Synergistic production of l-arabinose from arabinan by the combined use of thermostable endo- and exo-arabinanases from Caldicellulosiruptor saccharolyticus

The optimum conditions for the production of l-arabinose from debranched arabinan were determined to be pH 6.5, 75 °C, 20 g l−1 debranched arabinan, 42 U ml−1 endo-1,5-α-l-arabinanase, and 14 U ml−1 α-l-arabinofuranosidase from Caldicellulosiruptor saccharolyticus and the conditions for sugar beet arabinan were pH 6.0, 75 °C, 20 g l−1 sugar beet arabinan, 3 U ml−1 endo-1,5-α-l-arabinanase, and 24 U ml−1 α-l-arabinofuranosidase. Under the optimum conditions, 16 g l−1l-arabinose was obtained from 20 g l−1 debranched arabinan or sugar beet arabinan after 120 min, with a hydrolysis yield of 80% and a productivity of 8 g l−1 h−1. This is the first reported trial for the production of l-arabinose from the hemicellulose arabinan by the combined use of endo- and exo-arabinanases.