Asha Parmar

Cyanobacteria and microalgae: a positive prospect for biofuels.

Biofuel-bioenergy production has generated intensive interest due to increased concern regarding limited petroleum-based fuel supplies and their contribution to atmospheric CO2 levels. Biofuel research is not just a matter of finding the right type of biomass and converting it to fuel, but it must also be economically sustainable on large-scale. Several aspects of cyanobacteria and microalgae such as oxygenic photosynthesis, high per-acre productivity, non-food based feedstock, growth on non-productive and non-arable land, utilization of wide variety of water sources (fresh, brackish, seawater and wastewater) and production of valuable co-products along with biofuels have combined to capture the interest of researchers and entrepreneurs. Currently, worldwide biofuels mainly in focus include biohydrogen, bioethanol, biodiesel and biogas. This review focuses on cultivation and harvesting of cyanobacteria and microalgae, possible biofuels and co-products, challenges for cyanobacterial and microalgal biofuels and the approaches of genetic engineering and modifications to increase biofuel production.

Optimization of medium components for increased production of C-phycocyanin from Phormidium ceylanicum and its purification by single step process

Phycocyanin is a major protein produced by cyanobacteria, but very few phycocyanin-producing strains have been reported. In the present study, response surface methodology (RSM) involving a central composite design for four factors was successfully employed to optimize medium components for increased production of phycocyanin from Phormidium ceylanicum. The production of phycocyanin and interactions between sodium nitrate, calcium chloride, trace metal mix and citric acid stock were investigated and modeled. Under optimized condition P. ceylanicum was able to give 2.3-fold increase in phycocyanin production in comparison to commonly used BG 11 medium in 32 days. We have demonstrated the extraction, purification and characterization of C-phycocyanin using novel method based on filtration and single step chromatography. The protein was extracted by repeated freeze-thaw cycles and the crude extract was filtered and concentrated in stirred ultrafiltration cell (UFC). The UFC concentrate was then subjected to a single ion exchange chromatographic step. A purity ratio of 4.15 was achieved from a starting value of 1.05. The recovery efficiency of C-phycocyanin from crude extract was 63.50%. The purity was checked by electrophoresis and UV-Vis spectroscopy.

ALLOPHYCOCYANIN FROM A LOCAL ISOLATE GEITLERINEMA SP. A28DM (CYANOBACTERIA): A SIMPLE AND EFFICIENT PURIFICATION PROCESS1

Allophycocyanin (APC) is the least‐studied cyanobacterial bile‐pigment invariably present within the phycobilisome core of cyanobacteria. In the present study, we describe a simple, cost‐effective, and reproducible method for the purification of APC from a local isolate, Geitlerinema sp. A28DM. The pigment was extracted from the algal biomass and precipitated with 0.25% aqueous solution of the highly aromatic cationic dye “ethodin.” The precipitated APC was then subjected to a single size‐exclusion chromatographic step using Sephadex G‐100. Pure cyanobacterial APC (C‐APC) (A652/A280 of 3.2) was obtained and characterized by its absorption spectrum with maximum at 652 nm and a shoulder at 620 nm, and by SDS‐PAGE, showing two bands with molecular masses of 15 and 17.5 kDa, corresponding to α and β subunits of the biliprotein. The final yield of C‐APC was 66% from its content in the crude extract. The procedure appears to be promising for wider applications and larger production of APC.

Crystal Structure and Interaction of Phycocyanin with β-Secretase: A Putative Therapy for Alzheimer's Disease

Alzheimers disease (AD) represents a neurological disorder, which is caused by enzymatic degradation of an amyloid precursor protein into short peptide fragments that undergo association to form insoluble plaques. Preliminary studies suggest that cyanobacterial extracts, especially the light-harvesting protein phycocyanin, may provide a means to control the progression of the disease. However, the molecular mechanism of disease control remains elusive. In the present study, intact hexameric phycocyanin was isolated and crystallized from the cyanobacterium Leptolyngbya sp. N62DM, and the structure was solved to a resolution of 2.6 A. Molecular docking studies show that the phycocyanin αβ-dimer interacts with the enzyme β-secretase, which catalyzes the proteolysis of the amyloid precursor protein to form plaques. The molecular docking studies suggest that the interaction between phycocyanin and β-secretase is energetically more favorable than previously reported inhibitor-β-secretase interactions. Transgenic Caenorhabditis elegans worms, with a genotype to serve as an AD-model, were significantly protected by phycocyanin. Therefore, the present study provides a novel structure-based molecular mechanism of phycocyanin-mediated therapy against AD.

Folding and stability studies on C-PE and its natural N-terminal truncant.

The conformational and functional state of biliproteins can be determined by optical properties of the covalently linked chromophores. α-Subunit of most of the phycoerythrin contains 164 residues. Recently determined crystal structure of the naturally truncated form of α-subunit of cyanobacterial phycoerythrin (Tr-αC-PE) lacks 31 N-terminal residues present in its full length form (FL-αC-PE). This provides an opportunity to investigate the structure-function relationship between these two natural forms. We measured guanidinium chloride (GdmCl)-induced denaturation curves of FL-αC-PE and Tr-αC-PE proteins, followed by observing changes in absorbance at 565nm, fluorescence at 350 and 573nm, and circular dichroism at 222nm. The denaturation curve of each protein was analyzed for ΔGD(∘), the value of Gibbs free energy change on denaturation (ΔGD) in the absence of GdmCl. The main conclusions of the this study are: (i) GdmCl-induced denaturation (native state↔denatured state) of FL-αC-PE and Tr-αC-PE is reversible and follows a two-state mechanism, (ii) FL-αC-PE is 1.4kcalmol(-1) more stable than Tr-αC-PE, (iii) truncation of 31-residue long fragment that contains two α-helices, does not alter the 3-D structure of the remaining protein polypeptide chain, protein-chromophore interaction, and (iv) amino acid sequence of Tr-αC-PE determines the functional structure of the phycoerythrin.

Influence of light on phycobiliprotein production in three marine cyanobacterial cultures

Complementary chromatic adaptation, a photomorphogenetic response, known to occur in many cyanobacteria, enables them to efficiently absorb prevalent wavelengths of light in the environment. In the present study, we have described the influence of light on phycobiliprotein production in three marine phycoerythrin producing cyanobacterial cultures, namely, Lyngbya sp. A09DM, Phormidium sp. A27DM and Halomicronema sp. A32DM. A comparative study (UV-visible overlay spectra and SDS-PAGE analyses) of phycobiliproteins purified from all the three cultures grown in white, yellow, red and green lights has been confirmed. White light was taken as control. Red and green lights were taken to check their effect on phycocyanin and phycoerythrin production, respectively. Yellow light was studied as its wavelength falls in between green and red light. Lyngbya sp. A09DM was found to be the best chromatically adapting cyanobacterium followed by Halomicronema sp. A32DM. These two cultures can be placed in group III chromatic adaptors. Phormidium sp. A27DM was the least chromatically adapting culture and can be placed in group II chromatic adaptors. The study signifies that even light plays an important role along with nutrient availability in adapting cultures to changing environmental conditions.