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Microalgae-based biodiesel production has gained momentum over petroleum-based fuels due to its carbon neutrality and environment friendly properties. However, issues like high cost of cultivation and usage of inorganic fertilizers possess hindrance towards its commercial production and warrant new approaches of its eco-friendly cultivation techniques. In the present study, effect of hydrochar derived from hydrothermal carbonization (HTCb) of banana pseudostem as a supplement was investigated on the growth performance of microalgae, Graesiella emersonii MN877773, for biodiesel production. The study revealed that hydrochar supplementation (250 ppm) to the 10 days old microalgae culture improved (p < 0.05) biomass productivity (2 times higher; 0.018 g/L/day). There was also 27% increase (p < 0.05) in lipid content (16%) and improved lipid productivity (i.e. 0.003 g/L/day) noticed due to the reduction of culture solution pH from highly alkaline to slightly alkaline through hydrochar addition. Fatty acid profiling revealed presence of more amount of methyl palmitate (56% higher) with the high saturated/unsaturated fatty acid ratio (1.3). The vehicular properties of the biodiesel produced from the hydrochar treated microalgae were also found in compliance with the national and international standards with the high heating value of 40.2 MJ/kg. Microalgae grown in hydrochar-supplemented treatment also settled at the bottom within 1 h of resting period with the flocculation efficiency of 50%. This leads to the reduction (62%) in energy expenditure (5.5 kWh/g) and cost (0.4 US$/g) required for harvesting the microalgae. The present study accentuates that hydrochar supplementation at certain dosage to the pre-grown microalgae stimulates more production of quality lipids in the test microalgae with possibility to thrust sustainable biodiesel production. [ABSTRACT FROM AUTHOR]

The present study explores the use of periphyton to ameliorate toxic properties of arsenic (As) to Labeo rohita and also assesses the human food safety aspects. Fish were introduced to arsenite [As(III)] contaminated water (0.3 and 3 mg/L) along with periphyton. Biochemical, physiological and immunological parameters, including gene expression, were assessed after 30 days of exposure. Periphyton incorporation significantly improved (p < 0.05) the adverse effects of As on respiration, NH3 excretion and brain AChE activity by reducing oxidative stress and As bioaccumulation. The presence of periphyton in As(III) exposed fish (3 mg/L) increased the immune response (Immunoglobulin M and Complement C3) in the serum and the regulation of the respective immune genes in the anterior kidney was found to be similar to the control. A speciation study using LC-ICP-MS confirmed the high accumulation of As by periphyton (5.0–31.9 μg/g) as arsenate [As (V)], resulting in a lower amount of As in fish muscle. The calculated human health risk indices, Target Hazard Quotient (THQ) and Target Cancer risk (TCR) indicate that fish grown in periphyton-treated water may lower the human health risks associated with As. The study signifies the importance of periphyton-based aquaculture systems in As contaminated regions for safe fish production with enhanced yield. [ABSTRACT FROM AUTHOR]

Arsenic-contaminated food including farmed fish is one of the main routes of human exposure. Fish farmed in contaminated environment accumulates arsenic in different tissues with great variability. Thus, it is utmost important to quantify the risk associated with different farmed fish species in arsenic-contaminated aquaculture systems. In the present study, arsenic content was measured in twelve fish species (Labeo rohita, L. catla, Cirrhinus mrigala, Oreochromis niloticus, O. mossambicus, Liza tade, Puntius javanicus, L. calbasu, Glossogobius giuris, Macrobrachium rosenbergii, Ctenopharyngodon idella, and Bellamya bengalensis (gastropod)) collected from arsenic-contaminated aquaculture systems. Among the studied finfishes, C. idella was found to accumulate the lowest amount of arsenic (< 0.05 ± 0.00 mg kg−1) whereas the highest accumulation was noticed in O. mossambicus (1.0 ± 0.18 mg kg−1). However, the estimated carcinogenic and non-carcinogenic risks of human were found to be low for all the studied fishes. The calculated target hazard quotient (THQ) value for adults ranged from 0.01 to 0.08 whereas for children it ranged from 0.05 to 0.27 for low-arsenic-accumulating fishes (arsenic conc. < 0.5 mg kg−1). Based on these findings, C. mrigala, C. idella, and M. rosenbergii could be recommended as the candidate species for aquaculture in the arsenic-contaminated areas as farming of the low-arsenic-accumulating food fishes would also lower the risk of human exposure through food chain. [ABSTRACT FROM AUTHOR]