(411f) Optimization of Dilute Acid and Liquid Hot Water Pretreatment of Plantain Rachis for Monomeric Sugars Production

Optimization of Dilute Acid and Liquid Hot Water pretreatment of Plantain Rachis for Monomeric Sugars Production

Torres-Conde, A. , Universidad Nacional de Colombia – Sede Medellín. Facultad de minas

Ruiz-Colorado, A. , Universidad Nacional de Colombia – Sede Medellín. Facultad de minas

Garzón, L. , Instituto Colombiano del Petróleo (ICP)

Keywords: Monomeric sugars, hydrolysis, pretreatment, plantain.

Plantain rachis is an agricultural waste that represents an abundant cellulosic material and it has potential as a feedstock for producing cellulosic biofuels. Efficient conversion of lignocellulosic biomass into monomeric sugars requires particle size reduction, pretreatment, and enzymatic hydrolysis. Liquid hot water (LHW) and dilute acid (DA) pretreatments allow a selective solubility of hemicellulose that improves the accessibility of enzymes that hydrolyze cellulose. We present the optimization conditions of LHW pretreatment for temperatures between 170 and 200 °C, at times between 15 and 25 min and solids loading of 7 and 17% dry matter (w/w), optimal conditions of DA pretreatment are temperatures between 160 and 200 °C, at times of 5 and 10 min and H₂SO₄concentrations of 1 and 2% (w/w). The chosen design was a response surface - central composite design unblocked with 20 experiments including 6 repetitions at central point conditions for both pretreatments.

Chemical composition of pretreated and unpretreated plantain rachis was obtained following National Renewable Energy (NREL) Laboratory Analytical Procedures (LAPs). Unpretreated biomass was milled to pass through 20 mesh, moisture and ash content were measured, and a two-step (water-ethanol) extraction was done to remove soluble nonstructural components. Pretreated samples were subjected to the same analysis without taking into account the extraction step.

Saccharification (SAC) reactions was held for 72 hours and stirred (150 rpm) in 250 mL flasks at a pretreated unwashed solid loading of 10% dry matter(w/w), 0.05 M Na-citrate (pH 4.8) and cellulase dose of 66.07 FPU/g cellulose to bring the reactive volume to 100ml.  

Regarding LHW, the highest saccharification yields of 0.2807 g glucose/g initial biomass were obtained at 200 °C, 40 min and a solid loading of 16% dry matter (w/w), while the best condition through using DA for yield 0.2532 g glucose/g initial biomass was 200 °C, 8 min and H₂SO₄concentrations of 2.34% (w/w).

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