Optimization of chromium(VI) removal by indigenous microalga (Chlamydomonas sp.)-based biosorbent using response surface methodology

Phycoremediation of heavy metals has garnered considerable recent research interest. In this study, an indigenous microalga (Chlamydomonas sp.)-based biosorbent was employed for biosorption of Cr(VI) dissolved solids (Cr(VI)-DS), optimized using response surface methodology (RSM). The effects of microalga concentration, pH, and contact time were studied with 250 mg Cr(VI)-DS L^-1 . The biosorption of Cr(VI)-DS was higher at acidic pH (94.17% at pH 4) than at alkaline conditions (68.53% at pH 10). The interaction of pH and microalga concentration exerted significant (p < 0.05) influence on the biosorption. Under the optimized parameters of 1.5 g microalga L^-1 , pH 4, and contact time of 30 min, a predicted biosorption of 91.31% and biosorption capacity of 152 mg Cr(VI)-DS g^-1 biomass were documented. FTIR analysis attested the electronegative surface functional groups of the microalgae biomass, bracketed together with its high biosorption potency. The study evinced the potential of the indigenous microalga for remediation of hexavalent chromium. PRACTITIONER POINTS: Indigenous Ethiopian microalga (Chlamydomonas sp.) exhibited 94% Cr(VI) abatement with biosorption capacity of 152 mg Cr(VI) g^-1 . FTIR analysis of the biosorbent divulged the presence of electronegative functional groups (amino, carboxyl, hydroxyl, and carbonyl groups). Higher biosorption of Cr(VI)-DS under acidic pH (94.17% at pH 4) than alkaline pH (68.53% at pH 10). Significant (p < 0.05) interaction effect of pH and biomass concentration on the biosorption, evinced in RSM optimization 91% Cr(VI) removal achieved under optimal conditions of 1.5 g biosorbent L^-1 , 30 min of contact time, and pH 4.

Isolation of a freshwater microalgae and its application for the treatment of wastewater and obtaining fatty acids from tilapia cultivation

In the present study, isolated strains of the microalgae Chlamydomonas sp. (CH) and Chlorella vulgaris (CV) were used to treat aquaculture wastewater and to obtain fatty acids and from a fattening culture of tilapia. The microalgae were cultivated for 11 days in tubular photobioreactors with an operating volume of 2 L, constant aeration and illumination. High removal rates of NO₃^- and PO₄^3- were achieved for both Chlamydomonas sp. (84.7% and 96%, respectively) and Chlorella vulgaris (94.6 and 97.9%, respectively). The maximum biomass productivity achieved by Chlamydomonas sp. was 0.06 and 0.10 gL^-1d^-1 for Chlorella vulgaris. Therefore, tilapia wastewater contained the necessary nutrient concentration for algal growth and development. Chlamydomonas sp. biomass lipid content was 69%, while that of Chlorella vulgaris was 40%. The lipid profile of both microalgae was abundant in palmitic acid (78% for Chlamydomonas sp. and 35% for Chlorella vulgaris). This fatty acid is suitable for biodiesel production. Tilapia wastewater is low-cost alternative culture medium as it contains the necessary nutrient concentration for microalgae development and growth.

Enhancing lutein productivity of Chlamydomonas sp. via high-intensity light exposure with corresponding carotenogenic genes expression profiles

The marine microalga Chlamydomonas sp. JSC4 is a potential lutein source with high light tolerance. In this study, light intensity was manipulated to enhance cell growth and lutein production of this microalga. High lutein productivity (5.08 mg/L/d) was achieved under high light irradiation of 625 μmol/m²/s. Further increase in light intensity to 750 μmol/m²/s enhanced the biomass productivity to 1821.5 mg/L/d, but led to a decrease in lutein content. Under high light conditions, most carotenoids and chlorophyll contents decreased, while zeaxanthin and antheraxanthin contents increased. Inspection of gene expression profile shows that the lut1 and zep genes, responsible for lutein synthesis and flow of zeaxanthin into violaxanthin, respectively, were downregulated, while zeaxanthin biosynthesis gene crtZ was upregulated when the microalga was exposed to a high light intensity. This is consistent with the decrease in lutein content and increase in zeaxanthin content under high light exposure.

Chlamydomonas sp. as dynamic biorefinery feedstock for the production of methyl ester and ɛ-polylysine

An integrated production of methyl ester and ɛ-polylysine from Chlamydomonas sp. was studied using biorefinery approach. The harvesting efficiency of Chlamydomonas sp. was increased up to 92% by treatment with a flocculant FeCl₃ at 100 mg/L for 30 min. The DMC (dimethyl carbonate) mediated enzyme catalyzed in-situ transesterification of Chlamydomonas sp. yielded the maximum methyl ester of 92% under optimized conditions. The valued-added product ɛ-polylysine was produced from hydrolysate obtained from the spent biomass of Chlamydomonas sp. using Streptomyces sp. The key components of sugar and MgSO₄ used for ɛ-polysine production were optimized whereby the maximum ɛ-polylysine production was achieved at 50 g/L sugar and 0.3 g/L MgSO₄. The ɛ-polylysine production was further enhanced by supplementation of important amino acids (lysine and aspartate) and TCA cycle intermediates (citric acid and α-ketoglutaric acid). The maximum ɛ-polylysine production of 2.24 g/L was found with 4 mM citric acid supplementation after 110 h.

Biological effects of four iron-containing nanoremediation materials on the green alga Chlamydomonas sp

As nanoremediation strategies for in-situ groundwater treatment extend beyond nanoiron-based applications to adsorption and oxidation, ecotoxicological evaluations of newly developed materials are required. The biological effects of four new materials with different iron (Fe) speciations ([i] FerMEG12 - pristine flake-like milled Fe(0) nanoparticles (nZVI), [ii] Carbo-Iron^® - Fe(0)-nanoclusters containing activated carbon (AC) composite, [iii] Trap-Ox® Fe-BEA35 (Fe-zeolite) - Fe-doped zeolite, and [iv] Nano-Goethite - 'pure' FeOOH) were studied using the unicellular green alga Chlamydomonas sp. as a model test system. Algal growth rate, chlorophyll fluorescence, efficiency of photosystem II, membrane integrity and reactive oxygen species (ROS) generation were assessed following exposure to 10, 50 and 500 mg L^-1 of the particles for 2 h and 24 h. The particles had a concentration-, material- and time-dependent effect on Chlamydomonas sp., with increased algal growth rate after 24 h. Conversely, significant intracellular ROS levels were detected after 2 h, with much lower levels after 24 h. All Fe-nanomaterials displayed similar Z-average sizes and zeta-potentials at 2 h and 24 h. Effects on Chlamydomonas sp. decreased in the order FerMEG12 > Carbo-Iron® > Fe-zeolite > Nano-Goethite. Ecotoxicological studies were challenged due to some particle properties, i.e. dark colour, effect of constituents and a tendency to agglomerate, especially at high concentrations. All particles exhibited potential to induce significant toxicity at high concentrations (500 mg L^-1), though such concentrations would rapidly decrease to mg or µg L^-1 in aquatic environments, levels harmless to Chlamydomonas sp. The presented findings contribute to the practical usage of particle-based nanoremediation in environmental restoration.

Molecular cloning and expression analysis of major intrinsic protein gene in Chlamydomonas sp. ICE-L from Antarctica

Major intrinsic proteins (MIPs) form channels facilitating the passive transport of water and other small polar molecules across membranes. In this study, the complete open reading frame (ORF) of CiMIP1 (GenBank ID KY316061) encoding one kind of MIPs in the Antarctic ice microalga Chlamydomonas sp. ICE-L is successfully cloned using RACE. In addition, the expression patterns of CiMIP1 gene under different conditions of temperature and salinity are determined by qRT-PCR. The ORF of CiMIP1 gene encodes 308 amino acids, and the deduced amino acid sequence shows 74% homology with Chlamydomonas reinhardtii CrMIP1 (GenBank number 159471952). Phylogenetic analysis reveals that algal MIPs are divided into seven groups, and it is speculated that CiMIP1 most likely belongs to the MIPD subfamily. In addition, we are surprised to find that a third NPA motif exists at the carboxy terminus of the target protein except for two highly conserved ones. Expression analysis shows that the transcriptional levels of CiMIP1 gene are upregulated under either lower temperature or higher temperature and high salinity. In summary, the results together have provide new insights into the newly discovered gene in green algae and lay the foundation for further studies on the adaptation mechanism of Chlamydomonas sp. ICE-L to abiotic stresses.

Survival of chlorophyceae ingested by saprozoic nematodes

The saprozoic nematode, Pristionchus lheritieri ingested cells of four species of unicellular Chlorophyceae (grass-green algae) including Chlamydomonas reinhardi and unidentified species of Ankistrodesmus, Chlamydornonas and Scenedesmus. Additional tests with Ankistrodesmus sp. and Chlamydomonas sp., indicated cells of Ankistrodesmus survived passage through the alimentary canal and were subsequently cultured, while viable cells of Chlarnydomonas were only occasionally recovered.