PubMed · 4681321
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A Kleczkowski. 1972. Action spectra and their interpretation.. https://pubmed.ncbi.nlm.nih.gov/4681321/
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This study presents the metal toxicity as revealed by Chlorella pyrenoidosa using a short-term continuous test and the conventional batch test. Toxicity tests were conducted in a chemostat with a test duration of 1 day. Toxicity data of five different metals (Cd, Pb, Co, Ni, and Zn) derived from the continuous test were compared against results from the conventional batch tests. The batch test is characterized by its saturated nutrient status for algal growth and, on the other hand, the continuous test is conducted at a nutrient-limiting condition simulating more closely to the aquatic field environment. The continuous test consistently yielded smaller EC(50) values, which indicated that alga in the chemostat is approximately four to six times more sensitive than those from the batch culture. Similar phenomena between the two types of tests were observed based on the NOEC values. Compared to literature data (US EPA ECOTOX Database) from the same species of alga, differences in test sensitivity between the batch tests and chemostat technique varied from 9.25 to 160 times. Such distinct differences indicate that current toxicity database may not adequately reflect the impact of various metal toxicants on C. pyrenoidosa. The continuous test method presented herein is a sensitive and rapid assessment technique and, therefore, has a potential for more general applications such as routine checkup for regulatory purposes.
Cross-flow microfiltration was used for separation of green algae, Chlorella sp., from freshwater. The transmembrane pressure (TMP) was adjusted at 40, 50 and 60 kPa, respectively. The cross-flow velocity was set at 0.43 m/s for laminar flow and 0.84 m/s for turbulent flow, respectively. The results showed that flux increased as TMP increased from 40 to 50 kPa. But drastic flux decline was observed when operating at TMP of 60 kPa. Raising cross-flow velocity increased the initial flux of MF under TMP of 60 kPa. Nevertheless, implementing turbulent cross-flow did not improve the drastic flux decline under the highest TMP. Preozonation increased the dissolved organic carbon, decreased algal viability and made the size of algal cells smaller. It also increased dissolved polysaccharide that derived from extracellular organic matter (EOM). Different effects of preozonation on flux behavior of MF were observed when utilizing hydrophobic and hydrophilic membrane. Generally speaking, preozonation improved performance of microfiltration by reducing cake compressibility and the biomass loading when both membranes were used. However, dissolved polysaccharide released during preozonation was adsorbed onto the hydrophobic membrane. Consequently, fouling resistance of the hydrophobic membrane became higher. These arguments were verified by classification of hydrodynamic resistances.
Chlorella protothecoides, a lutein-producing microalga, was grown aerobically in a mineral medium prepared with 70% (v/v) deuterated water. HPLC/atmospheric pressure chemical ionization-mass spectrometry (HPLC/APCI-MS) analysis revealed approximately 58% replacement of hydrogen by deuterium atoms as indicated by the molecular mass cluster at around m/z 599. The rapidly growing microalga had much higher levels (58%) of deuterium substitution relative to previously reported (9-15%) natural sources of lutein.