Photosynthetic microalgae play an important role in solar-to-chemical energy conversion on Earth, but the increasing solar ultraviolet (UV) radiation seriously reduces the biological photosynthesis. ...Here, we developed a one-step approach to construct cell-in-shell hybrid structure by using direct adsorption of CeO sub(2) nanoparticles onto cells. The engineered CeO sub(2) nanoshell can efficiently protect the enclosed Chlorella cell due to its excellent UV filter property, which can also eliminate UV-induced oxidative stress. The experiments demonstrate that the resulted algae-CeO sub(2) composites can guarantee their biological photosynthetic process and efficiency even under UV. This study follows a feasible strategy to protect living organisms by using functional nanomaterials to improve their biological functions.
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IJS, KILJ, NUK, PNG, UL, UM
In order to purify various pollutants (3108 mg COD/L, 2120 mg NH sub(3)-N/L) in the undiluted anaerobic digestion effluent of food wastes (UADEFW), ozonation pretreatment was employed to improve ...pollutants removal by microalgae mutant Chlorella PY-ZU1 with 15% CO sub(2). Ozonation pretreatment broke Cdouble bond; length as m-dash C bonds and benzene rings of refractory organics such as unsaturated fatty acids and phenols in UADEFW and degraded them into low-molecular-weight organics such as methanoic acid and methanal, but excessive ozone induced the accumulation of toxic by-products. The microalgal growth rate and biomass yield markedly increased to the peaks of 456 mg/L/d and 4.3 g/L, respectively, when the UADEFW was pretreated with 2 mg-O sub(3)/mg-C of ozone. The removal efficiencies of NH sub(3)-N, TP and COD reached 99%, 99% and 68%, respectively. The lipid and carbohydrate contents of microalgal biomass increased because of the relative lack of nitrogen when microalgae was cultured with 15% CO sub(2) to purify the UADEFW with ozonation pretreatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
While photosynthetic microalgae, such as Chlorella, serve as feedstocks for nutritional oils and biofuels, heterotrophic cultivation can augment growth rates, support high cell densities, and ...increase triacylglycerol (TAG) lipid content. However, these species differ significantly in their photoautotrophic and heterotrophic characteristics. In this study, the phylogeny of thirty Chlorella strains was determined in order to inform bioprospecting efforts and detailed physiological assessment of three species. The growth kinetics and lipid biochemistry of C. protothecoides UTEX 411, C. vulgaris UTEX 265, and C. sorokiniana UTEX 1230 were quantified during photoautotrophy in Bold's basal medium (BBM) and heterotrophy in BBM supplemented with glucose (10 g L-1). Heterotrophic growth rates of UTEX 411, 265, and 1230 were found to be 1.5-, 3.7-, and 5-fold higher than their respective autotrophic rates. With a rapid nine-hour heterotrophic doubling time, Chlorella sorokiniana UTEX 1230 maximally accumulated 39% total lipids by dry weight during heterotrophy compared to 18% autotrophically. Furthermore, the discrete fatty acid composition of each strain was examined in order to elucidate lipid accumulation patterns under the two trophic conditions. In both modes of growth, UTEX 411 and 265 produced 18:1 as the principal fatty acid while UTEX 1230 exhibited a 2.5-fold enrichment in 18:2 relative to 18:1. Although the total lipid content was highest in UTEX 411 during heterotrophy, UTEX 1230 demonstrated a two-fold increase in its heterotrophic TAG fraction at a rate of 28.9 mg L(-1) d(-1) to reach 22% of the biomass, corresponding to as much as 90% of its total lipids. Interestingly, UTEX 1230 growth was restricted during mixotrophy and its TAG production rate was suppressed to 18.2 mg L-1 d-1. This constraint on carbon flow raises intriguing questions about the impact of sugar and light on the metabolic regulation of microalgal lipid biosynthesis.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study evaluated the growth of the green alga Chlorella sp. C2 under a nitrite-simulated NO environment and the removal rates of actual flue gas fixed salts (FGFSs) from Sinopec's Shijiazhuang ...refinery along with lipid production. The results showed that nitrite levels lower than 176.5 mM had no significant adverse effects on the cell growth and photosynthesis of Chlorella sp. C2, demonstrating that this green alga could utilize nitrite and NOx as a nitrogen source. High concentrations of nitrite (88.25-176.5 mM) also resulted in the accumulation of neutral lipids. A 60% nitrite removal efficiency was obtained together with the production of 33% algae lipids when cultured with FGFS. Notably, the presence of nitrate in the FGFS medium significantly enhanced the nitrite removal capability, biomass and lipid production. Thus, this study may provide a new insight into the economically viable application of microalgae in the synergistic combination of biological DeNO of industrial flue gases and biodiesel production.
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IJS, KILJ, NUK, PNG, UL, UM
•There are changes in physical and chemical properties in the aging of microplastics.•Aged microplastics pose a stronger inhibition on the growth of microalgae than that of virgin ...microplastics.•single microplastics and copper significantly inhibit the growth of microalgae and cause serious oxidative stress.•The interaction of microplastics and copper alleviates the negative effect of single microplastics and copper to microalgae.
Microplastics (MPs) could pose potential risks to microalgae, the primary producer of marine ecosystems. Currently, few studies focus on the interaction of aged MPs with other pollutants and their toxic effects to microalgae. Therefore, the present study aimed to investigate i) the aging of microplastics polyvinyl chloride (mPVC) in simulated seawater and the changes in physical and chemical properties; ii) the effects of single mPVC (virgin and aged) and copper on microalgae Chlorella vulgaris; and iii) the interaction of aged mPVC and copper and the oxidative stress towards C. vulgaris. In this study, some wrinkles, rough and fractured surface textures can be observed on the aged mPVC, accompanying with increased hydroxyl groups and aromatic carbon-carbon double bond but decreased carbon hydrogen bond. It was found that single virgin or aged mPVC at low concentration (10 mg/L) had significant inhibition on the growth of C. vulgaris but no inhibition at higher concentration (100, 1,000 mg/L), which can be reasonably explained by the aggregation and precipitation of mPVC at high concentration. The aging of mPVC inhibited the growth of C. vulgaris with the maximum growth inhibition ratio (IR) of 35.26% as compared with that of virgin mPVC (IR = 28.5%). However, the single copper could significantly inhibit the growth of C. vulgaris and the inhibitory effects increased with concentration (0.2, 0.5, 1.0 mg/L). Furthermore, both the single aged mPVC (10 mg/L) and copper (0.5 mg/L) caused serious cell damage, although the concentration of superoxide dismutase (SOD) and the intracellular malonaldehyde (MDA) increased. In contrast to single treatment, the growth of C. vulgaris can be enhanced by the combined group with copper (0.5 mg/L) and aged mPVC (10 mg/L).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Summary
Chlorella microalgae are increasingly used for various purposes such as fatty acid production, wastewater processing, or as health‐promoting food supplements. A mass spectrometry‐based survey ...of N‐glycan structures of strain collection specimens and 80 commercial Chlorella products revealed a hitherto unseen intragenus diversity of N‐glycan structures. Differing numbers of methyl groups, pentoses, deoxyhexoses, and N‐acetylglucosamine culminated in c. 100 different glycan masses. Thirteen clearly discernible glycan‐type groups were identified. Unexpected features included the occurrence of arabinose, of different and rare types of monosaccharide methylation (e.g. 4‐O‐methyl‐N‐acetylglucosamine), and substitution of the second N‐acetylglucosamine. Analysis of barcode ITS1–5.8S–ITS2 rDNA sequences established a phylogenetic tree that essentially went hand in hand with the grouping obtained by glycan patterns. This brief prelude to microalgal N‐glycans revealed a fabulous wealth of undescribed structural features that finely differentiated Chlorella‐like microalgae, which are notoriously poor in morphological attributes. In light of the almost identical N‐glycan structural features that exist within vertebrates or land plants, the herein discovered diversity is astonishing and argues for a selection pressure only explicable by a fundamental functional role of these glycans.
Significance Statement
The protein N‐glycosylation machinery of green algae has hitherto been considered as being essentially similar to that of land plants. The current work reveals a plethora of yet unknown N‐glycan structures only within the Chlorella clade – an economically relevant branch – with considerable repercussions on taxonomy and functional significance.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Chlorella minutissima was co-cultured with Escherichia coli in airlift reactors under mixotrophic conditions (glucose, glycerol, and acetate substrates) to determine possible effects of bacterial ...contamination on algal biofuel production. It was hypothesized that E. coli would compete with C. minutissima for nutrients, displacing algal biomass. However, C. minutissima grew more rapidly and to higher densities in the presence of E. coli, suggesting a symbiotic relationship between the organisms. At an initial 1% substrate concentration, the co-culture produced 200-587% more algal biomass than the axenic C. minutissima cultures. Co-cultures grown on 1% substrate consumed 23-737% more of the available carbon substrate than the sum of substrate consumed by E. coli and C. minutissima alone. At 1% substrate, total lipid and starch productivity were elevated in co-cultures compared to axenic cultures indicating that bacterial contamination was not detrimental to the production of biofuel precursors in this specific case. Bio-fouling of the reactors observed in co-cultures and acid formation in all mixotrophic cultures, however, could present challenges for scale-up.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Schematic diagram of MDZ removal in Chlorella vulgaris culture.
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•Metronidazole is efficiently removed during algal treatment.•Metronidazole is removed via sorption onto the ...biomass.•Metronidazole showed toxicity to C. vulgaris at stationary phase of life cycle.•The removal efficiency of C. vulgaris decreased with increase of antibiotic.
This current study investigated the removal of metronidazole from aqueous media by C. vulgaris. Two different initial sizes of inoculum (0.05 and 0.5 g L−1) were tested for a wide concentration range of metronidazole (1–50 μM). The effect of metronidazole concentrations on biomass production was studied for 20 days. The exopolymeric substances (EPS) were quantified and correlated with the removal of antibiotics from aqueous media. Specifically, MDZ stimulated the production of EPS in C. vulgaris, which played the major role in the adsorption of this antibiotic. Also, metronidazole significantly influenced the zeta potential of C. vulgaris in the test cultures, indicating a change in surface characteristics. This decrease in surface negative charge caused auto-flocculation phenomena at a stationary phase. Chronic and acute toxicity experiments showed that metronidazole was harmful to C. vulgaris at stationary phase. Results from this study would advance our knowledge on the treatment of metronidazole-contaminated waters with C. vulgaris as a green technology-oriented process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Exposure of microalgae Chlorella vulgaris and Spirulina platensis to Methylene blue resulted in acute toxicity.•Growth inhibition rate, pigment and protein content were inhibited due ...to toxicity.•Inhibition of pigment synthesis was primary reason of toxicity.
Microalgae are ecologically important species in aquatic ecosystems due to their role as primary producers. The inhibition of growth of microalgae due to dye pollution results in an upheaval in the trophic transfer of nutrients and energy in aquatic ecosystems. Therefore, this investigation aimed to evaluate the toxicity of a textile dye Methylene blue (MB) on two microalgae viz. Chlorella vulgaris and Spirulina platensis. An exposure of the unialgal populations of both the microalgae towards graded concentrations of the dye showed a concentration-dependent decrease in specific growth rate, pigment and protein content. In the toxicity study of 24 –96-h, following the OECD guidelines 201, the EC50 values of C. vulgaris and S. platensis ranged from 61.81 to 5.43 mg/L and 5.83 to 1.08 mg/L respectively revealing that S. platensis exhibited a higher level of susceptibility towards the dye as compared to C. vulgaris and the latter is more tolerant to the dye toxicity even at higher concentrations. The findings indicate that the response to dye is a species-specific phenomenon. Given the differences in the cell structure and enzymatic pathways in Spirulina platensis (a prokaryote) and Chlorella vulgaris (an eukaryote), the tolerance levels can differ. After 96-h exposure of C. vulgaris to MB (100 mg/L), the chlorophyll-a, b and carotenoid content were reduced 2.5, 5.96 and 3.57 times in comparison to control whereas in S. platensis exposure to MB (10 mg/L), the chlorophyll-a and carotenoid content were reduced 3.59 and 5.08 times in comparison to control. After 96-h exposure of C. vulgaris and S. platensis to the dye (20 mg/L), the protein content was found to be 4.34 and 2.75 times lower than the control. The protein content has decreased in accordance with the increase in dye concentration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Microalgae are able to metabolize inorganic selenium (Se) to organic forms (e.g. Se-proteins); nevertheless at certain Se concentration culture growth is inhibited. The aim of this work was to ...confirm the hypothesis that the limit of Se tolerance in Chlorella cultures is related to photosynthetic performance, i.e. depends on light intensity. We studied the relation between the dose and irradiance to find the range of Se tolerance in laboratory and outdoor cultures. At low irradiance (250 mu mol photons m super(-2) s super(- 1)), the daily dose of Se below 8.5 mg per g of biomass (<20 mu M) partially stimulated the photosynthetic activity (relative electron transport rate) and growth of Chlorella cultures (biomass density of ~1.5 g DW L super(-1)) compared to the control (no Se added). It was accompanied by substantial Se incorporation to microalgae biomass (~0.5 mg Se g super(-1) DW). When the Se daily dose and level of irradiance were doubled (16 mg Se g super(-1) DW; 500 mu mol photons m super(-2) s super(- 1)), the photosynthetic activity and growth were stimulated for several days and ample incorporation of Se to biomass (7.1 mg g super(-1) DW) was observed. Yet, the same Se daily dose under increased irradiance (750 mu mol photons m super(-2) s super(- 1)) caused the synergistic effect manifested by significant inhibition of photosynthesis, growth and lowered Se incorporation to biomass. In the present experiments Chl fluorescence techniques were used to monitor photosynthetic activity for determination of optimal Se doses in order to achieve efficient incorporation without substantial inhibition of microalgae growth when producing Se-enriched biomass.
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