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The extracellular fructosyltransferase (FTase) from Rhodotorula sp. LEB-V10 was immobilized on particles of niobium–graphite alloy and freeze dried (lyophilized), with and without additives. Twelve additives commonly applied as cryoprotectants were selected and evaluated both individually and in formulation; the biocatalyst was then studied according to its catalytic properties. Lyophilization with or without additives did not significantly affect the immobilized enzyme. After a period of 6 months, reductions in the initial enzymatic activity of about 7 and 4% were observed for the lyophilized enzyme when using 50 and 200 mM sodium acetate buffers, respectively. CMC, sorbitol, inositol and trehalose as single additives (all at 2.5%, w/v) in 100 mM sodium acetate buffer were capable to preserve the enzymatic activity after 6 months. However, formulations with more than one additive resulted in 36–14% less enzymatic activity after 6 months. After lyophilization, FOS synthesis features changed positively, by increasing the FOS yield from a non-lyophilizated yield of 58–68% with lyophilization. FOS composition changed as well, with 1F-fructofuranosyl-nystose (GF4) content increasing to 61% with lyophilization, which is 76 times higher than with the non-lyophilized enzyme. |
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