I wish to suggest constructing the electricity-carbohydrate-hydrogen (ECHo) cycle could meet four basic needs of humans: air, water, food and energy, while minimizing environmental footprints. In it, electricity is a universal high-quality energy carrier; hydrogen is a clear electricity carrier; and carbohydrate is a hydrogen carrier, an electricity storage compound and sources for food, feed and materials. By using this cycle, we could replace crude oil with a new oil -- carbohydrates (CH2O) with highest energy utilization efficiencies, feed the world, power cellular phone, produce plenty of renewable materials and liquid biofuels (e.g., ethanol, butanol, jet fuel), etc. .
We conduct our research project based on two platforms: cascade enzyme factories and microbial cell factories (e.g., E. coli and Bacillus subtilis).
Based on cascade enzyme factories, our specific projects include
Sweet hydrogen and sugar fuel cell vehicles. To break the Thauer limit for natural hydrogen-producing microorganisms, we have achieved the production of theoretical yield hydrogen from hexose (i.e., 12 H2 per glucose unit) [2,3] and xylose (i.e., 10 H2 per xylose) . Via it, we propose the use of sugar as a hydrogen carrier so to solve hydrogen storage and infrastructure challenges. The hypothetical sugar fuel cell vehicles would be the most energy efficiency vehicles. A small fraction of the USA biomass could be sufficient to replace all gasoline [5,6].
Highest energy density battery powered by sugars. We accomplish to produce 24 electrons per glucose for the first time . As a result, this sugar-powered biobattery has the highest energy density compared to primary, secondary and fuel cells. This battery is 100% biodegradable, highly safe, and fast refillable. This breakthrough is highlighted by Time Magazine, US News and World Report, BBC, etc.
Artificial photosynthesis for CO2 utilization . To surpass natural limits of plant photosynthesis, we propose a new system by integrating solar cell, water electrolysis, and CO2 fixation with 20-50 higher energy utilization efficiency and 500-1000 fold higher water conservation, compared to plant photosynthesis.
Synthetic starch made from celluose . For the first time we accomplish to convert beta-1,4-glucoisidic bond linked cellulose to alpha-1,-4-bond linked starch without sugar losses . As a result, feeding the world would be not a big problem in the future .
By utilizing microbial cell factories, our specific projects include
Cellulase engineering, metabolic engineering, and consolidated bioprocessing Bacillus subtilis. We have developed a novel enzyme screening platform based on solid cellulosic materials  and created the first really recombinant cellulolytic microorganisms that can grow on solid cellulosic materials based on its recombinant cellulases without help of other soluble nutrients . Now a start-up company -- Gate Fuels Inc. -- is leading its innovation.
Enzyme engineering by rational design and directed evolution. We are developing artificial redox enzymes that can work on low-cost biomimetic cofactors, which may be the last obstacle to cascade enzyme factories.
Low-cost recombinant protein production and purification as building blocks and synthetic metabolons for cascade enzyme factories and microbial cell factories .
Also, we are investigating the complicated relationship among heterologous cellulose, cellulases, cellulosomes and cellulolytic microorganisms. For example, we find out that increasing substrate accessibility is more important than removing lignin for biomass pretreatment . Displaying minicellulosomes on the surface of microorganisms can expedite microbial cellulose conversion rate by several folds .
 Zhang Y-HP*, Huang WD. 2012. Constructing the electricity-carbohydrate-hydrogen cycle for sustainability revolution. Trends in Biotechnology, 30: 301-306 (PDF) (opinion).
 Zhang Y-HP*, Evans BR, Mielenz JR, Hopkins RC, Adams MWW. 2007. High-yield hydrogen production from starch and water by synthetic enzymatic pathway. PLoS ONE 2(5): e456 (Open Access PDF).
 Ye X, Wang Y, Hopkins RC, Adams MWW, Evans BR, Mielenz JR, Zhang Y-HP*. 2009. Spontaneous high-yield production of hydrogen from cellulosic materials and water catalyzed by enzyme cocktails. ChemSusChem 2: 149-152.
 Martin del Campo JS, Rollin JR, Myung S, You C, Chandrayan S, Patiño R, Adams MWW, Zhang Y-HP*. 2013. Dihydrogen production from xylose and water mediated by synthetic cascade enzymes. Angewandte Chemie International Edition 52:4587-4590 (PDF). (Editor’s choice paper).
 Huang WD, Zhang Y-HP*. 2011. Energy efficiency analysis: biomass-to-wheel efficiency related with biofuels production, fuel distribution, and powertrain systems. PLoS One 6(7): e22113 (Open access PDF).
 Zhang Y-HP*. 2013. Next-generation biorefineries will solve the food, biofuels and environmental trilemma in the energy-food-water nexus. Energy Science and Engineering 1:25-41 (Open access PDF).
 Zhu ZG, Tam TK, Sun FF, You C, Zhang Y-HP*. 2014. A high-energy-density sugar biobattery based on a synthetic enzymatic pathway. Nature Communications. 5: 3026 (PDF).
 Zhang Y-HP*, Chun Y, Chen HG, Feng RL. 2012. Surpassing photosynthesis: high-efficiency and scalable CO2 utilization through artificial photosynthesis. ACS Symposium Series 1097: 275-292 (PDF) (Recent Advances in Post-Combustion CO2 Capture Chemistry), Oxford University Press, UK.
 You C, Chen HG, Myung S, Sathisuksanoh N, Ma H, Zhang XZ, Li JY, Zhang Y-HP*. 2013. Enzymatic transformation of non-food biomass to starch. Proceedings of the National Academy of Sciences of the USA. 110: 7182-7189 (Open access PDF). Highlighted by Science magazine "could wood feed the world".
 Zhang X-Z, Zhang Y-HP*. 2011. Simple, fast and high-efficiency transformation system for directed evolution of cellulase in Bacillus subtilis. Microbial Biotechnology 4: 98-105 (Highlighted).
 Zhang XZ, Zhu ZG, Sathitsuksanoh N, Zhang Y-HP*. 2011. One-step production of lactate from cellulose as sole carbon source without any other organic nutrient by recombinant cellulolytic Bacillus subtilis. Metabolic Engineering 13:364-372.
 Rollin J, Zhu ZG, Sathisuksanoh N, Zhang Y-HP*. 2011. Increasing substrate accessibility is more important than removing lignin: A comparison of cellulose solvent-based lignocellulose fractionation and soaking in aqueous ammonia.Biotechnology and Bioengineering 108: 22-30 (#1 most cited research paper in year 2011).
 You C, Zhang X-Z , Sathitsuksanoh N, Lynd LR, Zhang Y-HP*. 2012. Enhanced microbial cellulose utilization of recalcitrant cellulose by an ex vivo cellulosome-microbe complex. Applied and Environmental Microbiology 78(5):1437-1444.
Federal sources: NSF, DOE BESC, DOE ARPA-E, AFOSR, Army, USDA, Sun Grant
Companies: Shell, DuPont, Equation Group, Taiwan ITRI, Gate Fuels, Cell Free Bioinnovations
Foundations: ACS PRF, ORAU