Evaluation of the activated charcoals and adsorption conditions used in the treatment of sugarcane bagasse hydrolysate for xylitol production

Abstract

-Xylitol has sweetening, anticariogenic and clinical properties that have attracted the attention of the food and pharmaceutical industries. The conversion of sugars from lignocellulosic biomass into xylitol by D-xylose-fermenting yeast represents an alternative to the chemical process for producing this polyol. A good source of D-xylose is sugarcane bagasse, which can be hydrolyzed with dilute acid. However, acetic acid, which is toxic to the yeast, also appears in the hydrolysate, inhibiting microbe metabolism. Xylitol production depends on the initial D-xylose concentration, which can be increased by concentrating the hydrolysate by vacuum evaporation. However, with this procedure the amount of acetic acid is also increased, aggravating the problem of cell inhibition. Hydrolysate treatment with powdered activated charcoal is used to remove or decrease the concentration of this inhibitor, improving xylitol productivity as a consequence. Our work was an attempt to improve the fermentation of Candida guilliermondii yeast in sugarcane bagasse hydrolysate by treating the medium with seven types of commercial powdered activated charcoals (Synth, Carbon Delta A, Carbon Delta G, Carbon 117, Carbon 118L, Carbon 147 and Carvorite), each with its own unique physicochemical properties. Various adsorption conditions were established for the variables temperature, contact time, shaking, pH and charcoal concentration. The experiments were based on multivariate statistical concepts, with the application of fractional factorial design techniques to identify the variables that are important in the process. Subsequently, the levels of these variables were quantified by overlaying the level curves, which permitted the establishment of the best adsorption conditions for attaining high levels of xylitol volumetric productivity and D-xylose-to-xylitol conversion. This procedure consisted in increasing the original pH of the hydrolysate to 7.0 with CaO and reducing it to 5.5 with H 3 PO 4 . Next, the hydrolysate was treated under adsorption conditions employing CDA powdered activated charcoal (1%) for 30 min at 60ºC, 100 rpm and pH 2.5. The optimized xylitol volumetric productivity (0.50 g/L h) corresponded to a D-xyloseto-xylitol conversion of 0.66 g/g.

Valorization of sunflower meal through the production of ethanol from the hemicellulosic fraction

“…The inhibitors concentrations (acetic acid 3.56 g L -1 , furfural 0.03 g L -1 , HMF 0.03 g L -1 and total phenols 0.89 g L -1 ) are within or under the range of values usually found in other sources of hemicellulosic hydrolysates, in general, 1-3.41 g L -1 of acetic acid, 0.04-0.26 g L -1 of furfural, 0.008-1.56 g L -1 of HMF and 2.12-2.23 g L -1 of total phenols (Mussatto & Roberto, 2004;Canilha et al, 2005;Marton et al, 2006;Villarreal et al, 2006;Sene et al, 2011).…”

“…(Marton et al, 2006), rice straw, 18.33 g L -1 (Mussatto & Roberto, 2004) and wheat straw, 19.50 g L -1 (Canilha et al, 2005).…”

Efeito da destoxificação do hidrolisado de bagaço de cana sobre a remoção de fenóis, a perda de açúcares e a bioconversão de xilose em xilitol

“…Os subprodutos gerados durante o processo de hidrólise do bagaço afetam negativamente o metabolismo microbiano, prejudicando a conversão dos açúcares nos produtos de interesse (PALMQVIST; HAHN-HÄGERDAL, 2000;RODRIGUES et al, 200;FELIPE, 200;MARTON et al, 2006). Por outro lado, segundo Matos;, a hidrólise ácida poderá ser vantajosa e minimizar a formação de produtos de degradação, desde que as condições de hidrólise (temperatura, tempo de residência e concentração de ácido) sejam otimizadas.…”

Petroleum Wastewater Purification by Biomass Adsorption: Dynamics and Performance of a Fixed Bed Column

“…Applied as one of the final stages, it reduces significantly the concentration of many pollutants. In recent years, it has been applied increasingly to large-scale separations (Marcussen 1982;Moon and Lee 1984;Gutsche and Hartmann 1996;Wolborska and Pustelnik 1996).…”