Retention and Structure of Xylans fromEucalyptus GlobulusGenotypes with Different Pulpwood Characteristics

In this work, six different genotypes of Eucalyptus globulus were selected on the basis of their differences in wood density and pulp yield. The trees were separated into two groups of three genotypes each: group I (samples Eg1, Eg2, and Eg3) presented wood density values of 547–573 kg/m3 and pulp yields of 52.7–54.6%; group II (samples Eg4, Eg5, and Eg6) presented wood density of 471–485 kg/m3 and pulp yields of 49.8–52.3%. Chemical characterization showed that genotypes of group I also presented high glucose and low lignin content as compared with genotypes from group II. Xylans content was lower in samples of group I than group II. Kraft pulps from group I presented high retention of xylans in comparison with pulps from group II. This behavior was associated with a high degree of substitution (DS) of the xylose units with methylglucuronic acids in wood and in kraft pulps in samples of group I compared with group II. Xylans isolated from wood samples of group I also presented slightly higher molar mass than xylans from group II. Results showed that xylans from a single species presented differences in their retention and structure that affected the pulp yield of E. globulus.