In the prospect to reduce the process cost, thepossibility of hydrolyzing starch at a lower temperature was investigated by substituting Termamyl 120L by UEB-S amylase (Fig. 4D).
Three different doses were tested: 45 U, 90 U and 135 U. The hydrolysis was performed at 70◦C using 15% of PPW.
The saccharification step was performed as previously described.
The highest releaseof reducing sugars (69 g L−1) was obtained using 90 U of
UEB-Samylase for 2 h which was higher than that obtained by Termamyl120L.
It is also evident that enzymatic hydrolysis of PPW liberatesa higher amount of fermentable reducing sugar compared to acidichydrolysis.
The analysis of the two enzymatic hydrolysates by TLC(Fig. 5) revealed that Termamyl 120L hydrolysate contained glucose(G1), maltose (G2) and maltotriose (G3) whereas UEB-S amylasehydrolysate was mainly formed by glucose.
This indicates that UEB-S amylase (90 U) combined with amyloglucosidase (9 U) were more efficient to achieve a complete PPW hydrolysis.
The two enzymatic hydrolysates were then subject to fermentation to evaluate the ethanol production.
Three different concentrations of hydrolysates were tested (1, 2 and 6%, w/v).