Effect of Cellic®Ctec2 Supplementation on In-House Produced Enzymes for WELP Hydrolysis
The in-house produced enzymatic preparation was supplemented with Cellic®Ctec2 in amounts ranging between 1 and 100 % of total FPU/g cellulose of in-house enzyme preparation used. Figures 4.4, 4.5, and 4.6 show the glucose, xylose, and mannose production during 72 h of enzymatic hydrolysis with the boosting of different commercial enzymes (Cellic®Ctec2) for hydrolyzing WELP. It was observed that supplementation with commercial Cellic®Ctec2 improved the sugars released after 72 h hydrolysis compared to control mixture (Fig. 4.1). Highest
Fig. 4.1 Sugars (g/L) released after 72 h of enzymatic hydrolysis as an effect of in-house produced cellulase supplementation with commercial cellulase, Cellic®Ctec2, from wet-exploded loblolly pine
enzymatic hydrolysis yields were achieved with 100 % supplementation; interestingly, increasing the supplementation beyond 30 % did not significantly increase the yields. Supplementation with commercial cellulase not only improved cellulose conversion but also hemicellulose conversion, which demonstrates the ability of the commercial enzyme in improving the overall hydrolysis performance.
Concentrations of glucose, xylose, and mannose were determined as 25.39, 14.33, and 13.87 mg/mL (Figs. 4.1, 4.2, and 4.3) corresponding to 32 %, 74 %, and 77 % yields, respectively, using our non-supplemented in-house enzyme cocktail (control-1). At 1 % supplementation, a slight change in yield was observed compared to control-1, giving an increase in glucose, xylose, and mannose concentrations of 13 %, 11 %, and 9 %, respectively. At 10 % supplementation, the glucose, xylose, and mannose concentration increased by 32 %, 14 %, and 13 %, respectively, after 72 h, and the corresponding figures for 30 % addition were 46 %, 15 %, and 15 % at 30 %, respectively. Only small increases in the sugar release were found between 30 and 50 % supplementation as shown in Fig. 4.4, demonstrating an increase of 57 %, 17 %, and 17 % in glucose, xylose, and mannose yields, respectively. At 100 % supplementation, the highest sugar yields were found giving 68 %, 21 %, and 18 %, of glucose, xylose, and mannose, respectively. In general, Cellic®Ctec2 (cellulases) supplementation resulted in higher production of glucose compared to hemicellulose. These results were statistically supported by Tukey HSD analysis with 95 % confidence level (data not shown).
Cellic®Ctec2 is produced by Trichoderma spp., which secretes an array of lignocellulolytic enzymes including cellulases, xylanases, abrabinosidases, and P-xylosidase (Banerjee et al. 2010). Mainly they exhibit cellulase activity, while
Fig. 4.2 Sugars (g/L) released after 72 h of enzymatic hydrolysis as an effect of in-house produced cellulase supplementation with commercial hemicellulase, Cellic®Htec2, from wet-exploded loblolly pine
Fig. 4.3 Sugars (g/L) released after 72 h of enzymatic hydrolysis as an effect of in-house produced cellulase supplementation with commercial p-glucosidase, Novozym 188, from wet-exploded loblolly pine
other enzymes are expressed in low levels. Our results clearly show that high cellulase activity improves the enzymatic hydrolysis yields during hydrolysis of pretreated loblolly pine.