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Enzyme Research
Volume 2011, Article ID 538676, 7 pages
http://dx.doi.org/10.4061/2011/538676
Research Article

Debittering of Protein Hydrolysates by Lactobacillus LBL-4 Aminopeptidase

Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. 9, 1113 Sofia, Bulgaria

Received 4 May 2011; Revised 28 June 2011; Accepted 30 June 2011

Academic Editor: Alane Beatriz Vermelho

Copyright © 2011 Bozhidar Tchorbanov et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Yoghurt strain Lactobacillus LBL-4 cultivated for 8–10 h at pH ~6.0 was investigated as a considerable food-grade source of intracellular aminopeptidase. Cell-free extract manifesting >200 AP U/l was obtained from cells harvested from 1 L culture media. Subtilisin-induced hydrolysates of casein, soybean isolate, and Scenedesmus cell protein with degree of hydrolysis 20–22% incubated at 45C for 10 h by 10 AP U/g peptides caused an enlarging of DH up to 40–42%, 46–48%, and 38–40% respectively. The DH increased rapidly during the first 4 h, but gel chromatography studies on BioGel P-2 showed significant changes occurred during 4–10 h of enzyme action when the DH increased gradually. After the digestion, the remained AP activity can be recovered by ultrafiltration (yield 40–50%). Scenedesmus protein hydrolysate with DH 20% was inoculated by Lactobacillus LBL-4 cells, and after 72 h cultivation the DH reached 32%. The protein hydrolysates (DH above 40%) obtained from casein and soybean isolate (high Q value) demonstrated a negligible bitterness while Scenedesmus protein hydrolysates (low Q value) after both treatments were free of bitterness.