Changes in the structure and composition of pineapple leaf fiber after alkali and ionic surfactant pretreatments and their impact on enzymatic hydrolysis

Abstract

The current study investigated the effects of two different pretreatments (NaOH and alkaline surfactant assisted) on the chemical, morphological and enzymatic saccharification of pineapple leaf fiber (PALF). Results showed that both pretreatments significantly reduced lignin content of the biomass, achieving a 69.6 and a 76.3% reduction for NaOH and surfactant pretreated materials, respectively. SEM, CLSM and FTIR-ATR techniques were used to evaluate morphological changes in the fibers after pretreatments. Images obtained revealed cellulose exposure and lignin redistribution in the pretreated fibers. Surfactant pretreated material provided the best results after enzymatic hydrolysis compared to NaOH and untreated PALF. A final enzymatic hydrolysis yield of 81.8% was obtained after a 24 h process using surfactant pretreated fibers, in comparison to 75.9 and 45.1% yields for NaOH pretreated material and raw fibers, respectively. Nowadays, the use of agricultural residues for high added value products is of great importance for sustainable development. This work specifically studied an effective and green approach for lignin removal and enzymatic hydrolysis from pineapple leaf fiber that is an abundant waste in Costa Rica and an interesting feedstock for biorefinery processes design.