Study on the improvement of Rye bread quality by bacterial Laccase derived from Streptomyces coelicolor

Rye bread is gaining increasing attention due to its health benefits, although its poor gluten structure remains a notable drawback. While many studies have focused on the role of fungal laccase in improving bread quality, research on the application of bacterial laccase in this area is limited. Compared with most fungal laccases, bacterial laccases with a wide pH range and good thermal stability offer significant advantages in bread baking. This study aimed to investigate the effect and mechanism of action of SLAC-T (truncated form of full-length sequence), a bacterial laccase derived from Streptomyces coelicolor, in rye bread. It was discovered that SLAC-T has a molecular weight of 32 kDa, a specific enzyme activity of 81.6 U/mg, and maintains high activity at high temperatures of 60–80 °C and pH 4.0–8.0. Texture and quality analysis revealed that at an SLAC-T addition level of 6U, the hardness, chewiness, and cohesiveness of rye bread were significantly reduced. Specifically, these properties decreased to 4161.4 g, 2251.6 g, and 1240.7 g, respectively, compared to the control values of 4161.3 g, 2251.6 g, and 1240.7 g. At the same time, the specific volume of bread increased by 0.28 mL/g relative to the control 1.93 mL/g, reaching a maximum value of 2.21 mL/g. This study primarily explores the mechanism by which SLAC-T improves the quality of rye bread, providing a scientific basis for the use of bacterial laccase in bread production.