Abstract
A d-allulose 3-epimerase from Flavonifractor plautii was cloned and expressed in Escherichia coli and Corynebacterium glutamicum. The maximum activity of the enzyme purified from recombinant E. coli cells was observed at pH 7.0, 65°C, and 1 mM Co2+ with a half-life of 40 min at 65°C, Km of 162 mM, and kcat of 25280 1/s. For increased d-allulose production, recombinant C. glutamicum cells were permeabilized via combined treatments with 20 mg/L penicillin and 10% (v/v) toluene. Under optimized conditions, 10 g/L permeabilized cells produced 235 g/L d-allulose from 750 g/L d-fructose after 40 min, with a conversion rate of 31% (w/w) and volumetric productivity of 353 g/L/h, which were 1.4- and 2.1-fold higher than those obtained for nonpermeabilized cells, respectively.
Highlights
The International Society of Rare Sugars (ISRS) stated at the 2014 Rare Sugar Symposium that ‘D-psicose’ should be referred to as ‘D-allulose’ and use of the ‘D-psicose’ term should be discontinued because D-allulose is an isomerized product of D-allose
D-Allulose has been produced from D-fructose by the reactions of biocatalysts, including Dtagatose 3-epimerases (DTEases) from Pseudomonas cichorii [7] and Rhodobacter sphaeroides [8]; D-allulose 3-epimerases (DAEases) from Agrobacterium tumefaciens [9], Clostridium sp
D-allulose produced by E. coli is limited in its use as a food additive because E. coli is not a generally recognized as safe (GRAS) host [21]
Summary
The International Society of Rare Sugars (ISRS) stated at the 2014 Rare Sugar Symposium that ‘D-psicose’ should be referred to as ‘D-allulose’ and use of the ‘D-psicose’ term should be discontinued because D-allulose is an isomerized product of D-allose. D-Allulose (D-psicose, D-ribo2hexulose) is a rare sugar that is present in small amounts as a non-fermentable component of commercial carbohydrates [1] and as a free sugar in agricultural products [2] This sugar has attracted a great deal of attention in the field of functional foods owing to its health benefits. D-allulose produced by E. coli is limited in its use as a food additive because E. coli is not a generally recognized as safe (GRAS) host [21] This problem can be solved by transferring the DAEase gene to a GRAS host such as Corynebacterium glutamicum. To increase the production of D-allulose from D-fructose, recombinant C. glutamicum cells expressing DAEase from F. plautii were permeabilized using several types of substances, including antibiotics, detergents, and solvents; and the most effective antibiotic, detergent, and solvent for D-allulose production were selected. The increased production of D-allulose from D-fructose was achieved
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