Bioactive Peptides from Agriculture and Food Industry Co-Products: Peptide Structure and Health Benefits

Co-products from food processing are typically disposed or turned into low value animal feed. Proteinaceous co-products can be converted to bioactive peptides exerting health benefits, which can lead to development of nutraceuticals and functional foods. This is an effective means for valorization of these co-products. The release of encrypted peptides exhibits various bioactivities, including antihypertension, antioxidant, immunomodulatory activities among others, in vitro, and some activities have been demonstrated in vivo. Structure modification of bioactive peptides occurring under gastrointestinal digestion and cellular transport remains the important factor determining the health benefits of bioactive peptides. Understanding peptide transformation in gastrointestinal tract and in blood circulation before reaching the target organs would shed some lights on its bioavailability and subsequently ability to exert physiological impact. In this chapter, the potential health promoting properties of peptides encrypted in various sources of co-products will be reviewed based on evidence on in vitro, in vivo and clinical trial studies. Structural changes of bioactive peptides under physiological condition will also be discussed in relation to its bioactivities

A novel subtilase with NaCl-activated and oxidant-stable activity from Virgibacillus sp. SK37

<p>Abstract</p> <p>Background</p> <p>Microbial proteases are one of the most commercially valuable enzymes, of which the largest market share has been taken by subtilases or alkaline proteases of the <it>Bacillus </it>species. Despite a large amount of information on microbial proteases, a search for novel proteases with unique properties is still of interest for both basic and applied aspects of this highly complex class of enzymes. Oxidant stable proteases (OSPs) have been shown to have a wide application in the detergent and bleaching industries and recently have become one of the most attractive enzymes in various biotechnological applications.</p> <p>Results</p> <p>A gene encoding a novel member of the subtilase superfamily was isolated from <it>Virgibacillus </it>sp. SK37, a protease-producing bacterium isolated from Thai fish sauce fermentation. The gene was cloned by an activity-based screening of a genomic DNA expression library on Luria-Bertani (LB) agar plates containing 1 mM IPTG and 3% skim milk. Of the 100,000 clones screened, all six isolated positive clones comprised one overlapping open reading frame of 45% identity to the <it>aprX </it>gene from <it>Bacillus </it>species. This gene, designated <it>aprX-sk37 </it>was cloned into pET21d(+) and over-expressed in <it>E. coli </it>BL21(DE3). The enzyme product, designated AprX-SK37, was purified by an immobilized metal ion affinity chromatography to apparent homogeneity and characterized. The AprX-SK37 enzyme showed optimal catalytic conditions at pH 9.5 and 55°C, based on the azocasein assay containing 5 mM CaCl₂. Maximum catalytic activity was found at 1 M NaCl with residual activity of 30% at 3 M NaCl. Thermal stability of the enzyme was also enhanced by 1 M NaCl. The enzyme was absolutely calcium-dependent, with optimal concentration of CaCl₂at 15 mM. Inhibitory effects by phenylmethanesulfonyl fluoride and ethylenediaminetetraacetic acid indicated that this enzyme is a metal-dependent serine protease. The enzyme activity was sensitive towards reducing agents, urea, and SDS, but relatively stable up to 5% of H₂O₂. Phylogenetic analysis suggested that AprX-SK37 belongs to a novel family of the subtilase superfamily. We propose the name of this new family as alkaline serine protease-X (AprX).</p> <p>Conclusions</p> <p>The stability towards H₂O₂and moderately halo- and thermo-tolerant properties of the AprX-SK37 enzyme are attractive for various biotechnological applications.</p

Statističko optimiranje proizvodnje proteaza otpornih na povećani salinitet iz umjereno halofilne bakterije Virgibacillus sp. SK37

The objectives of this study are to optimize the conditions for providing high yield of NaCl-tolerant extracellular protease from Virgibacillus sp. SK37 based on a fi sh-based medium and to investigate the eff ects of the key factors (mass per volume ratios of dried anchovy, yeast extract and NaCl, and initial pH of the medium) on the secretion patt ern of proteases. Based on the predicted response model, the optimized medium contained 1.81 % of dried anchovy, 0.33 % of yeast extract and 1.25 % of NaCl at pH=7.8. Under these conditions, a 5.3-fold increase in protease production was achieved, compared with the broth containing only 1.2 % of dried anchovy (5 % of NaCl at pH=7). The cubic regression adequately described the protease production. Protease activity was determined using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) on the synthetic substrate (Suc-Ala-Ala-Pro-Phe-AMC). Proteases of molecular masses of 19, 34, 35 and 44 kDa were secreted in the presence of NaCl, whereas those of 22 and 42 kDa were the main proteases detected in the absence of NaCl. In addition, no secreted proteases were detected when initial pH of the medium was pH=6. The peptide mass fi ngerprint of the medium cultured with 10 % NaCl showed a higher abundance of peptides with lower mass of 500– 1000 m/z compared with the medium containing 0 % NaCl, indicating the higher proteolytic activity of the high-salt medium. The Virgibacillus sp. SK37 proteases showed a marked preference towards Lys, Arg and Tyr in the presence of NaCl and towards Lys and Arg in the absence of NaCl.Svrha je ovog rada bila optimirati uvjete proizvodnje izvanstaničnih proteaza otpornih na povećani salinitet s pomoću bakterije Virgibacillus sp. SK37, te ispitati utjecaj glavnih čimbenika (masa sušenih inćuna, ekstrakta kvasca i soli, te početna pH-vrijednost podloge) na proizvodnju proteaza. Metodom odzivnih površina utvrđeno je da optimalna podloga sadržava 1,81 % sušenih inćuna, 0,33 % ekstrakta kvasca i 1,25 % soli, te da je optimalni pH=7,8. Pri tim je uvjetima proizvodnja proteaze porasla 5,3 puta, u usporedbi s podlogom koja je sadržavala samo 1,2 % sušenih inćuna (5 % soli pri pH=7). Proizvodnja proteaze dobro je opisana kubnim modelom. Aktivnost je proteaze određena na sintetičkoj podlozi (Suc-Ala-Ala-Pro-Phe-AMC) pomoću SDS-PAGE metode. U podlozi sa soli izlučene su proteaze molekularne mase od 19, 34, 35 i 44 kDa, dok su u podlozi bez soli dominirale proteaze molekularne mase od 22 i 42 kDa. Osim toga, ustanovljeno je da se proteaze nisu izlučivale pri početnoj pH-vrijednosti podloge od 6. Identifikacijom peptida utvrđeno je da je u podlozi s 10 % soli bilo više peptida manje molekularne mase (500-100 m/z), u usporedbi s podlogom bez soli, iz čega se može zaključiti da je u podlozi s većim salinitetom aktivnost proteaza bila veća. Proteaze iz Virgibacillus sp. SK37 koje su se lučile u slanoj podlozi hidrolizirale su lizin, arginin i tirozin, a one u podlozi bez soli lizin i arginin

Gelation Characteristics of Tropical Surimi under Water Bath and Ohmic Heating

Gelation characteristics of tropical surimi, namely threadfin bream (TB), bigeye snapper (BS), goatfish (GF) and lizardfish (LF) prepared in the absence and presence of 10 g kg⁻¹ egg white proteins were evaluated using either ohmic (OH) or water bath (WB) heating. LF and GF surimi exhibited higher endogenous proteolytic activity than BS and TB. Ohmic heating markedly minimized proteolysis of LF and GF surimi as evidenced by a reduction of trichloroacetic acid (TCA)-soluble oligopeptide content of gels and more retention of myosin heavy chain (MHC). Ohmic heating increased breaking force and deformation of TB and BS surimi by 1.3 and 1.6 times, respectively, as compared to water bath heating. However, TB surimi gels heated by a higher applied voltage gradient of 16.7 V cm⁻¹ exhibited lower breaking force than those heated at 6.7 V cm⁻¹. Gels heated ohmically contained lower total sulfhydryl concentration, indicating the greater extent of disulfide bond formation as compared to gels heated in a 90 °C water bath. The rapid heating method with shorter heating time could improve water holding capacity and preserve color of tropical surimi gels when compared to water bath heating.Keywords: Water bath heating, Tropical surimi, Ohmic heating, GelationKeywords: Water bath heating, Tropical surimi, Ohmic heating, Gelatio

Comparative proteomics revealed duodenal metabolic function associated with feed efficiency in slow-growing chicken

The Korat chicken (KR), developed in Thailand, is a slow-growing breed developed as an alternative breed for Thai chicken producers. The growing interest in slow-growing chicken meat, due to its unique taste, distinct texture, health benefits, and higher broiler welfare have led to higher market demand for KR. However, its low feed efficiency (FE) has a significant negative impact on farm profitability. Understanding the molecular mechanism regulating FE allows for designing a suitable selection program and contributing to breeding more efficient chicken for poultry production. Thus, the objective of our study was to investigate the proteome differences and possible pathways associated with FE in male KR using a label-free quantitative proteomic approach. Seventy-five KR males were individually evaluated for FE, and duodenum samples from 6 animals (3 high-FE and 3 low-FE chickens) were collected at 10 wk of age for differential abundant proteins (DAPs), protein networks, functional enrichment, and pathway analyses. In this study, we found 40 DAPs significantly associated with FE pathways, including glycolysis/gluconeogenesis, peroxisome, oxidative phosphorylation, tight junction, and cysteine and methionine metabolism. Thus, variations in observed DAPs or genes related to DAPs could be interesting biomarker candidates for selection for higher feed utilization efficiency in chicken.Peer reviewe

Effects of Alkali and acid solubilization on gelation characteristics of rockfish muscle proteins

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