學生姓名:
劉倚君
指導教授:
方翠筠
學期:
111上
摘 要:
D-Allulose is a rare sugar that exists in extremely small quantities in nature. It is a potential alternative to sucrose and fructose. However, the chemical synthesis of D allulose is laborious and expensive. Therefore, the aim of these studies is to utilize novel enzymes from different microorganisms to produce D-allulose. In the study, a novel D tagatose 3-epimerase from Christensenella minuta (DTE-CM) was metal-dependent and had maximum activity at 1 mM Ni2+, and the highest relative activity was at 50 oC and pH 6, respectively, while compared with alkaline environment, the activity is higher in acidic environment. When 100 to 500 g/L D-fructose was added, the enzyme catalyzed reaction reached equilibrium in 1.5 to 10 h, producing 30.2 to 150 g/L D allulose under pH 6.0 and 50°C. DTE-CM has an equilibrium ratio between D-fructose and D-allulose of 30:70 and a conversion rate of 30%, which is the highest data so far for D-tagatose-3-epimerases. In the study, a novel D-allulose 3-epimerase from the metagenomic resource of a hot-water reservoir (DaeM) was metal-dependent and had maximal activity at 1 mM Co 2+ , and the relative activity of DaeM at pH 6 to 11 can maintain more than 85%, of which pH 7 is optimal for DaeM, and the enzyme activity is completely lost at pH 4.5. Using 700 mg/ml D-fructose and 12.6 U/ml DaeM for enzyme-catalyzed reaction at 80oC, about 31% of D-fructose was catalytically converted to D-Allulose in 7.5 hours and the concentration reached about 217 mg/ml. Based on these results the application of DTE-CM and DaeM as novel enzymes for the production of D-Allulose has excellent catalytic activity for D-fructose in acidic and high-temperature environments, respectively. They have great potential for D-Allulose biosynthesis from various D-fructose-containing products.
1111_專題討論摘要_劉倚君_11132026.pdf