L-arabinose isomerase (L-AI) is the key enzyme for D-galactose isomerization of D-tagatose by biological method. In this research, Lactobacillus plantarum WU14 with high D-tagatose yield was identified as Lactobacillu...L-arabinose isomerase (L-AI) is the key enzyme for D-galactose isomerization of D-tagatose by biological method. In this research, Lactobacillus plantarum WU14 with high D-tagatose yield was identified as Lactobacillus plantarum was isolated from the number of lactic acid bacteria from pickled vegetables. The crude L-arabinose isomerase activity of Lactobacillus plantarum WU14 with high D-tagatose yield was 13.95 U/mL under the optimal temperature 60°C, pH 7.17 and substrate concentration 0.8 mol/L, and the conversion rate of 56.12% could be gained after 28 hours. Protein structure and specific of L-Arabinose Isomerase of Lactobacillus plantarum WU14 were researched. The results showed that L-arabinose isomerase is mainly composed of alpha helix and random coil. Then the recombinant L-AI gene was inserted into the food-grade expression vector pRNA48 and expressed in L. lactis NZ9000 successfully. The target protein expression reached the maximum amount when the induced concentration of nisin reaches 30 ng/mL after 12 h. And the crude enzyme activity of recombinant bacteria reached 6.21 U/mL under 60°C. Otherwise the optimal conversion rate recombinant of L. lactis NZ9000/pRNA48-L-AI can reach 39.21% under the temperature of 50°C, pH 7.17 and D-galactose concentration was 0.6 mol/L.展开更多
D-allulose, also known by the name D-psicose or just allulose, is a rare keto-sugar epimer of D-fructose in the third carbon (C3), and naturally occurs in small quantity in fruits such as grapes and figs. It is low ca...D-allulose, also known by the name D-psicose or just allulose, is a rare keto-sugar epimer of D-fructose in the third carbon (C3), and naturally occurs in small quantity in fruits such as grapes and figs. It is low calorie sweetener produced enzymatically from D-fructose by enzymes D-ketose 3-epimerase (DKEase) family. D-allulose has a similar taste, texture and functionality as sweetener comparing to high calorie sweetener sugar table sucrose. D-allulose is poorly metabolized in the body with minimal impact on blood sugar levels making it a natural low-calorie sweetener. This property makes D-allulose an attractive sweetener for diabetes and for body weight management. Laboratory studies on D-allulose intake demonstrated its safety with no significant adverse effects. United States Food and Drug Administration (FDA) has granted D-allulose the status of Generally Recognized as Safe (GRAS). Plus, it is considered safe for human consumption by regulatory organizations in other countries except in European Union due to their request for further laboratory testing. Maximum acceptable daily intake of D-allulose is 0.9 grams per kilogram body weight. Excessive intake for more than the recommended daily intake could lead to some side effects such as gastrointestinal discomfort or laxative effects. In general, D-allulose is considered one of the preferred natural low calories sweeteners for those seeking an alternative to table sugar sucrose.展开更多
文摘L-arabinose isomerase (L-AI) is the key enzyme for D-galactose isomerization of D-tagatose by biological method. In this research, Lactobacillus plantarum WU14 with high D-tagatose yield was identified as Lactobacillus plantarum was isolated from the number of lactic acid bacteria from pickled vegetables. The crude L-arabinose isomerase activity of Lactobacillus plantarum WU14 with high D-tagatose yield was 13.95 U/mL under the optimal temperature 60°C, pH 7.17 and substrate concentration 0.8 mol/L, and the conversion rate of 56.12% could be gained after 28 hours. Protein structure and specific of L-Arabinose Isomerase of Lactobacillus plantarum WU14 were researched. The results showed that L-arabinose isomerase is mainly composed of alpha helix and random coil. Then the recombinant L-AI gene was inserted into the food-grade expression vector pRNA48 and expressed in L. lactis NZ9000 successfully. The target protein expression reached the maximum amount when the induced concentration of nisin reaches 30 ng/mL after 12 h. And the crude enzyme activity of recombinant bacteria reached 6.21 U/mL under 60°C. Otherwise the optimal conversion rate recombinant of L. lactis NZ9000/pRNA48-L-AI can reach 39.21% under the temperature of 50°C, pH 7.17 and D-galactose concentration was 0.6 mol/L.
文摘D-allulose, also known by the name D-psicose or just allulose, is a rare keto-sugar epimer of D-fructose in the third carbon (C3), and naturally occurs in small quantity in fruits such as grapes and figs. It is low calorie sweetener produced enzymatically from D-fructose by enzymes D-ketose 3-epimerase (DKEase) family. D-allulose has a similar taste, texture and functionality as sweetener comparing to high calorie sweetener sugar table sucrose. D-allulose is poorly metabolized in the body with minimal impact on blood sugar levels making it a natural low-calorie sweetener. This property makes D-allulose an attractive sweetener for diabetes and for body weight management. Laboratory studies on D-allulose intake demonstrated its safety with no significant adverse effects. United States Food and Drug Administration (FDA) has granted D-allulose the status of Generally Recognized as Safe (GRAS). Plus, it is considered safe for human consumption by regulatory organizations in other countries except in European Union due to their request for further laboratory testing. Maximum acceptable daily intake of D-allulose is 0.9 grams per kilogram body weight. Excessive intake for more than the recommended daily intake could lead to some side effects such as gastrointestinal discomfort or laxative effects. In general, D-allulose is considered one of the preferred natural low calories sweeteners for those seeking an alternative to table sugar sucrose.
