Fractionation of sugar beet pulp into pectin, cellulose, and arabinose by arabinases combined with ultrafiltration.

Incubation of beet pulp with two arabinases (alpha-L-arabinofuranosidase and endo-arabinase), used singularly or in combination at different units of activity per gram of beet pulp, caused the hydrolysis of arabinan, which produced a hydrolyzate consisting mainly of arabinose. Pectin and a residue enriched with cellulose were subsequently separated from the incubation mixture. The best enzymatic hydrolysis results were obtained when 100 U/g of beet pulp of each enzyme worked synergistically with yields of 100% arabinose and 91.7% pectin. These yields were higher than those obtained with traditional chemical hydrolysis. The pectin fraction showed a low content of neutral sugar content and the cellulose residue contained only a small amount of pentoses. Semicontinuous hydrolysis with enzyme recycling in an ultrafiltration unit was also carried out to separate arabinose, pectin, and cellulose from beet pulp in 7 cycles of hydrolysis followed by ultrafiltration. The yields of separation were similar to those obtained in batch experiments, with an enzyme consumption reduced by 3.5 times and some significant advantages over batch processes.