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Biotransformation of organic wastes into value-added products is gaining interest owing to waste management issues, exhaustion of fossil fuels and the demand for biodegradable plastics. Lactic acid is widely used for polymers, foods, beverages, medicines, cosmetics and clothing. However, the major obstacle in large-scale fermentation of lactic acid is achieving enhanced yield, productivity and optical purity with cheap resources. Therefore, we review methods and recovery techniques for production of microbial lactic acid using cheap fermentative substrates. New strategies allow to alleviate limitations associated with substrate inhibition, product inhibition, undesirable by-products, sensitivity to toxic compounds, inefficient utilization of mixed sugars and overuse of neutralizing agents. Efficient utilization of mixed sugars can be achieved with simultaneous saccharification and fermentation using mixed cultures, isolating carbon catabolic repression-negative strains and altering the metabolic pathway. Lactic acid productivity can be improved by co-culture, maintaining high cell density and periodically removing end-products accumulated in the fermentation medium. Inhibition by toxic compounds can be eliminated by using engineered feedstock which releases less inhibitors, by using inhibitor-tolerant microbes and by development of genetically engineered strains. Fed-batch fermentation was found to be better than other operation modes due to less substrate inhibition.

Energy and waste disposal issues are calling for advanced recycling methods such as conversion of organic waste into biohydrogen and biomethane. Here we review factors that influence yields, such as pH, temperature, substrate composition, biocatalyst, nutrient content, volatile fatty acids concentration, organic loading rate, hydraulic retention time and C/N ratio. The optimum pH is 5.5–6 for hydrogen production, and 6.8–7.2 for methane production. Hydrogen yield improved highly after reducing the retention time from 72 to 20 h. The highest methane productivity was achieved with C/N ratio of 16–27. We also discuss methods to improve efficiency such as co-digestion, pre-treatment, application of additives and optimal digester design. Co-digestion synergizes the effects on microbial communities, balances the nutrients, reduces the inhibitory effects and improves the economic viability. Co-digestion has enhanced the productivity by 25–400% compared to mono-digestion. Acid pre-treatment is the best method for lignocellulose hydrolysis, followed by enzyme pre-treatment. Microwave pre-treatment enhances the biomethane production 4–7 times. The batch mode improves the substrate degradation efficiency and hydrogen production by 25% compared to the continuous mode. The addition of trace metals alters the hydrogenase activity during anaerobic fermentation. Reaction kinetics and metabolomics, bioaugmentation, digestate recirculation, frequent feeding and development of bioreactor systems for two-stage anaerobic digestion are also presented.

In the last few decades, consciousness of fossil fuel resources and increased environmental concerns have given the need for emergence of alternative fuel. Biodiesel is one of the potential renewable energies produced from edible and non-edible biomass which could be a potential alternative for petrol-derived diesel. In this work, initially the process of biodiesel production from waste cooking oil using potassium hydroxide as catalyst and the process parameters were studied in laboratory. The maximum biodiesel yield of 97% was attained at 75 °C with 1 wt% catalyst concentration and oil-methanol molar ratio of 1:06 at 350 rpm and 90 min. Also, these process conditions were used for biodiesel production in the pilot plant and obtained 97% yield. Overall, mass balance for the pilot plant was studied to analyze the product yield loss. The fatty acid methyl ester formation in the plant was confirmed by characterization with FTIR and 1 H NMR. Further, the quality of biodiesel produced was compared for its physiochemical properties with the ASTM standards.

The present investigation aims to develop simultaneous extraction and conversion of inedible Madhuca longifolia seed oil into biodiesel by one-step acid-catalyzed in situ transesterification/reactive extraction process. Six different types of pretreatment were used to assess maximum yield of biodiesel. The maximum yield of 96% biodiesel was acquired with ultrasonic pretreatment at 1% moisture content, 0.61 mm seed grain size, 55 °C temperature, 400 rpm stirring speed, 15 wt% catalyst (H 2 SO 4 ) concentration, and with 1:35 seed oil to methanol ratio in a time period of 180 min. This reaction kinetics precedes first order also the finest value of rate constant and activation energy were calculated as 0.003 min −1 and 14.840 kJ mol −1 . The thermodynamic energy properties Δ G , Δ H , and Δ S are computed as 96457.172 J/mol, 12121.812 J/mol K, and − 257.12 J/mol K correspondingly. The enumerated outcome illustrates a heat absorb non-spontaneous/endergonic and endothermal reaction. The result of proposed work unveils ultrasonic pretreatment escalates the biodiesel efficiency and reactive extraction exemplifies the clean, cost-effective single-step approach for production of biodiesel from non-edible sources.

The aim of this study is to evaluate the pollution caused by fireworks on the day of what is known as Diwali festival which is celebrated every year in October–November. The increase in particle pollutants such as the particulate matter 2.5 (PM2.5) over a time period around the festival days is noted for a year of 2017 in the city of Chennai, South India, and this increase in pollutant levels is correlated with the increase in health issues present among public during this festival time. It was observed that PM2.5 varied from 30.06 ± 1.5 to 146.82 ± 7.3 µg/m3 with an average of 68.18 ± 26.84 µg/m3, and the mean concentration for three consecutive years (2015–2017) was lower than National Ambient Air Quality Standards. All the important pollutants such as sulphur dioxide (SO2), nitrogen dioxide (NO2) and PM2.5 have been measured during pre-Diwali, Diwali day and after Diwali at Choolaimedu (CM) and Chinmayanagar (CN) areas. Due to dense population, these areas are expected to have high levels of firework activity and are typical for the study. The gaseous pollutants SO2 and NO2 correlated with wind speed, wind direction, temperature and relative humidity. PM2.5 had good correlation with SO2. Eye irritation was found to be the most common health issue, which affected 44.3% of the total surveyed residents during these festival days.

The rapid development of electrochemical sensors holds great promise to serve as a next generation. However, the practical performances of electrochemical sensors are cruelly limited by stability, selectivity and sensitivity. These issues have been well addressed by introducing rational designs into the modified electrode for achieving the required performances. Herein, we demonstrate the ZnO–YMoO 4 for highly selective electrochemical detection of uric acid (UA). The ZnO–YMoO 4 nanostructure was characterised using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscope, transmission electron microscope with elemental mapping and energy-dispersive spectrometer. The ZnO–YMoO 4 modified electrode shows a much-improved electrochemical performance compared to those of the other electrodes. Interestingly, the ZnO is strongly firmed in the YMoO 4 , which provides a more sufficient pathway for the rapid electron and ion transportation. On the basis of these findings, our proposed sensor achieves a wide detection range from 0.1 to 120 nM with a correlation coefficient of 0.9839 and a low detection limit of 14.8 nM. Most markedly, the real-time monitoring of the proposed electrochemical sensor was proved by the successful determination of UA in milk samples. Our research work has opened a novel way to the rationale for the construction of highly efficient practical electrochemical sensors. Graphical abstract

DNA detection using solid state nanopores is limited by the difficulty of the detection of short DNA strands due to their very short dwell time. Here, we report on the fabrication of nanopores using a track-etching technique along with the atomic layer deposition of aluminum oxide. This method allows shaping of conical nanopores, controlling their diameter, and passivation of the surface by Al 2 O 3 . Through the optimized nanopore, short DNA (10 nM) having 10 and 40 nucleotides in length were detected both at the single stranded and double stranded levels. The analysis of current trace shows signal to noise ratio of 2 and 4 for ssDNA and dsDNA respectively and a dwell time at ms scale. This is possible because of both the high aspect ratio and the Al 2 O 3 coating that permit to decrease the DNA velocity. Graphical Abstract: Conical nanopores were prepared using a track-etching technique along with the atomic layer deposition of aluminum oxide. They allow for the detection of 10 and 40 in length single stranded and double stranded DNA.

The acclimated cells of Achromobacter xylosoxidans strain APZ wereemployed to decolorize a textile colorant, Reactive green 19A (RG19A) of greater tinctorial strength. The strain decolorized and simultaneously mineralized RG19A with a high average decolorization rate of 208.33 µgmin^sup -1^ under normal operating (pH 7.0 and 35°C) and static conditions. The spectral and chromatographic data described that the decolorization was due to biodegradation facilitated by the extracellular oxidoreductases secreted by A. xylosoxidans strain APZ. The extent of RG19A mineralization during biotransformation was monitored by measuring the percentage reduction in the concentration of chemical oxygen demand and released aromatic amines. Plant growth parameters of seedlings of Phaseolus mungo, Triticum aestivum and Sorghum bicolor seedlings were assessed to monitor toxicity reduction.

A novel poly [2,5-(1,3,4-thiadiazole)-benzalimine] abbreviated as TDPI adsorbent was synthesized using simple polycondensation technique. The synthetic route involves the preparation of 2,5-diamino-1,3,4-thiadiazole from 2,5-dithiourea and subsequent condensation with terephthalaldehyde. The resin was chemically characterized using Fourier transform infrared (FT-IR), 1H-NMR, and 13C-NMR spectroscopic analysis. Surface morphology and thermal stability were analyzed using scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). The effect of the pH value of solution, contact time, adsorbent dose, and initial metal ion concentration were investigated by batch equilibrium adsorption experiments. Kinetic studies show that the adsorption of metal ions onto the resin proceeds according to the pseudo-second-order model and the equilibrium data were best interpreted by the Redlich–Peterson isotherm. The experimental values of the adsorption capacities of Pb2+, Cu2+, Ni2+, and Cd2+ on to TDPI could reach up to 437.2, 491.6, 493.7, and 481.9 mg.g−1 respectively. The exothermic nature of the process, the affinity of the adsorbent towards the metal ions and the feasibility of the process are explained in the thermodynamic parameters. The resin stability and re-usability studies suggest that the resin is chemically stable (0.3 N HCl and H2SO4) and could be regenerated without any serious decline in performance.