permaculture

["Lawrence F. London, Jr." <lflj@bellsouth.net>]

------- Original Message --------
Subject: [SANET-MG] using carbon dioxide
Date: Sun, 26 Aug 2012 22:59:49 -0400
From: jcummins <jcummins@UWO.CA>
To: SANET-MG@LISTS.IFAS.UFL.EDU

/*Synechocystis sp. PCC6803 is a freshwater cyanobacterium capable of
both phototrophic growth by oxygenic photosynthesis in sunlight and
heterotrophic growth by glycolysis and oxidative phosphorylation during
dark periods. Transitions of light and dark phases are effectively
anticipated by a circadian clock. If */carbon dioxide  can be used to
produce ethylene  it seems that zero emission  could be possible.
Ethylene can be burnt but also be used to produce a lot of products.
Sustained photosynthetic conversion of CO2 to ethylene in recombinant
cyanobacterium Synechocystis 6803 Justin Ungerer ,  Ling Tao ,  Mark 
Davis ,  Maria Ghirardi , Pin-Ching Maness and Jianping Yu Energy 
Environ. Sci., 2012, Advance Article DOI: 10.1039/C2EE22555G
Ethylene is the most widely produced petrochemical feedstock globally.
It is currently produced exclusively from fossil fuels, and its
production is the largest CO2-emitting process in the chemical industry.
In this study, we report on a photobiological process for sustained
production of ethylene from CO2. The efe gene encoding an
ethylene-forming enzyme from Pseudomonas syringae pv. Phaseolicola was
previously expressed in cyanobacterial strains, but was not stable. We
modified the gene sequence to enhance its stability, and expressed it in 
Synechocystis sp. PCC 6803, leading to continuous ethylene production.
The same ethylene production rate was sustained across four successive
sub-cultures without apparent loss of ethylene-forming ability. Up to
5.5% of the fixed carbon was directed to ethylene synthesis, surpassing
the published carbon-partition rate into the TCA cycle. Nitrogen- and
phosphorus-enriched seawater can support both growth and ethylene
production. Factors limiting ethylene production, including efe
expression levels, light intensity and nutrient status, were identified
and alleviated, resulting in a peak production rate of 5650 ?L L-1 h-1
(7125 ?g L-1 h-1, 252 ?mol L-1 h-1, or 171 mg L-1 day-1), which is
higher than that reported for other algae biofuels and chemicals. This
study suggests that Synechocystis, expressing the modified efe gene, has 
potential to be an efficient biological catalyst for the uptake and
conversion of CO2 to ethylene.