Production of d‐allulose from d‐glucose by Escherichia coli transformant cells co‐expressing d‐glucose isomerase and d‐psicose 3‐epimerase genes
2017
Zhang, Wenli | Li, Hao | Jiang, Bo | Zhang, Tao | Mu, Wanmeng
BACKGROUND: d‐Allulose is a novel and low‐calorie rare monosaccharide that is a C‐3 epimer of d‐fructose. Because of its excellent physiological properties and commercial potential, d‐allulose has attracted researchers' interests. Based on the Izumoring strategy, d‐allulose is converted from d‐fructose by d‐psicose 3‐epimerase (DPEase), while d‐fructose is converted from d‐glucose by d‐glucose isomerase (GIase). In this study, we created a cellular system capable of converting d‐glucose to d‐allulose in a one‐step process that co‐expressed the GIase from Acidothermus cellulolyticus and the DPEase from Dorea sp. CAG. RESULTS: The co‐expression plasmid pETDuet‐Dosp‐DPE/Acce‐GI was generated and transformed into Escherichia coli BL21(DE3) cells. The recombinant co‐expression cells exhibited maximum catalytic activity at pH 6.5 and 75 °C. These cells were thermostable at less than 60 °C. The addition of Co²⁺ significantly increased the catalytic activity by 10.8‐fold. When the reaction equilibrium was reached, the ratio of d‐glucose, d‐fructose and d‐allulose was approximately 6.5:7:3, respectively. CONCLUSION: A recombinant co‐expression strain that catalysed the bioconversion of d‐allulose from d‐glucose in a one‐step process was created and characterised. When adding 500 g L⁻¹ d‐glucose as a substrate, 204.3 g L⁻¹ d‐fructose and 89.1 g L⁻¹ d‐allulose were produced. © 2016 Society of Chemical Industry
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