INVESTIGADORES
AREA Maria Cristina
congresos y reuniones científicas
Título:
Physical and chemical characteristics of pretreated pine sawdust and its enzymatic hydrolysis
Autor/es:
KRUYENISKI, J.; FERREIRA, P.J.; CARVALHO, M.G.V.S.; FELISSIA, F. E.; AREA, M. C.
Lugar:
Espoo
Reunión:
Congreso; IX Iberoamerican Conference on Pulp and Paper Research, CIADICYP 2016; 2016
Institución organizadora:
Aalto University, VTT, Åbo Akademi University, RIADICYP, PROVALOR
Resumen:
Pine sawdust, the most abundant and underutilized forest-industrial waste, can be used as raw material in a biorefinery. The process for obtaining ethanol from cellulose in lignocellulosic waste consists of pretreatment, hydrolysis and fermentation. The chemical composition of the substrate and its accessibility (both related to pretreatment) are the most significant factors on enzymatic hydrolysis (EH). The aim of this work was to evaluate the effect of the physical and chemical characteristics of a mixture of Pinus elliottii and Pinus taeda sawdust (forest-industrial residue) subjected to different pretreatments, on its enzymatic digestibility. Eight pretreated materials of various chemical compositions were selected to evaluate crystallinity and porosity. The analyzed samples included the following treatments: (1) initial sawdust (without pretreatment), (2) alkaline desresination followed by steam explosion (SE), (3) SE and subsequent alkaline washing, (4) soda - anthraquinone (AQ)- oxygen treatment, (5) kraft- AQ, (6) soda ?AQ delignification, and  (7, 8) soda ? ethanol (two samples). NREL (National Renewable Energy Laboratory) standards were used for the characterization of the fibrous material and as guide to evaluate enzymatic activity and hydrolysis. Crystallinity of the original and treated residual solids was determined by X-ray diffraction. Distribution of pore volume in the studied materials was evaluated by thermoporosimetry. The enzymatic hydrolysis was performed at 2% consistency, pH 4.8 and 50ºC, with an enzymatic charge of 20 FPU/ g glucan and 40 IU/ g glucan. The reaction was monitored monitored at 24, 48 and 72 h. Lignin content varied between 3.8 to 42.5% od depending on the pretreatment objective. Hydrolysis yield could be improved from 5.4% (exp. 1) to 96-100% (treatments 6 and 5 respectively). Correlation between EH yield and lignin content depends on the process objective (delignification or hemicelluloses extraction). Crystallinity index (CrI, calculated based on Segal equation) rises from 56.4% (without pretreatment) to a maximum of ̴76.0% in materials with low lignin content (< 7% od). CrI increases linearly from 47% to 70% glucan (CrI 56.4% to 76%) and it stabilizes at its maximal value from there to 80% glucan. The evaluation of ΔPore volume/ΔDiameter against ΔDiameter shows a clearly defined mode distribution in the range 0.66 to 1.32nm, demonstrating that the applied treatments made increase the number of pores but not the diameter of pore. The height of the peak increased in the following order of treatments: 1 < 6< 2-3 < 5<< 7-8 << 4, showing that oxygen delignification greatly increases porosity.