Culture of microalgae Chlorella minutissima for biodiesel feedstock production

Microalgae are among the most promising of non‐food based biomass fuel feedstock alternatives. Algal biofuels production is challenged by limited oil content, growth rate, and economical cultivation. To develop the optimum cultivation conditions for increasing biofuels feedstock production, the effect of light source, light intensity, photoperiod, and nitrogen starvation on the growth rate, cell density, and lipid content of Chlorella minutissima were studied. The fatty acid content and composition of Chlorella minutissima were also investigated under the above conditions. Fluorescent lights were more effective than red or white light‐emitting diodes for algal growth. Increasing light intensity resulted in more rapid algal growth, while increasing the period of light also significantly increased biomass productivity. Our results showed that the lipid and triacylglycerol content were increased under N starvation conditions. Thus, a two‐phase strategy with an initial nutrient‐sufficient reactor followed by a nutrient deprivation strategy could likely balance the desire for rapid and high biomass generation (124 mg/L) with a high oil content (50%) of Chlorella minutissima to maximize the total amount of oil produced for biodiesel production. Moreover, methyl palmitate (C16:0), methyl oleate (C18:1), methyl linoleate (C18:2), and methyl linolenate (C18:3) are the major components of Chlorella minutissima derived FAME, and choice of light source, intensity, and N starvation impacted the FAME composition of Chlorella minutissima. The optimized cultivation conditions resulted in higher growth rate, cell density, and oil content, making Chlorella minutissima a potentially suitable organism for biodiesel feedstock production. Biotechnol. Bioeng. 2011;108: 2280–2287. © 2011 Wiley Periodicals, Inc.     

Comparing Morphological and Molecular Estimates of Species Diversity in the Freshwater Genus Synura (Stramenopiles): A Model for Understanding Diversity of Eukaryotic Microorganisms

We performed a comparison of molecular and morphological diversity in a freshwater colonial genus Synura (Chrysophyceae, Stramenopiles), using the island of Newfoundland (Canada) as a case study. We examined the morphological species diversity in collections from 79 localities, and compared these findings to diversity based on molecular characters for 150 strains isolated from the same sites. Of 27 species or species-level lineages identified, only one third was recorded by both molecular and morphological techniques, showing both approaches are complementary in estimating species diversity within this genus. Eight taxa, each representing young evolutionary lineages, were recovered only by sequencing of isolated colonies, whereas ten species were recovered only microscopically. Our complex investigation, involving both morphological and molecular examinations, indicates that our knowledge of Synura diversity is still poor, limited only to a few well-studied areas. We revealed considerable cryptic diversity within the core S. petersenii and S. leptorrhabda lineages. We further resolved the phylogenetic position of two previously described taxa, S. kristiansenii and S. petersenii f. praefracta, propose species-level status for S. petersenii f. praefracta, and describe three new species, S. vinlandica, S. fluviatilis, and S. cornuta. Our findings add to the growing body of literature detailing distribution patterns observed in the genus, ranging from cosmopolitan species, to highly restricted taxa, to species such as S. hibernica found along coastal regions on multiple continents. Finally, our study illustrates the usefulness of combining detailed morphological information with gene sequence data to examine species diversity within chrysophyte algae.     

Comparative Genome Analysis Reveals Cyanidiococcus gen. nov., A New Extremophilic Red Algal Genus Sister to Cyanidioschyzon (Cyanidioschyzonaceae,Rhodophyta)

The taxonomic placement of strains belonging to the extremophilic red alga Galdieria maxima has been controversial due to the inconsistent phylogenetic position inferred from molecular phylogenetic analyses. Galdieria maxima nom. inval. was classified in this genus based on morphology and molecular data in the early work, but some subsequent molecular phylogenetic analyses have inferred strains of G. maxima to be closely related to the genus Cyanidioschyzon. To address this controversy, an isolated strain identified as G. maxima using the rbcL gene sequence as the genetic barcode was examined using a comprehensive analysis across morphological, physiological, and genomic traits. Herein are reported the chloroplast-, mitochondrion-, and chromosome-level nuclear genome assemblies. Comparative analysis of orthologous gene clusters and genome arrangements suggested that the genome structure of this strain was more similar to that of the generitype of Cyanidioschyzon, C. merolae than to the generitype of Galdieria, G. sulphuraria. While the ability to uptake various forms of organic carbon for growth is an important physiological trait of Galdieria, this strain was identified as an ecologically obligate photoautotroph (i.e., the inability to utilize the natural concentrations of organic carbons) and lacked various gene models predicted as sugar transporters. Based on the genomic, morphological, and physiological traits, we propose this strain to be a new genus and species, Cyanidiococcus yangmingshanensis. Re-evaluation of the 18S rRNA and rbcL gene sequences of the authentic strain of G. maxima, IPPAS-P507, with those of C. yangmingshanensis suggests that the rbcL sequences of “G. maxima” deposited in GenBank correspond to misidentified isolates.     

Differential thermal tolerance between algae and corals may trigger the proliferation of algae in coral reefs

Marine heatwaves can lead to rapid changes in entire communities, including in the case of shallow coral reefs the potential overgrowth of algae. Here we tested experimentally the differential thermal tolerance between algae and coral species from the Red Sea through the measurement of thermal performance curves and the assessment of thermal limits. Differences across functional groups (algae vs. corals) were apparent for two key thermal performance metrics. First, two reef‐associated algae species (Halimeda tuna and Turbinaria ornata) had higher lethal thermal limits than two coral species (Pocillopora verrucosa and Stylophora pistillata) conferring those species of algae with a clear advantage during heatwaves by surpassing the thermal threshold of coral survival. Second, the coral species had generally greater deactivation energies for net and gross primary production rates compared to the algae species, indicating greater thermal sensitivity in corals once the optimum temperature is exceeded. Our field surveys in the Red Sea reefs before and after the marine heatwave of 2015 show a change in benthic cover mainly in the southern reefs, where there was a decrease in coral cover and a concomitant increase in algae abundance, mainly turf algae. Our laboratory and field observations indicate that a proliferation of algae might be expected on Red Sea coral reefs with future ocean warming.     

New lipid‐producing,cold‐tolerant yellow‐green alga isolated from the rocky mountains of colorado

A new strain of yellow‐green algae (Xanthophyceae, Heterokonta), tentatively named Heterococcus sp. DN1 (UTEX accession number UTEX ZZ885), was discovered among snow fields in the Rocky Mountains. Axenic cultures of H. sp. DN1 were isolated and their cellular morphology, growth, and composition of lipids were characterized. H. sp. DN1 was found to grow at temperatures approaching freezing to accumulate large intracellular stores of lipids. H. sp. DN1 produces the highest quantity of lipids when grown undisturbed with high light in low temperatures_. Of particular interest was the accumulation of eicosapentaenoic acid, known to be important for human nutrition, and palmitoleic acid, known to improve biodiesel feedstock properties. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:853–861, 2013     

Accounting for Algae

Interest and research in the use of algae for energy is growing but an analysis of the different methods for the accounting for the carbon dioxide (CO ₂) emissions that result, is lacking. In this article, four accounting systems are evaluated for their completeness, simplicity, sectoral accuracy, and scale‐independence. Two options under the Kyoto Protocol (KP), a value‐chain (end‐user responsibility) approach, and Point of Uptake and Release (POUR) are evaluated. Algal material is used in biofuels, animal feeds, human foods, and food supplements, and a range of products such as paints, cosmetics, and plastics. There are also proposals for using algae as a soil amendment. This variety of uses for algal material together with the fact that it will probably contain carbon of fossil origin presents accounting challenges and reveals inconsistencies that have lain in the KPs treatment of biomass emissions. Furthermore, a key conclusion of the article is that neither proposed KP accounting approach for algae leads to correct accounting of emissions for all uses. Both value chain and POUR approaches more correctly and consistently account for algal emissions across uses. POUR offers the potential to provide comprehensive, consistent emission accounting across all uses of biomass, which represents a major step forward in accounting for CO ₂ emissions due to use of biomass.     

Interactions between carbon dioxide and oxygen in the photosynthesis of three species of marine red macroalgae

Summary

Red algae have the highest known selectivity factor (S_rel) for CO₂ over O₂ of ribulose bisphosphate carboxylase-oxygenase (RUBISCO). This allows the prediction that a red alga relying on diffusive supply of CO₂ to RUBISCO from air-equilibrated solution should have less O₂ inhibition of photosynthesis than would an otherwise similar non-red alga with a lower S_rel of RUBISCO. Furthermore, RUBISCO shows an increased S_rel values at low temperatures. The prediction that O ₂inhibition of photosynthesis should be small for marine red algae relying on diffusive CO₂ entry growing in the North Sea with an annual temperature range of 4–16°C was tested in O₂ electrode experiments at 12°C. Phycodrys rubens and Plocamium cartilagineum, which rely on diffusive CO₂ entry showed, as predicted, only a small inhibition at lower inorganic C concentrations. Palmaria palmata, which has a CO₂ concentrating mechanism, had the expected negligible O ₂ inhibition of photosynthesis at any inorganic C concentration except (non-significantly) for saturating inorganic C.     

Conversion of Nitrite to Nitrate by Nitrite-resistant Yeasts

Candida species YK 11 and YK 92 and Geotrichum candidum YK 57, which were isolated as nitrite-resistants, converted nitrite in the culture medium to nitrate stoichiometrically during growth. The nitrite-oxidizing reaction was confirmed under aerobic conditions in the intact cell system with 15 mm nitrite, 150 mm glucose, and 100mm Tris-HCl buffer (pH 7.0). Glucose or other carbohydrate which supported the microbial growth was indispensable for the reaction. The rate of oxidation (0.9 ~ 1.3 × 10⁵ μg-N/g of YK 92 cells·day) and the maximum amounts of nitrate formed in the culture medium (200 mm, 2800 μg-N/ml) were much larger than those of other heterotrophic nitrifiers and almost the same as those of Nitrobacter.

The nitrite-oxidizing activity was demonstrated in many types of yeast species.