In this study, the process conditions for Stargen 001, a potent
Granular Starch Hydrolyzing Enzyme developed by M/s Genencor
International Inc., USA were optimized with cassava
starch with the aim of improving the cost economics for bioethanol
production. The study showed that an initial thinning
of starch by Spezyme Xtra facilitated almost complete
hydrolysis of starch to sugars and its simultaneous utilization
by yeast (Saccharomyces cerevisiae) for ethanol production. The
optimum conditions for Spezyme-aided liquefaction of cassava
starch were pH 5.5, temperature 90 C, enzyme concentration
(20.0 mg for 10% starch slurry) and incubation time
(30 min). Approximately 15.3% conversion of cassava starch to
reducing groups could be achieved at this stage. Earlier studies
in our laboratory showed that Termamyl 60 L, a thermostable
a-amylase required a higher operating pH of 7.0, which
necessitated more expense on acid-mediated lowering of pH
to 4.5 for the subsequent saccharification reaction of cassava
starch by amyloglucosidase [25]. Further studies on the
enzyme catalysed liquefaction and saccharification of sweet
potato starch showed that liquezyme X (Novo Industries,
Denmark) could liquefy the starch at pH 7.0 and 90 C within
1 h, followed by saccharification by Dextrozyme GA at pH 4.0