(292c) Why Enzymatic Hydrolysis of Lignocelluloses Should be Conducted At Elevated pH 5.2-6.2 | AIChE

(292c) Why Enzymatic Hydrolysis of Lignocelluloses Should be Conducted At Elevated pH 5.2-6.2


Zhu, J. Y. - Presenter, USDA Forest Service
Lan, T. Q., South China University of Technology
Lou, H., South China University of Technology

We studied the mechanism of an observed significant enhancement in enzymatic saccharification of lignocelluloses at elevated pH of 5.5 – 6.0.  Four enzymatic hydrolysis lignin residues with different sulfonic acid group contents were isolated from lodgepole pine pretreated by either dilute acid or Sulfite Pretreatment to Overcome Recalcitrance of Lignocelluloses (SPORL). The adsorption isotherms of a commercial Trichoderma reesi cellulase cocktail (CTec2) to these lignin residues at 50oC were measured at a pH range of 4.5 – 6.0.  The zeta potentials of these lignin samples were also measured.  The study discovered that elevated pH significantly increased lignin surface charge (negative), causing lignin to become more hydrophilic, coordinately reducing its affinity to cellulase and consequently the nonspecific binding of cellulase.  The reduction in nonspecific cellulase binding to lignin is also attributed to enhanced electrostatic interactions at elevated pH through the increased negative charges of cellulase enzymes with low pI.  The results validate the hypothesis that the gains in enzymatic saccharification efficiencies at elevated pH for different pretreated lignocelluloses are solely the result of reduced nonspecific cellulase binding to lignin.  This study contradicts a well-established concept of “optimal pH 4.8 – 5.0” for enzymatic hydrolysis using Trichoderma reesi cellulase that is widely accepted and exclusively practiced in numerous laboratories throughout the world.  Because an elevated pH can be easily implemented commercially without capital cost and with only minimal operating cost, this study has both scientific importance and practical significance.


This paper has an Extended Abstract file available; you must purchase the conference proceedings to access it.


Do you already own this?



AIChE Pro Members $150.00
AIChE Graduate Student Members Free
AIChE Undergraduate Student Members Free
AIChE Explorer Members $225.00
Non-Members $225.00