Construction of a surface display system for the expression of L-arabinose isomerase for D-tagatose production

Abstract

D-tagatose (D-tag) is a valuable molecule with a high potential for sugar substitution. It is a ketohexose with low caloric value, 90% sweetener than sucrose and acts as a prebiotic. This rare sugar is naturally found in low quantities in dairy derived products and hot cocoa. Recently, it has gained popularity in the low-calorie sweetener market because of its antidiabetic and antihyperglycemic effects. Due to its low abundance, new manufacturing strategies are required to increase its production and availability. Biological method is the most studied for its bioconversion, for example the enzyme L-arabinose isomerase (L-AI) catalyzes the conversion of D-galactose to D-tag. Nevertheless, there are some enzymatic limitations to overcome to achieve a high yield conversion of D-tag. In this study, a recombinant plasmid was constructed to encode a surface display system for the expression of L-AI for D-tag production. It consisted of fusing the gene araA that encodes for L-AI from Lactobacillus sakei to the 3´ end of the PorB gene from Corynebacterium glutamicum. This expression vector that drives the fusion protein expression under the control of Lac and tac promoters was transformed into Escherichia coli DH5 alpha. Another construction that fuses the genes araA and PgsA is in process due to the presence of unexpected mutations in the encoding synthetic genes.