Freshwater Alga Chlorella Pyrenoidosa Research Articles

Toxic Effects of Tetracycline and Its Removal by the Freshwater Microalga Chlorella pyrenoidosa

The prevalence of tetracycline (TC) in aquatic environments has raised increasing concern due to its high ecotoxicology risk. The application of microalgae in the removal of antibiotics is a competitive alternative technology. However, the removal mechanism of TC by microalgae and its correlation with the ecotoxic response of microalgae are still not clear. In this study, the ecotoxicity of TC (0.5–10 mg L−1) and its removal by the freshwater alga Chlorella pyrenoidosa were investigated. The results show that TC has significant inhibitory effects on microalgal growth, photosynthetic pigment, and photosynthetic efficiency, with maximum inhibition rates of 49.68%, 62.54%, and 48.08%, respectively. However, the growth inhibition and photosynthesis impairment caused by TC seems to be reversible, as reflected by the decreased inhibition rates with prolonged exposure time. The simultaneous increases in the activities of superoxide dismutase (9.69–23.53%) and peroxidase (15.15–110.92%) and the contents of glutathione (17.62–64.17%) and malondialdehyde (25.16–35.25%) suggest that TC causes moderate oxidative stress. C. pyrenoidosa exhibits high removal efficiency (91.44–95.14%) for TC after 48 h of exposure with short half-lives of 11.31–13.48 h. Biodegradation (56.86–64.62%) is the primary removal mechanism of TC, accompanied by the abiotic process (24.68–40.97%), bioaccumulation (1.95–10.97%), and bioadsorption (0.09–0.38%). These findings demonstrate the toxicity resistance and high removal capacity of C. pyrenoidosa to TC, highlighting its potential application in the remediation of TC-contaminated water.

Toxic effects of 1,4-dichlorobenzene on photosynthesis in Chlorella pyrenoidosa

1,4-Dichlorobenzene (1,4-DCB) is a common organic contaminant in water. To determine the effects of this contaminant on photosynthesis in the freshwater alga Chlorella pyrenoidosa, algal cells were treated with 1,4-DCB at different concentrations for various times, and their photosynthetic pigment contents and chlorophyll fluorescence traits were analyzed. The results showed that 1,4-DCB exerted toxic effects on photosynthesis in C. pyrenoidosa, especially at concentrations exceeding 10mg/L. The inhibitory effects of 1,4-DCB were time- and concentration-dependent. After treatment with 1,4-DCB (≥10mg/L), the contents of photosynthetic pigments decreased significantly, the photosystem II reaction center was irreversibly damaged, and the quantum yield of photosystem II decreased significantly. Also, there were sharp decreases in the efficiency of photosynthetic electron transport and energy conversion. Photosystem II became overloaded as the amount of excitation energy distributed to it increased. All of these events weakened the photochemical reaction, and ultimately led to serious inhibition of photosynthesis.

Effect of hexachlorobenzene and acetone on algal growth: Physiology and ultrastructure

The effect of hexachlorobenzene (HCB) and acetone on growth and ultrastructure of the freshwater alga Chlorella pyrenoidosa was studied. The algal cells were grown for 76 h under continuous light in 10 ppm HCB with 0.33% acetone or in 0.33% acetone alone; the control cells were grown in nutrient solution only. As was deduced from determinations of dry matter, carbohydrates, chlorophyll content and total nitrogen, 0.33% acetone in nutrient solution slightly decreased the growth of the cells without having any influence on their ultrastructure while 3.33% acetone affected the ultrastructure of the cells severely. An incubation of Chlorella with 10 ppm HCB in nutrient solution containing 0.33% acetone led to a drastic decrease of all growth parameters studied, total nitrogen and chlorophyll content being affected most strongly. These latter observations were in accord with the changes in ultrastructure showing damage to the cell membranes, disintegrated cytoplasm and sometimes even break down of cell organelles leaving only starch grains, the pyrenoid and some endomembranes. In addition to these cells with severe lesions, quite normal cells were found.

Inhibition of Growth and Photosynthesis in Chlorella pyrenoidosa by a Polychlorinated Biphenyl and Several Insecticides1

The effects of DDT, dieldrin, carbaryl, parathion, piperonyl butoxide and Aroclor 1254®, a polychlorinated biphenyl containing 54% chlorine, on growth and photo-synthesis in the freshwater alga Chlorella pyrenoidosa Chick were measured. Inhibition was most easily demonstrated by varying the concentratIon of the alga and keeping the chemical concentration constant. Aroclor 1254 was the most active inhibitor of growth and photosynthesis in C. pyrenoidosa. Piperonyl butoxide, an insecticide synergist, and parathion were also strong inhibitors of growth and photosynthesis while DDT was less active. Dieldrin and carbaryl were least potent as inhibitors.

The Distribution of Trace Elements in Some Species of Phytoplankton Grown in Culture

INTRODUCTIONIn common with other plants, marine phytoplankton will only thrive if they are able to obtain essential trace elements. There is some evidence that shortages of available iron and manganese may occasionally restrict the growth of these organisms (Harvey, 1939, 1947). However, other essential trace metals are present in the sea at concentrations which, although very low, appear to be adequate to sustain abundant growth. The concentrations of trace elements necessary for optimum growth differ considerably from species to species (see e.g. Harvey, 1947; Goldberg, 1952). Krauss & Porter (1954) have demonstrated that manganese, iron and zinc are taken up by the freshwater alga Chlorella pyrenoidosa in proportion to their concentrations in the medium. However, this is not true for all elements, at least so far as the larger algae are concerned (Young & Langille, 1958). The concentrations of trace elements present in phytoplankton grown in culture may also depend on the age and density of the culture. Thus, Hayward (1969) has shown that although iron and zinc were initially rapidly taken up by Phaeodactylum tricornutum from a medium rich in chelated forms of these metals, their concentrations in the cells decreased as their numbers increased. The uptake of trace elements is not confined to those which have a definitely established physiological function.

Predicting Production in Light-Limited Continuous Cultures of Algae

Equations relating productivity, growth rate, cell concentration, and light absorption lead to the prediction that, when incident light is below saturating intensity, maximal productivity will occur at half the maximal growth rate. The freshwater alga Chlorella pyrenoidosa TX71105 and the marine alga Dunaliella tertiolecta were grown in a small continuous culture apparatus with turbidostatic control. With both cultures, the cell concentration showed a linear decrease with dilution rate. Productivity was maximal at about one-half the maximal dilution rate. Average mass per cell increased near the maximal dilution rate, causing some asymmetry in the productivity versus dilution rate curve. The chlorophyll content per unit mass decreased in this region, but the chlorophyll content per cell remained constant. Best production rate in a light-limited algal culture was obtained when the growth rate at very low cell concentration was determined in the apparatus and the dilution rate was set at one-half that value.

The origin of the marine polyunsaturated fatty acids. Composition of some marine plankton

Summary and ConclusionsShrimp, crabs, the marine diatomNitzschia closterium, Platymonas sp., and the fresh water algaChlorella pyrenoidosa were maintained or cultured in the laboratory. The crustacea were fed low‐fat, cottonseed oil, and menhaden oil rations. The fatty acid composition of all groups, as well as that of native phytoplankton and zooplankton catches, were determined as the extinction coeffcients, (E1%1cm.), at wavelengths of maximum absorption.It was found that both shrimp and crabs lost much of their polyunsaturated acids on the fat‐free diet and regained it again by ingestion, as do fish. The shrimp however appeared to synthesize more highly unsaturated acids from cottonseed oil than did other aquatic animals.Phytoplankton do produce a high level of polyunsaturated fatty acids.The importance of the determination of the structure of aquatic plant and animal fatty acids in the problem of the origin of the acids and their mechan ism of synthesis was discussed.

The unsaturated fatty acids of the alga chlorella

HE purpose of this paper is to elucidate further the composition of the unsaturated fatty acids of the fresh water alga Chlorella pyrenoidosa grown in pure culture in pilot plant quantities. In 1948 Milner (1) had shown the effect of certain environmental conditions on the yield of Chlorella and its lipid content. An excellent discussion of these results and the economic aspects of the problem appeared in 1951 (2) in this journal. Significant to us was the observation that the cell yield increased with increased nitrogen content of nutrient media but that the cells thus obtained had a low content of fatty acid. These however were highly unsaturated as indicated by iodine numbers of over 160. Restriction of nitrogen in the media gave poor yield of C hlorella, but the fatty acid content of the cells increased tenfold to over 60%. Iodine number of the fatty acids dropped to 125. The one sample which we examined was the low-lipid, high-iodine number type. The sample was obtained from Arthur D. Little Inc. Pilot plant studies at the laboratory were apparently aimed at high cell and high protein yields. Milner found that the fatty acids were almost all of C~s and C~s chain length, tte noted that the iodine number of the C~6 fraction indicated at least 17% of triene fatty acids. Polyunsaturated C~6 fatty acids are relatively rare. Heyes and Sborland (3) have re