We study the photosynthesis of plants, microalgae, cyanobacteria, and photosynthetic bacteria. Approaches include biophysics and biochemistry of the process, molecular biology and genetics of the organisms, and scale ups for product generation. Applied aspects include diverting the flow of photosynthesis to generate high-value compounds instead of the normally produced sugars. Products of interest are biofuels, feedstock for the synthetic chemistry industry and pharmaceuticals. Our trademark is product generation directly from photosynthesis, bypassing the need to harvest and process the respective biomass.
Photosynthetic Biofuels and Chemicals
Expertise and Philosophy
The expertise of the Melis lab is in the field of photosynthesis and metabolism. We work with land plants, microalgae, cyanobacteria, and non-oxygenic (anaerobic) photosynthetic bacteria. Our platform includes most aspects of photosynthesis, beginning with organism cultivation, the efficiency of light absorption and utilization, electron transport and biochemical energy generation, and chloroplast and cellular metabolism. Included are the biophysics and biochemistry of the process, the molecular biology and genetics of the organisms, as well as scale ups in the cultivation of the various organisms for product generation.
The concept of “Photosynthetic Biofuels”, envisioned and pioneered by us, entails the direct application of photosynthesis for the generation of biofuels, in a process where a single organism acts both as catalyst and processor, synthesizing and secreting ready to use fuels.
The lab contributed with a breakthrough in the field, when in 2000 we demonstrated, for the first time, how to divert the natural flow of photosynthesis in green microalgae and to sustainably generate hydrogen gas, instead of the normally produced oxygen. This technology is currently employed by many laboratories in several countries, and serves as the platform for further photobiological hydrogen production research in the field.
The Melis lab also pioneered and currently leads an international effort to improve, by up to 300%, the efficiency and productivity of photosynthesis in mass cultures under bright sunlight conditions. This is implemented upon genetically optimizing the size of the array of chlorophyll molecules that serve as antennae to absorb sunlight for the photosynthetic apparatus.
In 2010, the Melis lab pioneered yet a new platform for the renewable generation of isoprene (C5H8) hydrocarbons in cyanobacteria and microalgae, derived entirely from sunlight, carbon dioxide (CO2) and water (H2O), and generated immediately from the primary products of photosynthesis. The process of generating isoprene currently serves as a case study in the development of technologies for the renewable generation of a multitude of biofuels and other useful bio-products.
Hydrogen and hydrocarbon biofuels production via microalgal photosynthesis
- Maximize the solar-to-chemical conversion efficiency of photosynthesis under mass culture conditions
- Improve the continuity and yield of the green microalgal hydrogen and hydrocarbon production
- Develop suitable photobioreactors for biofuels production.
Microalgae for Hydrogen & Hydrocarbon Biofuels Production
The Melis lab has developed cells with a truncated chlorophyll antenna size containing 0.15x10e9 Chl/cell, vs. fully pigmented cells that contain 1.0x10e9 Chl/cell. The goal of this project is to improve the solar-to-chemical conversion efficiency of photosynthesis under bright sunlight from the normally 3% in wild type to 30% in the truncated Chl antenna mutants.
|Visual demonstration of the effect of differential pigmentation in the cells of the green alga Dunaliella salina. Note the greater transmittance of light through the Chl-deficient culture (left-side bottle) and the strong absorbance of light by the fully pigmented cells (right-side bottle).|
|Hydrogen production in a sealed (anaerobic) liquid culture of the green alga Chlamydomonas reinhardtii, showing the hydrogen bubbles as they emanate from the medium. (From Melis and Happe 2001)|
Through its Oleomics™ Project, the Melis Lab seeks to identify and exploit biosynthetic pathways leading to hydrocarbon biofuels production by unicellular green algae. Employed in this project are Chlamydomonas reinhardtii, a model green microalga amenable to genetic manipulation, and Botryococcus braunii, a prolific lipid-accumulating unicellular green alga.
Genetic maps of wild type and IspS transformants, illustrating a strategy for heterologous transformation of cyanobacteria, and conferring volatile isoprene hydrocarbons production. (From Lindberg et al. 2010)
|A mechanically compressed Botryococcus braunii var. Showa microcolony, revealing droplets of triterpenoid botryococcene hydrocarbons (Btc-oil) squeezed from the “flattened” micro-colony toward the growth medium. (From Eroglu and Melis 2010)|
Melis A, Chen H-C (2007) Modulation of sulfate permease for photosynthetic hydrogen production. United States Patent 7,176,005 (issued 13-Feb-2007)
Tetali SD, Mitra M, Melis A (2007) Development of the light-harvesting chlorophyll antenna in the green alga Chlamydomonas reinhardtii is regulated by the novel Tla1 gene. Planta 225: 813-829
Park S, Khamai P, Garcia-Cerdan JG, Melis A (2007) REP27, a tetratricopeptide repeat nuclear-encoded and chloroplast-localized protein functions in the D1/32 kD reaction center protein turnover and PSII repair from photodamage. Plant Physiology 143: 1547-1560
Melis A, Seibert M, Ghirardi ML (2007) Hydrogen fuel production by transgenic microalgae. In: Leon R, Gavan A, Fernandez E (eds) Transgenic Microalgae as Green Cell Factories. Landes Bioscience, Austin, Texas. Chapter 10, pp. 110-121
Melis A (2007) Photosynthetic H2 metabolism in Chlamydomonas reinhardtii (unicellular green algae). Planta 226: 1075-1086
Bailey S, Melis A, Mackey KR, Cardol P, Finazzi G, van Dijken G, Berg GM, Arrigo K, Shrager J, Grossman A (2008) Alternative photosynthetic electron flow to oxygen in marine Synechococcus. Biochim Biophys Acta 1777(3): 269-276
Berberoglu H, Pilon L, Melis A (2008) Radiation characteristics of Chlamydomonas reinhardtii CC125 and its truncated chlorophyll antenna transformants tla1, tlaX, and tla1-CW+. Intl J Hydrogen Energy 33: 6467-6483
Lindberg P, Melis A (2008) The chloroplast sulfate transport system in the green alga Chlamydomonas reinhardtii. Planta 228:951-961
Melnicki MR, Bianchi L, De Philippis R, Melis A (2008) Hydrogen production during stationary phase in purple photosynthetic bacteria. Intl J Hydrogen Energy 33:6525-6534
Ruehle T, Hemschemeier A, Melis A, Happe T (2008) A novel screening protocol for the isolation of hydrogen producing Chlamydomonas reinhardtii strains. BMC Plant Biology 8:107 (13 pages); PDF doi:10.1186/1471-2229-8-107
Eroglu E, Melis A (2008) ”Density Equilibrium” method for the quantitative and rapid in situ determination of lipid, hydrocarbon, or biopolymer content in microorganisms. Biotech Bioeng, DOI 10.1002/bit.22182
Mitra M, Melis A (2008) Optical properties of microalgae for enhanced biofuels production. Optics Express. 16(26):21807-20. PDF 1 Mb
BioOptics World article re paper
Eroglu E, Melis A (2009) ”Density Equilibrium” method for the quantitative and rapid in situ determination of lipid, hydrocarbon, or biopolymer content in microorganisms. Biotech Bioeng 102:1406-1415
Hemschemeir A, Melis A, Happe T (2009) Analytical approaches to photobiological hydrogen production in unicellular green algae. Photosynth Res. 102:523-540
Melnicki MR, Eroglu E, Melis A (2009) Changes in hydrogen production and polymer accumulation upon sulfur-deprivation in purple photosynthetic bacteria. Intl J Hydrogen Energy 34:6157-6170
Melis A (2009) Solar energy conversion efficiencies in photosynthesis: minimizing the chlorophyll antennae to maximize efficiency. Plant Science 177: 272-280
Dewez D, Park S, García-Cerdán JG, Lindberg P, Melis A (2009) Mechanism of the REP27 protein action in the D1 protein turnover and photosystem-II repair from photodamage. Plant Physiol. 151:88-99
Lindberg P, Park S, Melis A (2010) Engineering a platform for photosynthetic isoprene production in cyanobacteria, using Synechocystis as the model organism. Metabol Engin 12:70-79
Eroglu E, Melis (2010) Extracellular terpenoid hydrocarbon extraction and quantitation from the green microalgae Botryococcus braunii var. Showa. Biores Technol 101:2359-2366
Mitra M, Melis A (2010) Genetic and biochemical analysis of the TLA1 gene in Chlamydomonas reinhardtii. Planta 231:729-740
Melis A and Mitra M (2010) Suppression of Tla1 gene expression for improved solar energy conversion efficiency and photosynthetic productivity in plants and algae. United States Patent 7,745,696 (issued 29-June-2010)
Eroglu E, Okada S, Melis A (2011) Hydrocarbon productivities in different Botryococcus strains: comparative methods in product quantification. J Appl Phycol In Press DOI 10.1007/s10811-010-9577-8
Honors and Awards