, (PV): P. vulgaris, (LP): L. purpureus, 0D: 0 day of fermentation, 1D: 1 day after fermentation, 2D: 2 days after fermentation, 3D: 3 days after fermentation.