Stepwise Extraction of Hemicelluloses with Water and Alkali from Larch Wood and their Sugar Compositions

The aim of the present study was to isolate hemicelluloses by stepwise extraction with water and alkali from larch (Larix principis-rupprechtii Mayr) sapwood and heartwood. One water-soluble arabinogalactan (AG) and three alkali-soluble hemicelluloses- arabinoglucuronoxylan (AGX), galactoglucomannan (GGM) and glucomannan (GM) were obtained. The yield of AG extracted with hot-water from larch heartwood was 7.57%, it was 17.96% in total of three alkali-extracted hemicelluloses. There was no significant difference in the yield of hemicelluloses from sapwood and heartwood. Monosaccharide compositions of the hemicelluloses were determined by high performance liquid chromatography after acid hydrolysis. The results showed that galactose and mannose were the main glycosyl units of hemicellulose, followed by xylose. Galactose mainly derived from AG, whereas mannose and xylose originated from alkali-extracted hemicelluloses.

Yeast cultivation for single-cell protein production using the carbohydrate hydrolysate of steam-exploded eucalyptus wood

This study was aimed at producing single-cell (SCP) protein from the carbohydrate hydrolysate of steam-exploded eucalyptus (Eucalyptus urophylla) wood. Two yeast strains including Saccharomyces cerevisiae and Candida utilis 2.587 were used for batch fermentation. Results showed that the total reducing sugars (TRS), glucose and xylose in hydrolysate had concentrations of 17.52, 10.71, and 4.30 g•L-1, respectively. During fermentation, yeast strains of S. cerevisiae and C. utilis 2.587 used monosaccharides sequentially, and secondary growth occurred. The yeast biomass contained 43.59% crude protein and was rich in all essential amino acids such as lysine, leucine, and valine. Total amino acid reached 401.45 g•kg-1, and corresponded with the standard recommended by the Food and Agriculture Organization of the United Nations for amino acids, except sulfur-containing amino acids.