Studies on the Growth of Chlorella vulgaris in Culture Media with Different Carbon Sources

Diminishing oil reserves, rising oil prices and a significant increase in atmospheric carbon dioxide levels have led to an increasing demand for alternative fuels. Microalgae have been suggested as a suitable means for fuel production because of their advantages related to higher growth rates, higher photosynthetic efficiency and higher biomass production, compared to other terrestrial energy crops. During photosynthesis, microalgae can fix carbon dioxide from different sources, including the atmosphere, industrial exhaust gases and soluble carbonate salts. To determine the most optimal conditions for the growth of Chlorella vulgaris in order to produce lipids that can be transformed into biodiesel fuel, different nutritional conditions were investigated. For this purpose, three media, namely Jaworski’s medium, an enriched solution from modified Dual Solvay process and natural mineral water, were prepared and analyzed for biomass production, chlorophyll content and lipid content. The best growth resulted in an enriched solution from the modified Solvay process. This medium was diluted in different dilution ratios (1:100, 1:50, 1:10) and the best results were obtained in a medium diluted in a 1:10 ratio on the fifth day of culturing (3.72 · 106 cells mL–1; 4.98 μg mL–1 chlorophyll a)

Evidence of selection for resistance to paralytic shellfish toxins during the early life history of soft-shell clam (Mya arenaria) populations

Abstract This study identifies early, postmetamorphic soft-shell clams, Mya arenaria, as the life-history stage most susceptible to effects of blooms of paralytic shellfish poisoning (PSP) toxin-producing Alexandrium spp. Laboratory experiments used progeny from predominantly susceptible (naïve) or resistant (annually exposed) NW Atlantic populations. Growth and survival of toxified veliger larvae did not differ from those fed nontoxic algae. In contrast, postlarvae (4-12-mm shell length) from both populations exposed to a highly toxic Alexandrium tamarense isolate (, 100 cells mL 21 , 64-69 pg saxitoxin equivalents [STXeq] cell 21 ) suffered burrowing incapacitation, toxin accumulation, and mortalities within 1 week of toxin exposure. These effects were greater and occurred sooner in the naïve population. Short-term toxification in the laboratory caused a significant shift in the genotypic composition of this population, determined with a molecular marker for sodium-channel resistance. Clams with the sensitive genotype were selectively eliminated relative to resistant or heterozygote clams. Ingestion of toxic cells (too large for larval capture) is thus required to elicit toxic effects. Exposure to mixed, toxic, and nontoxic algal suspensions demonstrated that adverse effects to fitness (survival and growth) were dose-dependent, occurring only at $ 50 cells mL 21 of the isolate used (PR18b). Paralysis and thus increased predatory risk occurred even at 10 cells mL 21 . Postlarvae , 12 mm, which can co-occur with red tides throughout the Atlantic range of M. arenaria, were more susceptible to PSP than large (. 30 mm) juveniles. Natural selection for resistance in Atlantic populations will thus vary latitudinally with the timing, duration, and intensity of toxic blooms

Leveraging ligand affinity and properties: discovery of novel benzamide-type cereblon binders for the design of PROTACs

Immunomodulatory imide drugs (IMiDs) such as thalidomide, pomalidomide, and lenalidomide are the most common cereblon (CRBN) recruiters in proteolysis-targeting chimera (PROTAC) design. However, these CRBN ligands induce the degradation of IMiD neosubstrates and are inherently unstable, degrading hydrolytically under moderate conditions. In this work, we simultaneously optimized physiochemical properties, stability, on-target affinity, and off-target neosubstrate modulation features to develop novel nonphthalimide CRBN binders. These efforts led to the discovery of conformationally locked benzamide-type derivatives that replicate the interactions of the natural CRBN degron, exhibit enhanced chemical stability, and display a favorable selectivity profile in terms of neosubstrate recruitment. The utility of the most potent ligands was demonstrated by their transformation into potent degraders of BRD4 and HDAC6 that outperform previously described reference PROTACs. Together with their significantly decreased neomorphic ligase activity on IKZF1/3 and SALL4, these ligands provide opportunities for the design of highly selective and potent chemically inert proximity-inducing compounds

Neurotoxic Alkaloids: Saxitoxin and Its Analogs

Saxitoxin (STX) and its 57 analogs are a broad group of natural neurotoxic alkaloids, commonly known as the paralytic shellfish toxins (PSTs). PSTs are the causative agents of paralytic shellfish poisoning (PSP) and are mostly associated with marine dinoflagellates (eukaryotes) and freshwater cyanobacteria (prokaryotes), which form extensive blooms around the world. PST producing dinoflagellates belong to the genera Alexandrium, Gymnodinium and Pyrodinium whilst production has been identified in several cyanobacterial genera including Anabaena, Cylindrospermopsis, Aphanizomenon Planktothrix and Lyngbya. STX and its analogs can be structurally classified into several classes such as non-sulfated, mono-sulfated, di-sulfated, decarbamoylated and the recently discovered hydrophobic analogs—each with varying levels of toxicity. Biotransformation of the PSTs into other PST analogs has been identified within marine invertebrates, humans and bacteria. An improved understanding of PST transformation into less toxic analogs and degradation, both chemically or enzymatically, will be important for the development of methods for the detoxification of contaminated water supplies and of shellfish destined for consumption. Some PSTs also have demonstrated pharmaceutical potential as a long-term anesthetic in the treatment of anal fissures and for chronic tension-type headache. The recent elucidation of the saxitoxin biosynthetic gene cluster in cyanobacteria and the identification of new PST analogs will present opportunities to further explore the pharmaceutical potential of these intriguing alkaloids

Uptake and fate of diarrhetic shellfish toxins from the dinoflagellate Prorocentrum lima in the bay scallop Argopecten irradians

Bivalve molluscs can acquire diarrhetic shellfish poisoning (DSP) toxins via ingestion of toxigenic dinoflagellates. The dynamics and fate of DSP toxins were investigated in the bay scallop Argopecten irradians exposed to cells of the epibenthic dinoflagellate Prorocentrum lima, a known producer of DSP toxins, in controlled laboratory microcosms. Toxin parameters determined were uptake and detoxification rates, and anatomical compartmentalization. Toxins in tissue and algal extracts were analyzed by liquid chromatography-mass spectrometry (LC-MS). No mortalities occurred and feeding inhibition was not observed for juvenile and adult bay scallops during the 2 wk exposure to P, lima cells. Clearance rates were similar for scallops exposed to equivalent biovolume cell concentrations of toxigenic P. lima and the non-toxic diatom Thalassiosira weissflogii; however, absorption efficiency of organic matter was significantly lower with a diet of P. Lima than T. weissflogii, Although DSP toxin concentrations in viscera of bay scallop exceeded commonly accepted regulatory levels (0.2 mug g(-1) whole tissue) within 24 h of exposure to P. lima, after 2 wk of exposure total DSP toxin retained in scallop tissues was <1 % of the total toxin ingested over the same period. Most of the total toxin body burden was in the viscera (76 %); however, in adult scallops a significant portion was associated with gonadal tissue (12 %). Toxin levels were relatively low in gill, mantle and adductor tissue (< 12% of total toxin body burden). During the depuration period, rapid release of DSP toxins from scallops indicated that toxins were poorly bound to all tissues, with the exception of the viscera. Detoxification of viscera consisted of a rapid loss of weakly bound toxin components within the initial 3 d of depuration, followed by a much slower release of the remaining toxin at a rate of 8.4 % d(-1).Peer reviewed: YesNRC publication: Ye

Uptake, metabolism and loss of clay-flocculated brevetoxins in a surface deposit-feeding clam

Blooms of the brevetoxin-producing Karenia brevis in the Gulf of Mexico cause fish kills, food poisoning and respiratory irritation in humans. Sedimentation of toxic cells following clay application could reduce toxin incorporation by commercially important suspension-feeding bivalves and direct public health impacts, but may potentially lead to brevetoxin (PbTx)accumulation by benthic depositfeeders. The goal of this study was to determine whether deposit-feeding could provide a pathway of toxin transfer from deposited clay-K.brevis aggregates. We investigated PbTx uptake, metabolism and detoxification kinetics in a depositfeeding, tellinid clam exposed to clay-deposited brevetoxins. We demonstrate that brevetoxins can be rapidly accumulated by depositfeeding from sedimented K. brevis cells (exceeding the regulatory level of 0.8 mg PbTx g-1 within ~12h as determined by ELISA). LC-MS analysis showed that PbTx-2, the dominant toxin in the clay/cell layer, was rapidly transformed into PbTx-3 and its cysteine derivatives in clam tissues. Detoxification of tissues following deposit-feeding occurred but toxicities remained around the regulatory level for 15 days. This toxicity was due largely to the persistence of the more potent PbTx-3-cys metabolites in tissues. Deposit-feeding clams do not pose a direct threat to humans but may provide a pathway for brevetoxin food web transferPeer reviewed: NoNRC publication: Ye