Access to secure water sources has become one of the biggest challenges for human sustainability. Climate change and associated droughts make it difficult to guarantee the usual water source and move to groundwater use or to the re-use of treated wastewater remains unviable due the lack on the capacity of monitoring water quality. Moreover, reusing treated wastewater from repositories near anthropogenic sources represents a risk of high concentrations of emerging contaminants. The strategies involve a higher risk of encountering toxic elements with a heavy burden on human and environmental health. New accessible and reliable tools are required to detect any hazard from the waterbodies in real time to ensure safe management and also to decrease mismanagement or ilegal water discharges. One of the available options is to look into enzyme-based biosensors that can detect toxic elements in the water. The proposed biosensors require sensible elements to be accessible and durable for their proper function. The present revision shows in first place, the actual need of real time monitoring due the different sources and effects of emergent pollutants. Secondly, describes how enzymes can be immobilized for its application in biosensors and the rol enzymes play as bioreceptor element in biosensing. Thirdly, describes the transduction methods that can be observed, and finally the actual application of enzyme biosensors for the detection of different toxic elements. According to the presented literature enzyme-based biosensors have been successfully applied for the detection of a wide number of pollutants reaching detection limits comparable to traditional methods such as up to 0.018 nM of mercury. Furthermore, laccase seems to be the more applied enzyme in literature, but positive results are not limited to this enzyme and other candidates have been explored showing good detection rate.
Microalgae are a promising solution in shrimp farming overexploitation. This study assessed the efficacy of microalgae as a food additive for Penaeus vannamei growth and their effect on immune system stimulation against Vibrio parahaemolyticus. Three diets were formulated with 0, 1, and 3% (DC, D1, and D3, respectively) of a mixture of three different microalga species, Tetraselmis suecica, Dunaliella salina, and Chaetoceros muelleri, and growth, survival, and post-harvest quality in shrimp culture were evaluated. Two bioassays were performed: a 60-day feeding trial and an immersion infection bioassay against V. parahaemolyticus. D1 was the best treatment and significantly different to DC (P ≤ 0.05), achieving a food conversion factor of 1.24 ± 0.11 and 1.85 ± 0.38; specific growth rate 1.58 ± 0.03% d-1 and 1.35 ± 0.11% d-1; and weight gain of 5.68 ± 0.32 g and 4.79 ± 0.33 g, respectively. Protein content in shrimp muscle was positively increased by microalgae inclusion, achieving 20.8 ± 0.2% (D1) to 21.7 ± 0.3% (D3), 19.2 ± 0.1% (DC). In the infection bioassay, D1 and D3 reached a 100% survival rate, and histological damage in the hepatopancreas was not observed, suggesting immune system stimulation. These results indicated that microalgae added to food are an excellent source of proteins, carbohydrates, lipids, and promoters of antimicrobial activity that allowed additional protection against mortality caused by V. parahaemolyticus.
BACKGROUND Recently, wastewater effluents from animal farms have been treated using microalgae for the removal of organic and inorganic compounds. Swine wastewater (SW) and wastewater treated by anaerobic digestion (TW) were used as culture media for a wild strain of microalga, Chlorella sp. (Chlorophyta), previously isolated for our research group. This was cultivated under laboratory conditions in a batch culture, and then inoculated in a cascade thin‐layer reactor under outdoor conditions. The kinetic behavior, nutrient removal (COD, NH4+‐N, NO3−‐N and PO34−‐P) efficiency and biochemical composition of the microalga biomass were evaluated. RESULTS SW supported the highest growth (339 × 106 cells mL−1 and μ = 0.42 d−1) and the maximal removal of COD (91%), nitrates (87%), ammonium (45%) and phosphate (70%) in a batch culture. Whereas, in continuous cultivation, an adequate operation was achieved at temperatures up to 42 °C, with removals greater than 80% of COD, 70% of nitrates, 90% of ammonium and 60% of phosphates. Also, the produced biomass achieved the highest content of proteins (386 mg g−1 dry weight), carbohydrates (291.49 mg g−1 dry weight) and saturated and monounsaturated fatty acids, reaching 74.76% of total fatty acids. CONCLUSIONS The SW medium showed greater growth of Chlorella than TW using the outdoor thin‐layer cascade reactor. This is an opportunity to use wastewater as nutrient to obtain biomass enriched in compounds with various possibilities for application. © 2019 Society of Chemical Industry
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