Fig. 1. Enzymatic hydrolysis of the best alkali-treated cotton gin substrates at different total solids (%) and enzyme loadings (mg g−1 ss): cotton gin dust (A) and cotton gin waste (B).Figure optionsDownload full-size imageDownload as PowerPoint slide
The results obtained after 24 and 92 h of hydrolysis under different experimental conditions are shown in Table 5 and these are presented as conversion (%) in relation to the substrate glucan content and as the corresponding BMY 14802 concentration (g L−1) in the substrate hydrolysate. Since these values were statistically different for different pretreatment conditions (p < 0.05 in the ANOVA), the Tukey’s test was used to identify which of the individual responses were different from one another.
The largest glucan conversion after 24 h was obtained with the lowest substrate total solids (5 wt%) and the highest enzyme loading (11.5 FPU g−1 of dry substrate), as demonstrated by CGD-2 and CGW-7 in Table 5. These experiments resulted in 40.8 ± 1.0 and 36.5 ± 0.9% of glucan conversion, respectively, and these values were statistically different (p < 0.05) when compared to all other hydrolysis conditions. However, the highest concentration of fermentable sugars was obtained at 15 wt% total solids with 11.5 FPU g−1 of dry substrate (or 85 mg of enzyme g−1) for both pretreated materials, being 24.1 ± 0.4 g L−1 of glucose for CGD-1 and 22.9 ± 0.8 g L−1 of glucose for CGW-6.