An Acid-Adapted Endo-[alpha]-1,5-l-arabinanase for Pectin Releasing

An arabinanase gene was cloned by overlap-PCR from Penicillium sp. Y702 and expressed in Pichia pastoris. The recombinant enzyme was named AbnC702 with 20 U/mg of endo-arabinanase activity toward linear [alpha]-1,5-l-arabinan. The optimal pH and temperature of AbnC702 were 5.0 and 50 °C, respectively. The recombinant AbnC702 was highly stable at pH 5.0-7.0 and 50 °C. It could retain about 72.3 % of maximum specific activity at pH 5.0 after incubation for 2.5 h, which indicated AbnC702 was an acid-adapted enzyme. The K m and V max values were 24.8±4.7 mg/ml and 88.5±5.6 U/mg, respectively. A three-dimensional structure of AbnC702 was made by homology modeling, and the counting of acidic/basic amino residues within the region of 10 Å around the active site, as well the hydrogen bonds within the area of 5 Å around the active site, might theoretically interpret the acid adaptability of AbnC702. Analysis of hydrolysis products by thin layer chromatography (TLC) combined with high-performance liquid chromatography (HPLC) verified that the recombinant AbnC702 was an endo-1,5-[alpha]-l-arabinanase, which yielded arabinobiose and arabinotriose as major products. AbnC702 was applied in pectin extraction from apple pomace with synergistic action of [alpha]-L-arabinofuranosidase.