Cell wall polysaccharides from woody bamboo shoots of Guadua chacoensis and Phyllostachys aurea

CIANCIA, MARINA; ZELAYA, VICTOR MARTÍN; VEGA, ANDREA S.; FERNADEZ, PAULA VIRGINIA

Moscú

Simposio; XVIII European Carbohydrate Symposium; 2015

Woody bamboos were traditionally exploited to use their culms in housing, furniture, floors, cosmetics, pharmaceuticals, as well as the production of bamboo viscose, paper pulp, charcoal, and derived products from the carbonization process. Young shoots are a food source for humans. As they constitute one of the mostly fast growing natural resources, they have great potential to be used as a valuable feedstock for biorefinery. In the present work, cell wall polysaccharides from shoots of two different species, G. chacoensis, native of South America, and introduced P. aurea, were studied.Sequential extraction of the cell wall polysaccharides, which represent 35 and 32 % of the shoots dry weight, respectively, was carried out with water in the presence of a-amylase, 0.05 M CDTA at pH=6, 0.05 M Na2CO3, and KOH 1M and 4M solutions. Extraction was repeated twice with each solvent, obtaining 10 extracts and a final residue for each species. Extracts were analyzed and their structure investigated by methylation analysis and NMR spectroscopy. For both species, the residue of the extraction procedure was constituted by cellulose as major carbohydrate component.As expected for Gramineae, the most important yields were obtained for extracts rich in hemicelluloses, however, pectins were obtained in significant quantities. Preliminary results show that these fractions were rich in RGI in P. aurea, while in G. chacoensis modified homogalacturonans predominate.For both species, the most important fractions were those obtained with 1M KOH. Structural analysis showed that they were constituted by arabinoxylans, however the degree of ramification was much higher in those from P. aurea (25 and 53 % or the first and second extracts, respectively, while for G. chacoensis, it was 9 and 6 %, respectively). In addition, arabinoxylans from both extracts of P. aurea showed similar quantities of 5-linked and terminal arabinofuranose units. On the other hand, mostly terminal arabinofuranose units were detected in 1M KOH extracts from G. chacoensis, while terminal a-D-galactose and (4-O-methyl)-a-D-glucuronic acid were present in extracts from both species.These results clearly show that although woody bamboo shoots of both species synthesize cell wall polysaccharides with those structures expected for grasses, important structural differences are evident. These differences could determine the possible applications of these row materials, for example, xylooligosaccharide production by enzymatic degradation of arabinoxylans should be easier from Guadua chacoensis than from Phyllostachys aurea.