Conversion of NaHCO3 to Na2 CO3 with a growth of Arthrospira platensis cells in 660 m2 raceway ponds with a CO2 bicarbonation absorber

Life-cycle assessment of flue gas CO2 fixation from coal-fired power plant and coal chemical plant by microalgae

The technology of flue gas CO₂ fixation by microalgae is highly attractive in the era of CO₂ neutrality. However, CO₂ emission along the whole process has yet to be sufficiently evaluated. Here, a life-cycle assessment was performed to evaluate the energy conversion characteristics and environmental impacts of flue gas CO₂ fixation from coal-fired power plant (Case 1) and coal chemical plant (Case 2) by microalgae. The results show that total energy consumption and CO₂ gas emissions for Case 1 are 27.5-38.0 MJ/kg microalgae power (MP) and 5.7-7.7 kg CO₂ equiv/kg MP, respectively, which are lower than that for Case 2 (122.5-181.3 MJ/kg MP and 32.7-48.6 kg CO₂ equiv/kg MP). The CO₂ gas aeration rate and microalgae growth rate are the two most sensitive parameters for the energy conversion and net CO₂ emission. Therefore, increasing the CO₂ aeration efficiency and microalgae growth rate are key to advance the technology of flue gas CO₂ fixation by microalgae which will contribute to carbon naturality.

Deciphering and engineering photosynthetic cyanobacteria for heavy metal bioremediation

Environmental pollution caused by heavy metals has received worldwide attentions due to their ubiquity, poor degradability and easy bioaccumulation in host cells. As one potential solution, photosynthetic cyanobacteria have been considered as promising remediation chassis and widely applied in various bioremediation processes of heavy-metals. Meanwhile, deciphering resistant mechanisms and constructing tolerant chassis towards heavy metals could greatly contribute to the successful application of the cyanobacteria-based bioremediation in the future. In this review, first we summarized recent application of cyanobacteria in heavy metals bioremediation using either live or dead cells. Second, resistant mechanisms and strategies for enhancing cyanobacterial bioremediation of heavy metals were discussed. Finally, potential challenges and perspectives for improving bioremediation of heavy metals by cyanobacteria were presented.

Orange light spectra filtered through transparent colored polyvinyl chloride sheet enhanced pigment content and growth of Arthrospira cells

Microalgae are significantly affected by the spectra composition with various wavelengths. The development of light harvesting pigments can be controlled with specific wavelength of filtered light received by microalgae. Coverage of open raceway pond using transparent colored polyvinyl chloride sheets (PVCS) to filter light spectra, was assessed for the capacity to enhance biomass growth rate. Results showed that orange PVCS filtered light spectra at wavelengths from 480 to 665 nm, increased biomass dry weight (3.3 g/L) by 61% compared with control condition (white PVCS = 350-750 nm). Light spectra filtered through orange PVCS were more easily absorbed by the light harvesting pigment protein complex (phycobilisome) of Arthrospira platensis cells and subsequently transferred to intracellular photosynthesis reaction centers. Therefore, A. platensis cells cultivated with light spectra filtered through orange PVCS contained 62.7 mg/L chlorophyll-a and 23.5 mg/L carotenoid, which were 40% and 29% higher than control condition (with white PVCS).

Conversion of NaHCO3 to Na2 CO3 with a growth of Arthrospira platensis cells in 660 m2 raceway ponds with a CO2 bicarbonation absorber

The weight ratio of Na2 CO3 /NaHCO3 was investigated in order to improve microalgal productivity in large-scale industrial operations by converting NaHCO3 to Na2 CO3 with a growth of Arthrospira platensis cells in 660 m2 raceway ponds. Two microalgal cultivation systems with a NaHCO3 by-product (SPBP) and a CO2 bicarbonation absorber (CBAP) were firstly thoroughly introduced. There was a 13.3% decrease in the initial weight ratio of Na2 CO3 /NaHCO3 resulting in a 25.3% increase in the biomass growth rate with CBAP, compared to that of SPBP. Increased sunlight intensity, solution temperature and pH all resulted in both a higher HCO 3 - absorbance and CO 3 2 - release, thereby increasing the weight ratio of Na2 CO3 /NaHCO3 during the growth of A. platensis. The biomass growth rate was peaked at 39.9 g m-2  day-1 when the weight ratio of Na2 CO3 /NaHCO3 was 3.7. Correspondingly, the cell pigments (chlorophyll a and carotenoid) and trichome size (helix pitch and trichome length) reached to a maximum state of 8.47 mg l-1 , 762 μg l-1 , 57 and 613 μm under the CBAP system.