Overview of Carbon Capture Technology: Microalgal Biorefinery Concept and State-of-the-Art

The impending danger of climate change and pollution can now be seen on the world panorama. The concentration of CO2, the most important Green House Gas (GHG), has reached to formidable levels. Although carbon capture and storage (CCS) methods have been largely worked upon, they are cumbersome in terms of economy and their long term environmental safety raises a concern. Alternatively, bio-sequestration of CO2 using microalgal cell factories has emerged as a promising way of recycling CO2 into biomass via photosynthesis which in turn could be used for the production of bioenergy and other value-added products. Despite enormous potential, the production of microalgae for low-value bulk products and bulk products such as biofuels, is heretofore, not feasible. To achieve economic viability and sustainability, major hurdles in both, the upstream and downstream processes have to be overcome. Recent technoeconomic analyses and life-cycle assessments of microalgae-based production systems have suggested that the only possible way for scaling up the production is to completely use the biomass in an integrated biorefinery set-up wherein every valuable component is extracted, processed and valorized. This article provides a brief yet comprehensive review of the present carbon sequestration and utilization technologies, focusing primarily on biological CO2 capture by microalgae in the context of bio-refinery. The paper discusses various products of microalgal biorefinery and aims to assess the opportunities, challenges and current state-of-the-art of microalgae-based CO2 bioconversion, which are essential to the sustainability of this approach in terms of the environment as well as the economy

Nitrogen and phosphorous scavenging potential in microalgae

52-56Growth potential and N and P scavenging ability was examined in microalgal strains grown under secondary treated sewage effluent. The mean dry weight and the pigments were highest in microalgae under standard BG-11 medium in comparison to those grown in sewage effluent. There was a marked reduction in available nitrogen and phosphorous with the growth of microalgae in the sewage water. A significant correlation coefficient between N and P removal and dry weight and pigments has indicated the usefulness of sewage effluent for cultivation of microalgae with the efficient N and P scavenging ability. Chlorella vulgaris was most efficient in scavenging ammonical nitrogen while nitrate-scavenging ability was highest in Oscillatoria. All the microalgal genera also removed available phosphorous efficiently

Quantification and purification of C-phycocyanin from cyanobacterial strains Anabaena and Phormidium

625-629The cyanobacteria Anabaena and Phormidium are potential source of phycobiliproteins and C phycocyanin (C-pc). Here, we carried out extraction and purification of phycocyanin (PC) from the above selected cyanobacterial isolates using one-step anion exchange chromatography. Crude C-phycocyanins were extracted and concentrated by ammonium sulfate fractionation at saturation of 35%, then purified on a DEAE-sepharose with Fast Flow chromatography column having continuous pH gradient elution from pH 5.1 to 3.76. The process resulted in recovery of high purity C-pc from above cyanobacteria. The purity ratios (A620/A280) of phycocyanin reached 3.34 for Phormidium and 3.1 for Anabaena, respectively. The purity was further demonstrated and confirmed through fluorescence emission spectroscopy. The total recovery yield of pure C-pc was 14% after completion of the process, and the recovered pigment remained stable over a pH range of 4-9. This purification method for recovery of high purity pigment was fairly efficient compared to the existing methods. . As phycocyanin has higher antioxidant activity and hence, the above cyanobacterial strains Anabaena and Phormidium with considerable amount of C-pc, may serve to be a potential source as food supplement as well as for pharmaceuticals industries

Similarity analysis of <i>Spirulina/Arthrospira</i> strains on the basis of phycocyanin operon locus (cpcB-IGS-cpcA) and 16S rRNA gene sequences

84-90Spirulina/Arthrospira is a species of cyanobacteria used in health foods, animal feed, food additives and fine chemicals. The present study conducted a comparison of the 16S rRNA and cpcBA-intergenic spacer (cpcBA-IGS) gene sequences in Spirulina/Arthrospira strains from culture collection of CCUBGA, IARI, New Delhi. All the strains of Spirulina used in this study had shown nearly 99% similarity amongst them. About fifty sequences (cpcBA-IGS) of Spirulin a strains taken from NCBI with ten from the present strains of Spirulina, a neighbour-joing (NJ) tree was constructed with the help of MEGA 5.0. The tree showed 99% similarity. All the sequences were put to Multiple Sequence Alignment with the help of T-Coffee (version 7.38) and BioEdit (version 7.38) software. Similarity studies undertaken based upon 16S rRNA and cpcBA-IGS genes sequence analysis indicated similarity coefficient of 0.84. S. platensis and Arthrospira sp. showed 100 percent similarity. Therefore, the current study supports some previous conclusions based on 16S rRNA gene and cpcBA-IGS sequences, which found that Arthrospira taxa are monophyletic. However, compared to 16S rRNA sequences, cpcBA-IGS sequences might be better suited to resolve close relationships and interspecies variability

Influence of light intensity, temperature and CO₂ concentration on growth and lipids in green algae and cyanobacteria

482-487<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">Effects of the environmental variables such as light intensity (µmol photons m-2s-1), temperature (°C) and CO2 concentration (ppm) on chlorophyll, total soluble proteins and lipids <span style="mso-bidi-font-weight: bold">were studied in selected microalgal strains from Chlorophyceae (Chlamydomonas sp., Scenedesmus sp., Chlorella sp., <i style="mso-bidi-font-style: normal">Kirchneriella sp.) and cyanobacteria (Nostoc sp.1, <i style="mso-bidi-font-style: normal">Anabaena sp., Nostoc sp. 2, Cylindrospermum sp.). Cultures were grown under controlled conditions at the National Phytotron Facility, Indian Agricultural Research Institute (IARI), New Delhi. Our results showed that chlorophyll concentration enhanced with increased CO2. <i style="mso-bidi-font-style: normal">Chlorella exhibited the highest chlorophyll at 850 ppm CO2 and 28°C; for Chlamydomonas it was at 78 µmol photons m-2s-1 light intensity. In Cylindrospermum, total soluble proteins decreased with enhanced CO2, and were highest at 18<span style="font-size:11.0pt;font-family:Symbol;mso-ascii-font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-hansi-font-family:="" "times="" roman";mso-bidi-font-family:mangal;mso-ansi-language:en-gb;="" mso-fareast-language:en-us;mso-bidi-language:hi;mso-char-type:symbol;="" mso-symbol-font-family:symbol;mso-bidi-font-weight:bold"="" lang="EN-GB">°C. In Anabaena, a light intensity of 65<span style="font-size:11.0pt; font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-bidi-font-family:mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;="" mso-bidi-language:hi"="" lang="EN-GB"> <span style="font-size:11.0pt; font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-bidi-font-family:mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;="" mso-bidi-language:hi;mso-bidi-font-weight:bold"="" lang="EN-GB">µmol photons m-2s-1 was best for maximum total soluble proteins. In <i style="mso-bidi-font-style: normal">Chlorella, CO2 @ 850 ppm was most suited for maximum lipid accumulation. In Kirchneriella, increase in temperature, from 18<span style="font-size:11.0pt; font-family:Symbol;mso-ascii-font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-hansi-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi;mso-char-type:symbol;mso-symbol-font-family:symbol;mso-bidi-font-weight:="" bold"="" lang="EN-GB">°C up to 37<span style="font-size:11.0pt;font-family:Symbol; mso-ascii-font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-hansi-font-family:"times="" roman";mso-bidi-font-family:mangal;mso-ansi-language:="" en-gb;mso-fareast-language:en-us;mso-bidi-language:hi;mso-char-type:symbol;="" mso-symbol-font-family:symbol;mso-bidi-font-weight:bold"="" lang="EN-GB">°C, increased total lipids; the highest was at 28°<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi;mso-bidi-font-weight:bold"="" lang="EN-GB">C. In Chlamydomonas, the light intensity of 78 µmol photons m-2s-1 was optimum for lipid accumulation and the maximum total lipids was 30.8 (% dry wt.).</span