Mixotrophic transition induced lipid productivity in Chlorella pyrenoidosa under stress conditions for biodiesel production.

Influence of mixotrophic mode and its transition to various trophic modes under stress conditions was assessed during two stage cultivation of Chlorella pyrenoidosa. Significant lipid productivity was triggered under low light intensity, glucose + bicarbonate supplementation and nitrogen starvation. The association between biomass and lipid productivity, fatty acid composition during mixotrophic transition was critically evaluated. Biomass in growth phase (GP) and stress phase (SP) was 6.14 g/l and 5.14 g/l, respectively, in mixotrophic mode. Higher lipid productivity of 284 g/kg and 154.3 g/kg of neutral lipids was achieved in SP in mixotrophic-mixotrophic (MM) and mixotrophic-heterotrophic (MH) modes, respectively. Stress conditions resulted in high unsaturated fatty acid methyl esters in MH mode. In addition, neutral lipid content was 58% in MH and 52% in MM, that can be attributed to carbon source that is supplemented even in stress phase. Exploring such novel strategies can generate sustainable avenues for biodiesel production.

Endocrine disruption by Bisphenol A, polychlorinated biphenyls and polybrominated diphenyl ether, in zebra fish (Danio rerio) model: an in silico approach.

Endocrine disrupting chemicals may induce adverse health effects in humans and wildlife. Recent studies demonstrate that endocrine disrupting chemicals like Bisphenol A (BPA), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ether (PBDE) affect the reproductive characters shared by wide range of creatures including fish. An attempt was made to evaluate the toxicity of these chemicals on the vitellogenin protein of zebra fish (Danio rerio) using in silico approach. The protein structure of zebra fish vitellogenin was predicted using homology modelling, and the stereochemical quality of the model was validated by Ramachandran plot. The 3-D structure of vitellogenin was docked with the aforementioned chemicals that have demonstrated endocrine-disrupting activity. The pair-wise alignments between vitellogenin with phosvitin, lipovitellin-2 and YGP40 obtained by CLUSTALW alignment suggest that the vitellogenin contained lipovitellin-2- phosvitin- and YGP40-related amino acid sequences. Based on the prediction of CASTp and CLUSTALW, BPA and PCB predominantly interacted with lipovitellin-2 site of the protein, while PBDE interacts predominantly with the YGP40 site of the vitellogenin protein. The results indicate that the endocrine-disrupting chemicals (BPA, PCB and PBDE) dock with the vitellogenin cleavage sites lipovitellin-2 and YGP40 that play a crucial role in lipid-protein complex formation in the egg yolk. We hypothesize that these chemicals could potentially impair the egg yolk formation and eventually impact the zebra fish population which occupies an important niche among testing models used in drug discovery and related toxicity studies.

Acute effects of mercuric chloride on glycogen and protein content of zebra fish, Danio rerio.

Presence of mercury and other heavy metals above permissible levels in water bodies across the globe is posing a serious threat to aquatic biota and public health. Occurrence of mercury above the permissible limits in the aquatic ecosystem of Hyderabad city is well established. In this context, we carried out static- renewal bioassays on the zebra fish, Danio rerio exposed to different concentrations of mercuric chloride, and the 96-h median lethal concentration (LC50) was found to be 0.077 mgl(-1). Behavioral manifestations like loss of scales, hyper secretion of mucus, surfacing and darting movements, loss of balance, irregular swimming patterns were noticed in the fish exposed to 0.077 mgl(-1). The present study also examined the toxic effects of mercuric chloride on vital biochemical constituent's total glycogen and total protein. Significant decrease (p < 0.001) in glycogen and protein content of fish exposed to 0.077 mgl(-1).

Ecotoxicology of hexavalent chromium in freshwater fish: a critical review.

Chromium (Cr) is a naturally occurring element found in rocks, animals, plants, and soil, predominantly in its insoluble trivalent form [Cr(III)]. Intense industrialization and other anthropogenic activities have led to the global occurrence of soluble hexavalent chromium Cr(VI), which is readily leached from soil to groundwater or surface water, in concentrations above permissible levels. The ecotoxicology of Cr(VI) is linked to its environmental persistence and the ability to induce a variety of adverse effects in biologic systems, including fish. In aquatic ecosystems, Cr(VI) exposure poses a significant threat to aquatic life. This paper reviews the fate and transport of Cr(VI) in the environment and its acute and chronic effects on fish. We also discuss Cr(VI) toxicity at the cellular, biochemical, and genetic levels. An attempt is made in this review to comprehend the staggered data on the toxic effects of Cr(VI) to various species of fish. Such data are extremely useful to the scientific community and public officials involved in health risk assessment and management of environmental contaminants as a guide to the best course of action to restore ecosystems and, in turn, to preserve human health.

Acute effects of hexavalent chromium on survival, oxygen consumption, hematological parameters and some biochemical profiles of the Indian major carp, Labeo rohita.

An attempt has been made in the present investigation to determine the acute toxicity of hexavalent chromium and its toxicological effects on survival, physiological, hematological and biochemical parameters of the widely consumed Indian major carp, Labeo rohita. Short-term acute toxicity tests were performed adopting renewal bioassay technique (USEPA, 1975) over a period of 96 h, using different concentrations of potassium dichromate to the fish and the 96 h LC[50] value was found to be 111.45 mg/l (Cr(+6) as 39.40 mg/l). ANOVA results showed that the normal respiratory activity of the fish was significantly affected and there is a depression in the metabolic rate at the end of 24, 48, 72 and 96 h exposure. The metal also induced significant decrease (p<0.001) in the hematological parameters of the fish like total erythrocyte count, hemoglobin percent and absolute value Mean cell hemoglobin (MCH) both at the end of 24h and 96 h exposure indicating anemia. Appreciable decline in the biochemical profiles such as total glycogen, total lipids and total protein contents of the fish was also observed. However, the decrease in protein content was significant only at the end of 96 h. This study reflects the extent of the toxic effects of hexavalent chromium and the metal induced cumulative deleterious effects at various functional levels in the widely consumed freshwater fish, Labeo rohita.

Studies on the development of potential biomarkers for rapid assessment of copper toxicity to freshwater fish using Esomus danricus as model.

Living in an environment that has been altered considerably by anthropogenic activities, fish are often exposed to a multitude of stressors including heavy metals. Copper ions are quite toxic to fish when concentrations are increased in environmental exposures often resulting in physiological, histological, biochemical and enzymatic alterations in fish, which have a great potential to serve as biomarkers. Esomus danricus was chosen as model in the present study and the metabolic rate, gill morphology, total glycogen, total protein, superoxide dismutase and catalase were critically evaluated. The 96h LC50 value was found to be 5.5mg/L (Cu as 1.402 mg/L). Fish groups were separately exposed to lethal (5.5 mg/L) and sub lethal concentrations (0.55 mg/L) of copper sulphate over a period of 96h to examine the subtle effects caused at various functional levels. Controls were also maintained simultaneously. Significant decrease in the metabolic rate (p<0.001) of the fish was observed in both the concentrations studied. Studies employing Automated Video Tracking System revealed gross changes in the architecture of gill morphology like loss, fusion, clubbing of secondary gill lamellae, and detachment of gill rakers following softening of gill shaft in fish under lethal exposures indicating reduced respiratory surface area. Biochemical profiles like total glycogen and total protein in gills and muscle of fish exposed to 5.5 mg/L showed appreciable decrease (p<0.05 to 0.001) from control. Significant inhibition of superoxide dismutase (60.83%), catalase (71.57%) from control was observed in fish exposed to 5.5 mg/L at the end of 96h exposure only. Interestingly, in fish exposed to 0.55 mg/L enzyme activity is not affected except for catalase. Toxic responses evaluated at various functional levels are more pronounced in fish exposed to 5.5 mg/L and these can serve as potential biomarkers for rapid assessment of acute copper toxicity in environmental biomonitoring.