| Autor: |
Miao M; Key Laboratory of China National Light Industry and Food Bioengineering, College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Haidian District, Beijing 100083, China., Li S; Key Laboratory of China National Light Industry and Food Bioengineering, College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Haidian District, Beijing 100083, China.; Mengniu Hi-tech Dairy Product Beijing Co., Ltd., Beijing 101100, China., Yang S; Key Laboratory of China National Light Industry and Food Bioengineering, College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Haidian District, Beijing 100083, China., Yan Q; College of Engineering, China Agricultural University, No. 17 Qinghua East Road, Haidian District, Beijing 100083, China., Xiang Z; Key Laboratory of China National Light Industry and Food Bioengineering, College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Haidian District, Beijing 100083, China., Jiang Z; Key Laboratory of China National Light Industry and Food Bioengineering, College of Food Science and Nutritional Engineering, China Agricultural University, No. 17 Qinghua East Road, Haidian District, Beijing 100083, China.; Food Laboratory of Zhongyuan, Luohe 462300, China. |
| Abstrakt: |
In situ galacto-oligosaccharide (GOS) synthesis in milk using β-galactosidases is an effective method for developing prebiotic dairy products. However, the low lactose concentration in milk (∼4.6%, w/w) reduces the GOS yield. In this study, a modified β-galactosidase from Bacillus circulans (mBgaD-D) with enhanced transglycosylation activity at low lactose concentration was developed through directed evolution and saturation mutagenesis. The GOS yield by mBgaD-D increased from 22.8% (wild type) to 30.8% in 50 g/L lactose (phosphate buffer). P mgut was a strong sorbitol-inducible promoter from Bacillus subtilis . The expression of mBgaD-D in B. subtilis , coupled with the P mgut promoter, resulted in a 6.4-fold increase (compared to the P 43 promoter) in extracellular enzyme activity. Additionally, adding whey powder to boost the initial lactose concentration further improved the GOS yield, which reached 43% under the optimized conditions. Combining mBgaD-D and whey powder enhanced milk sweetness, producing no sugar-added, GOS-enriched yogurt (GOSY). The GOS content in GOSY was 4.1/100 g, providing an appropriate level of sweetness and yielding a yogurt that is elastic as well as firm. GOSY also increased the population of Bifidobacterium spp. during a 24 h in vitro fecal fermentation. Thus, fortifying yogurt with mBgaD-D and whey powder can enhance its technological properties and health benefits. |
