Trends in Biotechnology
Volume 32, Issue 11, November 2014, Pages 551-555
Journal home page for Trends in Biotechnology

Opinion
Increasing algal photosynthetic productivity by integrating ecophysiology with systems biology

https://doi.org/10.1016/j.tibtech.2014.09.007Get rights and content

Highlights

Oxygenic photosynthesis is the process by which plants, algae, and cyanobacteria convert sunlight and CO2 into chemical energy and biomass. Previously published estimates suggest that algal photosynthesis is, at best, able to convert approximately 5–7% of incident light energy to biomass and there is opportunity for improvement. Recent analyses of in situ photophysiology in mass cultures of algae and cyanobacteria show that cultivation methods can have detrimental effects on a cell's photophysiology – reinforcing the need to understand the complex responses of cell biology to a highly variable environment. A systems-based approach to understanding the stresses and efficiencies associated with light-energy harvesting, CO2 fixation, and carbon partitioning will be necessary to make major headway toward improving photosynthetic yields.

Section snippets

Oxygenic photosynthesis is inefficient

Algae and cyanobacteria could represent the next generation of biofuels and provide a major source of sustainable transportation fuel to reduce society's dependence on fossil fuels 1, 2. There are several technological hurdles to overcome before the process can become commercially viable, including the essential improvement of the photosynthetic process [3]. Previously published exercises have suggested that algal photosynthesis is, at its best in controlled culture conditions, able to convert

The ecophysiology of dense algal growth

Dense culturing is required to reach high aerial yields of algal biomass, which effectively reduces light penetration into the culture to only a few centimeters [6]. The cells perceive this as a net light-limited scenario and photoacclimate. Photoacclimation involves an increase in the cellular concentration of pigment–protein antenna complexes, photosystems, or both to capture more light and vice versa. This further reduces light penetration into the cell suspension. It also increases the

In situ physiology

There have been relatively few published studies investigating the physiology of photosynthesis in algal mass culture. This is probably due to the financial constraints of constructing and operating large-scale algal aquaculture facilities. However, the data reported thus far are beginning to provide insights into the physiology associated with industrial scenarios.

Torzillo et al. [13] found that reducing the biomass of the diatom Phaeodactylum to 0.3 from 0.6 g/l in a 4.85-cm tubular

Systems biology of algae and cyanobacteria – state of the art

Systems approaches to predicting and manipulating metabolism have resulted in increases of heterotrophic fermentation yields [22] and also can be used to predict increases in plant biomass functions [23]. The development of these tools for algal and cyanobacterial systems over the past few years now has us poised to tackle the inefficiencies mentioned above. Model organisms such as Chlamydomonas, Synechocystis, Synechococcus, Phaeodactylum, Thalassiosira, and, most recently, Nannochloropsis all

Concluding remarks and future perspectives

Our understanding of algal biology has reached a major milestone. Sensitive physiological methods to measure photosynthesis and physiology can now be coupled with systems biology approaches. Improving photosynthesis will require close collaboration between algal physiologists and experts in metabolic modeling. Together, they can take the tools that are outlined above and apply them to discovering and manipulating new targets that are relevant to increasing the productivity of photosynthetic

Acknowledgments

The author is indebted to Roger Prince and Joe Weissman for enlightening conversations about algal biofuels. He thanks two anonymous reviews for their helpful comments. He regrets that he was unable to reference all of the excellent work done in systems biology and photosynthesis that has helped him to form this Opinion; he has tried to direct the reader to as broad a spectrum of recent work as possible. Research in his laboratory on photosynthetic efficiency in diatoms is supported by DOE-BER (

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