2.7. VHG fermentation by a non-thermal process
Cassava root mash adjusted to 32% (w/w) solid content was pretreated with 0.5% (w/w) enzyme preparation and incubated at 45◦C, pH 5.0 for 2 h. The pretreated mash was used as the substrate for ethanol fermentation in a 5-L bioreactor with a total volume of 2.6 L. Low-temp amylase (in-house enzyme prepared from an Aspergillus strain) was added at 0.35 IU/g of raw starch degrading amylase activity (as assayed on raw cassava starch) for starch hydrolys is and 0.06% (w/v) S. cerevisiae dried powder (Thermosacc®Dry yeasts) was inoculated simultaneously. The fermentation mixture was incubated at 32◦C, pH 4.5 for 96 h with mixing at 150 rpm.The mash samples were collected and analyzed as described above.