Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Physical Sciences, Agriculture, Multidisciplinary, Chemistry, Applied, Food Science & Technology, Agriculture, Chemistry, xylanase, arabinoxylan, bread making, substrate selectivity, secondary binding site, WATER-UNEXTRACTABLE ARABINOXYLAN, WHEAT-FLOUR BREADMAKING, NONSTARCH POLYSACCHARIDES, GLYCOSIDE HYDROLASE, ACTIVE-SITE, INHIBITION SENSITIVITY, LIQUID-CHROMATOGRAPHY, ENDOXYLANASES, FUNCTIONALITY, PENTOSANS, Bacillus subtilis, Bacterial Proteins, Binding Sites, Bread, Endo-1,4-beta Xylanases, Flour, Pseudoalteromonas, Substrate Specificity, Triticum, 03 Chemical Sciences, 07 Agricultural and Veterinary Sciences, 09 Engineering, Food Science, 30 Agricultural, veterinary and food sciences, 34 Chemical sciences, 40 Engineering

Abstract:

To investigate the importance of substrate selectivity for xylanase functionality in bread making, the secondary binding site (SBS) of xylanases from Bacillus subtilis (XBS) and Pseudoalteromonas haloplanktis was modified. This resulted in two xylanases with increased relative activity toward water-unextractable wheat arabinoxylan (WU-AX) compared to water-extractable wheat arabinoxylan, i.e., an increased substrate selectivity, without changing other biochemical properties. Addition of both modified xylanases in bread making resulted in increased loaf volumes compared to the wild types when using weak flour. Moreover, maximal volume increase was reached at a lower dosage of the mutant compared to wild-type XBS. The modified xylanases were able to solubilize more WU-AX and decreased the average degree of polymerization of soluble arabinoxylan in dough more during fermentation. This possibly allowed for additional water release, which might be responsible for increased loaf volumes. Altered SBS functionality and, as a result, enhanced substrate selectivity most probably caused these differences.