Hetero-modification of halloysite nanoclay to immobilize endoinulinase for the preparation of fructooligosaccharides.

ABSTRACT

Present investigation describes immobilization efficiency of endoinulinase onto hetero-functionalized halloysite nanoclay using 3-aminopropyltriethoxysilane and glutaraldehyde as crosslinkers. Under optimal conditions (APTES 0.75%, sonication time 2.25 h, glutaraldehyde 0.75%, activation-time 65 min, immobilized endoinulinase load 60 IU and coupling-time 1 h), maximum yield in enzyme activity (70.65%) and immobilization (89.61%) was obtained. Developed immobilized biocatalyst shown maximum activity at 65 °C and pH 5.0 with wide range thermal (50-80 °C) and pH (4.0-9.0) stability. Increase in half-life (28.70-fold) of immobilized endoinulinase was observed as compared to free enzyme. An enhanced Km and reduced Vmax of endoinulinase for inulin was recorded after immobilization. Maximum FOSs production 98.42% was obtained, under optimized conditions (inulin 10%; immobilized endoinulinase load 85 IU; hydrolysis-time 10 h and agitation rate 130 rpm) containing kestose (36.26%), nystose (27.02%), fructofuranosylnystose (9.98%) and FOSs DP 5-9 (25.15%). Developed immobilized biocatalyst exhibited a splendid operational stability for 18 batch cycles.