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In the present work, optimization of hot water extraction, structural characteristics, functional properties, and biological activities of polysaccharides extracted from watermelon rinds (WMRP) were investigated. The physicochemical characteristics and the monosaccharide composition of these polysaccharides were then determined using chemical composition analysis, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and gas chromatography-flame ionization detection (GC-FID). SEM images showed that extracted polysaccharides had a rough surface with many cavities. GC-FID results proved that galactose was the dominant sugar in the extracted polysaccharides, followed by arabinose, glucose, galacturonic acid, rhamnose, mannose, xylose and traces of glucuronic acid. The findings revealed that WMRP displayed excellent antihypertensive and antioxidant activities. Those polysaccharides had also a protection effect against hydroxyl radical-induced DNA damage. Functional properties of extracted polysaccharides were also evaluated. WMRP showed good interfacial dose-dependent proprieties. Overall, the results suggested that WMRP presents a promising natural source of antioxidants and antihypertensive agents.

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ABSTRACT: This research focused on isolation, identification and characterization of new strains of fungi and bacteria, which were able to produce extracellular xylanase, mannanase, pectinase and α-amylase. Fungi isolates were identified on the basis of analyses of 18S gene sequencing and internal transcribed spacer region. The closest phylogenetic neighbors according to 18S gene sequence and ITS region data for the two isolates M1 and SE were Aspergillus fumigatus and Aspergillus sydowii, respectively. I4 was identified as Bacillus mojavensis on the basis of the 16S rRNA gene sequencing and biochemical properties. The enzyme production was evaluated by cultivating the isolated microorganisms in liquid-state bioprocess using wheat bran as carbon source. Two fungi (M1, and SE) and one bacterium (I4) strains were found to be xylanase producer, and several were proven to be outstanding producers of microbial xylanase. The strains producing xylanase secreted variable amounts of starch-debranching enzymes and produced low level β-mannan-degrading enzyme systems. The bacterium strain was found to be capable of producing pectinolytic enzymes on wheat bran at high level. Some of the strains have good potential for use as sources of important industrial enzymes.

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Carrot (Daucus carota) peels, local agricultural waste product, is rich in lignocellulolytic material, including pectin which can act as an inducer of pectinase production. Pectinolytic enzymes production by Bacillus mojavensis I4 was studied in liquid state fermentation using carrot peel as a substrate. Medium composition and culture conditions for the pectinase production by I4 were optimized using two statistical methods: Taguchi design was applied to find the key ingredients and conditions for the best yield of enzyme production and The Box-Behnken design was used to optimize the value of the four significant variables: carrot peels powder, NH4Cl, inoculum size and incubation time. The optimal conditions for higher production of pectinase were carrot peels powder 6.5 %, NH4Cl 0.3 %, inoculum level 3 % and cultivation time 32 h. Under these conditions, the pectinase experimental yield (64.8 U/ml) closely matched the yield predicted by the statistical model (63.55 U/ml) with R (2) = 0.963. The best pectinase activity was observed at the temperature of 60 °C and at pH 8.0. The enzyme retained more than 90 % of its activity after 24 h at pH ranging from 6.0 to 10.0. The enzyme preserved more than 85 % of its initial activity after 60 min of pre-incubation at 30-40 °C and more than 67 % at 50 °C. The extracellular juice of I4 was applied in the process of sesame seeds oil extraction. An improvement of 3 % on the oil yield was obtained. The findings demonstrated that the B. mojavensis I4 has a promising potential for future use in a wide range of industrial and biotechnological applications.

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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.

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