PHAECTORY: Good reasons for a new chassis

The widely spread diatom Phaeodactylum tricornutum is particularly interesting. Its entire genome has been sequenced, an easy biolistic method for transfection is well established as well as protocols for the cultivation are available. Taking this into account it appeared to us as the perfect organism to produce complex proteins for the iGEM competition.

"Classical" large-scale biotechnology is mostly applied in bacteria and other fungi. Both need to be fed with carbon sources and the purification of the desired products e.g. functional high-value proteins is cost intensive, very time consuming and difficult. This is due to the fact that the cells need to be disrupted hence proteins/metabolites have to be removed from the medium.

PHAECTORY

By using a green cell factory of plants or algae it is possible to produce all kinds of products even high-value proteins like human antibodies in a large-scale background. Looking at previous iGEM-projects we recognized that no practical green chassis was introduced into the competition although these organisms perform photosynthesis, which enables a carbon dioxide neutral handling. In the photosynthetic process light energy is converted into chemical energy, which can be used to fuel different cellular reactions in the cell. Concerning the problem of global warming these organisms offer the possibility to reduce the emission of green house gases and work against the extensive use of fossil fuels. Moreover, it is not necessary to feed green algal cell factories with carbohydrates. The world population is continuously growing resulting in a scarceness of nutrition. The iGEM team Marburg aims at introducing a green cell factory, which is driven by sunlight, produces no carbon dioxide and above all does not compete with the nutrition-producing sector.

The microalga P. tricornutum is a green organism incorporating all above-mentioned advantages. This fast-growing organism lives with carbon dioxide and light and is able to produce substances like bioplastic, biofuels, spider silk and other complex proteins (Hempel and Maier, 2012, BIOforum). This year, the iGEM team Marburg decided to produce a human antibody against the Hepatitis B virus (PHAECTORY). An important feature of PHAECTORY is that the antibody is directly secreted into the medium, which enormously simplifies purification. In general, microalgae secret only very few additional substances and therefore all products produced in PHAECTORY are already present in a high purity (Hempel et al., 2011, Plos One).

In order to introduce this organism as a chassis to the iGEM community, we build a toolbox, which contains expression vectors, promoters, selection markers, reporter proteins and signal peptides for P. tricornutum. This allows every future iGEM team to produce their own complex proteins, which can easily be processed.