Combined CLEAs of invertase and soy protein for economically feasible conversion of sucrose in a fed-batch reactor

Abstract

Invertase was immobilized using the cross-linked enzyme aggregate (CLEA) methodology using soy protein as co-feeder. The immobilized invertase retained around 30% of the initial activity after enzyme leaching assay. Maximum activity for the immobilized invertase was at 50.8°C (5.8°C higher than the soluble invertase) and at pH 5.0 (similar to the soluble invertase). The catalytic efficiency (kcat/Km) of invertase did reduce approximately tenfold after immobilization, probably due to diffusional delays. The immobilized invertase could be recycled tenfold in 4h-batches of hydrolysis of sucrose at 40°C and pH 6.0, maintaining the reaction conversion above 75%. The hydrolysis of sucrose catalyzed by immobilized invertase showed to be economically feasible in an operational window built based on economic metrics for a fed-batch process, with three intermittent feeds of sucrose to restore the substrate concentration at 100gL−1 when the conversion reaches 95%. This work represents an advance in the field, because using a carrier-free and recyclable biocatalyst the specific productivity (gram of products per gram of biocatalyst per hour) of invert sugar was as high as those previously reported for invertase immobilized on solid carriers, which may dilute its volumetric activity and increase the cost of the biocatalyst.