Peptidomic analysis of antioxidant and ACE-inhibitory peptides obtained from tomato waste proteins fermented using Bacillus subtilis

In this study, tomato seeds were obtained as by-products and submitted to fermentation with the proteolytic strain Bacillus subtilis A14h. The resulting peptide mixture was fractionated and purified through different chromatographic steps. Fractions were assayed for antioxidant and angiotensin converting enzyme (ACE)-inhibitory activities and peptides were identified by using nano-liquid chromatography coupled to mass spectrometry in tandem (nLC-MS/MS). Most of the identified peptides were smaller than 1000 Da and had different aromatic and hydrophobic amino acid residues. Their sequences were novel but some of them showed active domains previously reported in other bioactive peptides. The hexapeptide DGVVYY showed an IC50 value of 2 µM in angiotensin-I converting enzyme (ACE-I) inhibitory activity, whereas the pentapeptide GQVPP displayed a 97% of DPPH activity at 0.4 mM. The results revealed that B. subtilis fermentation of tomato by-products could be a good strategy for obtaining added-value peptides that might be used as an ingredient in functional foods and nutraceuticals.This work was funded by Grant of Ministry of Science, Research and Technology of Iran, Research Council of University of Tehran (Tehran, Iran) and Emerging Research Group Grant from Generalitat Valenciana (Valencia, Spain) (GV/2015/138). Also a Juan de la Cierva de Incorporación postdoctoral contract to Dr. Mora is acknowledged. Q-ToF nLC-MS/MS was carried out in the SCSIE University of Valencia Proteomics Unit (Spain), a member of ISCIII ProteoRed Proteomics Platform.Peer reviewe