Synthesis of vanillyl-maltoside using glucosidases by response surface methodology

Amyloglucosidase from Rhizopus mold and β-glucosidase from sweet almond, catalysed synthesis of vanillyl-maltoside was optimized using response surface methodology. A central composite rotatable design involving 32 experiments of five variables at five levels was employed. Among the variables employed, glucosidases (10–50% w/w of maltose), vanillin (0.5–2.5 mmol), incubation period (24–120 h), buffer volume 0.4–2.0 ml (0.04–0.2 mM) and pH (4.0–8.0); enzyme, buffer concentration and buffer pH were found to be significant with both the enzymes. Surface plots generated clearly brought out the maltosylation behaviour of the two glucosidases in this reaction with both the enzymes exhibiting yields in the range 5–60%. Saddle-shaped surface plots observed with both the enzymes exhibited total reversal of the maltosylation behaviour at certain critical crossover points like 30% (w/w maltose) enzyme concentration, buffer pH 6.0 and a buffer concentration of 1.25 ml (0.125 mM), implying that a critical enzyme to buffer concentration and pH dictate the extent of vanillin maltosylation. Validation experiments conducted at certain random selected conditions as well as those conducted at optimum conditions obtained from the reduced model showed good correspondence between predicted and experimental yields.