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Three acidophilic enrichment consortium were developed from mine water sample of copper mine site at Khetri, India were compared for their copper leaching efficiency. Out of these one was mesophilic (35°C) and two were moderately thermophilic (50°C). Consortia were named as mesophilic acidophilic chemolithotrophic consortia (MACC), thermophilic acidophilic chemolithotrophic consortia (TACC), and Sulfobacillus acidophilic consortia (SAC). Copper extraction ability of both the thermophilic consortia (77–78% extraction) was almost double to that of mesophilic consortia (40% extraction) at 10% pulp density after 55 days. Both the thermophilic consortia were equally effective in leaching of other metals like Ni, Co, Zn, Mn. After 55 days, the percentage of extractions of copper by TACC was 76, 74, 67, 48 and 45 at 5%, 10%, 15%, 20% and 30% pulp density, respectively. Total number of bacteria was maximum at 5% pulp density which decreases with increase in pulp density. Sulfobacillus-like bacteria were seen in the Sulfobacillus enrichment cultures. Moderately thermophilic consortia proved to be better in leaching performance than the mesophilic counterpart. [Copyright &y& Elsevier]

This study investigated the effects of varying zero-valent iron (ZVI) (0 to 5,000 mg/L) on fermentative hydrogen (H 2 ) production, metabolic pattern, and taxonomic profile by using kitchen waste as substrate. The study demonstrated that the supplementation of 500 mg ZVI/L resulted in the highest H 2 yield (219.68 ± 11.19 mL H 2 /g-volatile solids (VS) added ), which was 19% higher than the control. The metabolic pattern analysis showed that acetic and butyric acid production primarily drove the H 2 production. The taxonomic analysis further revealed that Firmicutes (relative abundance (RA): 80-96%) and Clostridium sensu stricto 1 (RA: 68-88%) were the dominant phyla and genera, respectively, during the exponential gas production phase, supporting the observation of accumulation of acetic and butyric acids. These findings suggest that supplementation of ZVI can enhance H 2 production from organic waste and significantly influence the metabolic pattern and taxonomic profile, including the metalloenzymes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Microalgae are a promising source of raw material (i.e., proteins, carbohydrates, lipids, pigments, and micronutrients) for various value-added products and act as a carbon sink for atmospheric CO 2 . The rigidity of the microalgal cell wall makes it difficult to extract different cellular components for its applications, including biofuel production, food and feed supplements, and pharmaceuticals. To improve the recovery of products from microalgae, pretreatment strategies such as biological, physical, chemical, and combined methods have been explored to improve whole-cell disruption and product recovery efficiency. However, the diversity and uniqueness of the microalgal cell wall make the pretreatment process more species-specific and limit its large-scale application. Therefore, advancing the currently available technologies is required from an economic, technological, and environmental perspective. Thus, this paper provides a state-of-art review of the current trends, challenges, and prospects of sustainable microalgal pretreatment technologies from a microalgae-based biorefinery concept., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

This study evaluated the combined impact of salinity (2.5, 13, and 19.3 g NaCl/L) and inoculum pretreatment (acid/alkali) on the genomic and metabolic profiles of mesophilic fermentative bacteria for hydrogen (H 2 ) production from food waste. Experimental results revealed that acid-treated inoculum showed the highest H 2 yield (201.12 ± 13.84 mL H 2 /g of volatile solids added) under medium salinity levels compared to other experimental conditions. A 7-56% increase in H 2 yield was observed for pretreated inoculum than untreated inoculum. Genomic analysis and metabolic pattern revealed that the H 2 production was mainly through Clostridial-type fermentation under medium to high salinity levels, whereas Enterococcus-type fermentation under low salinity levels. Further, the genomic analysis uncovered that phyla Firmicutes (69.71-96.81%) and genus Clostridium sensu stricto 1 (33.28-94.04%) dominated during the exponential gas production phase. Overall, this study showed the significance of inoculum pretreatment for the bioconversion of food waste at different salinity levels., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Biotransformation of organic substrates via acidogenic fermentation (AF) to high-value products such as C1-C6 carboxylic acids and alcohol serves as platform chemicals for various industrial applications. However, the AF technology suffers from low product titers due to thermodynamic constraints. Recent studies suggest that augmenting AF redox potential can regulate the metabolic pathway and provide seamless electron flow by lowering the activation energy barrier, thus positively influencing the substrate utilization rate, product yield, and speciation. Hence, the augmented AF system with an exogenous electricity supply is termed as electro-fermentation (EF), which has enormous potential to strengthen the fermentation technology domain. Therefore, this critical review systematically discusses the current understanding of EF with a special focus on the extracellular electron transfer mechanism of electroactive bacteria and provides perspectives and research gaps to further improve the technology for green chemical synthesis, sustainable waste management, and circular bio-economy., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

This study systematically evaluated and compared different inoculum pretreatment methods to quickly select dark fermentative bacteria from anaerobic sludge for the bioconversion of food waste. The hydrogen (H 2 ) production rate was found to be highest for 'heat + CO 2 ' treated inoculum at 140.75 ± 2.61 mL/L/h compared to control experiments (60.27 ± 2.61 mL/L/h). At the same time, H 2 yield was found to be highest for alkali-treated inoculum at 157.25 ± 7.62 mL/g of volatile solids (VS) added compared to control experiments (91.61 ± 1.93 mL/g VS). Analysis of organic acids suggests a Clostridial-type fermentation with acetate (0.52 to 1.60 g/L) and butyrate (1.69 to 2.42 g/L) being the major by-products. The microbial data analysis showed that Firmicutes (63.64-90.39%), Bacteroidota (1.16-21.88%), and Proteobacteria (2.09-9.93%) were dominant at the phylum level, whereas genus-level classification showed Clostridium sensu stricto 1 (6.37-42.63%), Streptococcus (1.87-28.96%), Prevotella (0.57-16.59%), and Enterococcus (0.56-14.51%) dominated under different experimental conditions., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Microbial fuel cells (MFCs) technology have the potential to decarbonize electricity generation and offer an eco-friendly route for treating a wide range of industrial effluents from power generation, petrochemical, tannery, brewery, dairy, textile, pulp/paper industries, and agro-industries. Despite successful laboratory-scale studies, several obstacles limit the MFC technology for real-world applications. This review article aimed to discuss the most recent state-of-the-art information on MFC architecture, design, components, electrode materials, and anodic exoelectrogens to enhance MFC performance and reduce cost. In addition, the article comprehensively reviewed the industrial effluent characteristics, integrating conventional technologies with MFCs for advanced resource recycling with a particular focus on the simultaneous bioelectricity generation and treatment of various industrial effluents. Finally, the article discussed the challenges, opportunities, and future perspectives for the large-scale applications of MFCs for sustainable industrial effluent management and energy recovery., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study investigated the feasibility of hydrogen (H 2 ) and L-lactic acid production from starch under capnophilic lactic fermentation (CLF) conditions by using Thermotoga neapolitana. Batch experiments were performed in 120 mL serum bottles and a 3 L pH-controlled continuous stirred-tank reactors (CSTR) system with potato and wheat starch as the substrates. A H 2 yield of 3.34 (±0.17) and 2.79 (±0.17) mol H 2 /mol of glucose eq. was achieved with, respectively, potato and wheat starch. In the presence of CO 2 , L-lactic acid production by the acetyl-CoA carboxylation was significantly higher for the potato starch (0.88 ± 0.39 mol lactic acid/mol glucose eq.) than wheat starch (0.33 ± 0.11 mol lactic acid/mol glucose eq.). A kinetic model was applied to simulate and predict the T. neapolitana metabolic profile and bioreactor performance under CLF conditions. The CLF-based starch fermentation suggests a new direction to biotransform agri-food waste into biofuels and valuable biochemicals., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Chalcopyrite is the primary copper mineral used for production of copper metal. Today, as a result of rapid industrialization, there has been enormous demand to profitably process the low grade chalcopyrite and "dirty" concentrates through bioleaching. In the current scenario, heap bioleaching is the most advanced and preferred eco-friendly technology for processing of low grade, uneconomic/difficult-to-enrich ores for copper extraction. This paper reviews the current status of chalcopyrite bioleaching. Advanced information with the attempts made for understanding the diversity of bioleaching microorganisms; role of OMICs based research for future applications to industrial sectors and chemical/microbial aspects of chalcopyrite bioleaching is discussed. Additionally, the current progress made to overcome the problems of passivation as seen in chalcopyrite bioleaching systems have been conversed. Furthermore, advances in the designing of heap bioleaching plant along with microbial and environmental factors of importance have been reviewed with conclusions into the future prospects of chalcopyrite bioleaching., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The effect of an adapted dissimilatory iron reducing bacterial consortium (DIRB) towards bio-reduction of Sukinda chromite overburden (COB) with enhanced recovery of nickel and cobalt is being reported for the first time. The remarkable ability of DIRB to utilize Fe(III) as terminal electron acceptor reducing it to Fe(II) proved beneficial for treatment of COB as compared to previous reports for nickel leaching. XRD studies showed goethite as the major iron-bearing phase in COB. Under facultative anaerobic conditions, goethite was reduced to hematite and magnetite with the exposure of nickel oxide. FESEM studies showed DIRB to be associated with COB through biofilm formation with secondary mineral precipitates of magnetite deposited as tiny globular clusters on the extra polymeric substances. The morphological and mineralogical changes in COB, post DIRB application, yielded a maximum of 68.5% nickel and 80.98% cobalt in 10 days using 8M H2SO4., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Simultaneous storage and growth model has recently gained increased acceptance among researchers that can better interpret the processes occurring in activated sludge processes during aerobic biodegradation of organic carbon. The model underwent further improvement and was successfully calibrated using respirometric measurements, acetate being a test substrate. However, model based interpretation of titrimetry needs to be verified for proper validation of this model since pH and dissolved oxygen dynamics occur simultaneously in a batch reactor. Hence, in this paper, it is aimed to modify the existing model by introducing stoichiometric parameters involved in titrimetry in each step of the growth and storage phases along with the consideration of non-linear carbon dioxide transfer rate in liquid phase. The model calibration was done for three different acetate concentrations using titrimetric, respirometric and combined respirometric-titrimetric measurements. The parameter estimation results from all three combinations were found to be very close that supports the validity of the model., (2009 Elsevier Ltd. All rights reserved.)