Assaâd Sila

Biochemical and antioxidant properties of peptidic fraction of carotenoproteins generated from shrimp by-products by enzymatic hydrolysis

The composition, functional properties and in vitro antioxidative activity of the peptidic fraction of carotenoproteins from shrimp (Parapenaeus longirostris) by-products generated by enzymatic treatment with Alcalase was evaluated. The peptidic fraction of carotenoproteins (PFCP) contained 80.8 ± 0.21% protein, 2.74 ± 0.3% lipid, 14.4 ± 0.14% ash, 1.13 ± 0.08% chitin and 1.08 ± 0.02 μg total carotenoid/g of sample. The amino acid profile of PFCP showed a high percentage of essential amino acids, such as arginine, lysine, histidine and leucine. Therefore, PFCP had a high nutritional value and could be used as a supplement to poorly balanced dietary proteins. PFCP showed an excellent solubility and possessed interfacial properties, which were governed by their concentrations. The antioxidant activities of PFCP at different concentrations were evaluated using various in vitro antioxidant assays, including the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical method, reducing power, chelating effects assay and β-carotene bleaching. The antioxidant activity of PFCP, based on their protection of supercoiled DNA strand from scission by peroxyl and hydroxyl radicals into the nicked circular form was also investigated. Results from this study suggest that the peptidic fraction of carotenoproteins is a good source of natural antioxidants and peptides with interesting functionalities.

Structural, functional, and ACE inhibitory properties of water-soluble polysaccharides from chickpea flours

The present study aimed to characterize and investigate the functional and angiotensin-I converting enzyme (ACE) inhibition activities of chickpea water-soluble polysaccharides (CPWSP). Physico-chemical characteristics were determined by nuclear magnetic resonance spectroscopy (NMR), Fourier transform-infrared spectroscopy (FT-IR) analysis, and X-ray diffractometry (XRD). Functional properties (water holding capacity: WHC, water solubility index: WSI, swelling capacity: SC, oil holding capacity: OHC, foaming, and emulsion properties) and ACE activities were also investigated using well-established procedures. The FT-IR spectra obtained for the CPWSP revealed two significant peaks, at about 3500 and 500 cm(-1), which corresponded to the carbohydrate region and were characteristic of polysaccharides. All spectra showed the presence of a broad absorption between 1500 and 670 cm(-1), which could be attributed to CH, CO, and OH bands in the polysaccharides. CPWSP had an XRD pattern that was typical for a semi-crystalline polymer with a major crystalline reflection at 19.6 °C. They also displayed important techno-functional properties (SWC, WSI, WHC, and OHC) that can be modulated according to temperature. The CPWSP were also noted to display good anti-hypertensive activities. Overall, the results indicate that CPWSP have attractive chemical, biological, and functional properties that make them potential promising candidates for application as alternative additives in various food, cosmetic, and pharmaceutical preparations.

Water-soluble polysaccharides from agro-industrial by-products: functional and biological properties.

Water-soluble polysaccharides were isolated from almond (AWSP) and pistachio (PWSP) juice processing by-products. Their chemical and physical characteristics were determined using NMR and Infrared spectroscopic analysis. The complexities of the spectra reflected the heterogeneity of these polysaccharides. The ACE inhibitory activities (IC50 AWSP=2.81mgmL(-1) and IC50 PWSP=2.59mgmL(-1)) and antioxidant properties of AWSP and PWSP were investigated based on the DPPH radical-scavenging capacity assay (IC50 AWSP=2.87mgmL(-1) and IC50 PWSP=1.61mgmL(-1)). Reducing power, β-carotene bleaching inhibition (IC50AWSP=4.46mgmL(-1) and IC50 PWSP=3.39mgmL(-1)), and ferrous chelating assays (IC50 AWSP=0.22mgmL(-1) and IC50 PWSP=0.19mgmL(-1)) were also performed. The findings revealed that water-soluble polysaccharides exhibited antioxidant and antihypertensive activities. AWSP and PWSP showed excellent interfacial concentration-dependent properties. Overall, the results suggested that both AWSP and PWSP are promising sources of natural antioxidants and ACE inhibitory agents and could, therefore, be used as alternative additives in food, pharmaceutical and cosmetic preparations.

Effects of enzymatic hydrolysis on conformational and functional properties of chickpea protein isolate.

The impact of enzymatic hydrolysis by Alcalase on the conformational and functional properties of chickpea protein isolate (CPI) was investigated. The physicochemical, interfacial tension and surface characteristics of CPI and their hydrolysates (CPH) according to the degree of hydrolysis (DH) were also determined. These parameters were then related to the changes in the emulsification activity (EAI) and stability (ESI). The enzymatic hydrolysis was found to improve protein recovery and solubility, leading to a reduction in the molecular weight bands with a concomitant increase in the intensity and appearance of protein bands having apparent molecular mass below 20 kDa. The interfacial tension decreased from ∼ 66.5 mN m(-1) for CPI to ∼ 59.1 m Nm(-1) for CPH. A similar trend was observed for the surface charge which declined from -27.55 mV to -16.4 mV for the CPI and CPH, respectively. These changes were found to have a detrimental effect on the EAI and ESI values.

Recovery, viscoelastic and functional properties of Barbel skin gelatine: investigation of anti-DPP-IV and anti-prolyl endopeptidase activities of generated gelatine polypeptides.

The characteristics and functional properties of gelatine from freshwater fish skin (Barbus callensis) were investigated. The gelatine extraction efficiency was improved by an acid-swelling process in the presence of barbel crude acid protease extract. Barbel skin gelatine (BSG) contained 92.15% protein, 0.31% lipid and 0.72% ash. The amino acid profile of BSG showed a high percentage of imino acids. The electrophoretic profile showed that BSG is mainly composed of α- and β-components. BSG showed an excellent solubility and possessed interfacial properties, which were governed by the protein concentration. Biological activities of the hydrolysates obtained after digestion of BSG with several commercial proteases were evaluated. The results suggested that these hydrolysates are a good source of natural inhibitors of dipeptidyl peptidase-IV and prolyl endopeptidase and could potentially be used as dietary ingredients in the management of type 2-diabetes and/or neuropathological disorders.

Chitin and chitosan from the Norway lobster by-products: Antimicrobial and anti-proliferative activities

Chitin was recovered through enzymatic deproteinization of the Norway lobster (Nephrops norvegicus) processing by-products. The obtained chitin was characterized and converted into chitosan by N-deacetylation, the acid-soluble form of chitin. Chitosan samples were then characterized by Fourier transform infrared spectroscopy (FTIR) and 13 Cross polarization magic angle spinning nuclear magnetic resonance (CP/MAS)-NMR spectroscopy. The antimicrobial activity and anti-proliferative capacity of chitosan were evaluated. Antimicrobial activity assays indicated that prepared chitosan exhibited marked inhibitory activity against the bacterial and fungal strains tested. Further, cytotoxic effects of chitosan samples on human colon carcinoma cells HCT116 was evaluated using the MTT assay. Chitosan showed the antiproliferative capacity against the colon-cancer-cell HCT116 in a dose dependent manner with IC50 of 4.6mg/ml. Indeed, HCT116 cell proliferation was significantly inhibited (p<0.05) between 13.5 and 67.5% at 0.5-6mg/mL of chitosan after 24h of cell treatment. The chitosan showed high antitumor activity which seemed to be dependent on its characteristics such as acetylation degree.

Extraction, characterization and antimicrobial activity of sulfated polysaccharides from fish skins

Sulfated polysaccharides were extracted from gray triggerfish (GTSP) and smooth hound (SHSP) skins. Their chemical and physical characteristics were determined using X-ray diffraction and Infrared spectroscopic analysis. The antibacterial activities of GTSP and SHSP against Listeria monocytogenes (ATCC 43251), Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 25922), Salmonella enterica (ATCC 43972) and Enterobacter sp were evaluated by determining clear growth inhibition zone diameters and the minimum inhibitory concentration (MIC) values and by essays in liquid media. GTSP and SHSP were fractionated by a Diethylaminoethyl-cellulose chromatography. Fraction FGII, from GTSP, and fraction FSII, from SHSP, showed the most important inhibitory effects against the tested bacterial species. The sulfated polysaccharides from fish skins did not show hemolytic activity towards bovine erythrocytes. Overall, the results suggested that those polysaccharides could offer promising sources of polysaccharides for future application as dietary ingredients in the nutraceutical industry.

Characterisation of trypsin purified from the viscera of Tunisian barbel (Barbus callensis) and its application for recovery of carotenoproteins from shrimp wastes

Trypsin was purified from the viscera of barbel by precipitation using ammonium sulphate (0-80%), Sephadex G-100, and Mono Q-Sepharose ion exchange chromatography. The trypsin was purified 27-fold, with 79U/mg specific activity and 31% recovery. The enzyme had a molecular weight of 24kDa; purified trypsin appeared as a single band on native-PAGE. The optimum pH and temperature for enzyme activity were pH 10.0 and 55°C with BAPNA used as a substrate. The N-terminal amino acid sequence of the first 12 amino acids of the purified trypsin was IVGGYECTPYSQ. The Michaelis-Menten constant (Km) and catalytic constant (kcat) values of the enzyme were 0.018mM and 1.21s-1, respectively. The study also investigated the effects of purified trypsin on the recovery of carotenoproteins from shrimp (Parapenaeus longirostris) shells through hydrolysis using 1.0U barbel trypsin/g shrimp shells for 1h at 30°C. The freeze-dried carotenoproteins recovered contained 71.09% protein, 16.47% lipid, 7.78% ash, and 1.79% chitin.

Ability of natural astaxanthin from shrimp by-products to attenuate liver oxidative stress in diabetic rats

BACKGROUND Reactive oxygen species play a crucial role in the pathogenesis of diabetes and its complications. The present study was undertaken, in vivo, to examine the protective effect of astaxanthin extracted from the shell waste of deep-water pink shrimp (Parapenaeus longirostris) against oxidative stress of alloxanic adult male rats. RESULTS Alloxan treatment revealed a significant elevation in plasma glycemia and lipid parameters such as total lipid, total cholesterol and triglycerides compared to the control group (C). In addition, liver malonaldialdehyde levels (MDA), an index of lipid peroxidation, significantly increased compared to control group. The activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) and reduced glutathione (GSH) levels decreased significantly compared to control group. Moreover, diabetic rats presented a significant increase in the activities of aspartate transaminase (AST) alanine transaminase (ALT) and alkaline phosphatase (ALP) in plasma, indicating considerable hepatocellular injury. Astaxanthin treatment restores these parameters near to control values. Histological studies on the liver tissue of alloxan and astaxanthin treated rats confirmed the protective effects of astaxanthin. CONCLUSIONS The results revealed that astaxanthin may be helpful in preventing diabetic complications in adult rats by reversing hepatotoxicity. It can be one of the ingredients in a number of healthy products.

Digestive Alkaline Proteases from the Goby (Zosterisessor ophiocephalus): Characterization and Potential Application as Detergent Additive and in the Deproteinization of Shrimp Wastes

Alkaline proteases from the viscera of the goby (Zosterisessor ophiocephalus) were extracted and characterized. Proteolytic crude extract from goby viscera was active and stable in alkaline solution. The optimum pH and temperature were 10.0 and 50°C, respectively, using casein as a substrate. The crude alkaline protease was extremely stable in the pH range of 5.0–12.0. Zymography activity staining using casein as a substrate showed the presence of at least four distinct proteases. The alkaline proteases showed extreme stability toward nonionic surfactants (Tween 80 and Triton X-100) and were relatively stable toward oxidizing agents, retaining more than 60% of their initial activity in the presence of 2% sodium perborate. Furthermore, the alkaline crude enzyme extract showed relative stability and compatibility with commercial liquid and solid detergents. Wash performance analysis revealed that goby crude extract could effectively remove a variety of stains, such as blood and chocolate. Further, alkaline proteases from goby viscera were found to be effective in the deproteinization of shrimp wastes. A high level of deproteinization 80.0% ± 1.5 was recorded with an enzyme/substrate ratio (E/S) of 20 U/mg. These results suggest that enzymatic deproteinization of the shrimp shell wastes, using Z. ophiocephalus proteases, could be applicable to the chitin production process.