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Dhillon G.S.,University of Quebec | Brar S.K.,University of Quebec | Kaur S.,University of Quebec | Kaur S.,Banaras Hindu University | And 2 more authors.
Biomass and Bioenergy | Year: 2012

Objectives: The potential of lactoserum as a crude inducer and moistening medium for fungal cellulase and hemicellulase induction was tested through solid-state fermentation. Methodology: Solid-state fermentation was conducted in Erlenmeyer flasks and plastic trays using apple pomace (AP) as solid substrate by Aspergillus niger NRRL 567 and A. niger NRRL 2001. Results: Solid-state tray fermentation resulted in cellulase activities (IU g -1 dry weight basis) of 383.7 ± 17.9, 425.3 ± 21.3, 336.1 ± 16.2 and 4868 ± 39.8, respectively for FPase (filter paper cellulase), CMCase (carboxymethyl cellulase), BGL (β-glucosidase) and xylanase using A. niger NRRL 567. Similarly, A. niger NRRL 2001 resulted in enzyme activities (IU g -1) of 401 ± 23.8, 544.7 ± 24.5, 285.4 ± 11.7 and 4580.7 ± 34.5, respectively for FPase, CMCase, BGL and xylanase. The enzyme loading of FPase 50 IU g -1 substrate in the hydrolysis of AP resulted in (g kg -1): 509.3 ± 22.9 total sugar (48 h), 109.3 ± 5.7 reducing sugar (48 h), 16.1 ± 0.8 glucose (60 h) and 10.4 ± 2.0 xylose, respectively whereas hydrolysis of BSG resulted in (g kg -1): 375.7 ± 16.2 total sugars (36 h), 114.6 ± 4.0 reducing sugar (60 h), 18.1 ± 0.9 glucose (60 h) and 19.8 ± 2.0 xylose (48 h), respectively. Conclusions: This study demonstrated the potential of SSF as a simple and cheap technology for higher cellulase and hemicellulase production using negative cost AP waste which could eventually help to utilize abundant lignocellulosic biomass for production of biofuels and other value-added products. © 2012 Elsevier Ltd.

Hajlaoui H.,Institute National Of Recherche En Genie Rural | Ayeb N.E.,University of Monastir | Garrec J.P.,French National Institute for Agricultural Research | Denden M.,Institute Superieur Agronomique Of Chott Mariem
Industrial Crops and Products | Year: 2010

The comparative effects of salt stress on osmotic adjustment and solutes accumulation in relation to root-leaf tissue senescence of two silage maize varieties were examined. Studies were carried out with seedlings of two forage maize varieties (Aristo and Arper) subjected to 0, 34, 68 and 102 mM NaCl for 6 weeks under glasshouse conditions. Osmotic potential (OP), osmotic adjustment (OA) and solutes accumulation were quantified in primary roots and in three leaf stages (young, mature and senescent leaves). Moreover, in order to assess the distribution of proline and glycine betaine during root development, the two components were analyzed at different position from the primary root apex of both varieties. The total dry matter was significantly dropped with increasing salinity and reduction was greater in Aristo than in Arper. Salt stress impact in terms of ionic status was more pronounced in roots than in leaves and in older leaves than younger ones. In this setting, Aristo displayed a more sensitivity than Arper. A close relationship between the age of root-leaf tissue and proline and glycine betaine allocation, as salinity response, was shown. During the stress treatment, the accumulation of the two components was higher in growing regions of roots and in young leaves. While total free amino acids (FAA) and sugars were accumulated in roots as well as leaves but preferentially in the mature leaves. The capacity of OA was greater in young than in mature and/or senescent leaves and the contribution efficiency of organic solutes to this occurrence tended to be higher in Arper than in Aristo. Moreover, glycine betaine and proline appeared to be the main solutes that contributed ably to OA mainly in growing regions followed by sugars and other FAA. Inorganic solutes (K+ and Ca2+), however, did not seem to play an important role in OA since their amounts were often reduced in response to salt tolerance. © 2009 Elsevier B.V. All rights reserved.

Sdiri S.,Instituto Valenciano Of Investigaciones Agrarias | Navarro P.,Instituto Valenciano Of Investigaciones Agrarias | Monterde A.,Instituto Valenciano Of Investigaciones Agrarias | Benabda J.,Institute Superieur Agronomique Of Chott Mariem | Salvador A.,Instituto Valenciano Of Investigaciones Agrarias
Postharvest Biology and Technology | Year: 2012

In the Mediterranean area, early-season citrus fruit reach acceptable internal maturity standards for marketing, while the fruit are still green. A degreening treatment is widely used as a postharvest practice to improve the external color. Nevertheless, the application of ethylene during this treatment can be associated with calyx senescence. The aim of this study was to evaluate new degreening treatments in order to reduce this disorder. 'Clemenules' mandarins and 'Navelina' oranges, harvested at different external colors, were submitted to different degreening treatments, combining periods with and without ethylene exposure. In both cultivars, the periods without ethylene exposure during degreening reduced the incidence of calyx disorders. To obtain a typical 'Clemenules' variety color with the lowest incidence of calyx alteration, the optimum degreening treatment was based on 72 h with ethylene and 48 h without ethylene when fruit were harvested with a color index of between -9 and -3. On the other hand, a treatment of 24 h with ethylene plus 48 h without ethylene is recommended for fruit with an external color index higher than -2. For 'Navelina' oranges, highly sensitive to calyx senescence during degreening, a treatment consisting of 24 h with ethylene plus 48 h without ethylene is recommended, which involves harvesting the fruit with a color index of over 0. © 2011 Elsevier B.V..

Hichem H.,Institute National Of Recherche En Genie Rural | El Naceur A.,University of Monastir | Mounir D.,Institute Superieur Agronomique Of Chott Mariem
Photosynthetica | Year: 2010

The effect of four different NaCl concentrations (from 0 to 102 mM NaCl) on seedlings leaves of two corn (Zea mays L.) varieties (Aristo and Arper) was investigated through chlorophyll (Chl) a fluorescence parameters, photosynthesis, stomatal conductance, photosynthetic pigments concentration, tissue hydration and ionic accumulation. Salinity treatments showed a decrease in maximal efficiency of PSII photochemistry (F v/F m) in dark-adapted leaves. Moreover, the actual PSII efficiency (φ PSII), photochemical quenching coefficient (q p), proportion of PSII centers effectively reoxidized, and the fraction of light used in PSII photochemistry (%P) were also dropped with increasing salinity in light-adapted leaves. Reductions in these parameters were greater in Aristo than in Arper. The tissue hydration decreased in salt-treated leaves as did the photosynthesis, stomatal conductance (g s) and photosynthetic pigments concentration essentially at 68 and 102 mM NaCl. In both varieties the reduction of photosynthesis was mainly due to stomatal closure and partially to PSII photoinhibition. The differences between the two varieties indicate that Aristo was more susceptible to salt-stress damage than Arper which revealed a moderate regulation of the leaf ionic accumulation. © Springer Science+Business Media B.V. 2010.

Ben Chaaban S.,Institute Superieur Agronomique Of Chott Mariem | Chermiti B.,Institute Superieur Agronomique Of Chott Mariem | Kreiter S.,Montpellier SupAgro
Bulletin of Insectology | Year: 2011

The old world date mite Oligonychus afrasiaticus (McGregor) (Prostigmata Tetranychidae) is an important spider mite pest of the date palms Phoenix dactylifera L. in most of North Africa and the Middle East. This study was conducted between 2004 and 2006 in an orchard of date palm trees located in southwest Tunisia. The objective of this study was the inventory of mites that revolve around the date palm, to quantify abundance of O. afrasiaticus in trees over different types of ground cover and to document its dispersal. The starting of O. afrasiaticus infestation on fruits varied between years, ranging from the first to the third week of July. Mite populations on pinnae remained low from May through December, not exceeding two mites per pinnae, whereas on fruit they reached peak populations of approximately 14 motile forms of mite per fruit in 2006. Indigenous phytoseiid were not found on fruits between mid-Julys till the end of August, when pest populations peaked. Plants such as Sorghum bicolor (L.) Moench, Solanum melongena L., and Cucumis melo L. contained densities of O. afrasiaticus during early spring, and may have formed the source for later date palm infestation. Fruit bunch infestation was not prevented or even alleviated by glue barriers so infestation of date palm by O. afrasiaticus may occur via aerial dispersal of motile forms. In ground cover phytoseiid and tetranychid mites were scarce, two of tetranychid species are new to science were founded.

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