Improvement of the Characteristics of Steamed Bread by Supplementation of Recombinant alpha-L-arabinofuranosidase Containing xylan-binding domain

Abstract

ABSTRACTCurrent study investigated the potential to increase the activity of α-L-arabinofuranosidase (TmAra) from Thermotoga marotima on insoluble arabinoxylan (IAX) through fusion to a family 6 xylan-binding domain (CtXBD6) from Clostridium thermocellum. CtXBD6 was fused to the carboxyl terminus of TmAra, and active forms of both TmAra and TmAraCtXBD6 were produced in E. coli and purified to homogeneity for biochemical characterization. TmAraCtXBD6 had similar temperature and pH profiles to TmAra with a decrease in the thermostability and pH stability at pH 7.0–8.2. It exhibited stronger IAX-binding and hydrolytic activity than TmAra. TmAra and TmAraCtXBD6-treated IAX were added to wheat flour to investigate the rheological and textural properties of the finished product. IAX alone had significant increase in dough development time (DDT) and dough stability (DS) and decrease in the softening degree (SD), crumb firmness (CF) and specific volume (SV). On adding TmAra and TmAraCtXBD6 to treat IAX texture, SV and DS improved but decreased DDT, SD, and CF. TmAraCtXBD6 reduced CF and increased SV, and had higher springiness, cohesiveness, and crumb chewiness than TmAra. These results demonstrated that the fusion of CtXBD6 into arabinofuranosidase enables the increase in catalytic performance on insoluble AX substrates, which can be used as more efficient biocatalysts that can improve the quality of AX-rich products.