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Prototroph's Blog

Developments in microalgal harvesting: Genetically engineered auto/bio-flocculation.

Developments in microalgal harvesting
biotechnology: Genetically engineered auto/bio-flocculation.


Harvesting microalgae at large scales
represents a significant barrier to economically feasible production of algal biomass
for liquid fuels and other useful products. Some estimates approximate microalgal
harvesting costs at 30%-50% of total production (energy use and capital
investment). Seeking a cost effective cell harvesting technology, we have
generated transgenic Chlamydononas reinhardtii that can autoflocculate
(or “bioflocculate”) via heterologous protein expression. In layman’s terms: we
have produced prototype strains of genetically modified unicellular algae that
can harvest themselves. Thus, there is no need to add any sort of chemical or biological flocculant. Flocculation is carried out by engineered cellular mechanisms. We have also generated recombinant expression vectors
allowing for genetically induced flocculation once the culture has reached
stationary phase. Our strains are experimental in nature and are not intended
for use in the field. We are currently trying to publish our results in a peer
reviewed research journal. We have also tried to patent this technology;
however, Saphire energy has already patented an advanced version of genetically
induced autoflocculation technology (although we took a different technical
approach).


I just wanted to let the online
community of algal enthusiasts know about this exiting technology as it has the
capacity to eliminate a significant fraction of production costs associated
with microalgal culturing processes.  Keep
in mind, however, this technology is likely a few (or many) years away from
actual implementation or field readiness…


I also wanted to throw this idea out so engineers and designers can start to rethink how this type of harvesting
technology can influence bioreactor and culture system design.


I’m not sure anyone knows how
microalgae will be harvested ten or fifteen years from now. That being said, I’m
guessing genetically induced autoflocculation may be the future gold standard
of microalgal harvesting technology.   


-Prototroph

Fri July 15 2011 12:58:55 AM by Prototroph 28

Nitrogen fixation blog

Something to think about that doesn't receive a lot of press and needs more dialogue in the community. Nitrogen is a major component of cellular biomass and is essential for metabolic and cellular functions. Eukaryotic algae, such a Chlorella, Dunellia, Chlamydomonas ect... cannot fix atmospheric nitrogen and thus must reduce Nitrate/Nitrite to ammonia in order to synthesize biomass. Current algal biomass industrial models plan on adding bio-available nitrate or ammonium salts to the culture media. This is fine on a small scale, you just throw in a few grams of "miracle-grow" and the algae go crazy. However, on a large scale one must think about the energy cost of this N fertilization. Atmospheric N gas is in no short supply but the industrial production of ammonia from N gas requires a lot of energy. The Haber process for example, requires temperatures of 500'C and pressures ranging up to 10,000 kilopascales. I'm no chemical engineer nor an economist, but if you need millions of gallons of biodiesel from millions of kgs of biomass then you are going to need a crap load of energetically and economically expensive ammonia. Not to mention that for every unit of energy you put into N fertilization you will effectively loose a unit of energy output from algal fuel production (energy investment vs. payoff). Does anyone know what percentage of algal energy output would go into N-fixation/fertilization using eukaryotic algae? Could you send me a message?

A few solutions:

Many species of photosynthetic cyanobacteria can fix atmospheric nitrogen to ammonia in aerobic environments, like a pond or PBR. This biological process is a wonder of biochemistry, finely tuned over millions of years. The overall rxn uses 16 ATP and 16 electrons to produce two molecules of ammonia and hydrogen gas (both valuable to humans). Heterocystic and mucosol cyanobacteria can run this possess in an aerobic environment by protecting the enzymatic machinery from oxygen poisoning. Thus, engineered oil producing cyanobacteria could be used to efficiently grow energy rich biomass.

Have your heart set (or dollars spent) on eukaryotic algae? It seems possible to co-cultivate eukaryotic algae with N-fixing bacteria in a symbiotic relationship; much like N-fixing leguminous plants (soybeans). There's allot of work to be done here.

Using N rich waste/sewage water or compost "tea" may well be the key. The complex microbial communities associated with sewage and compost, however, add a level of complexity to the already challenging large scale culture of algae - talk about contamination! ughhh
Sat May 08 2010 07:16:53 PM by Prototroph 3