The enzymatic degradation of xylans is the most versatile way to obtain the high value-added functional compounds or the fermentable sugars for renewable energy. The endo-β-xylanases are the major enzymes which hydrolyze the internal β-1,4-linkages of xylan backbones to produce the mixtures of xylooligosaccharides including xylobiose and xylotriose. Among them, glucuronoxylanase GH30 can exclusively hydrolyze the internal β-1,4-linkages of xylans decorated with methylglucuronic acid branches.

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... the present study, two xylanolytic enzyme (PaXN_10 and PaGuXN_30) genes were cloned from Paenibacillus amylolyticus KCTC 3005, and expressed in Escherichia coli, respectively. PaXN_10 (38.7 kDa) belongs to the endo-β-xylanase GH10 family, while PaGuXN_30 (58.5 kDa) is a member of glucuronoxylanase GH30. They share the same optimal reaction conditions at 50°C and pH 7.0. Enzymatic characterization proposed that P. amylolyticus can utilize the hardwood glucuronoarabinoxylans via the cooperative actions of xylanases GH10 and GH30. The extracellular PaGuXN_30 is secreted into the medium and hydrolyzes glucuronoarabinoxylans to release a series of aldouronic acid mixtures with a methylglucuronic acid branch. The resultant products being transported into the microbial cell are successively degraded into the smaller xylooligosaccharides by the intracellular PaXN_10, which will be utilized for the cellular metabolism.