Extensive use of synthetic dyes in many industrial applications releases large volumes of wastewater. Wastewaters from dying industries are considered hazardous and require careful treatment prior to ...discharge into receiving water bodies. Dyes can affect photosynthetic activities of aquatic flora and decrease dissolved oxygen in water. The aim of this study was to evaluate the effect of Congo red on growth and metabolic activity of Chlorella vulgaris after 96h exposure. Exposure of the microalga to Congo red reduced growth rate, photosynthesis and respiration. Analysis of chlorophyll a fluorescence emission showed that the donor side of photosystem II was affected at high concentrations of Congo red. The quantum yield for electron transport (φEo), the electron transport rate (ETR) and the performance index (PI) also decreased. The reduction in the ability to absorb and use the quantum energy increased non-photochemical (NPQ) mechanisms for thermal dissipation. Overall, Congo red affects growth and metabolic activity in photosynthetic organisms in aquatic environments.
•Algal growth was related to the rate of Congo red utilization.•Chlorophyll a fluorescence was affected by Congo red concentrations (5–25mgL−1).•Congo red reduced electron transport (ETR) and inhibited metabolic rate (photosynthesis and respiration) in Chlorella vulgaris.
The problem of phosphorus and nitrogen deficiency in agricultural soils has been solved by adding chemical fertilizers. However, their excessive use and their accumulation have only contributed to ...environmental contamination. Given the high content of nutrients in biosolids collected from a food industry waste treatment plant, their use as fertilizers was investigated in Zea mays plants grown in sandy loam soil collected from a semi-desert area. These biosolids contained insoluble phosphorus sources; therefore, given the ability of Azotobacter nigricans to solubilize phosphates, this strain was incorporated into the study. In vitro, the suitable conditions for the growth of Z. mays plants were determined by using biosolids as a fertilizer and A. nigricans as a plant-growth-promoting microorganism; in vitro, the ability of A. nigricans to solubilize phosphates, fix nitrogen, and produce indole acetic acid, a phytohormone that promotes root formation, was also evaluated. At the greenhouse stage, the Z. mays plants fertilized with biosolids at concentrations of 15 and 20% (v/w) and inoculated with A. nigricans favored the development of bending strength plants, which was observed on the increased stem diameter (>13.5% compared with the negative control and >7.4% compared with the positive control), as well as a better absorption of phosphorus and nitrogen, the concentration of which increased up to 62.8% when compared with that in the control treatments. The interactions between plants and A. nigricans were observed via scanning electron microscopy. The application of biosolids and A. nigricans in Z. mays plants grown in greenhouses presented better development than when Z. mays plants were treated with a chemical fertilizer. The enhanced plant growth was attributed to the increase in root surface area.
Heavy metal detoxification in eukaryotic microalgae Perales-Vela, Hugo Virgilio; Peña-Castro, Julián Mario; Cañizares-Villanueva, Rosa Olivia
Chemosphere (Oxford),
06/2006, Letnik:
64, Številka:
1
Journal Article
Recenzirano
Microalgae are aquatic organisms possessing molecular mechanisms that allow them to discriminate non-essential heavy metals from those essential ones for their growth. The different detoxification ...processes executed by algae are reviewed with special emphasis on those involving the peptides metallothioneins, mainly the post transcriptionally synthesized class III metallothioneins or phytochelatins. Also, the features that make microalgae suitable organisms technologies specially to treat water that is heavily polluted with metals is discussed.
•High cell density of Scenedesmus incrassatulus biomass was achieved in heterotrophic culture.•Vitamins were suggested as regulatory factor in enhancing pigment synthesis.•Two stage ...hetrotrophy/photoinduction process was employed for S. incrassatulus culture.•Two stage hetrotrophy/photoinduction process improved the biomass and lutein productivity.
A biomass production process including two stages, heterotrophy/photoinduction (TSHP), was developed to improve biomass and lutein production by the green microalgae Scenedesmus incrassatulus. To determine the effects of different nitrogen sources (yeast extract and urea) and temperature in the heterotrophic stage, experiments using shake flask cultures with glucose as the carbon source were carried out. The highest biomass productivity and specific pigment concentrations were reached using urea+vitamins (U+V) at 30°C. The first stage of the TSHP process was done in a 6L bioreactor, and the inductions in a 3L airlift photobioreactor. At the end of the heterotrophic stage, S. incrassatulus achieved the maximal biomass concentration, increasing from 7.22gL−1 to 17.98gL−1 with an increase in initial glucose concentration from 10.6gL−1 to 30.3gL−1. However, the higher initial glucose concentration resulted in a lower specific growth rate (μ) and lower cell yield (Yx/s), possibly due to substrate inhibition. After 24h of photoinduction, lutein content in S. incrassatulus biomass was 7 times higher than that obtained at the end of heterotrophic cultivation, and the lutein productivity was 1.6 times higher compared with autotrophic culture of this microalga. Hence, the two-stage heterotrophy/photoinduction culture is an effective strategy for high cell density and lutein production in S. incrassatulus.
Discharge of dye-containing wastewater by the textile industry can adversely affect aquatic ecosystems and human health. Bioremoval is an alternative to industrial processes for detoxifying water ...contaminated with dyes. In this work, active and inactive biomass of the microalga
Chlorella vulgaris
was assayed for the ability to remove Congo Red (CR) dye from aqueous solutions. Through biosorption and biodegradation processes,
Chlorella vulgaris
was able to remove 83 and 58 % of dye at concentrations of 5 and 25 mg L
−1
, respectively. The maximum adsorption capacity at equilibrium was 200 mg g
−1
. The Langmuir model best described the experimental equilibrium data. The acute toxicity test (48 h) with two species of cladocerans indicated that the toxicity of the dye in the effluent was significantly decreased compared to the initial concentrations in the influent.
Daphnia magna
was the species less sensitive to dye (EC
50
= 17.0 mg L
−1
), followed by
Ceriodaphnia dubia
(EC
50
= 3.32 mg L
−1
). These results show that
Chlorella vulgaris
significantly reduced the dye concentration and toxicity. Therefore, this method may be a viable option for the treatment of this type of effluent.
Antibiotics are increasingly being used in human and veterinary medicine, as well as pest control in agriculture. Recently, their emergence in the aquatic environment has become a global concern. The ...aim of this study was to evaluate the effect of streptomycin on growth and photosynthetic activity of Chlorella vulgaris after 72h exposure. We found that growth, photosynthetic activity and the content of the D1 protein of photosystem II decreased. Analysis of chlorophyll a fluorescence emission shows a reduction in the energy transfer between the antenna complex and reaction center. Also the activity of the oxygen evolution complex and electron flow between QA and QB were significantly reduced; in contrast, we found an increase in the reduction rate of the acceptor side of photosystem I. The foregoing can be attributed to the inhibition of the synthesis of the D1 protein and perhaps other coded chloroplast proteins that are part of the electron transport chain which are essential for the transformation of solar energy in the photosystems. We conclude that micromolar concentrations of streptomycin can affect growth and photosynthetic activity of Chlorella vulgaris. The accumulation of antibiotics in the environment can become an ecological problem for primary producers in the aquatic environment.
•Exposure to streptomycin reduces.•The autotrophic growth of C. vulgaris.•The content of D1-PSII protein and photosynthetic pigments.•The function of oxygen-evolving complex and the electron transport.
Cr(VI) removal by
Scenedesmus incrassatulus was characterized in a continuous culture system using a split-cylinder internal-loop airlift photobioreactor fed continuously with a synthetic effluent ...containing 1.0
mg Cr(VI)
l
−1 at dilution rate (
D) of 0.3
d
−1. At steady state, there was a small increase (6%) on the dry biomass (DB) concentration of Cr(VI)-treated cultures compared with the control culture. 1.0
mg Cr(VI)
l
−1 reduced the photosynthetic pigments content and altered the cellular morphology, the gain in dry weight was not affected. At steady state, Cr(VI) removal efficiency was 43.5
±
1.0% and Cr(VI) uptake was 1.7
±
0.1
mg Cr(VI)
g
−1 DB. The system reached a specific metal removal rate of 458
μg Cr(VI)
g
−1 DB
d
−1, and a volumetric removal rate of 132
μg Cr(VI) l
−1
d
−1.
In the present paper we investigated the effects of sub-lethal concentrations of Cu
2+ in the growth and metabolism of
Scenedesmus incrassatulus. We found that the effect of Cu
2+ on growth, ...photosynthetic pigments (chlorophylls and carotenoids) and metabolism do not follow the same pattern. Photosynthesis was more sensitive than respiration. The analysis of chlorophyll
a fluorescence transient shows that the effect of sub-lethal Cu
2+ concentration
in vivo, causes a reduction of the active PSII reaction centers and the primary charge separation, decreasing the quantum yield of PSII, the electron transport rate and the photosynthetic O
2 evolution. The order of sensitivity found was: Growth
>
photosynthetic pigments content
=
photosynthetic O
2 evolution
>
photosynthetic electron transport
>
respiration. The uncoupled relationship between growth and metabolism is discussed.
The microalga Scenedesmus incrassatulus was cultivated in batch and fed-batch culture modes under three different nitrogen concentrations (N). Considering that nitrogen limitation results in ...carotenoid accumulation, main objectives of this work were to assess carotenoid concentration and the following fluorescence parameters: maximum photosynthetic efficiency (Fv/Fm), operational photosynthetic efficiency (Fq′/Fm′) and the non-photochemical quenching (NPQ) at different N concentrations in the culture media, using batch and fed-batch culture modes. In all treatments, carotenoid concentration reached maximal level when N concentration in the medium was almost completely depleted. Carotenoid concentrations in fed-batch treatments were up to 3 times higher than batch culture treatments. Maximum dry weight of 4.05±0.04gL−1 and cell concentration of 8.24×107cellmL−1 was obtained using the higher N concentration in fed-batch, these values were approximately 3 times higher than the obtained in batch culture. Fv/Fm showed the highest magnitude when the initial N concentration in the culture medium was higher, for both culture modes. Results showed that the fed-batch culture of S. incrassatulus promotes a higher Fv/Fm than batch culture (up to 0.78). The application of fed-batch culture had the effect of stabilizing the values of Fv/Fm during feeding period. In all fed-batch treatments the maximum Fq′/Fm′ was detected during the feeding period, which had maximum values ranging from 0.47–0.58. In fed-batch culture mode NPQ showed no direct relationship with total carotenoid concentration. ETR was higher in fed batch than in batch cultivation. In batch cultivation mode ETR had values ranging from 2 to 56μmolelectronsm−2s−1. ETR increased 6 fold in fed-batch cultivation when irradiance was increased, having values up to 610μmolelectronsm−2s−1. A good cultivation strategy for biocompound production could be the use of fed batch cultivation aimed to return nutrients like nitrogen to its initial condition.
This work evaluates the volumetric mass transfer coefficient (
k
L
a), the gas hold-up (
ɛ) and the mixing time (
t
m) as a function of superficial gas velocity (
U
G) in a flat-panel photobioreactor ...(PBR) with high light path. CO
2 utilization efficiency and volumetric power consumption (
P/
V) were also evaluated. A 50
L working volume photobioreactor was developed, 0.67
m in length, 0.57
m in height and 0.15
m in width (light path). The height-width ratio was 3.8, which is lower than reported in most PBRs. Initially, experiments were performed with air and tap water (biphasic system) and, subsequently, using a
Spirulina sp. culture (triphasic system: air, culture medium, cells). Minimum and maximum superficial gas velocity values were 5
×
10
−5 and 8.4
×
10
−3
m
s
−1, respectively. Maximum values for
k
L
a and
ɛ were 20.34
h
−1 (0.0057
s
−1) and 0.033 in the biphasic system, and 31.27
h
−1 (0.0087
s
−1) and 0.065 in the triphasic system. CO
2 utilization efficiency was 30.57%. Results indicate that the hydrodynamic and mass transfer characteristics of this photobioreactor are more efficient than those reported elsewhere for tubular and other flat-plate PBRs, which opens the possibility of using PBRs with higher light paths than yet proposed.
