Anastasios Melis

Professor, UC Berkeley
Faculty Biologist, LBNL-EETD
Ph.D.  Florida State University
B.S.  University of Athens

471A Koshland Hall
Berkeley, California 94720
melis@berkeley.edu
office: 510-642-8166   lab: 510-642-6209   fax: 510-642-4995

CV       Recent publications      People

Expertise and Philosophy

The expertise of the Melis lab is in the field of photosynthesis. 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 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 we demonstrated, for the first time, how to divert the natural flow of photosynthesis in microalgae and to generate hydrogen gas, instead of the normally produced oxygen. This advance pointed to organism genetic engineering, by which to divert the flow of photosynthesis toward alternative high-value bioproducts instead of the normally produced sugars. A number of "blueprints" are currently in the R&D stage, leading to the generation of biofuels, feedstock for the synthetic chemistry industry, and neutraceuticals. The trademark of our approach is product generation directly from photosynthesis, and spontaneous product separation from the organism, bypassing the need to harvest and process the respective biomass.

Hydrogen and hydrocarbon biofuels production via microalgal photosynthesis

Hydrogen and hydrocarbon biofuels may become the primary 21st century energy carriers in California and the nation. Modification of photosynthesis in green microalgae may permit the generation of these biofuels as clean, renewable and economically viable commodities. However, specific biological problems associated with a sustained, high yield photosynthetic production of these biofuels remain to be addressed.

Current Objectives:

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 advanced tubular photobioreactors for biofuels production.

Green Algae 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 green alga Chlamydomonas reinhardtii, showing
hydrogen bubbles.

Hydrogen production in a sealed (anaerobic) liquid culture of the green alga Chlamydomonas reinhardtii, showing the hydrogen bubbles as they emanate from the medium.

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.

Photosystem-II damage and repair cycle in chloroplasts.

Photosynthetic organisms use a specialized repair mechanism, entailing disassembly of inactive photosystem-II units and selective degradation and replacement of photodamaged D1/32 kD reaction-center proteins. The Melis Lab applies DNA insertional mutagenesis in the model green alga Chlamydomonas reinhardtii to isolate and characterize photosystem-II repair mutants, identify the genes and enzymes involved, and investigate intermediate photosystem-II repair configurations.

Schematic presentation of a temporal sequence of events in the photosystem-II (PSII) damage and repair cycle in chloroplasts.

The rate of photodamage is directly proportional to the incident light intensity.
The rate of PSII disassembly is not limiting, leading to
Formation of a D1-containing 160-kD protein complex.
Degradation of photo-damaged D1 in the 160 kD complex is rate-limiting in the repair process.
It is followed by a de novo D1 biosynthesis,
Insertion of the nascent D1 polypeptide in thylakoids, and
Reassembly of the PSII holocomplex to yield a functional PSII holocomplex.

Under high irradiance conditions, photodamaged reaction centers accumulate in thylakoids in the form of 160 kD complexes.

The PSII damage and repair cycle entails high rates of D1 protein biosynthesis.

Recent publications

Melis A (2005) Bioengineering of green algae to enhance photosynthesis and hydrogen production. Chapter 12 in Artificial Photosynthesis: From Basic Biology to Industrial Application, AF Collins and C Critchley (eds.), Wiley-Verlag & Co., pp. 229-240

Park S, Polle JE, Melis A, Lee TK, Jin E (2006) Up-regulation of photoprotection and PSII-repair gene expression by irradiance in the unicellular green alga Dunaliella salina. Mar. Biotech. 8:120–128.

Yokthongwattana K, Melis A (2006) Photoinhibition and recovery in oxygenic photosynthesis: Mechanism of a photosystem II damage and repair cycle. In, Photoprotection, Photoinhibition, Gene Regulation, and Environment, Advances in Photosynthesis and Respiration (Series Editor, Govindjee), Volume 21: 175–191; Springer, The Netherlands

Melis A, Melnicki M (2006) Integrated biological hydrogen production. Intl. J. Hydrogen Energy 31: 1563-1573

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

Honors and awards

Research Achievement Award - US Department of Energy, Hydrogen Program - 2004

University Research Award - DaimlerChrysler Corporation - 2003

CNR Teaching Award - College of Natural Resources - 1994

Recent Teaching

135 - Physiology and Biochemistry of Plants

135L - Laboratory for Physiology and Biochemistry Plant

180 - Environmental Plant Biology

199 - Supervised Independent Study

222 - Biochemistry of Biofuels: Concepts and Foundations

290 - Graduate Seminar

299 - Research in Ag. Chem.