Satya Prakash Shukla

Chlorella mirabilis as a potential species for biomass production in low-temperature environment

Successful adaptation/acclimatization to low temperatures in micro-algae is usually connected with production of specific biotechnologically important compounds. In this study, we evaluated the growth characteristics in a micro-scale mass cultivation of the Antarctic soil green alga Chlorella mirabilis under different nitrogen and carbon sources followed by analyses of fatty acid contents. The micro-scale mass cultivation was performed in stable (in-door) and variable (out-door) conditions during winter and/or early spring in the Czech Republic. In the in-door cultivation, the treatments for nitrogen and carbon sources determination included pure Z medium (control, Z), Z medium + 5% glycerol (ZG), Z medium + 5% glycerol + 50 μM KNO3 (ZGN), Z medium + 5% glycerol + 200 μM NH4Cl (ZGA), Z medium + 5% glycerol + 1 mM Na2CO3 (ZNC), Z medium + 5% glycerol + 1 mM Na2CO3 + 200 μM NH4Cl (ZGCA) and Z medium + 5% glycerol + 1 mM Na2CO3 + 50 μM KNO3 (ZGCN) and were performed at 15°C with an irradiance of 75 μmol m−2 s−1. During the out-door experiments, the night-day temperature ranged from −6.6 to 17.5°C (daily average 3.1 ± 5.3°C) and irradiance ranged from 0 to 2,300 μmol m−2 s−1 (daily average 1,500 ± 1,090 μmol m−2 s−1). Only the Z, ZG, ZGN, and ZGC treatments were used in the out-door cultivation. In the in-door mass cultivation, all nitrogen and carbon sources additions increased the growth rate with the exception of ZGA. When individual sources were considered, only the effect of 5% glycerol addition was significant. On the other hand, the growth rate decreased in the ZG and ZGN treatments in the out-door experiment, probably due to carbon limitation. Fatty acid composition showed increased production of linoleic acid in the glycerol treatments. The studied strain of C. mirabilis is proposed to be a promising source of linoleic acid in low-temperature-mass cultivation biotechnology. This strain is a perspective model organism for biotechnology in low-temperature conditions.

Nutrient requirements of polar Chlorella-like species

Eukaryotic micro-algae, well adapted to extremely low and varying temperatures, varying light intensities, as well as low availability of essential macronutrients and other resources, represent ideal producers in low-temperature biotechnological processes. In order to identify the nutrient requirements of six biotechnologically perspective Arctic and Antarctic soil Chlorella-like strains at various temperature and light regimes, the algae were cultivated in a unit for cross gradients of temperature (-4 to 24°C) and irradiance (5 to 65 µmol m -2 s -1 ), and at different nutrient treatments in each temperature- irradiance combination. The nutrient treatments included two different carbon (bicarbonate and carbonate concentrations of 1 and 5 mM) and nitrogen (nitrate concentrations of 50 amd 100 µM and ammonium concentrations 100 and 500 µM) forms at two different concentrations for each. Temperature and irradiance growth requirements were similar in the majority of strains reflecting thus comparable conditions in the original microhabitat, regardless of its geographic position. All studied strains tolerated low temperatures (1 to 5°C), but were able to grow even at temperatures above 20°C, thus, they were considered to be psychrotolerant. All experimental strains were able to grow at very low irradiances. Nutrient manipulation either did not affect the growth limits and optimum, or narrowed the growth optima; the response was strain- specific. Ammonium and nitrate additions resulted in decreased growth rates in all tested strains, with the exception of one strain in which growth stimulation was observed. The decrease in growth rate was probably due to nutrient oversaturation in the inhibited strains. Carbonate addition stimulated growth of all strains. Bicarbonate also increased the growth rate in all strains with one exception, in which bicarbonate inhibited growth, indicating thus carbon limitation during cultivation and different carbon uptake mechanisms.

Perspectives of Low-Temperature Biomass Production of Polar Microalgae and Biotechnology Expansion into High Latitudes

The adaptation mechanisms of polar microalgae (including cyanobacteria and eukaryotic microalgae) evolved to withstand the harsh polar environment characterized by low temperature, freeze-thaw cycles, desiccation, salinity, and high and variable photosynthetically active and ultraviolet radiation. Hence, polar microalgae developed ecological, physiological, and molecular defensive and adaptive strategies, which include the synthesis of a tremendous diversity of compounds originating from different metabolic pathways which protect them against the abovementioned stresses. Production of different biological compounds and various biotechnological applications, for instance, water treatment technology in low-temperature environments and many others, are the perspectives for humans, which widely explore the polar regions. In this review, the nonmarine environmental conditions in polar environments and microalgal adaptations are summarized with respect to possible biotechnological applications. The review also provides a survey of the possible compounds to be exploited from polar microalgae. Possible constructions of photobioreactors for mass cultivation of microalgae are proposed for operations in polar regions.

Recent Technologies for Wastewater Treatment: A Brief Review

There is an unprecedented increase in per capita use of, especially water, during the past few decades. In view of the vital significance of water resources, unsustainable use of water resources would cause serious impediment to the growth of economy and standard of living worldwide. Therefore, new approaches for a sustainable utilization of water resources are of utmost importance for a secure future. In recent past, a number of new wastewater treatment technologies have been developed which paved the way for achieving the sustainability through judicious water resource utilization and management. The new wastewater treatment technology, especially the integration of urban water and waste management systems, is a promising approach for the improvement of sustainability of global water resources.

Chemical Modification and Performance Evaluation of an Agro-Waste for Column Mode Removal of Textile Dyes

Abstract The performance of a newly designed column bed device packed with chemically modified agro‐waste (sugarcane bagasse) is evaluated for efficient removal of two textile dyes, Optilan yellow and Lanasyn brown and textile industry dye effluent. The parameters used for performance evaluation are removal efficiency (R%), adsorption capacity (q), and breakthrough (C e/C 0). The column exhibits >90% removal of both the dyes and >80% removal of textile industry dye effluent. The experimental data are fitted to three models, viz., Thomas, Adams–Bohart, and Yoon–Nelson for understanding the kinetic behavior of adsorption. The results reveal that the Yoon–Nelson model is the best‐fitted model for both the dyes with R 2 values 0.995 and 0.905 for Optilan yellow and Lanasyn brown, respectively. However, Thomas and Yoon–Nelson fit the best for textile industry effluent. Overall, this investigation provides baseline information about the column mode removal of textile dyes using the agro‐waste material as an adsorbent. The Fourier transform infrared spectroscopy spectra show the characteristic vibrational mode of C—H stretching of hydroxyl group around 2800–3000 cm−1. The change in the vibrational pattern is evident after alginic acid treatment, indicating delignification of the bagasse after treatment.

Triclosan toxicity alters behavioral and hematological parameters and vital antioxidant and neurological enzymes in Pangasianodon hypophthalmus (Sauvage, 1878)

Triclosan and its metabolites are detected in a diverse aquatic environment and are major concerns for various aquatic organisms. The present study investigated the impact of acute and sub-lethal exposure of triclosan on behaviour, activities of acetylcholinesterase and selected antioxidant enzymes, haematological and serum gas-electrolyte parameters of Pangasianodon hypophthalmus. The 96 h LC50 of triclosan for P. hypophthalmus was estimated as 1458 μg L-1. Further, sub-lethal triclosan exposure to 1/15th (97 μg L-1), 1/10th (145 μg L-1) and 1/5th (291 μg L-1) of 96 h LC50 concentration for a period of 45 days lead to decrease in total erythrocyte count, haemoglobin content and packed cell volume of blood while total leukocyte count increased significantly (p < 0.05) as compared to control. A concentration-dependent increase in the serum chloride and decrease in partial pressure of oxygen in blood serum was noted on 45th day. An increased activity of catalase and superoxide dismutase in gill and liver tissues and inhibition of acetylcholinesterase activity in brain was observed on 15th, 30th and 45th day of exposure which was dependent on both - concentration of triclosan and duration of exposure. A significant high activity of glutathione-S-transferase in gill and liver tissue was observed in triclosan exposed groups in comparison to control during the experimental period. The study shows that long-term sub-lethal exposure of triclosan to fish can lead to several physiological alterations such as enzymatic scavenging of oxygen radicals and the normal neurological functions mediated by the enzyme acetylcholinesterase. With increasing anthropogenic activity, the study provides a convincing evidence for the necessity of a regulated use and safer disposal of triclosan to the environment.