-This work presents a kinetic study of the enzymatic hydrolysis of three cellulosic substrates: filter paper (FP), used as a low recalcitrance substrate model; steam exploded sugarcane bagasse (SB); and weak acid pretreated SB (1:20 dry bagasse:H 2 SO 4 solution 1% w/w), the last two delignified with 4% NaOH (w/w). The influence of substrate concentration was assessed in hydrolysis experiments in a shaker, using Accellerase® 1500, at pH 4.8, in 50 mM sodium citrate buffer. Cellulose loads (weight substrate /weight total ) were changed between 0.5%-13% (for FP) and 0.99%-9.09% (for SB). For FP and low loads of steam exploded SB, it was possible to fit pseudo-homogeneous Michaelis-Menten models (with inhibition). For FP and higher loads of steam exploded SB, modified Michaelis-Menten models were fitted. Besides, it was observed that, after retuning of the model parameters, it is possible to apply a model fitted for one situation to a different case. Chrastil models were also fitted and they were the only feasible approach for the highly recalcitrant acid-treated SB.
Brazil, being one of the main beer producers, generates brewer’s spent grain as a main by-product of this industry, which is mainly composed of cellulose, hemicelluloses, lignin and extractives. The alkaline pretreatment of brewer’s spent grain received from two breweries is studied in this work, namely breweries Imperial (B1) and Colombina (B2). Factorial design (22) was realized with three experiments at the central point: contact time (30, 60, 90 min) and NaOH concentration (4%, 6%, 8%). It was found that the presence of extractives causes interference in the characterization of the material. The delignification process allowed obtaining materials with lower lignin percentages when higher NaOH concentrations were used, reaching percentages of lignin loss with values between 85-95%, in both materials, but for these conditions, the losses of cellulose were considerable – of 35-43%. Enzymatic hydrolysis of the pretreated materials achieved conversions greater than 70%, emphasizing that the greatest conversions were obtained with material B1, where almost the whole cellulose was hydrolyzed.
Lignocellulosic biomass is mainly composed of cellulose, hemicellulose, and lignin. Fuzzy logic, in turn, is a branch of many-valued logic based on the paradigm of inference under vagueness. This paper presents a methodology, based on computational intelligence, for modeling the kinetics of a complex reactional system. The design of a fuzzy interpolator to model cellulose hydrolysis is reported, within the perspective of applying kinetic models in bioreactor engineering. Experimental data for various types of lignocellulosic materials were used to develop the interpolator. New experimental data from the enzymatic hydrolysis of a synthetic substrate, on the other hand, were used to validate the methodology. The accuracy of the results indicates that this is a promising approach to extend the application of models fitted for specific situations to different cases, thus enhancing their generality.
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