Date

2019

Author

Leyluhan Yurtseven, Berna

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Hydrolysis of biomass obtained as the waste of industrial or agricultural production has gained significant interest in recent years. In this study, 2 different biomasses were studied. In the 1st part of the study, sugar beet pulp (SBP) hydrolysis was optimized using Response Surface Methodology (RSM). Sugar beet pulp is an important by product of sugar manufacturing and its hydrolysis could yield valuable sugars that can be used in fermentation processes. As the parameters of SBP hydrolysis by RSM, effect of enzyme concentration, hydrolysis time and pulp amount were examined. A central composite design with 5 levels was constructed using; substrate loadings, two different enzyme- Pectinex Ultra SP-L and Cellic Ctec3 concentrations and hydrolysis time. It was found that at 20% SBP subtrate loadings, as the volume of Pectinex Ultra SP-L was increased above 250 µl, yield reached its maximum- above 90 g/L. As the SBP loading increased, even while using lower volumes of Cellic Ctec3 -around 150 µl, yield reached its maximum. Analysis showed that combining Pectinex Ultra SP-L with Cellic Ctec3 resulted in a synergetic response. RSM estimates indicated that the optimal point for maximum reduced sugar yield was beyond the experimental range used in this thesis. In addition to RSM, classification and regression tree (CART) method was used to investigate the effects of substrate amount, enzyme loadings and hydrolysis time. Regression tree analysis results confirmed the estimations from RSM. Moreover, classification tree analysis results form a basis for future optimization studies. In the 2nd part of the study, corn cob was used as the substrate for hydrolysis. Corn cob is a high lignin product and its hydrolysis requires the use of different pretreatment methods. In this study, rather than using a pretreatment method, surfactants were utilized to increase the accessibility of the enzymes to the cellulosic network through lignin. Tween 20 and 80 were used as the surfactants. Hydrolysis was performed in 0.05 M sodium citrate buffer at a pH of 4.8. Celluclast 1.5L and Novozyme 188 were used at a fixed concentration of 150 mL as the enzymes and the hydrolysis was monitored for 24 hours. Results showed that effect of surfactant addition was not significant on hydrolysis (p<0.05) as long as lignin was not removed by a pretreatment method.

Subject Keywords

Enzymes., Enzymatic hydrolysis, Surfactant, Tween 20, Tween 80, Corn cob, Sugar beet pulp (SBP), Pectinex Ultra SP-L, Cellic Ctec3, Celluclast 1.5L, Novozyme 188.

URI

http://etd.lib.metu.edu.tr/upload/12624785/index.pdf
https://hdl.handle.net/11511/44754

Collections

Graduate School of Natural and Applied Sciences, Thesis