Extraction, variability, enzymatic biosoftening and evaluation of physico-mechanical properties of Agave americana L. Fibre

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Mafaesa, Manonyane Albertina M.
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University of the Free State
Unconventional natural textile fibre and enzymatic biotechnologies have positive eco-socio-economic impacts. They are increasingly demanded to substitute the conventional natural and petroleum-based synthetic fibres. The Agave americana L fibre is considered as a potential alternative to synthetic fibres. It is a natural, local, long, strong, absorbent, organic, renewable, eco-sustainable and prospective lignocellulosic fibre which is negligible, understudied and underutilised in textiles. This is due to its high lignin content that causes high fibre coarseness, stiffness and less cohesiveness; the properties which make it difficult to spin into a textile yarn. The overall aim of this research study was to extract the Agave americana L. fibre with a triangulation water retting, investigate the inter-intra-plant fibre variability, enzymatic biosoftening and the physico-mechanical textile properties of Agave americana L. fibre. Agave americana L. leaves were hand-harvested, ribbon stripped and water retted in closed drums to conduct triangulation water retting. The retted fibre was then manually separated from the pithy leaf biomass, washed and dried. The enzymatic biosoftening of the fibre was conducted with individual and sequential methods through biodelignification with MnP, bioscouring with pectinase, bio bleaching with xylanase and biopolishing with cellulase. The physico-mechanical properties and variability of the raw and enzyme-biosoftened fibre were appraised through visual-hand and instrumental evaluation methods. The triangulation water retting was found highly effective, ecologically sustainable and produced good quality fibre at a comparable time for other plant fibres retted with other eco-friendly methods. Microscopic cross-sectional views revealed that the raw Agave americana L. fibre is an irregular, compact, multi-cellular, thick composite consists of overlapping ultimate fibres which have large, diverse and polygonal central lumens. The composite is embedded in the natural cementing extracellular fibre components; mainly lignin, hemicellulose pectin and waxes. The enzymatic biosoftened fibre appeared as a flat multi-cellular composite with lumens smaller than those of raw fibre. The longitudinal SEM images show that the raw fibre is an elongated dimensionally varied, compact, rigid, rough-surfaced multi-cellular composite entrenched with impurities and middle lamellae residues. The enzymatic biosoftening processes have eliminated surface impurities and most of the noncellulosic fibre components. This elimination caused apparent fibre morphological surface smoothness with less irregular cell wall features than the raw Agave americana L. fibre. The structural fibre defibrillation was found subsequent to surface cleanliness and it intensified with the type and number of sequential enzymatic biosoftening processes applied. Thus, sequential manganese peroxidase, pectinase, xylanase and cellulase biosoftened fibre experienced the highest biosoftening smoothness and structural defibrillation. The fibre enzymatic biosoftening efficacy was designated by weight loss percentage. The weight loss percentage ranged from 6.2 % to 24 %. The fibre tensile maximum load ranged from 4.64-22.61 N, displacement from 20.12-50.40 mm and initial Young's modulus; from 0-598.3 MPa. The stress-strain curve showed typical viscoelastic behaviour of a brittle fibre with apparent intra-and-inter plant fibre variability. The fibre showed the bending length ranges from 5.6 to 7.4 cm, out of 8cm. The most improved Agave americana L. fibre physical properties were observed from the sequential biosoftening processes. The variability and stress-strain behaviour of Agave americana L. fibre are analogous to those of other lignocellulosic fibres. The enzymatic biosoftening of the local Agave americana L. fibre increases its serviceable efficacy without polluting the environment and endangering bioreserves. The Agave americana L. fibre is a sustainable potential textile fibre because it possesses satisfactory textile mechanical properties and the physical properties which have textile fibre draw-backs which can be improved by eco-friendly enzymatic biosoftening processes to upgrade its textile performance quality and appearance. The Agave americana L. fibre‘s potential textile alternative to synthetic fibres could preserve both synthetic and conventional natural fibre resources.
Thesis (Ph.D. (Consumer Science))--University of the Free State, 2020, Agave americana L. plant and fibre, Biodelignification, Bioscouring, Biobleaching, Biopolishing, Enzymatic biosoftening, Fibre extraction, Lignocellulolytic enzymes, Lignocellulosic fibre, Triangulation water retting, Physico-mechanical properties, Fibre variability