Extração e caracterização de xilanas de sabugos de milho

Abstract

Resumo: Neste trabalho, duas frações de xilana, denominadas xilana A e xilana B, foram isoladas a partir de sabugos de milho através de três processos diferentes, combinando métodos de extração aquosa, remoção de lipídeos, deslignificação e extração alcalina. Os produtos obtidos durante os processos foram analisados por termogravimetria. A etapa de deslignificação foi responsável por uma acentuada degradação dos polímeros, evidenciada por queda de rendimento e resistência térmica. Os espectros obtidos no infravermelho evidenciaram a ausência de ácidos urônicos na cadeia polimérica. As viscosidades intrínsecas obtidas para a xilana A (56 mL/g) e xilana B (75 mL/g) associadas aos resultados do infravermelho sugerem um número maior de grupos substituintes, constituídos basicamente por resíduos de L-arabinose, para a xilana B. Xilana, hemicelulose, polissacarídeo, deslignificação. Palavras-chave:

Extraction, Addition and Characterization of Hemicelluloses from Corn Cobs to Development of Paper Properties

“…Hemicelluloses were obtained following methodology described in literature (Silva et al, 1998), with adaptations. The procedure was repeated several times until the obtain desired amounts of hemicelluloses.…”

“…In the specific case of corn cobs, it is considered that the xylans usually present a chemical structure formed by 4-O-methyl-D -glucuronic acid, L-arabinose and D-xylose in the ratio 2:07:19 (Silva et al, 1998). In recent years, evidence has emerged that the arabinoxylans (xylan which has a large number of residues in the side chains of arabinose) contained in the cereal grains are interconnected in cell wall by cross-linking occurring by esterification with the diferulic acid, and/or by formation of complexes with proteins.…”

“…In recent years, evidence has emerged that the arabinoxylans (xylan which has a large number of residues in the side chains of arabinose) contained in the cereal grains are interconnected in cell wall by cross-linking occurring by esterification with the diferulic acid, and/or by formation of complexes with proteins. These structures would be responsible for the difficulty of extraction and purification of xylan and the digestion time cereal grains (Silva et al, 1998). Several studies have been carried out showing the processes of isolation of hemicelluloses (Yllner and Enström, 1956;Yllner and Enström, 1957;Aurell, 1965;Hansson and Hartler, 1969;Henriksson and Gatenholm, 2001;Schönberg et al, 2001;Linder et al, 2003;Danielsson and Lindström, 2005;Danielsson, 2007;Köhnke and Gatenholm, 2007;Köhnke et al, 2008;Muguet et al, 2010;Silva, 2011) and the relationship between the cellulose and hemicellulose levels in paper properties (Schönberg et al, 2001;Danielsson and Lindström, 2005;Köhnke and Gatenholm, 2007;Köhnke et al, 2008;Muguet et al, 2010;Milanez et al, 1982;Molin and Teder, 2002;Anjos et al, 2005;Molina et al, 2008;Manfredi and Oliveira, 2010).…”

Estudo do amido de farinhas comerciais comestíveis

“…O evento de degradação do polissacarídeo ocorre por despolimerização quando a temperatura aplicada excede os 300 °C [31][32][33][34] .…”

Application of cationic hemicelluloses produced from corn husk as polyelectrolytes in sewage treatment

“…Xylans are the principal component of the hemicelluloses and are composed by chains of β-D-xylose branched with oligosaccharides and different carbohydrates such as L-arabinose and uronic acids [4][5][6][7] . The amorphous character and low molecular weight of hemicellulose allow a better accessibility of the polymeric chain and, consequently, lead to better reactivity when compared to other lignocellulosic compounds, such as cellulose.…”