Application of Factorial Design to the Study of Xylitol Production from Eucalyptus Hemicellulosic Hydrolysate

Abstract

This study deals with the bioconversion of xylose into xylitol by Candida guilliermondii FTI 20037 using eucalyptus hemicellulosic hydrolysate obtained by acid hydrolysis. The influence of various parameters (ammonium sulfate, rice bran, pH, and xylose concentration) on the production of xylitol was evaluated. The experiments were based on multivariate statistical concepts, with the application of factorial design techniques to identify the most important variables in the process. The levels of these variables were quantified by the response surface methodology, which permitted the establishment of a significant mathematical model with a coefficient determination of R2 = 0.92. The best results (xylitol = 10.0 g/L, yield factor = 0.2 g/g, and productivity = 0.1 g/[L x h]) were attained with hydrolysate containing ammonium sulfate (1.1 g/L), rice bran (5.0 g/L), and xylose (initial concentration of 60.0 g/L), after 72 h of fermentation. The pH of fermentation was adjusted to 8.0 and the inoculum level utilized was 3 g/L.

Xylitol production from wheat straw hemicellulosic hydrolysate: hydrolysate detoxification and carbon source used for inoculum preparation

“…At the same time, they were higher than those observed in eucalyptus hydrolysates (3,17) and in an immobilized cell system (6). It is difficult to compare the results obtained by different researchers since many variables influence the xylose-to-xylitol bioconversion in hemicellulosic hydrolysates.…”

Evaluation of nutrient supplementation to charcoal-treated and untreated rice straw hydrolysate for xylitol production by Candida guilliermondii

“…yeast extract and peptone) and various minerals have been used to supplement xylose culture media for xylitol production by yeasts (Azuma et al, 2000;Walter et al, 2001;Canettieri et al, 2001). However, when hemicellulose hydrolysates are used as culture media, the need for supplementation should be minimised, since they contain not only fermentable sugars, but also compounds that are essential for cell growth (Preziosi-Belloy et al, 2000;Canettieri et al, 2001). Considering that the cost of the culture medium is a decisive factor in determining the economic viability of the bioconversion process, it is very important to define the minimal nutrient requirements for the hydrolysate bioconversion.…”

Avaliação da casca de aveia para produção biotecnológica de xilitol

“…A xilose utilizada na produção biotecnológica de xilitol é proveniente de hidrolisados hemicelulósicos obtidos de resíduos agroindustriais tais como bagaço de cana-deaçúcar (Dominguez et al, 1996;Felipe et al, 1997a e b;Alves et al, 1998;Verde, 2001;Marton, 2002;Rodrigues et al, 2003), cavacos de eucalipto (Parajó et al, 1998;Canettieri et al, 2003), palha de arroz (Mussatto e Roberto 2002) e palha de trigo (Canilha, 2001).…”

“…Hidrólise ácida da casca de aveia. A casca de aveia foi hidrolisada em reator de aço inoxidável com capacidade de 1,5 L nas seguintes condições: temperatura 156ºC; H 2 SO 4 0,35% (m/v); relação sólido: diluição ácida (1: 4,5) por 27 minutos (Canettieri et al, 2001). Tratamento do hidrolisado hemicelulósico de casca de aveia.…”