Harnessing co-expressed L-arabinose and L-ribose isomerases to enhance the biosynthesis of L-ribose

L-Ribose is an essential rare sugar used in several industries, including pharmaceutical, food, cosmetics, and agriculture. Recently, the enzymatic production of L-ribose has garnered significant attention due to its considerable advantages over synthetic methods. This study introduces a novel approach for producing L-ribose from L-arabinose. Initially, the genes encoding L-arabinose isomerase (L-AI) from Bacillus subtilis str. 168 (BsL-AI) and L-ribose isomerase (L-RI) from Actinotalea fermentans ATCC 43279 (AfL-RI) were cloned to construct the recombinant plasmid containing the pANY1-BsL-AI/AfL-RI vector and co-expressed in Escherichia coli BL21(DE3). Subsequently, the of co-expression exhibited optimal activity at pH 8.5 and 40 °C in 50 mM Tris-HCl buffer, with 1 mM Mn²⁺ ion. The activity was increased by 33 % and 12 % with Mn²⁺ and Co²⁺ ions, respectively, compared to the control having no metal ions. The scheme comprising 50 g L⁻¹ of co-expressed cells remained comparatively stable up to 60 °C for 2 h. Finally, the co-expression scheme produced 23.52 g L⁻¹ (24 %), 25.87 g L⁻¹ (26 %) and 27.97 g L⁻¹ (28 %) of L-ribose when utilizing L-arabinose concentration of 30, 50 and 100 g L⁻¹, respectively, with 50 g L⁻¹ of co-expressed cells. This study presents a viable methodology for the utilization of L-arabinose to produce L-ribose in slightly alkaline conditions utilizing a co-expression scheme concealing BsL-AI and AfL-RI genes.