The high content of sucrose and raffinose reduces the prebiotic value of soybean oligosaccharides. Fructan sucrases can catalyze the conversion of sucrose and raffinose to high-value products such as fructooligosaccharides and melibiose. To obtain a fructan sucrase that can efficiently convert soybean oligosaccharides, we first mined the fructan sucrase gene from microorganisms in the coastal areas of Xisha Islands and Bohai Bay and then characterized the enzymatic and catalytic properties of the enzyme. Finally, recombinant extracellular expression of this gene was carried out in Bacillus subtilis. The results showed that a novel fructan sucrase, BhLS 39, was mined from Bacillus halotolerans. With sucrose and raffinose as substrates, BhLS 39 showed the optimal temperatures of 50 ℃ and 55 ℃, optimal pH 5.5 for both, and K_cat/K_m ratio of 3.4 and 6.6 L/(mmol·s), respectively. When 400 g/L raffinose was used as the substrate, the melibiose conversion rate was 84.6% after 30 min treatment with 5 U BhLS 39. Furthermore, BhLS 39 catalyzed the conversion of sucrose to produce levan-type-fructooligosaccharide and levan. Then, the recombinant extracellular expression of BhLS 39 in B. subtilis was achieved. The co-expression of the intracellular chaperone DnaK and the extracellular chaperone PrsA increased the extracellular activity of the recombinant BhLS 39 by 5.2 folds to 17 U/mL compared with that of the control strain. BhLS 39 obtained in this study is conducive to improving the quality and economic benefits of soybean oligosaccharides. At the same time, the strategy used here to enhance the extracellular expression of BhLS 39 will also promote the efficient recombinant expression of other proteins in B. subtilis.
Oligosaccharides/metabolism* ; Glycine max/metabolism* ; Bacillus subtilis/metabolism* ; Sucrase/biosynthesis* ; Raffinose/metabolism* ; Fructans/metabolism* ; Sucrose/metabolism* ; Bacillus/genetics* ; Recombinant Proteins/biosynthesis* ; Bacterial Proteins/biosynthesis*

Protein Engineering and Enzyme Engineering is a professional core course for life science-related majors in higher education, aiming to help students apply theoretical knowledge to engineering practice. The rapid development of biomanufacturing has placed new demands on the training of protein and enzyme engineers. However, due to the complexity and strong interdisciplinary nature of the course contents, traditional offline teaching modes have poor teaching performance and are unable to meet the era's demand for high-tech innovative talents in the field of biomanufacturing. To solve the above problems, we carried out the exploration and practice of blended teaching in Protein Engineering and Enzyme Engineering. We designed the teaching philosophy characterized by collaboration of online and offline learning, integration of pre-class preparation, in-class learning, and post-class review, linkage of online platforms, learning resources, teachers, and students, and enhancement via scientific research, scientific contests, course experiments, production practice, and lesson learning. We developed a three-phase (pre-class, in-class, and post-class) teaching program and established a two-level (online-offline) teaching evaluation mechanism. This teaching mode upholds the student-oriented concept, strengthens the deep integration of theory and practice, and focuses on cultivating students' innovative thinking and practical ability. The practical results show that this teaching mode can improve the teaching quality of Protein Engineering and Enzyme Engineering, enhance students' scientific and technological innovation ability, and meet the national demand for biomanufacturing talents.
Protein Engineering ; Teaching ; Enzymes/genetics* ; Humans