Memoire Online - Agave americana L. morphological and biochemical characterization in Kasserine, Tunisia

Agave americana L. morphological and biochemical characterization in Kasserine, Tunisia.

Abstract

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.

1- Introduction

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.

2- Material and methods

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

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.

3-Results and discussion

For aged samples, the total length shows an average of 167.5 cm and 56.6 cm respectively for aged and young leaves. This considerable length is proven by Nobel (1976) and Bertrand (1959). For young samples, it is 85.32 cm and 50.2 cm for aged and young leaves. The significant difference is probably due to meristematic activity which is yet not optimum for young samples (Nobel, 1976).

For an aged sample, the basal segment is about 26.69% of the leaf's length; 44.71cm high from the bottom bow. The medium part is about 23.62% and

measures 39.57 cm. The apical segment is about 43.35% and measures 72.62 cm. for a young sample, the basal part rises 28.9 cm from the bottom which is nearly 51.06% of the leaf, medium part is 30.86% as 17.47 cm while apical part is 18.07% about 10.23 cm. Aged samples can reach 217 cm and young ones 98.17 cm. by aging, this is because of meristematic activity of leaves and the specie's nature; it is succulent, rising and stretch out (Bertrand, 1959). The fibers contained in Agave are long ones and can reach 2mm each (Han and Rowel, 1995).

Table1: Total and maximum average length of Agave americana L. in Kasserine, Tunisia

Sample Length (cm)	Total		Maximum
	Young leaf	Aged leaf	Young leaf	Aged leaf
Young	50.2	85.32
Aged	56.6	167.5	98.17	217

	Top		Medium		Bottom
	Length (cm)	%	Length (cm)	%	Length (cm)	%
Young	10.23	18.07	17.47	30.86	28.9	51.06
Aged	72.62	43.35	39.57	23.62	44.71	26.69

Length (cm)	At bottom row	At the apex
Young sample	30.82	20.85
Aged sample	66.45	32.05

The bottom is much thicker, it's where happens water accumulation as hydro potential low (Down, 1976). The thorn of the apex shows the limited transpiration of this specie so keeps water. The leaf is also highly concentrated in fibers. It's so recommended to use the bottom for any economic and industrial use because of the better efficiency.

The average weight of young samples' leaves is about 1968 g and 974 g respectively for aged and young leaves that rise to 2945 g and 1479 g for aged

samples. Despite the equal age of young leaves extracted from young and aged samples, they don't

have the same weight. This can be explained by the fact of vegetative growth and photosynthetic activity aren't optima for young samples. Their fibers aren't well constructed and concentrated in cellulose. It's more efficient to use aged samples in industries that relies on vegetative biomass.

Data reported on the chemical properties of nonwood fibers and especially Agave americana are few. This data vary greatly, studies have varied in fiber (source, age) growing time and methodology.

The three segments of the leaf show average rates respectively from bottom: 13%; 20.49% and 28.34%. It is a significant criteria to be considered to judge the efficiency of Agave in several uses; especially industrial one. It could have a bad influence on Agave's economic profitableness. In deed, Agave's profitablessness is estimated, for 1 tonne of dry material, by nearly only 206 kg of useful one.

The distinct parts of Agave's leaves show respectively an average of humidity 86.99%; 71.65%; 79.50%. The anatomy of the whole leaf is behind its important amount of water (79.38%). It contains few stomas, is covered by an impermeable wax and has thorn all along its circumference which diminishes transpiration so much. Every possible industrial use requires dehydration, this humidity rate can be a serious handicap but his juicy plant (2.5l) is so useful in human alimentation (tequila drink). Its moistness allows the high populations in arid climate as the field site. So, It gains a tolerance even desert one.

The leaf contains an average of 0.46% of ashes. The contain is for bottom 0.66%, medium part 0.4% and apex 0.34%. Ashes, which are micro and macro-elements, aren't essential components of Agave. This poor proportion is so recommended in industrial uses especially in paper mill.

From bottom to apex, pH is respectively 5.01; 5.05; and 5.96. The leaf's pH is about 5.34. its acidity causes a cutaneous irritation within manipulations. Despite its high sugar concentration (Digest, 1980), it is not recommended in livestock alimentation. Even if it provides alcoholic drinks, its acidity can be harmful for health.

Cellulose rate (%)	Vegetal material	Bottom	Medium	Apex	Leaf
	NaOH method	74.9	57.8	34	55.56
	Alcohol method	68.42	51.15	35	51.52
Average		7.66	54.47	34.5	53.54

The cellulose rate shows a significant difference between the three parts of the leaf. Basal segment is the most concentrated. In deed, it's related to the change of chemical properties associated to fibers number and growth (Han and Rowell, 1997). Polysaccharides synthesis is optimal at bottom; the fiber's growth begins by getting its definitive length then it gets thicker and cellulose charged (Person, 1987). In the industries based on cellulose extracts, it's important to avoid the apex highly lignin concentrated that disturbs.

The average rate 55.56% is considerable and is even higher than other fiber species exploited in industrial uses. From Agave, cellulose pulps can be manufactured safely.

Lock G.W. (1962) thirty years's sisal research in Tanzania Longmans, Breen and Coltd.

Mauset J.D., Kesling R. (1997) comparative anatomy of Neoraimondia roseiflora and Neocardenasia berzogania(Cactaceae) : Haseltonia, vol 5 : 37-50.

Msahli (2002) étude du potentiel textile des fibres d'Agave Americana L., thèse pour l'obtention du titre de Docteur en sciences d'ingénieur an ENSITM.

Nobel (1976) water relations and photosynthesis of a desert CAM plant, Plant physiology. Vol 58: 576-582.

Nobel P.S. (1977) water relations of flowering of Agave desrti. Botanical Gazette, vol 138: 1-6.

Person, C.J.(1987) Agronomy of grass land systems Cambridge University press,169 p.

Pfaffli I, Sisco M.,(1995). fiber Atlas Identification of Papermarketing Fibers. Springer: 290-299.

References

Bertrand A.(1959) plantes grasses autres que les cactées. Deuxième édition revue te corrigée, la maison rustique : librairie Agricole, Horticole, Forestière et Ménagère : 53-60.

Chaieb M. & Boukhris M(1998); flore succincte et illustrées des zones arides et sahariennes de Tunisie.

Cuénod A, Pottie G., Labbe A. .(1954) flore de la Tunisie; cryptogames vasculaires, Gymnospermes et Monocotylédones :234.

Digest R. (1980) savoir tout faire au jardin. Première édition, S.A.216, boulevard Saint Germain, 75007 Paris : 91 ; 442-443 ; 454.

Han J.S. and J.S.Rowell, 1995. chemical composition of fibers, paper and composites from agrobased resources, Rowell, Young, and Rowel , eds, CRC Press, Inc.

Herbert R. (1954) Mathews textile fibers, their physical, microscopy and chemical propreties, 2^nd Ed London: Chapman et Hall, Limited : 360-438.

Lewin , Pearce M. EM (1985) Handbook of fiber science and technology, vol IV, Fiber Chemistry New York