Fatma Chaari

Structural, functional, and antioxidant properties of water-soluble polysaccharides from potatoes peels

Water-soluble polysaccharides were extracted from potato peel waste (PPW). The structure of the polysaccharides from PPW (PPPW) was examined by means of Fourier transform-infrared spectroscopy (FT-IR) analysis, X-ray diffractometry (XRD) and gas chromatography-mass spectrometry (GC-MS). The results suggest that the extracted polysaccharides form a semi-crystalline polymer constituted essentially of the functional groups CO, CH and OH. Acid hydrolysis of this polymer yielded glucose (76.25%) as the dominant sugar functional properties (water holding capacity: WHC, oil holding capacity: OHC, foaming, and emulsion properties) of this polymer were studied. The PPPW showed interesting water-holding and fat-binding capacities which were 4.097 ± 0.537 g/g and 4.398 ± 0.04 g/g, respectively. In addition, it presented good foaming and emulsion properties. The antioxidant activity of this polymer was also studied and revealed that the polysaccharides showed interesting 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity (IC50 PPPW=11.578 mg/mL), reducing power and β-carotene bleaching inhibition activities, and also a strong ABTS radical scavenging activity (IC50 PPPW=2mg/mL). Overall, the results suggest that the polysaccharide is a promising source of natural antioxidants and can be used as additive in food, pharmaceutical and cosmetic preparations.

Structural data and biological properties of almond gum oligosaccharide: application to beef meat preservation.

Enzymatic hydrolysis of almond gum generates low molecular weight oligosaccharides (OAG) with a yield of 33.5%. The generated oligosaccharides were purified and identified. OAG analyses show that the most prominent residues were galactose and arabinose with traces of xylose, rhamnose, glucose and mannose. The glycosyl linkage positions were analyzed using gas chromatography-mass spectrometry showing a main chain composed of galactose units [ → 3)-Gal-(1 → ] branched mainly with arabinose residues [Ara-(1 → ]. The antioxidant and antimicrobial activities of OAG were investigated. As regards the in vitro antioxidant activities, the OAG showed a high total antioxidant activity (347 μg ascorbic acid equivalent/mL), an important DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activity (IC50 = 0.64 mg/mL) and a high reducing capacity (RP0.5AU = 3.6 mg/mL). Furthermore, OAG had a high antimicrobial activity against Salmonella thyphimirium, Bacillus cereus, Actinomycetes sp, Klebsiella pneumoniae, Escherichia coli, Alternaria alternate and Candidat albicans. Finally, OAG efficiency was tested using 0.5%; 0.75% and 1% concentrations in beef meat preservation. Microbial growth and lipid oxidation were monitored during 9 days at 4 °C. The results showed significant inhibitions (p < 0.05) of lipid oxidation and microbial growth in ground beef meat containing OAG.

Polysaccharide from garlic straw: extraction, structural data, biological properties and application to beef meat preservation

A novel polysaccharide (GSP) was isolated from garlic straw (Allium sativum L.) by hot water technique. The structural characterization, antioxidant and antimicrobial activities were investigated. The results showed that GSP was mainly composed of glucose, mannose, galactose and xylose and the major functional groups identified from FT-IR spectrum includes 1631.38 cm−1 (–COO–) and 3193 cm−1 (–OH). In addition, GSP had high DPPH radical scavenging activity, a strong reducing power and inhibited the peroxidation of linoleic acid. The antimicrobial activity of GSP was evaluated against a panel of 7 bacteria and 2 fungal strains using agar diffusion method. Results have shown that GSP exhibited moderate to strong antimicrobial activity against the tested species. These interesting results incite the experimental inoculation of GSP in minced beef meat preservation amended with different concentrations of the GSP and stored at 4 °C for 9 days. The obtained results showed significant inhibitions (p ≤ 0.05) of lipid oxidation over 9 days of aerobic storage and also improvement of meat colour stability while differences in total aerobic cell populations did not change noticeably over storage. Finally, sensory characteristics, e.g. colour, odour and texture, of treated meat with GSP, were higher than the control.

Improved Mannanase Production from Penicillium occitanis by Fed-Batch Fermentation Using Acacia Seeds

By applying a fed-batch strategy, production of Penicillium occitanis mannanases could be almost doubled as compared to a batch cultivation on acacia seeds (76 versus 41 U/mL). Also, a 10-fold increase of enzyme activities was observed from shake flask fermentation to the fed-batch fermentation. These production levels were 3-fold higher than those obtained on coconut meal. The high mannanase production using acacia seeds powder as inducer substrate showed the suitability of this culture process for industrial-scale development.

Antibacterial and antioxidant properties of mixed linkage beta-oligosaccharides from extracted β-glucan hydrolysed by Penicillium occitanis EGL lichenase

The aim of this study was first to ascertain the chemical composition and the physicochemical properties of cereal extracted β-glucan from barley flour. Secondly, to assess the antioxidant properties and the antibacterial properties of extracted β-glucan hydrolysates. The proximate composition, FT-IR and scanning electron microscopy of extracted β-Glucan were studied. Hydrolysates from extracted β-glucan, obtained by lichenase EGL from Penicillium occitanis, were a mixed linkage beta-oligosaccharides (MLBO) of trisaccharides and tetrasaccharides. MLBO showed a DPPH radical scavenger with IC50 about 1.8 ± 0.01 mg/mL whereas the IC50 of extracted β-glucan was about 5 ± 0.01 mg/mL. MLBO showed a high antioxidative capacity (175 μmol/mL α-tocopherol equivalents) at 5 mg/mL. The antimicrobial activity was confirmed against all tested bacteria especially at 20 mg/mL of MLBO while no inhibition was observed for all the strains used after the addition of either EGL or extracted β-glucan.

Multistage process for the production of bioethanol from almond shell

This work describes the feasibility of using almond shell as feedstock for bioethanol production. A pre-treatment step was carried out using 4% NaOH for 60min at 121°C followed by 1% sulfuric acid for 60min at 121°C. Enzymatic saccharification of the pre-treated almond shell was performed using Penicillium occitanis enzymes. The process was optimized using a hybrid design with four parameters including the incubation time, temperature, enzyme loads, and polyethylene glycol (PEG) concentration. The optimum hydrolysis conditions led to a sugar yield of 13.5%. A detoxification step of the enzymatic hydrolysate was carried out at pH 5 using 1U/ml of laccase enzyme produced by Polyporus ciliatus. Fermenting efficiency of the hydrolysates was greatly improved by laccase treatment, increasing the ethanol yield from 30% to 84%. These results demonstrated the efficiency of using almond shell as a promising source for bioethanol production.

Immobilization of His-tagged recombinant xylanase from Penicillium occitanis on Nickel-chelate Eupergit C for increasing digestibility of poultry feed

Recombinant xylanase 2 from Penicillium occitanis expressed with an His-tag in Pichia pastoris, termed PoXyn2, was immobilized on nickel-chelate Eupergit C by covalent coupling reaction with a high immobilization yield up to 93.49%. Characterization of the immobilized PoXyn2 was further evaluated. The optimum pH was not affected by immobilization, but the immobilized PoXyn2 exhibited more acidic and large optimum pH range (pH 2.0–4.0) than that of the free PoXyn2 (pH 3.0). The free PoXyn2 had an optimum temperature of 50 °C, whereas that of the immobilized enzyme was shifted to 65 °C. Immobilization increased both pH stability and thermostability when compared with the free enzyme. Thermodynamically, increase in enthalpy and free energy change after covalent immobilization could be credited to the enhanced stability. Immobilized xylanase could be reused for 10 consecutive cycles retaining 60% of its initial activity. It was found to be effective in releasing reducing sugar from poultry feed. Immobilization on Eupergit C is important due to its mechanical resistance at high pH and temperature. Hence, considerable stability and reusability of bound enzyme may be advantageous for its industrial application.

Identification of polysaccharides extracted from pea pod by-products and evaluation of their biological and functional properties

A three-variable Box-Behnken design was employed to obtain the best possible combination of extraction time, ratio (raw material/water) and extraction temperature to allow maximum extraction yield of polysaccharides from pea pod (PPP). The preferred extraction conditions were: extraction time 195 min, extraction temperature 70 °C and ratio of raw material/water 1/40. Under these conditions, the experimental yield was 16.21 ± 1.12%, which is in close agreement with the value predicted by response surface methodology model yield (16.08 ± 0.95%). The molecular weight distribution of PPP showed two peaks with MW of 5217 kDa and 50 kDa, respectively. The main monosaccharides in PPP were galactose, xylose and arabinose, whereas the major functional groups identified from FT-IR spectrum included CO, OH and CH. In addition, PPP had high 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and a moderate reducing power. The antibacterial activity of PPP was also observed against the tested microorganisms and at 50 mg/mL PPP could inhibit the growth of the Gram-negative and Gram-positive bacteria. Generally, these results suggest that the PPP has significant antioxidant activity and good antibacterial activity and can potentially be used as additive in food, pharmaceutical and cosmetic preparations.

Effects of almond gum as texture and sensory quality improver in wheat bread

Summary The aim of this work was to investigate the effect of almond gum as dietary fibre source in enhancing the wheat bread quality. Different amounts of almond gum (2%, 5% and 10% (w/w)) were used in bread formulation. The volume, texture, crust and crumb colour, as well as the sensorial properties, were evaluated and compared to control (without almond gum). The obtained results showed that almond gum addition enhanced significantly the volume of bread. The highest volume was obtained using 2% almond gum concentration with 23.6% increase, compared to control. Using almond gum in bread formulation improved considerably its texture with a notable decrease in hardness by 61.7% and 42.5% when using 2% and 5% almond gum, respectively. The sensory analysis scores showed that the better overall acceptability was found for breads supplemented with 2% almond gum, as compared to control and breads supplemented with 5% or 10% almond gum.