Agave americana L. morphological and biochemical characterization in Kasserine, Tunisia
par afef tlili
Université de Sousse, Tunisie - ingénieur national agronome 2007
Agave americana L. morphological and biochemical characterization in Kasserine, Tunisia.
Laboratoire de chimie, Institut supérieur agronomique de Chott-Mariem,
Université de Sousse, Tunisie.
Trying to value this newly introduced fauna in Tunisia, the Agave americana's natural resources were studied in the area of kasserine. The measures on young and aged samples has shown that the Agave is a huge specie (maximum length: 217 cm, maximum thickness: 308.2 cm; maximum weight: 1968 g). Its morphological criteria do increase by aging.
The biochemical criteria were proven only on aged subjects, the potential reliable industry. Throw a comparison established with Alfa (Stipa tenaicissima L. (, the referential specie in Tunisia which is qualified with its availability and strong potentials, it was shown the higher brut cellulose concentration in the Agave leaf (53.54%). The bottom segment, which is more efficient for industrial use, contains 71.66% of brut cellulose. The Agave leaf contains fewer mineral ashes (0.46%), more humidity (79.38%) and has a pH 5.34, less acid than Alfa leaf.
Keywords: Agave americana L.; kasserine; Tunisia; fibers; cellulose; mineral ashes.
release on lignocellulosic fibers extracted from several species. In Tunisia, the major available source of fibers is Alfa grass. However, its national productions are decreasing; the Alfa grassland slicks show a severe degradation by nearly 1500ha/year (Ksontini et al., 1998). This drop is due to the ecological and environmental perturbations, the Industrial overexploitation and its hard regeneration.
The literature is very poor concerning the structural aspect of Agave americana L. and its suitability to several uses. Information about its chemical composition is also irrelevant.
In this present task, we first analysed the morphologic aspects of Agave. Second, we chemically evaluated it.
The study was conduced in two localities in the area ok Kasserine, the west center of Tunisia. They are continental sites where the climate is Mediterranean superior arid with hot summers, mild winters and a dry season longer than 3 months.; the soil is salty and a bit developed; it's 400m to 600m altitude, has a heavy slot and 300 to 400 mm annual raining and an average temperature between 15 and 17°c. Climatological data were supplied by national institute of meteorology.
They both have the same vegetation, a steppe dominated by Stipa tenaicissima with small shrubs and herbs.
The changing competitive economic and tech- nologic growth inspires the agronomy a new push. Its time for research and valorisation of existing fauna formerly unexploited. So, came out the national and international interest accorded to Agave americana; a specie for so long given up and depreciated in order to profit its ecologic, agronomic and either economic performances. The curiosity towards Agave was ori-ginnally based on the surprising adaptability of Agave to both of climatic and cultural requi-rements(Chaieb and Boukhris, 1998) and its easy dissemination (Bertrand,1959).This fauna was introduced from subtropical climates (Lock, 1962) and since belongs to national vegetal patrimony (Cuénod, 1954).
Nevertheless, the best use of Agave is con-fronted by the deficiency of its morphologic identity and specific physiologic proprieties on national scale. This can be a handicap towards its rational and efficient exploitation. So many uses of Agave on industrial scale are so far recognised which inspires a consideration and a rediscover of this resource in order to intensify the possible profits.
Because of the abundance of cellulosed fibers in its tissues (Msahli, 2002), we seek to introduce Agave in industrial use especially if we consider the productions
rarety of cellulose fauna and the fact of that many
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In order to specify the Agave, we use young and aged samples collected from several field sites in Kasserine. The choice of samples is random in order to represent the specie. Also, several morphologic criteria must be respected as the homogeneity, the parasitic and morphologic anomaly indemnity. We take measures of young and aged leaves taken from each sample.
The cutting is specific; we must preserve young samples and at least 20 leaves in each stem. Each leaf is then cut in 3 parts and so we distinguish the basal segment; the thickest one by nearly 54cm; the medium segment which is about 40 cm and the top one with about 88cm.
The studied parameters are the length (total, partial and maximum); the thickness (top and basic) and the weight. After measures, an average is taken for each parameter.
We studied dryness D(%); profitableness P(%); humidity H(%) by introducing the samples 3 hours in steamroom 105°heat. D(%)=(Wf*100)/Wd; P(%)=W*D(%); H(%)=(Wf-Wd)*100/Wf.
Mineral ashes content A(%) is obtained by severe calcination after introducing dry samples 1 h in mitten oven 800#177;25°c. A(%)=(W2*100)/W1*D(%) (Wf: fresh weight; Wd: dry weight; W2: final weight; W1: primary weight).
pH is revealed by putting a 4g sample in 100ml of distilled water within 3 days while the osmotic exchange happens.
In order to specify the raw cellulose amount; we used two protocols. The NaOH method consists on introducing each 1g sample is 5cm length in 300 ml of concentrated soda NaOH 33% in 46h. Then a 30 mn of boiling are required. We wash with hot water and filter, the sample must be hold in the contains. We neutralise soda with 100ml of acetic acid 20%. After 5mn of reaction, we filter and we get back the filter paper that we put in the steamroom in 105°c. A constant weight is to get after 2h. In the alcohol protocol, we put each sample in absolute ethanol 95%. We put the test tubes in Mary bath 100°c. 7h later, we pour out the alcohol and with micropipettes, we add 6ml of pure nitric acid 65%; 2ml apart. After a reaction time, we filter and get back the filter paper that we put 2h in the steamroom 105°c. The raw cellulose rate is C (%) = (W2-W1)*100/W1.