Simultaneous optimization of factors affecting native starch pretreatment and enzymatic hydrolysis using magnetic covalent immobilized α-amylase

Abstract

Abstract In this study, for the first time the effects of different factors on hydrolysis of low concentration of corn starch were investigated in two steps. In the first step, thermal hydrolysis with pH variation and sonication treatment and finally enzymatic hydrolysis of starch were investigated by one factor at a time method. The best conditions of maximum reducing sugar production and maximum releasing of amylose were starch with pH = 4.5, sonication time 30 min and 24 hours solution storage in 4°C with enzymatic hydrolysis by 335 ppm immobilized enzyme for 15 min. In the second step, the effects of three variables on starch hydrolysis to determine the optimal conditions were investigated by 23 factorial design with multiple responses desirability method. Starch concentration 0.5% (w/v), initial starch pH of 4.5 and enzymatic hydrolysis temperature 50°C were determined as optimum conditions for achieving maximum changes in reducing sugar concentration 92.48 (mg/g starch) and ratio of final and initial soluble amylose content of hydrolysate solution 0.62 (by more than 75% separation of immobilized enzyme on MNPs after the process by external magnetic field. Also, experiment showed the possibility of immobilized enzyme reusing, which can retain 40% of its ability to produce reducing sugar and retain magnetic features of nanoparticles after 6 cycles.