Methods and systems for enzymatic hydrolysis of pretreated biomass at high solids concentrations

Abstract

A method of enzymatically hydrolyzing pretreated lignocellulosic biomass at high solids concentration includes introducing pretreated biomass to a hydrolysis reactor, to hydrolyze the cellulose to glucose monomer and glucose oligomers, and circulating a liquid stream, from which glucose is removed to reduce glucose inhibition of cellulose hydrolysis. A surfactant may be added to the hydrolysis reactor. Heat and/or acid treatment of the glucose oligomers may be used to generate additional glucose monomer. Some variations introduce pretreated biomass to a hydrolysis reactor to hydrolyze cellulose to glucose monomer and glucose oligomers, followed by conveying a portion of the solid phase to a mechanical refiner and/or a unit under reduced pressure, to generate a refined and/or exploded solid phase; and recycling the refined and/or exploded solid phase, optionally reheated, back to an input of the hydrolysis reactor.

What is claimed is: 
     
         1 . A method of enzymatically hydrolyzing pretreated lignocellulosic biomass at high solids concentration, said method comprising:
 (a) providing pretreated lignocellulosic biomass containing cellulose;   (b) introducing said pretreated lignocellulosic biomass to a hydrolysis reactor under effective hydrolysis conditions and in the presence of enzymes including cellulases, to hydrolyze said cellulose to glucose monomer and glucose oligomers; and   (c) circulating a liquid stream in a circulation line configured from an output of said reactor back to an input of said hydrolysis reactor, wherein at least a portion of said glucose monomer is removed from said circulation line to reduce glucose inhibition of cellulose hydrolysis,   wherein said method further comprises a glucose oligomer hydrolysis step to generate additional glucose monomer from said glucose oligomers.   
     
     
         2 . The method of  claim 1 , wherein said glucose oligomer hydrolysis step is integrated with step (b). 
     
     
         3 . The method of  claim 1 , wherein said glucose oligomer hydrolysis step is integrated with step (c). 
     
     
         4 . The method of  claim 1 , wherein at least a portion of said glucose oligomers is also removed from said circulation line to reduce glucose oligomer inhibition of cellulose hydrolysis. 
     
     
         5 . The method of  claim 1 , wherein additional cellulase enzymes are introduced to said circulation line, to convert said glucose oligomers to said additional glucose monomer. 
     
     
         6 . The method of  claim 1 , wherein said method further comprises introducing a surfactant to said hydrolysis reactor during step (b) or step (c). 
     
     
         7 . The method of  claim 6 , wherein said surfactant includes lignin. 
     
     
         8 . A method of enzymatically hydrolyzing pretreated lignocellulosic biomass at high solids concentration, said method comprising:
 (a) providing pretreated lignocellulosic biomass containing cellulose;   (b) introducing said pretreated lignocellulosic biomass to a hydrolysis reactor under effective hydrolysis conditions and in the presence of enzymes including cellulases, to hydrolyze a portion of said cellulose to glucose monomer and glucose oligomers present in a liquid phase, wherein non-hydrolyzed cellulose remains in a solid phase; and   (c) conveying a portion of said solid phase to a mechanical refiner, to generate a refined solid phase; and   (d) recycling said refined solid phase back to an input of said hydrolysis reactor.   
     
     
         9 . A method of enzymatically hydrolyzing pretreated lignocellulosic biomass at high solids concentration, said method comprising:
 (a) providing pretreated lignocellulosic biomass containing cellulose;   (b) introducing said pretreated lignocellulosic biomass to a hydrolysis reactor under effective hydrolysis conditions and in the presence of enzymes including cellulases, to hydrolyze a portion of said cellulose to glucose monomer and glucose oligomers present in a liquid phase, wherein non-hydrolyzed cellulose remains in a solid phase;   (c) feeding a portion of said solid phase to a unit under reduced pressure, to generate an exploded solid phase; and   (d) recycling said exploded solid phase, optionally reheated, back to an input of said hydrolysis reactor.   
     
     
         10 . The method of either one of  claim 8  or  9 , wherein said method further comprises an oligomer hydrolysis step of said glucose oligomers to generate additional glucose monomer. 
     
     
         11 . The method of either one of  claim 8  or  9 , wherein said method further comprises introducing a surfactant to said hydrolysis reactor. 
     
     
         12 . The method of either one of  claim 8  or  9 , wherein said pretreated lignocellulosic biomass is a pulp material, derived from wood or lignocellulosic biomass, selected from the group consisting of kraft pulp, sulfite pulp, soda pulp, mechanical pulp, thermomechanical pulp, chemimechanical pulp, and combinations thereof. 
     
     
         13 . The method of either one of  claim 8  or  9 , wherein said pretreated lignocellulosic biomass is obtained from steam or hot-water extraction of lignocellulosic biomass. 
     
     
         14 . The method of either one of  claim 8  or  9 , wherein said pretreated lignocellulosic biomass is present in said hydrolysis reactor at a solids concentration of about 20 wt % or more. 
     
     
         15 . The method of either one of  claim 8  or  9 , wherein a first amount of enzymes is introduced at a first solids concentration, wherein a second amount of enzymes is introduced at a second solids concentration, and wherein said second solids concentration is higher than said first solids concentration.