Modification of the Secondary Binding Site of Xylanases Illustrates the Impact of Substrate Selectivity on Bread Making.
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.
Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven , Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
Sofie
S
Leys
Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven , Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
Anneleen
A
Pauly
Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven , Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
Jan A
JA
Delcour
Laboratory of Food Chemistry and Biochemistry & Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven , Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
Christophe M
CM
Courtin
D001412:Bacillus subtilis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D001939:Bread / Q000032:analysis*; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005433:Flour / Q000032:analysis*; D031161:Pseudoalteromonas / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity; D014908:Triticum / Q000737:chemistry
D001426:Bacterial Proteins; D043364:Endo-1,4-beta Xylanases
arabinoxylan; bread making; secondary binding site; substrate selectivity; xylanase