Team:SUIS Shanghai/Description
Description
Microalgae has recently attracted attention as a potential feedstock for helping countries develop a biorenewable based green economy. China is a country that has shown great promise for developing algal biorefineries through its great abundance and diversity of microalgae(Li et al., 2015). Presently, microalgal biomass cultivation is regarded as a potential way to overcome our current reliance on both energy and products derived from fossil fuels.
Biomass is an organic matter that was stored in living or recently living objects. It is a renewable source of energy and raw materials, which can be readily converted to heat and/or electricity using existing well-established technologies. However, in order to design an economically feasible production processes it is necessary, as part of the biorefinery concept, to utilize all constituents of the microalgal biomass(Hariskos & Posten, 2014). This means not just energy, but other more valuable products should be produced and harvested for consumers.
Biorefineries and High Value Product (HPV) first concept.
The conversion of biomass into a variety of products, can improve the prospects of microalgal biofuels by combining them with the production of high value co-products. The selection of strains for microalgae biorefinery should follow a “High Value Product first” approach where the first stages of screening organisms for biofuel production should focus on various high value compounds such as PUFAs, carotenoids or ability to express heterologous proteins as well as one biofuel products. This approach is to should be produced in a biorefinery system to maximise financial and environmental profits resulting from integration of microalgae (Li et al., 2015). See Figure 1.
Figure 1 - High Value Product First selection process for the screening of microalgae for biofuel production. Strains should be chosen which provide at least one high value product (HVP) in addition to a biofuel product. It is recommended that the HVP take precedence in the screening process. (Adapted from Li et al., 2015)
Again however the issue of biomass is a limiting factor as the total quantity of microalgal biomass produced in current industrial processes is disappointingly low. Currently there is intensive global research efforts aimed at increasing and modifying the accumulation of lipids, alcohols, hydrocarbons, polysaccharides, and other energy storage compounds in photosynthetic organisms through direct genetic engineering efforts (Radakovits et al., 2010). However, up until recently little attention has been paid to exploring and controlling the naturally occuring ecology of microalgae and particularly their interactions with other organisms in their natural environments for biotechnology useful applications.
Bacterial - MicroAlgal Interactions.
Microalgae and bacteria have existed together from the early days of evolution. It is through this coevolution that has brought about many photosynthetic microalgae and aquatic bacteria symbiotic relationships, that play integral roles in both marine and freshwater ecology (Tandon et al., 2017).
It has been well documented that Microalgae undertake a wide range of mutualistic interactions with bacteria and indeed several studies show that heterotrophic bacteria play a ubiquitous role in algal growth and survival (Ramanan et al., 2016). Previous generations have often viewed the presence of bacteria in microalgae cultures as mere contaminants. Nowadays however, these algae-bacteria interactions are being seen as promising areas of research in biotechnology with many suggesting that in order to fully release the potential of microalgae as a renewable source of fuel and high value products, there must be further research into the complex interactions that exist between these two species (Cooper & Smith, (2015) and Ramanan et al., (2016); and Kazamia et al., (2012)).
We viewed the exploration of algal ecology for the exploitation of biotechnology a promising avenue to be explored by the synthetic biology community, as many recent studies have shown a positive effect of algae-bacteria interaction on algal growth. The algal growth, for instance, has been shown to be enhanced by growth promoting factors produced by bacteria, such as indole-3-acetic acid. Additionally, Vitamin B12 produced by bacteria in algal cultures and bacterial siderophores are also known to be involved in promoting faster microalgal growth (Fuentes et al., 2016).
The growth of some microalgal communities in the natural marine habitat are often regulated by iron. Iron is essential for both photosynthesis and respiration so it follows that iron limitations halts the productivity of marine bacteria and eukaryotic phytoplankon (Shady et al., 2009). Many species of bacteria therefore produce small organic molecules called siderophores, that bind to iron and help facilitate the uptake of the siderophore-iron complex via specific cell membrane transport proteins. Many green algae species and diatoms exploit this adaptation in bacteria by producing their own transport proteins out their outer cell membranes (Shaked et al., 2005).
Fig 2 - Nutrient exchange between bacteria and microalgae is an example of mutualism which has evolved from the early days of life. In the age of synthetic biology there are opportunities for the rational design of bacteria or a consortia of bacteria to enhance industrial microalgae products. (Image adapted from: Fuentes et al., (2016))
Vibrioferrin
One such siderophore, Vibrioferrin (VF), is produced by several species of marine bacteria that are usually found in close association with some microalgae. VF originally isolated from the bacterium Vibrio parahaemolyticus, may be well suited for the enhancement of microalgae growth, because it is remarkably sensitive to light. Upon binding with iron in the presence of light, the vibrioferrin-iron complex (Fe(III)-VF) undergoes photolysis at 10- to 20-fold higher rate than other siderophores. Importantly, the product of this Fe-VF photolytic reaction (FeIII’) appears to have no affinity for iron, unlike the product produced by dissociation of iron from siderophores produced by free-living bacteria. FeIII’ is highly bioavailable to microalgae and can then be assimilated in large amounts by both the bacteria and microalgae species in the relationship. Algae uptake of iron in the presence of sunlight resulted in a >20 fold increase in iron acquisition from seawater media. (9).
Fig 3 - Engineered E.coli can produce vibrioferrin which first binds to iron (FeIII), then undergoes photolysis in light conditions eventually resulting in an reduced iron moiety (FeIII’) which is highly bioavailable to certain strains of microalgae.
Project Aim
Our aim is to engineer E.coli, so that it is capable of the heterologous expression of the vibrioferrin biosynthesis gene cluster and transport protein, and thus produce the siderophore, releasing it into the growth media for co-culturing or isolation of the compound for addition to growth media.
References:
Li, Liu, Cheng, Mos, & Daroch. (2015). Biological potential of microalgae in China for biorefinery-based production of biofuels and high value compounds. New BIOTECHNOLOGY, 32(6), 588-596.
Hariskos, I., & Posten, C. (2014). Biorefinery of microalgae – opportunities and constraints for different production scenarios. Biotechnology Journal, 9(6), 739-752.
Radakovits, Randor, Jinkerson, Robert E., Darzins, Al, & Posewitz, Matthew C. (2010). Genetic Engineering of Algae for Enhanced Biofuel Production. Eukaryotic Cell, 9(4), 486-501.
Tandon, Puja, Jin, Qiang, & Huang, Limin. (2017). A promising approach to enhance microalgae productivity by exogenous supply of vitamins. Microbial Cell Factories, 16(1), 219.
Cooper, & Smith. (2015). Exploring mutualistic interactions between microalgae and bacteria in the omics age. Current Opinion in Plant Biology, 26(C), 147-153.
Ramanan, Rishiram, Kim, Byung-Hyuk, Cho, Dae-Hyun, Oh, Hee-Mock, & Kim, Hee-Sik. (2016). Algae–bacteria interactions: Evolution, ecology and emerging applications. Biotechnology Advances, 34(1), 14-29.
Kazamia, Aldridge, & Smith. (2012). Synthetic ecology – A way forward for sustainable algal biofuel production? Journal of Biotechnology, 162(1), 163-169.
Juan Luis Fuentes, Inés Garbayo, María Cuaresma, Zaida Montero, Manuel González-Del-Valle, & Carlos Vílchez. (2016). Impact of Microalgae-Bacteria Interactions on the Production of Algal Biomass and Associated Compounds. Marine Drugs, 14(5), .
Shady A. Amin, David H. Green, Mark C. Hart, Frithjof C. Küpper, William G. Sunda, & Carl J. Carrano. (2009). Photolysis of iron–siderophore chelates promotes bacterial–algal mutualism. Proceedings of the National Academy of Sciences, 106(40), 17071-17076.
Shaked, Y., Kustka, A., & Morel, F. (2005). A general kinetic model for iron acquisition by eukaryotic phytoplankton. Limnology and Oceanography, 50(3), 872-882.
IGEM | WANYUAN | SUIS
Website: wanyuan.suis.com.cn
Mail Box: suisigem@outlook.com
No.509, Pingji Rd, Minhang District, Shanghai
Back To Top
Home Page
Contact