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The online version of this article (doi:10.1007/s11693-011-9073-8) contains supplementary material, which is available to authorized users.

Corynebacterium glutamicum, a soil bacterium, is used to produce amino acids such as lysine and glutamate. C. glutamicum is often exposed to osmolality changes in its medium, and the bacterium has therefore evolved several adaptive response mechanisms to overcome them. In this study we quantify the metabolic response of C. glutamicum under osmotic stress using elementary mode analysis (EMA). Further, we obtain the optimal phenotypic space for the synthesis of lysine and formation of biomass. The analysis demonstrated that with increasing osmotic stress, the flux towards trehalose formation and energy-generating pathways increased, while the flux of anabolic reactions diminished. Nodal analysis indicated that glucose-6-phosphate, phosphoenol pyruvate, and pyruvate nodes were capable of adapting to osmotic stress, whereas the oxaloacetic acid node was relatively unresponsive. Fewer elementary modes were active under stress indicating the rigid behavior of the metabolism in response to high osmolality. Optimal phenotypic space analysis revealed that under normal conditions the organism optimized growth during the initial log phase and lysine and trehalose formation during the stationary phase. However, under osmotic stress, the analysis demonstrated that the organism operates under suboptimal conditions for growth, and lysine and trehalose formation.

The promise of algae to address the renewable energy and green-product production demands of the globe has yet to be realized. Over the past ten years, however, there has been a substantial investment and interest in realizing the potential of algae to meet these needs. Tremendous progress has been achieved. Ten years ago, the price of gasoline produced from algal biomass was 20-fold greater than it is today. Technoeconomic models indicate that algal biocrude produced in an optimized cultivation, harvesting, and biomass conversion facility can achieve economic parity with petroleum while reducing carbon-energy indices substantially relative to petroleum-based fuels. There is also an emerging recognition that algal carbon capture and sequestration as lipids may offer a viable alternative to direct atmospheric CO2 capture and sequestration. We review recent advances in basic and applied algal biomass production from the perspectives of algal biology, cultivation, harvesting, energy conversion, and sustainability. The prognosis is encouraging but will require substantial integration and field testing of a variety of technology platforms to down select the most economical and sustainable systems to address the needs of the circular economy and atmospheric carbon mitigation.