Chhabra, Meenu

In this study, a promising microbial fuel cell (MFC) system has been developed, wherein algae is cultivated in the cathode chamber, algae biomass is harvested and lipids are extracted. The lipid extracted algal (LEA) biomass was then used as an electron donor substrate. The performance of MFCs fed with LEA biomass was compared with that of fruit waste fed MFCs (FP-MFCs), wherein LEA-fed MFC was superior in all aspects. Power density of 2.7 W m−3 was obtained by LEA-fed MFCs which is 145% and 260% higher than FP MFC and control MFC respectively. The volumetric algae productivity of 0.028 kg m−3 day−1 in cathode chamber was achieved. The system was able to generate 0.0136 kWh Kg−1 COD day−1 of electric energy and 0.0782 kWh m−3 day−1 of algal oil energy. The proposed system is a net energy producer which does not rely heavily on the external supply of electron donor substrates.

In this study, Microbial Fuel Cell (MFC) capable of treating saline starch water was developed. Sodium chloride (NaCl) concentrations ranging from 500 mM to 3000 mM were tested at the anode. Nitrate was used as an electron acceptor at the biocathode. The halophilic bacteria were isolated from Sambhar Lake, India. Results indicated successful removal of starch (1.83 kg/m3-d) and nitrate (0.13 kg/m3-d NO3−-N) with concomitant power output of 207.05 mW/m2 at 1000 mM NaCl concentration. An increase in power density from 71.06 mW/m2 to 207.05 mW/m2 (2.92 folds) was observed when NaCl concentration was increased from 500 mM to 1000 mM. A decline in power density was observed when the salt concentrations >1000 mM were used. Concentration of 3000 mM supported power output as well as the highest starch degradation (3.2 kg/m3-d) and amylase activity of 2.26 IU/ml. The halophilic exoelectrogens were isolated and identified. The present study demonstrates the utility of MFC for degrading starch in saline water.

Oleaginous yeast closely related to Cystobasidium oligophagum was isolated from soil rich in cellulosic waste. The yeast was isolated based on its ability to accumulate intracellular lipid, grow on carboxymethylcellulose (CMC) and produce lipase. It could accumulate up to 39.44% lipid in a glucose medium (12.45 ± 0.97 g/l biomass production). It was able to grow and accumulate lipids (36.46%) in the medium containing CMC as the sole carbon source. The specific enzyme activities obtained for endoglucanase, exoglucanase, and β-glucosidase were 2.27, 1.26, and 0.98 IU/mg respectively. The specific enzyme activities obtained for intracellular and extracellular lipase were 2.16 and 2.88 IU/mg respectively. It could grow and accumulate lipids in substrates including glycerol (42.04%), starch (41.54%), xylose (36.24%), maltose (26.31%), fructose (24.29%), lactose (21.91%) and sucrose (21.72%). The lipid profile of the organism was suitable for obtaining biodiesel with desirable fuel properties.

Spectroelectrochemicalinvestigation of racemic alanine on poly crystalline metal surfaces was studied in 1M LiClO4 medium, to achieve cost effective separation of biologically important molecules from the racemic mixture. Analysis of the FTIR spectrum of racemic alanine in 1M LiClO4 indicated degradation of the same. Upon prolonged exposure in LiClO4, byproducts from degradation of alanine increasedin concentration as also observed from UV-Vis spectroscopy. Cyclic Voltammetry studies unraveled different adsorption behaviors on different metal surfaces for the racemic and the enantiomeric solution of alanine. Further FTIR analysis of the alanine solution after Cyclic Voltammetry revealed possible presence of cyanide (-C=N) and terminal alkyne as byproducts. As predicted by Monte Carlo simulations earlier, Circular Dichroism implied the dextro rotation of the racemic alanine solution after Cyclic Voltammetry. These results support the preferential adsorption of L-alanine over D-alanine from racemic mixture that could be attributed to the umbrella inversion of the molecule after adsorption on the metal surface in presence of applied electric field in the LiClO4 environment. A plausible mechanism for the formation of terminal alkyne and - C=N byproducts had also been attempted.

Abstract Background: Laccases have good potential as bioremediating agents and can be used continuously in the immobilized form like many other enzymes. Methods: In the present study, laccase from Cyathus bulleri was immobilized by entrapment in Poly Vinyl Alcohol (PVA) beads cross-linked with either nitrate or boric acid. Immobilized laccase was used for dye decolorization in both batch and continuous mode employing a packed bed column. The products of degradation of dye Acid Red 27 were identified by LC MS/MS analysis. Results: The method led to very effective (90%) laccase immobilization and also imparted significant stability to the enzyme (more than 70% after 5 months of storage at 4°C). In batch decolorization, 90-95% decolorization was achieved of the simulated dye effluent for up to 10-20 cycles. Continuous decolorization in a packed bed bioreactor led to nearly 90% decolorization for up to 5 days. The immobilized laccase was also effective in decolorization and degradation of Acid Red 27 in the presence of a mediator. Four products of degradation were identified by LC-MS/MS analysis. Conclusions: The immobilized laccase in PVA-nitrate was concluded to be an effective agent in treatment of textile dye effluents.

Microbial fuel cells (MFCs) are emerging wastewater treatment systems with a proven potential for denitrification. In this study, we have developed a high-rate denitrifying MFC. The anode consisted of cow manure and fruit waste and the cathode consisted of cow manure and soil. The initial chemical oxygen demand (COD)/nitrate nitrogen (NO3−-N) was varied from 2 to 40 at the cathode while keeping the anode ratio fixed at 100. NO3−-N removal rate of 7.1 ± 0.9 kg NO3−-N/m3 net cathodic compartment (NCC)/day was achieved at cathode COD/NO3−-N ratio 7.31 with the current density of 190 ± 9.1 mA/m2 and power density of 31.92 ± 4 mW/m2 of electrode surface area. We achieved an open-circuit voltage (OCV) of 410 ± 20 mV at initial cathodic NO3−-N of 0.345 g/l. The cathode COD/NO3−-N ratio had a significant influence on MFC’s OCV and nitrate removal rate. Lower OCV (<150 mV) and NO3−-N removal rates were observed at COD/NO3−-N ratio >12 and <7. Experiments done at different cathode pH values indicated that the optimum pH for denitrification was 7. Under optimized biochemical conditions, nitrate removal rate of 6.5 kg NO3−-N/m3 net cathodic compartment (NCC)/day and power density of 210 mW/m2 were achieved in a low resistance MFC. The present study thus demonstrates the utility of MFCs for the treatment of high nitrate wastes.

Microalgal biorefineries have emerged as significant reservoirs of therapeutic compounds, including pigments and proteins. Facilitating a robust circular bioeconomy necessitates the augmentation of pigment synthesis alongside algae biofuel production. Nevertheless, inherent constraints in ketocarotenoid synthesis exist in naturally fast-growing microalgae strains, such as Chlamydomonas reinhardtii. To address this limitation, we overexpressed two pivotal enzymes in the carotenoid biosynthetic pathway, namely β-carotene hydroxylase (crt) and β-carotene ketolase (bkt), in C. reinhardtii utilizing strong promoters to amplify carotenoid production. The genetically modified (GM) microalgae were validated through PCR, Southern hybridization, and Western blot assays, confirming the presence and expression of both genes in the C. reinhardtii strains. These GM lines exhibited a substantial enhancement over wild-type (WT) algae, showcasing a remarkable 5.39-fold increase in β-carotene concentration and twofold increase in total carotenoids compared to the WT microalgae. Notably, the GM microalgae achieved astaxanthin production up to 1.47 ± 0.063 mg/g DCW, a compound absent in WT C. reinhardtii. These findings indicate the successful functionalization of Hematococcus pluvialis genes through nuclear expression in C. reinhardtii, facilitating ketocarotenoid production. This study presents a valuable strategy to boost carotenoid production in microalgae by stable overexpression of two heterologous genes within the nuclear genome of C. reinhardtii. Graphical abstract: (Figure presented.) Graphical abstract for the study carried out which represents the in silico plasmid vector designing, algae transformation by electroporation, selection on antibiotic plates, PCR amplification for GM confirmation, Southern hybridization to confirm gene integration, Western blotting to check protein expression, pigment quantification, and algae growth determination.

The effect of non-equilibrium cold plasma (NECP) treatment on functional and nutritional properties of finger millet flour was investigated. Finger millet flour was treated at two different exposure times for 5 min and 10 min, and functional and nutritional properties such as Water and oil holding capacity, water binding capacity, color, and dispersibility of the control and plasma treated flour were studied. There was no significant difference in the color intensity and the whitening index (WI) with the treatment. The functional properties such as water holding capacity (WHC), oil absorption capacity (OAC), foaming and emulsifying capacity have shown significant increment with treatment time. FTIR and DSC results depicted the depolymerization of starch in the treated flour. Plasma treatment was observed to enhance the functional properties of the finger millet flour, whilst the physical properties remained unchanged. Overall plasma treatment can be explored for development of a process to enhance functionality of finger millet flour for applications in food systems. There remains plenty of scope for commercial level expansion.

A sensitive and rapid electrochemical sensor has been developed to detect Escherichia coli (E. coli) bacteria that is crucial for ensuring safe drinking water. E. coli significantly contributes to waterborne contamination, driven by overexploitation and insufficient cleanliness around water bodies. This work incorporates synthesis and characterization of graphene oxide (GO), sensor preparation, and sensor testing in the presence of varying E. coli dilutions via H2O2 decomposition. GO is used as a sensing layer and drop casted on the working electrode of screen printed electrode (SPE). The sensor is exposed to different bacterial solutions using varied bacterial concentrations and fixed percent solution of H2O2. The interface of GO and bacterial solution results in a change in potential. The cross-sensitivity tests have also been performed in the presence of chemical compounds found in wastewater samples, Pseudomonas aeruginosa and Citrobacter youngae. The sensor demonstrates a detection limit of 2.8 CFU/mL, with a sensitivity of 5.1 mV-mL/CFU, fast response time and excellent repeatability when tested with E. coli. Its performance has also been assessed by comparing the sensing results for regular tap water, reverse osmosis (RO) water, and deionized water samples. This work paves the way for developing a chip-based system to detect E. coli in water.

This study investigated the effect of co-culturing the photobiont and mycobiont in the microbial fuel cell (MFC) cathode on biomass production, lipid generation, and power output. Chlorella vulgaris provides oxygen and nutrients for the yeast Cystobasidium oligophagum JRC1, while the latter offers CO2 and quench oxygen for higher algal growth. The MFC with co-culture enhanced the lipid output of biomass by 28.33%, and the total yield and productivity were 1.47 ± 0.18 g/l and 0.123 g/l/day, respectively. Moreover, with co-culture, the open circuit voltage of 685 ± 11 mV was two times higher than algae alone. The specific growth rate (day−1) at the cathode was 0.367 ± 0.04 in co-culture and 0.288 ± 0.05 with C. vulgaris only. The power density of the system was 5.37 ± 0.21 mW/m2 with 75.88 ± 1.89% of COD removal. The co-culture thus proved beneficial at the MFC cathode in terms of total energy output as 11.5 ± 0.035 kWh/m3, which was 1.4-fold higher than algae alone.