In vitro amylolytic degradation of natural and graft copolymerised cassava and potato starches

<p align="justify">Various enzymatic hydrolyses to maximise
degradation of the starch moiety of grafted starch
(starch–g-polyacrylonitrile) were tried. The percentage
of a- and b-amylolyses of grafted starch were 55 and 50
compared to 80 and 70 respectively for natural starches.
Sequential degradation with a-amylase and glucoamylase
of grafted starch showed 70% hydrolysis. The maltooligosaccharide profile by HPLC of the hydrolysates
of grafted starch showed oligomers up to a degree of
polymerisation (DP) 3, whereas the natural starch hydrolysates showed up to DP 7. The percentage hydrolysis,
as well as the enzyme degradation profile, remained
similar for both potato and cassava starches. Further
treatment of the grafted starch hydrolysates with Bacillus
cereus cells showed the presence of very low molecular
weight polyacrylonitrile chains grafted onto maltooligosaccharides. The size exclusion chromatography
analysis of grafted starch indicated the amylose component
of starch that undergoes graft copolymerisation.</p>