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. 2023 Apr 28;33(4):527-532.
doi: 10.4014/jmb.2210.10051. Epub 2022 Dec 26.

Increased Production of γ-Aminobutyric Acid from Brewer's Spent Grain Through Bacillus Fermentation

Tao Kim  1 , Sojeong Heo  1 , Hong-Eun Na  1 , Gawon Lee  1 , Jong-Hoon Lee  2 , Ji-Yeon Kim  3 , Do-Won Jeong  1
Affiliations

Increased Production of γ-Aminobutyric Acid from Brewer's Spent Grain Through Bacillus Fermentation

Tao Kim et al. J Microbiol Biotechnol. .

Abstract

Brewer's spent grain (BSG) is a waste product of the beer industry, and γ-aminobutyric acid (GABA) is a physiologically active substance important for brain and neuron physiology. In this study, we used the bacterial strains Bacillus velezensis DMB06 and B. licheniformis 0DA23-1, respectively, to ferment BSG and produce GABA. The GABA biosynthesis pathways were identified through genomic analysis of the genomes of both strains. We then inoculated the strains into BSG to determine changes in pH, acidity, reducing sugar content, amino-type nitrogen content, and GABA production, which was approximately doubled in BSG inoculated with Bacillus compared to that in uninoculated BSG; however, no significant difference was observed in GABA production between the two bacterial strains. These results provide the experimental basis for expanding the use of BSG by demonstrating the potential gain in increasing GABA production from a waste resource.

Keywords: Bacillus licheniformis 0DA23-1; Bacillus velezensis DMB06; Brewer’s spent grain; fermentation; γ-amino butyric acid.

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Conflict of interest statement

Conflict of Interest

The authors have no financial conflicts of interest to declare.

Figures

Fig. 1
Fig. 1. Predicted biosynthesis pathways of amino acids and γ-aminobutyric acid (GABA) in Bacillus velezensis DMB06 and B. licheniformis 0DA23-1.
In the pathways, the names of enzyme-encoding genes and amino acids are depicted in green and blue boxes, respectively. The black arrows correspond to potential reactions catalyzed by enzymes encoded in the genomes of the Bacillus strains.
Fig. 2
Fig. 2. Changes in pH (A), acidity (B), reducing sugar (C), and amino-type nitrogen content (D) during fermentation of brewer’s spent grain (BSG) by B. velezensis DMB06 or B. licheniformis 0DA23-1.
Different letter indicates significant difference at p < 0.05 using Duncan’s multiple range test.
Fig. 3
Fig. 3. Viable Bacillus number (A) and GABA (B) production in BSG by B. velezensis DMB06 or B. licheniformis 0DA23-1.
Different letter indicates significant difference at p < 0.05 using Duncan’s multiple range test.
Fig. 4
Fig. 4. Principal component analysis loadings for fermentation of BSG by B. velezensis DMB06 and B. licheniformis 0DA23-1; (A) physicochemical factors and (B) factor scores.
Numbers (0, 24, and 48) indicate the incubation times of samples in h.
See this image and copyright information in PMC

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