A small change to a baking enzyme helped bread rise more and stay softer during storage in laboratory tests. The work focused on xylanase, an enzyme that modifies components of wheat flour, and on a natural obstacle to its activity: an inhibitor already present in the grain.
Researchers led by Dong Zhang and colleagues at Jiangnan University reported the findings in a 2023 study in Foods. Their modified enzyme, AusMPKK, produced a larger increase in loaf volume than its parent enzyme at a lower dose measured in activity units.
Why change a bread-making enzyme?
Flour contains arabinoxylans, carbohydrates that bind water and influence dough structure. Their effects depend on properties such as solubility and chain length. They are not simply unwanted ingredients: some forms can support bread quality, while others interfere with the development of the dough network.
Xylanases cut bonds in the arabinoxylan backbone, changing how these carbohydrates behave. However, wheat also contains proteins that inhibit certain xylanases. Adding more enzyme may therefore give diminishing returns if the flour limits its activity.
The team worked with AusM, an already engineered xylanase derived from an Aspergillus usamii enzyme. They used structural modelling and sequence comparisons to identify changes intended to reduce its sensitivity to the wheat inhibitor SyXIP-I. The resulting AusMPKK variant was less susceptible to that inhibition in the reported assays.
What happened in the baking tests?
At 1,000 activity units per kilogram of flour, AusMPKK increased specific loaf volume by 26.5% relative to bread made without added xylanase. Specific volume expresses loaf volume relative to its mass, making it more informative than size alone.
The parent AusM gave its largest reported increase, 19.7%, at 4,000 units per kilogram. That comparison concerns enzyme activity doses; it does not establish that the modified protein would cost one-quarter as much to manufacture or use.
The researchers also measured crumb hardness with a texture analyser. After seven days, bread treated with 1,000 units per kilogram of AusMPKK was 16.05% less hard than bread treated with 4,000 units per kilogram of AusM. The loaves were stored in polyethylene bags at 4 °C, so the result applies to those storage conditions.
Softer bread is only part of the picture
These measurements support an improvement in loaf volume and resistance to firming. They do not establish better taste, consumer preference or a longer microbiologically safe shelf life. Those questions require different tests.
Temperature claims also need care. AusMPKK showed its highest measured activity at about 60 °C in an enzyme assay. That does not mean it remains active throughout baking at the oven’s much higher set temperature.
The practical question is whether similar benefits persist across flour varieties, recipes and production conditions. A lower effective activity dose is promising, but manufacturing economics and commercial performance remain separate questions.
For readers interested in another enzyme-design trade-off, our report on the PB92 protease examines how improving heat resistance can affect activity.
Source
Zhang, D. et al. (2023). Directed Modification of a GHF11 Thermostable Xylanase AusM for Enhancing Inhibitory Resistance towards SyXIP-I and Application of AusMPKK in Bread Making. Foods, 12(19), 3574. Read the study.
Update note: This archived report retains its original publication date and URL. The revision distinguishes measured baking outcomes from taste, shelf-life and commercial claims.
