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. 2025 Jan 7;14(2):145.
doi: 10.3390/foods14020145.

Study on Fermentation Preparation, Stability, and Angiotensin-Converting Enzyme Inhibitory Activity of Tomato Pomace Peptide

Ying Mu  1 , Ruxianguli Maimaitiyiming  1 , Jingyang Hong  1 , Yu Wang  1 , Yao Zhao  1 , Ruoqing Liu  1 , Liang Wang  1 , Keping Chen  2 , Aihemaitijiang Aihaiti  1
Affiliations

Study on Fermentation Preparation, Stability, and Angiotensin-Converting Enzyme Inhibitory Activity of Tomato Pomace Peptide

Ying Mu et al. Foods. .

Abstract

The substantial quantity of discarded tomato pomace (TP) results in the waste of valuable resources. This study utilizes these tomato by-products by mixing them with water in a specific proportion and fermenting the mixture in two stages: first with yeast, and then with lactic acid bacteria. The most suitable microbial strains for TP fermentation were identified by evaluating parameters such as peptide content, degree of hydrolysis, and gel electrophoresis analysis. Subsequently, tomato pomace peptides (TPPs) were separated into peptides of different molecular weights using ultrafiltration. The IC50 values, ACE inhibitory activities, and in vitro stability of these peptides were compared, and their secondary structures and microstructures were characterized. The results indicated that the soluble protein concentration increased from 26.25 mg/g to 39.03 mg/g after 32 h of fermentation with strain RV171. After an additional 32 h of fermentation with Bifidobacterium thermophilum, the peptide content reached 49.18 ± 0.43%. SDS-PAGE gel electrophoresis showed that the TPP molecular weights were predominantly below 10 kDa. The IC50 results demonstrated that fractions with smaller molecular weights exhibited greater ACE inhibitory activities. Structural analysis confirmed that the TP hydrolysate was indeed a peptide.

Keywords: ACE inhibitory activity; peptide; stability; structure characterization; tomato pomace; two-stage fermentation.

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Conflict of interest statement

Author Keping Chen was employed by the company Xinjiang Huize Food Limited Liability Company. He participated in Supervision, project administration in the study. The role of the company was that of the Chairman of the Board of Directors. The authors declare that this study received funding from Keping Chen. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
(a) Changes in peptide content (%) during the fermentation of TP using six different yeast strains. (b) Changes in the conversion of soluble protein (%) during the fermentation of tomato pomace by six different yeast strains. (c) Results of hydrolysis (%) of fermentation residues from different yeast strains are expressed as the mean ± standard deviation (SD) of three replicates. (d) Effect of fermentation time on peptide content (%). (e) Effect of the solid–liquid ratio on peptide content (%). (f) Effect of inoculum amount on peptide content (%). Lowercase letters indicate significance (p < 0.05).
Figure 1
Figure 1
(a) Changes in peptide content (%) during the fermentation of TP using six different yeast strains. (b) Changes in the conversion of soluble protein (%) during the fermentation of tomato pomace by six different yeast strains. (c) Results of hydrolysis (%) of fermentation residues from different yeast strains are expressed as the mean ± standard deviation (SD) of three replicates. (d) Effect of fermentation time on peptide content (%). (e) Effect of the solid–liquid ratio on peptide content (%). (f) Effect of inoculum amount on peptide content (%). Lowercase letters indicate significance (p < 0.05).
Figure 2
Figure 2
(a,b) The change in peptide content (%) during tomato pomace fermentation was assessed for each of the 12 bacterial taxa (TP). Data are presented as the mean ± standard deviation of three replicates. (c) The hydrolysis results (%) of different bacterial fermentation residues are presented as the mean ± standard deviation (SD) of three replicates. Lowercase letters denote statistical significance (p < 0.05).
Figure 3
Figure 3
SDS-PAGE pattern of TP after fermentation: (a) 1—marker; 2—TP; 3—Saccharomyces cerevisiae BV818; 4—Saccharomyces cerevisiae RV171; 5—Hanseniaspora uvarum; 6—Pichia guilliermondii; 7—Torulaspora delbrueckii; 8—Saccharomyces cerevisiae EC 1118. (b) SDS-PAGE after lactic acid fermentation: 1—marker; 2—TP; 3—Saccharomyces cerevisiae RV171; 4—Pediococcus acidilactici; 5—lactobacillus rhamnosus; 6—Lactobacillus paracasei subsp. paracasei; 7—Bacillus subtilis; 8—Lactobacillus reuteri; 9—thermophilic bifidobacteria.
Figure 4
Figure 4
The molecular weight distribution of the fermented peptides derived from the four strains. (a) Molecular weight distribution of peptides fermented by Bifidobacterium thermophilus. (b) Molecular weight distribution of peptides derived from Lactobacillus rhamnosus fermentation. (c) Molecular weight distribution of peptides resulting from Pediococcus acidilactici fermentation. (d) Molecular weight distribution of peptides obtained from Bacillus subtilis fermentation.
Figure 5
Figure 5
(a) Variations in ACE inhibitory IC50 values of TPPs before and after ultrafiltration. (b) Peptide retention in samples treated with different ion concentrations. (c) ACE inhibitory activity of samples treated with different ion concentrations. (d) Effect of different pH-treated samples on peptide content. (e) Effect of samples treated with different pH on ACE inhibition rates. (f) Effect of samples treated with different temperatures on peptide content. (g) Effect of samples treated with different temperatures on ACE inhibition rate. Different letters indicate statistically significant differences among treatments for each sample (p < 0.05).
Figure 5
Figure 5
(a) Variations in ACE inhibitory IC50 values of TPPs before and after ultrafiltration. (b) Peptide retention in samples treated with different ion concentrations. (c) ACE inhibitory activity of samples treated with different ion concentrations. (d) Effect of different pH-treated samples on peptide content. (e) Effect of samples treated with different pH on ACE inhibition rates. (f) Effect of samples treated with different temperatures on peptide content. (g) Effect of samples treated with different temperatures on ACE inhibition rate. Different letters indicate statistically significant differences among treatments for each sample (p < 0.05).
Figure 6
Figure 6
(a,c,e) Changes in ACE inhibition of samples after treatment with different mass fractions of methanol, ethanol, and propanol. (b,d,f) The variations in ACE inhibition in samples treated with different mass fractions of methanol, ethanol, and propanol are shown separately. Different letters indicate statistically significant differences among treatments for each sample (p < 0.05).
Figure 6
Figure 6
(a,c,e) Changes in ACE inhibition of samples after treatment with different mass fractions of methanol, ethanol, and propanol. (b,d,f) The variations in ACE inhibition in samples treated with different mass fractions of methanol, ethanol, and propanol are shown separately. Different letters indicate statistically significant differences among treatments for each sample (p < 0.05).
Figure 7
Figure 7
Effect of various metal ions on the stability of tomato pomace peptides with different molecular weights. (a1,a2) Changes in peptide retention and ACE inhibition in samples treated with different concentrations of K+. (b1,b2) Changes in peptide retention and ACE inhibition in samples treated with different concentrations of Mn2+. (c1,c2) Changes in peptide retention and ACE inhibition in samples treated with different concentrations of Fe2+. (d1,d2) Changes in peptide retention and ACE inhibition in samples treated with different concentrations of Cu2+. Different letters indicate statistically significant differences among treatments for each sample (p < 0.05).
Figure 8
Figure 8
(a) UV spectrum of three molecular weight components. (b) Fourier infrared spectrum of components with molecular weights greater than 3 kDa. (c) Fourier infrared spectrum of components with molecular weights between 1 and 3 kDa. (d) Fourier infrared spectrum of components with molecular weights less than 1 kDa.
Figure 9
Figure 9
Scanning electron microscopy images of components with different molecular weights: (a) >3 kDa; (b) 1–3 kDa; (c) <1 kDa.
See this image and copyright information in PMC

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