Welcome to the Zhang Group Webpage!

     2008-2010     DuPont Young Professor Award
     2008              Outstanding new faculty award from the College of Engineering of Virginia Tech
     2008-2010    Air Force Young Investigator Award (AFOSR)
     2006              Best and Brightest Person of Esquire Magazine
     2006             Ralph E. Powe Junior Faculty Enhancement Award

Research Interests and Directions

Courses Taught

BSE 5984 Enzyme Engineering (fall 2008, 2010)
BSE 3524 Unit Operation (spring 2009)

Research Statement

1. Cellulose- and Organic-Solvent Lignocellulose Fractionation (COSLIF) Technology
The largest challenge of cellulosic ethanol biorefineries is to effectively break recalcitrant lignocellulose and release soluble fermentable sugars. In response to this challenge, we have invented a novel Version 1 cellulose-solvent based lignocellulose fractionation technology [1], which can separate lignocellulose to four parts: amorphous cellulose, hemicellulose sugars, lignin, and acetic acid in the below flowchart. It features modest reaction condition (~50^oC, atmospheric pressure), amorphous cellulose generation, and efficient chemical recycling as shown below. As compared to (dilute acid) steam explosion, this technology can produce at least 20% more sugar yields and increase 20% revenues from acetic acid.

In addition, we have developed Version 2 and 3 lignocellulose fractionation, which have solved two main shortcomings of Version 1 -- reducing solvent use volume by several fold and avoiding dilute sugar reconcentration.

The improvement of specific cellulase activities can be implemented through cellulase engineering -- rational design and directed evolution for each cellulase component as well as the reconstitution of cellulase components [2]. We are applying the combinatorial technologies involving DNA mutagenesis techniques, enzyme cell surface display techniques, and evolutionary engineering for improving cellulase activity on insoluble substrate cellulose.

3. Cellulose Hydrolysis Mechanisms Mediated by Cellulase, Cellulosome, and Cellulolytic Microbe

Cellulose biodegradation requires three types of cellulases (endoglucanase, exoglucanases, and beta-glucosidase) to work together [3]. The unidentified characteristics of heterogeneous cellulose, the complicated interaction between solid cellulose and cellulase components, and the synergic/competitive relationship among various cellulase components limit our understanding of this de-polymerization process and also lags behind the developments in lignocellulose pretreatment and cellulase improvement.

We have developed a generic functionally based mathematical model to simulate this complicated process [4]. A new rapid method has been developed to determine the degree of polymerization of cellulose [5]; a new kind of non-substitution, high reactivity, homogeneous, regenerated amorphous cellulose (RAC) has been prepared for studying cellulose hydrolysis [6]. Now we are developing several new technologies which will help us to characterize key substrate characteristics, and elucidate in-depth mechanisms that will provide new insights into lignocellulose pretreatment and cellulase improvement.

In addition, we have discovered a new cellulose hydrolysis mechanism for microbial cellulose hydrolysis mediated by a complexed cellulase system -- the Clostridium thermocellum cellulosome [7,8].

4. Enzymatic Hydrogen Production by Synthetic Enzymatic Pathway[9]
The overall reaction is C₆H₁₀O₅ + 7 H₂O --> 12 H₂ + 6 CO₂. Our idea is to utilize energy stored in sugars to break up water and produce energy in the form of hydrogen or oxidate sugars using water rather than oxygen. This technology would be perfect for mobile applications because of mild reaction conditions (~20-80 degree C and high hydrogen yields), complete conversion, after the technology improvement. We first propose SUGAR CARS which storage sugar, convert sugar to hydrogen on board, generate electricity via fuel cells, and drive motor. This technology would solve the technical challenges associated with hydrogen storage, distribution, production, and safety simultaneously. The synthetic enzymatic pathway is shown below,

What is more important, the integration of this technology with PEM fuel cell would achieve the highest energy efficiency from chemical energy to mechanical energy. The details of life cycle analysis pertaining to the carbohydrate hydrogen economy vs other hypocretical future economies, such as methanol economy, electron economy, are being conducted.

References:

[1] Zhang Y.-H.P., Ding S.-Y., Mielenz J.R., Cui J.-.B., Elander R.T., Laser M, Himmel M.E., McMillan, J.D., Lynd, L.R. 2007. Fractionating recalcitrant lignocellulose at modest reaction conditions. Biotechnology and Bioengineering 97(2): 214-223.

[2] Zhang Y.-H.P., Himmel E. M., Mielenz J.R. 2006. Outlook for cellulase improvement: Screening and selection strategies. Biotechnology Advances, 22(5): 452-481.

[3] Zhang Y.-H.P., and Lynd L.R. 2004. Toward an aggregated understanding of enzymatic hydrolysis of cellulose: non-complexed cellulase systems. Biotechnology and Bioengineering 88:797-824.

[4] Zhang Y.-H.P., Lynd L.R. 2006. A functionally-based model for hydrolysis of solid cellulose by fungal cellulase. Biotechnology and Bioengineering, 94(5): 888-898.

[5] Zhang Y.-H.P., and Lynd L.R. 2005. Determination of the number average degree of polymerization of cellodextrins and cellulose with application to enzymatic cellulose hydrolysis Biomacromolecules 6: 1510-1515.

[6] Zhang Y.-H.P., Cui X.B., Lynd L.R., and Huang L. 2006. A transition from cellulose swelling to cellulose dissolution by o-phosphoric acid: Evidences from supramolecular structures and enzymatic hydrolysis. Biomacromolecules 7(2): 644-648.

[7] Zhang Y.-H.P., and Lynd L.R. 2005. Cellulose utilization by Clostridium thermocellum: bioenergetics and hydrolysis product assimilation. Proceedings of the National Academy of Sciences of USA 102:7321-7325.

[8] Lu Y.P., Zhang Y.-H.P., Lynd L.R. 2006. Evidence for enzyme-microbe synergy in cellulose utilization by Clostridium thermocellum. Proceedings of the National Academy of Sciences of USA 103(44): 16165-16169.

[9] Zhang Y.-H.P., Mielenz J.R., Evans B.R., Hopkins R.C., Adams M.W.W. 2007. High-yield hydrogen production from starch and water by synthetic enzymatic pathway. PLOS ONE 2(5): e456.

Driving Tomorrow by Sugars

Select Honors

Research Interests and Directions

Biomass Conversion and Biorefinery

Cellulose- and Organic- Solvent Lignocellulose Fractionation (COSLIF)

in vitro Synthetic Biology (Synthetic Enzymatic Pathway Engineering for Biocommodity Production)

Enzyme Engineering

Cellulose hydrolysis mechanisms mediated by free cellulases, cellulosomes, and cellulolytic microbes

(Bio)Chemical Process Integration, Optimization and Modeling

Life Cycle Analysis

Courses Taught

Research Statement

Select Collaborators:

The Zhang Lab
Home Biography Research Members Publications Activities News Awards Contact	Driving Tomorrow by Sugars through Imagination, Invention and Innovation Select Honors 2008-2010 DuPont Young Professor Award 2008 Outstanding new faculty award from the College of Engineering of Virginia Tech 2008-2010 Air Force Young Investigator Award (AFOSR) 2006 Best and Brightest Person of Esquire Magazine 2006 Ralph E. Powe Junior Faculty Enhancement Award Research Interests and Directions Biomass Conversion and Biorefinery Cellulose- and Organic- Solvent Lignocellulose Fractionation (COSLIF) in vitro Synthetic Biology (Synthetic Enzymatic Pathway Engineering for Biocommodity Production) Enzyme Engineering Cellulose hydrolysis mechanisms mediated by free cellulases, cellulosomes, and cellulolytic microbes (Bio)Chemical Process Integration, Optimization and Modeling Life Cycle Analysis Courses Taught BSE 5984 Enzyme Engineering (fall 2008, 2010) BSE 3524 Unit Operation (spring 2009) Research Statement Our research integrates chemical engineering design principles with protein biochemistry, microbiology, and modern biotechnology to solve several most important challenges for biofuels (transportation fuels, second generation cellulosic ethanol, butanol, and alkanes; third generation hydrogen and electricity) production from non-food renewable lignocellulose as below. Three main directions are: (1) cellulose solvent based lignocellulose fractionation, (2) cellulase engineering and cellulose hydrolysis mechanisms mediated by free cellulase, cellulosome, and cellulolytic microbes; and (3) enzymatic hydrogen and electricity production. 1. Cellulose- and Organic-Solvent Lignocellulose Fractionation (COSLIF) Technology The largest challenge of cellulosic ethanol biorefineries is to effectively break recalcitrant lignocellulose and release soluble fermentable sugars. In response to this challenge, we have invented a novel Version 1 cellulose-solvent based lignocellulose fractionation technology [1], which can separate lignocellulose to four parts: amorphous cellulose, hemicellulose sugars, lignin, and acetic acid in the below flowchart. It features modest reaction condition (~50^oC, atmospheric pressure), amorphous cellulose generation, and efficient chemical recycling as shown below. As compared to (dilute acid) steam explosion, this technology can produce at least 20% more sugar yields and increase 20% revenues from acetic acid. In addition, we have developed Version 2 and 3 lignocellulose fractionation, which have solved two main shortcomings of Version 1 -- reducing solvent use volume by several fold and avoiding dilute sugar reconcentration. *2. Cellulase Engineering via* Biomolecular Engineering The improvement of specific cellulase activities can be implemented through cellulase engineering -- rational design and directed evolution for each cellulase component as well as the reconstitution of cellulase components [2]. We are applying the combinatorial technologies involving DNA mutagenesis techniques, enzyme cell surface display techniques, and evolutionary engineering for improving cellulase activity on insoluble substrate cellulose. 3. Cellulose Hydrolysis Mechanisms Mediated by Cellulase, Cellulosome, and Cellulolytic Microbe** Cellulose biodegradation requires three types of cellulases (endoglucanase, exoglucanases, and beta-glucosidase) to work together [3]. The unidentified characteristics of heterogeneous cellulose, the complicated interaction between solid cellulose and cellulase components, and the synergic/competitive relationship among various cellulase components limit our understanding of this de-polymerization process and also lags behind the developments in lignocellulose pretreatment and cellulase improvement. We have developed a generic functionally based mathematical model to simulate this complicated process [4]. A new rapid method has been developed to determine the degree of polymerization of cellulose [5]; a new kind of non-substitution, high reactivity, homogeneous, regenerated amorphous cellulose (RAC) has been prepared for studying cellulose hydrolysis [6]. Now we are developing several new technologies which will help us to characterize key substrate characteristics, and elucidate in-depth mechanisms that will provide new insights into lignocellulose pretreatment and cellulase improvement. In addition, we have discovered a new cellulose hydrolysis mechanism for microbial cellulose hydrolysis mediated by a complexed cellulase system -- the Clostridium thermocellum cellulosome [7,8]. 4. Enzymatic Hydrogen Production by Synthetic Enzymatic Pathway[9] The overall reaction is C₆H₁₀O₅ + 7 H₂O --> 12 H₂ + 6 CO₂. Our idea is to utilize energy stored in sugars to break up water and produce energy in the form of hydrogen or oxidate sugars using water rather than oxygen. This technology would be perfect for mobile applications because of mild reaction conditions (~20-80 degree C and high hydrogen yields), complete conversion, after the technology improvement. We first propose SUGAR CARS which storage sugar, convert sugar to hydrogen on board, generate electricity via fuel cells, and drive motor. This technology would solve the technical challenges associated with hydrogen storage, distribution, production, and safety simultaneously. The synthetic enzymatic pathway is shown below, What is more important, the integration of this technology with PEM fuel cell would achieve the highest energy efficiency from chemical energy to mechanical energy. The details of life cycle analysis pertaining to the carbohydrate hydrogen economy vs other hypocretical future economies, such as methanol economy, electron economy, are being conducted. See Our Vision about the Future Transportation and Energy Storage . References: [1] Zhang Y.-H.P., Ding S.-Y., Mielenz J.R., Cui J.-.B., Elander R.T., Laser M, Himmel M.E., McMillan, J.D., Lynd, L.R. 2007. Fractionating recalcitrant lignocellulose at modest reaction conditions. *Biotechnology and Bioengineering* 97(2): 214-223. [2] Zhang Y.-H.P., Himmel E. M., Mielenz J.R. 2006. Outlook for cellulase improvement: Screening and selection strategies. *Biotechnology Advances, 22(5): 452-481. [3] Zhang Y.-H.P., and Lynd L.R. 2004. Toward an aggregated understanding of enzymatic hydrolysis of cellulose: non-complexed cellulase systems. Biotechnology and Bioengineering* 88:797-824. [4] Zhang Y.-H.P., Lynd L.R. 2006. A functionally-based model for hydrolysis of solid cellulose by fungal cellulase. *Biotechnology and Bioengineering, 94(5): 888-898. [5] Zhang Y.-H.P., and Lynd L.R. 2005. Determination of the number average degree of polymerization of cellodextrins and cellulose with application to enzymatic cellulose hydrolysis Biomacromolecules* 6: 1510-1515. [6] Zhang Y.-H.P., Cui X.B., Lynd L.R., and Huang L. 2006. A transition from cellulose swelling to cellulose dissolution by o-phosphoric acid: Evidences from supramolecular structures and enzymatic hydrolysis. Biomacromolecules 7(2): 644-648. [7] Zhang Y.-H.P., and Lynd L.R. 2005. Cellulose utilization by Clostridium thermocellum: bioenergetics and hydrolysis product assimilation. *Proceedings of the National Academy of Sciences of USA* 102:7321-7325. [8] Lu Y.P., Zhang Y.-H.P., Lynd L.R. 2006. Evidence for enzyme-microbe synergy in cellulose utilization by Clostridium thermocellum. *Proceedings of the National Academy of Sciences of USA* 103(44): 16165-16169. [9] Zhang Y.-H.P., Mielenz J.R., Evans B.R., Hopkins R.C., Adams M.W.W. 2007. High-yield hydrogen production from starch and water by synthetic enzymatic pathway. *PLOS ONE* 2(5): e456. Select Collaborators: DOE BioEnergy Science Center Oak Ridge National Laboratory (Jonathan Mielenz, Barbara Evans, etc.) National Renewable Energy Laboratory (Mike Himmel, James McMillan, etc.) Dartmouth College (Lee Lynd) Unversity of Georgia (Mike W Adams) Purdue University (Nancy Ho) Pacific Northwestern National Laboratory Edgewood Chemical Biological Center -- US Army Redcom Laboratory Some biofuel companies. If you are interested in our technology transfer (lignocellulose fractionation and enzymatic hydrogen production), please feel free to contact me or VTIP. Imagination, Innovation, Implementation (3I Biofuels Lab)