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Abstract The constantly evolving and growing global health crisis, antimicrobial resistance (AMR), endangers progress in medicine, food production, and life expectancy. Limited data on population-level prevalence, including seasonal and temporal variations, hampers accurate risk assessment for AMR transmission, despite its paramount importance on both global and national fronts. In this study, we used quantitative real-time PCR (q-PCR) to analyze 123 antibiotic resistance genes (ARGs) and 13 mobile genetic elements (MGEs) in wastewater of a selected urban community. Sampling was conducted monthly over a 5-month period (December 2021–April 2022) to assess resistance diversity, temporal dynamics, co-abundance of ARGs, MGEs, and resistance mechanisms. Approximately 50% of the tested ARG subtypes were consistently detected in all months, with frequency ranging from 52 to 61% with maximum absolute abundance in the winter months (December and January). In co-abundance analysis, specific genes were clustered into modules, highlighting shared distribution patterns and functional associations among the ARGs and MGEs. Detected clinically significant genes (ndm-1 and cfiA) and other variants (blaoxy, aph, aacC, tet-35, tet M, tet-32) are capable of imparting resistance to 3rd and 4th generation (gen) β-lactam, aminoglycoside, tetracycline, and multidrug classes. These contribute significantly to core/persistent resistance. This study deepens our comprehension of temporal/seasonal fluctuations in ARG and MGE distribution, providing valuable evidence to guide AMR control policies and promote responsible antibiotic/antimicrobial use for preserving effectiveness.

Abstract Biogenic waste (solid/liquid/gaseous) utilization in biological processes has disruptive potential of inclining towards carbon neutrality, while producing diverse products output. Anaerobic fermentation (methanogenesis and acidogenesis) routes are crucial bioprocesses for production of various renewable chemicals (carboxylate platform/organic acids, short/medium chain alcohols, aldehydes, biopolymers) and fuels (methane, hydrogen, hythane, biodiesel and electricity), while individual operations posing process limitations on their conversion efficiency. Advantageous benefit of using the individual bioprocess technicalities is of utmost importance in the context of sustainability to conceptualize and execute integrated waste biorefinery. The opinion article intends to document/familiarize the waste‐fed biorefinery potential with application of hybrid advancements towards multiple product/energy/renewable chemical spectrum leading to carbon neutrality bioprocesses. Unique and notable challenges with diverse process integrations along with electrochemical/interspecies‐redox metabolites‐materials synergy/enzymatic interventions are specifically emphasized on application‐oriented waste feedstock potential towards achieving sustainability.

Graphical Abstract

Graphene electrodes demonstrates superior performance in a microbial fuel cell attributed to large surface area for bacterial colonization and high electrical conductivity. The present study compares performance of various carbon-based electrodes viz. carbon cloth, graphene oxide and chemically reduced graphene oxide, in microbial fuel cell. The study comprises of physical characterization of electrodes using X-ray diffraction and Raman spectrometry techniques. To evaluate the electrical properties of electrodes, electrochemical characterization was carried out by using cyclic voltammetry and electrochemical impedance spectroscopy. Higher performance of reduced graphene oxide as compared to carbon electrode could be attributed to better bacterial colonization, higher charge storing capacity and lower charge transfer resistance at interface. This study emphasis on use of simple chemically synthesized graphene electrodes to obtain improved performance in a cost-effective MFC reactor configuration having economic stainless-steel cathode, mixed culture for inoculation and deionized water as catholyte. Keywords: Microbial fuel cell, Reduced graphene oxide, Wastewater treatment, Chemical reduction, Graphene electrodes

In the present work, we have reported the synthesis of 3D graphene structures by simple chemical reduction method for application in microbial fuel cell (MFC) as an anode. The synthesis procedure includes synthesis of graphene oxide by modified Hummers method followed by simultaneous reduction of graphene oxide and the formation of hydrogels. The 3D graphene structures are characterized using X-ray diffraction and Raman spectroscopy techniques. Electrochemical characterization is carried out to study the capacitive properties and impedance studies of electrodes in conductive electrolyte. 3D graphene electrodes show remarkably high capacitive current, charge storage and lower charge transfer resistance as estimated through cyclic voltammetry and Nyquist plots. In order to evaluate the performance of 3D graphene electrodes in MFC, power density and polarization curves are recorded in three configurations by varying terminal electron acceptors (TEA) viz., dissolved oxygen (MFC-DO), potassium ferricyanide and MFC without TEA (MFC-NDO). 3D graphene electrodes exhibits maximum power density of 0.49 mW/m2 in potassium ferricyanide followed by MFC-DO (0.36 mW/m2) and MFC-NDO (0.34 mW/m2). Present work highlights the viability of chemically synthesized 3D graphene electrodes as an efficient anode material in MFC. Keywords: Microbial fuel cell, 3D graphene, Wastewater treatment, Chemical reduction, Graphene electrodes

One of the crowning glories of 20th century was the development of petroleum-based plastics. Eighty years later, with pioneering advances and series of breakthroughs in research and industrial innovations, plastics have become an integral part of our everyday lives. While the applications of plastics are multifarious, their unrestricted disposal is causing damage to the ecosystem services and biodiversity. Furthermore, the plastic economy entirely relies on non-renewable, climate-changing petrochemical resources. A circular economy (CE), which aims to retain plastics at their highest value for a longest period of time in the system is one of the strategies to overcome these challenges. The present article discusses about strategies that can be employed to incorporate circularity and concepts of CE in plastics production systems. It emphasizes that although CE aims at design out waste, it needs to go a step ahead and also consider the impact of raw materials, the entire product value chain and end-of life options to achieve sustainability. It captures the emerging area of biodegradable low carbon polymers from renewable resources with an emphasis on technical and environmental advantages that contribute to the reduction in carbon footprints. Research carried out from a sustainability standpoint by considering CO2 emissions right from production stage to end-of-life that helps in achieving a low carbon economy is reviewed. Some challenges that need to be addressed for future work, the potential role of sustainability analysis in enhancing the use of biopolymers are summarized. Furthermore, it sheds light on integrating a low carbon economy with the CE to achieve a holistic and sustainable plastics production value chain.

Microbial electrosynthesis system (MES; single-chambered) was fabricated and evaluated with carbon cloth/graphite as a working/counter electrode employing an enriched microbiome. Continuous syngas sparging (at working electrode; WE) enabled the growth of endo electrogenic bacteria by availing the inorganic carbon source. Applied potential (−0.5 V) on the working electrode facilitated the reduction in syngas, leading to the synthesis of fatty acids and alcohols. The higher acetic acid titer of 3.8 g/L and ethanol concentration of 0.2 g/L was observed at an active microbial metabolic state, evidencing the shift in metabolism from acetogenic to solventogenesis. Voltammograms evidenced distinct redox species with low charge transfer resistance (Rct; Nyquist impedance). Reductive catalytic current (−0.02 mA) enabled the charge transfer efficiency of the cathodes favoring syngas conversion to products. The surface morphology of carbon cloth and system-designed conditions favored the growth of electrochemically active consortia. Metagenomic analysis revealed the enrichment of phylum/class with Actinobacteria, Firmicutes/Clostridia and Bacilli, which accounts for the syngas fermentation through suitable gene loci.

In microbial electrochemical systems, transport of electrons from bacteria to an electrode is the key to its functioning. However, the roles of several electron transport proteins, especially the membrane-bound dehydrogenases which link cellular metabolism to EET pathway are yet to be identified. NDH-2 is a non-proton pumping NADH dehydrogenase located in the inner membrane of several bacteria like Bacillus subtilis, Escherichia coli, etc. Unlike NADH dehydrogenase I, NDH-2 is not impeded by a high proton motive force thus helping in the increase of metabolic flux and carbon utilization. In the current study, NADH dehydrogenase II protein (NDH-2) was heterologously expressed from B. subtilis into E. coli BL21 (DE3) for enhancing electron flux through EET pathway and to understand its role in bioelectrogenesis. We found that E. coli expressing NDH-2 has increased the electron flux through EET and has shown a ninefold increase in current (4.7 μA) production when compared to wild strain with empty vector (0.52 μA). Furthermore, expression of NDH-2 also resulted in increased biofilm formation which can be corroborated with the decrease in charge transfer resistance of NDH-2 strain and increased NADH oxidation. It was also found that NDH-2 strain can reduce ferric citrate at a higher rate than wild type strain suggesting increased electron flux through electron transport chain due to NADH dehydrogenase II activity. Purified NDH-2 was found to be ∼42 kDa and has FAD as a cofactor. This work demonstrates that the primary dehydrogenases like NADH dehydrogenases can be overexpressed to increase the electron flux in EET pathway which can further enhance the microbial fuel cells performance.

Microalgae are multifaceted photosynthetic microorganisms with emerging business potential. They are present ubiquitously in terrestrial and aquatic environments with rich species diversity and are capable of producing significant biomass. Traditionally, microalgal biomass is being used as food and feed in many countries around the globe. The production of microalgal-based bioactive compounds at an industrial scale through biotechnological interventions is gaining interest more recently. The present review provides a detailed overview of the key algal metabolites, which plays a crucial role in nutraceutical, functional foods, and animal/aquaculture feed industries. Bioactive compounds of microalgae known to exhibit antioxidant, antimicrobial, antitumor, and immunomodulatory effects were comprehensively reviewed. The potential microalgal species and biological extracts against human pathogens were also discussed. Further, current technologies involved in upstream and downstream bioprocessing including cultivation, harvesting, and cell disruption were documented. Establishing microalgae as an alternative supplement would complement the sustainable and environmental requirements in the framework of human health and well-being.

Optimization of process parameters is crucial to understand the acidogenic fermentation process and its regulation towards the production of specific metabolites, viz., biohydrogen (H2), methane (CH4), biohythane (H2+CH4), and volatile fatty acids (VFA). Design of experiments (DOE) based on orthogonal array (OA) was employed to optimize and evaluate the influence of eight critical factors on multiple metabolic output parameters. Analysis of the experimental data revealed a specific influential regime of selected factors in terms of biogas generation and/or VFA synthesis. Application of pretreated inoculum as biocatalyst and high substrate concentration showed substantial enhancement of both H2 and VFA production. High COD of 10 g/L in combination with pretreated inoculum resulted in higher cumulative hydrogen production (CHP), while the higher fraction of acetic acid in the fermentation broth resulted in a higher degree of acidification (DOA). H2/H2+CH4 ratio varied from 0.1 to 0.97 and the application of untreated inoculum was shown to favor biohythane (H2+CH4) production. Overall, this communication holistically documented the feasibility of regulating acidogenic fermentation process towards a spectrum of metabolic end products of high value, while waste treatment was also achieved.

Microalgae are gaining commercial interests in the areas food, feed and biofuel sector. They have intrinsic ability to harness energy from sunlight and photosynthetically valorize CO2 into various bio-based products viz., triacylglycerols (TAGs), mono/poly-unsaturated fatty acids (MUFA, PUFA), pigments etc. Microalgae have adapted to grow in various nutritional environments due to their metabolic versatility and resilience. Strategic evaluation of newly isolated strain Chlorella sp. from a residential lake was performed. The strain was investigated by varying the nutritional modes to gain insights into biomass and fatty acids production. Maximum biomass (3.59 g/L) was observed in mixotrophic condition followed by heterotrophic (1.58 g/L) and autotrophic condition (0.59 g/L). The maximum lipid yield (670 mg/g DCW) was observed in mixotrophic condition whereas maximum total lipid content (36%) was observed in heterotrophic condition. Significant correlation was noticed between fluorescence parameters measured by OJIP and non-photochemical quenching (NPQ) with the function of nutritional mode variations. Autotrophic condition showed higher photosynthetic activity which was well correlated with high fluorescence intensity as represented by OJIP, NPQ1, and NPQ2 curves. Good balance of saturated fatty acids (SFA) and unsaturated fatty acids was observed in autotrophic mode, whereas polyunsaturated fatty acids (PUFA) and mono unsaturated fatty acid (MUFA) content were relatively higher in mixotrophic and heterotrophic conditions.

Microalgae are most versatile organisms having ability to grow under diverse conditions and utilize both organic and inorganic carbon sources. Microalgal photosynthesis can be employed to transform carbon dioxide (CO2) into essential bioactives and photofuels. In this study, microalgal growth under modified headspace gas compositions which are CO2 + H2 (1:1), CO2, H2 and Air was evaluated to determine the photosynthetic efficiency and bioactives production. A marked enhancement was observed in quantum yield (Fv/Fm: 0.77) and CO2 biosequestration rate (0.39 g.L.-1d−1) under CO2 + H2 headspace gas condition as compared to the other experimental variations. The chemoselective functioning of Rubisco under varying gas concentrations was determined, where elevated CO2 conditions negate the oxygenase activity under a high CO2/O2 ratio which enabled higher CO2 sequestration. The enhanced CO2 sequestration and altered redox conditions through H2 addition under the monophasic operation have also led to a higher average degree of unsaturation (DU) and carbon chain length (CCL) of the fatty acids produced. This study provides an approach to augment photosynthetic efficiency and lipogenesis through non-genetic modifications along with the feasibility to cultivate microalgae in integration with industrial flue gases. Exploiting the true potential of microalgae would provide sustenance from climatic changes and environmental pollution concurrently producing biobased products analogous to the fossil-derived products.