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Abstract Background Photosynthetic microalgae are emerging as potential biomass feedstock for sustainable production of biofuels and value-added bioproducts. CO2 biomitigation through these organisms is considered as an eco-friendly and promising alternative to the existing carbon sequestration methods. Nonetheless, the inherent relatively low photosynthetic capacity of microalgae has hampered the practical use of this strategy for CO2 biomitigation applications. Results Here, we demonstrate the feasibility of improving photosynthetic capacity by the genetic manipulation of the Calvin cycle in the typical green microalga Chlorella vulgaris. Firstly, we fused a plastid transit peptide to upstream of the enhanced green fluorescent protein (EGFP) and confirmed its expression in the chloroplast of C. vulgaris. Then we introduced the cyanobacterial fructose 1,6-bisphosphate aldolase, guided by the plastid transit peptide, into C. vulgaris chloroplast, leading to enhanced photosynthetic capacity (~ 1.2-fold) and cell growth. Molecular and physiochemical analyses suggested a possible role for aldolase overexpression in promoting the regeneration of ribulose 1,5-bisphosphate in the Calvin cycle and energy transfer in photosystems. Conclusions Our work represents a proof-of-concept effort to enhance photosynthetic capacity by the engineering of the Calvin cycle in green microalgae. Our work also provides insights into targeted genetic engineering toward algal trait improvement for CO2 biomitigation uses.

Background: Photosynthetic microalgae are emerging as potential biomass feedstock for sustainable production of biofuels and value-added bioproducts. CO2 biomitigation through these organisms is considered as an eco-friendly and promising alternative to the existing carbon sequestration methods. Nonetheless, the inherent relatively low photosynthetic capacity of microalgae has hampered the practical use of this strategy for CO2 biomitigation applications. Results: Here, we demonstrate the feasibility of improving photosynthetic capacity by the genetic manipulation of the Calvin cycle in the typical green microalga Chlorella vulgaris. Firstly, we fused a plastid transit peptide to upstream of the enhanced green fluorescent protein (EGFP) and confirmed its expression in the chloroplast of C. vulgaris. Then we introduced the cyanobacterial fructose 1,6-bisphosphate aldolase, guided by the plastid transit peptide, into C. vulgaris chloroplast, leading to enhanced photosynthetic capacity (~ 1.2-fold) and cell growth. Molecular and physiochemical analyses suggested a possible role for aldolase overexpression in promoting the regeneration of ribulose 1,5-bisphosphate in the Calvin cycle and energy transfer in photosystems. Conclusions: Our work represents a proof-of-concept effort to enhance photosynthetic capacity by the engineering of the Calvin cycle in green microalgae. Our work also provides insights into targeted genetic engineering toward algal trait improvement for CO2 biomitigation uses. [ABSTRACT FROM AUTHOR]

Recent developments in the field of microalgal biotechnology, including CO biomitigation and the discovery of new species of microalgae that are tolerant to extremely high CO levels (40-100 vol%), have renewed interest in the physiological effects and mechanisms of high-CO tolerance in photoautotrophs. Photosynthetic apparatus state transitions that increase ATP generation, upregulation of H-ATPases pumping protons out of the cell, rapid shutdown of CO-concentrating mechanisms, and adjustment of membranes' fatty acid composition are currently believed to be the key mechanisms governing cellular pH homeostasis and hence microalgae's tolerance to high CO levels, which is especially characteristic of extremophile and symbiotic species. The mechanisms governing acclimation to high CO comprise the subject of this review and are discussed in view of the use of CO enrichment to increase the productivity of microalgal cultures, as well as the practice of carbon capture from flue gases. [ABSTRACT FROM AUTHOR]

Abstract: Integrated multitrophic aquaculture (IMTA) aims to be an ecologically balanced aquaculture practice that co-cultures species from multiple trophic levels to optimise the recycling of farm waste as a food resource. It provides an opportunity for product diversification and an increase in economic return if managed at the optimal stocking densities for each co-cultured species. A generic IMTA ecosystem model, incorporating dynamic energy budgets for a number of co-culture species from different trophic levels was developed to design IMTA farms for optimisation of multispecies productivity. It is based on the trophic similarity in the ecophysiological behaviour of cultured organisms to describe the uptake and use of energy. This approach can accommodate different species within a trophic group and is transferable to IMTA operations based on finfish–shellfish-detritivore-primary producer systems. Model simulations were firstly performed considering the monoculture of mussels and finfish, each “farm” interacting with the natural variability of the local environment. The next step was running the IMTA model with the co-culture groups added in: one run was with finfish as the key species in co-culture with seaweed and sea cucumbers and the other with mussels as the key culture species in association with seaweed and sea cucumbers. Scenario simulations show that conversion from monoculture to IMTA would considerably reduce waste products and increase farm productivity. Although the development of IMTA practices will depend on acceptable levels of waste products, feasibility and profitability of culture operations, the IMTA model provides a research tool for designing IMTA practices and to understand species interactions and predict productivity of IMTA farms. The refinement of the model and its power to predict multispecies productivity depends on emerging data from trial and commercial sea-based IMTA operations. [Copyright &y& Elsevier]

Background: Photosynthetic microalgae are emerging as potential biomass feedstock for sustainable production of biofuels and value-added bioproducts. CO 2 biomitigation through these organisms is considered as an eco-friendly and promising alternative to the existing carbon sequestration methods. Nonetheless, the inherent relatively low photosynthetic capacity of microalgae has hampered the practical use of this strategy for CO 2 biomitigation applications., Results: Here, we demonstrate the feasibility of improving photosynthetic capacity by the genetic manipulation of the Calvin cycle in the typical green microalga Chlorella vulgaris . Firstly, we fused a plastid transit peptide to upstream of the enhanced green fluorescent protein (EGFP) and confirmed its expression in the chloroplast of C. vulgaris . Then we introduced the cyanobacterial fructose 1,6-bisphosphate aldolase, guided by the plastid transit peptide, into C. vulgaris chloroplast, leading to enhanced photosynthetic capacity (~ 1.2-fold) and cell growth. Molecular and physiochemical analyses suggested a possible role for aldolase overexpression in promoting the regeneration of ribulose 1,5-bisphosphate in the Calvin cycle and energy transfer in photosystems., Conclusions: Our work represents a proof-of-concept effort to enhance photosynthetic capacity by the engineering of the Calvin cycle in green microalgae. Our work also provides insights into targeted genetic engineering toward algal trait improvement for CO 2 biomitigation uses.