Co-fermenting lactic acid and glucose towards caproic acid production.

The functional role of lactate (HLac), as a co-substrate along with glucose (Glu) as well as an electron donor for the synthesis of caproic acid (HCa), a medium chain fatty acid (MCFAs) was studied. A varied HLac and Glu ratios were thus investigated in fed-batch anaerobic reactors (R1-R5) operated at pH 6 with a heat-treated anaerobic consortium. R1 and R5 were noted as controls and operated with sole Glu and HLac, respectively. Strategically, ethanol (HEth) was additionally supplemented as co-electron donor after the production of short chain carboxylic acids (SCCAs) for chain elongation in all the reactors. The reactor operated with HLac and Glu in a ratio of 0.25:0.75 (1.25 g/L (HLac) and 3.75 g/L (Glu)) showed the highest HCa production of 1.86 g/L. R5 operated with solely HLac yielded propionic acid (HPr) as the major product which further led to the higher valeric acid (HVa) production of 1.1 g/L within the reactor. Butyric acid (HBu) was observed in R1, which used Glu as carbon source alone indicating the importance of HLac as electron co-donor. Clostridium observed as the most dominant genera in shotgun metagenome sequencing in R2 and R3, the reactors that produced the highest HCa in comparison to other studied reactors. The study thus provided insight into the importance of substrate and electron donor and their supplementation strategies during the production of MCFAs.

Surveillance of SARS-CoV-2 spread using wastewater-based epidemiology: Comprehensive study.

SARS-CoV-2 pandemic is having a devastating effect on human lives. Recent reports have shown that majority of the individuals recovered from COVID-19 have serious health complications, which is going to be a huge economic burden globally. Given the wide-spread transmission of SARS-CoV-2 it is almost impossible to test every individual in densely populated countries. Recent reports have shown that sewage-based surveillance can be used as holistic approach to understand the spread of the pandemic within a population or area. Here we have estimated the spread of SARS-CoV-2 in the city of Hyderabad, India, which is a home for nearly 10 million people. The sewage samples were collected from all the major sewage treatment plants (STPs) and were processed for detecting the viral genome using the standard Reverse Transcription Polymerase Chain Reaction (RT-PCR) method. Interestingly, inlet samples of STPs were positive for SARS-CoV-2, while the outlets were negative, which indicates that the standard sewage treatment methods are efficient in eliminating the SARS-CoV-2 viral particles. Based on the detected viral gene copies per litre and viral particle shedding per individual, the total number of individuals exposed to SARS-CoV-2 was estimated. Through this study we suggest that sewage-based surveillance is an effective approach to study the infection dynamics, which helps in efficient management of the SARS-CoV-2 spread.

Cathodic selenium recovery in bioelectrochemical system: Regulatory influence on anodic electrogenic activity.

Metal(loid)s are used in various industrial activities and widely spread across the environmental settings in various forms and concentrations. Extended releases of metal(loid)s above the regulatory levels cause environmental and health hazards disturbing the ecological balance. Innovative processes for treating the metal(loid)-contaminated sites and recovery of metal(loid)s from disposed waste streams employing biotechnological routes provide a sustainable way forward. Conventional metal recovery technologies demand high energy and/or resource inputs, which are either uneconomic or unsustainable. Microbial electrochemical systems are promising for removal and recovery of metal(loid)s from metal(loid)-laden wastewaters. In this communication, a bioelectrochemical system (BES) was designed and operated with selenium (Se) oxyanion at varied concentrations as terminal electron acceptor (TEA) for reduction of selenite (Se4+) to elemental selenium (Se0) in the abiotic cathode chamber. The influence of varied concentrations of Se4+ towards Se0 recovery at the cathode was also evaluated for its regulatory role on the electrometabolism of anode-respiring bacteria. This study observed 26.4% Se0 recovery (cathode; selenite removal efficiency: 73.6%) along with organic substrate degradation of 74% (anode). With increase in the initial selenite concentration, there was a proportional increase in the dehydrogenase activity. Bioelectrochemical characterization depicted increased anodic electrogenic performance with the influence of varied Se4+ concentrations as TEA and resulted in a maximum power density of 0.034 W/m2. The selenite reduction (cathode) was evaluated through spectroscopic, compositional and structural analysis. X-ray diffraction and Raman spectroscopy showed the amorphous nature, while Energy Dispersive X-ray spectroscopy confirmed precipitates of the deposited Se0 recovered from the cathode chamber. Scanning electron microscopic images clearly depicted the Se0 depositions (spherical shaped; sized approximately 200 nm in diameter) on the electrode and cathode chamber. This study showed the potential of BES in converting soluble Se4+ to insoluble Se0 at the abiotic cathode for metal recovery.

Single-Stage Operation of Hybrid Dark-Photo Fermentation to Enhance Biohydrogen Production through Regulation of System Redox Condition: Evaluation with Real-Field Wastewater.

Harnessing hydrogen competently through wastewater treatment using a particular class of biocatalyst is indeed a challenging issue. Therefore, biohydrogen potential of real-field wastewater was evaluated by hybrid fermentative process in a single-stage process. The cumulative hydrogen production (CHP) was observed to be higher with distillery wastewater (271 mL) than with dairy wastewater (248 mL). Besides H2 production, the hybrid process was found to be effective in wastewater treatment. The chemical oxygen demand (COD) removal efficiency was found higher in distillery wastewater (56%) than in dairy wastewater (45%). Co-culturing photo-bacterial flora assisted in removal of volatile fatty acids (VFA) wherein 63% in distillery wastewater and 68% in case of dairy wastewater. Voltammograms illustrated dominant reduction current and low cathodic Tafel slopes supported H2 production. Overall, the augmented dark-photo fermentation system (ADPFS) showed better performance than the control dark fermentation system (DFS). This kind of holistic approach is explicitly viable for practical scale-up operation.

CO2 supplementation to domestic wastewater enhances microalgae lipid accumulation under mixotrophic microenvironment: effect of sparging period and interval.

Bio-sequestration of CO(2) through microalgae cultivation is considered as a viable option for biofuel production as well as CO(2) mitigation. Influence of CO(2) sparging period and interval was evaluated on the growth and lipid accumulation of microalgae cultivated in domestic wastewater under mixotrophic microenvironment. Process performance was assessed in two phases viz., growth (GP) and starvation phases (SP) each with 8 days of retention time. Experimental variations depicted marked influence on biomass growth and lipid accumulation of microalgae with the function of harvesting period. Sparging period of 120 s documented maximum biomass growth (GP, 3.4 mg/ml) and lipid productivity (SP, 27.3%) while in intervals, 4h (120 s) condition showed maximum biomass (3.2mg/ml) and lipid productivity (27.8%). Total chlorophyll components documented higher concentrations of Chl b supporting the observed higher lipid productivity. Fatty acid composition varied with the experimental variations and represented higher degree of saturation indicating their utility as biodiesel.

Aerobic remediation of petroleum sludge through soil supplementation: microbial community analysis.

The effect of soil concentration on the aerobic degradation of real-field petroleum sludge was studied in slurry phase reactor. Total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) showed effective removal but found to depend on the soil concentration. Aromatic fraction (48.12%) documented effective degradation compared to aliphatics (47.31%), NSO (28.69%) and asphaltenes (26.66%). PAHs profile showed efficient degradation of twelve individual aromatic compounds where lower ring compounds showed relatively higher degradation efficiency compared to the higher ring compounds. The redox behaviour and dehydrogenase activity showed a linear increment with the degradation pattern. Microbial community composition and changes during bioremediation were studied using denaturing gradient gel electrophoresis (DGGE). Among the 12 organisms identified, Proteobacteria was found to be dominant representing 50% of the total population (25% of γ-proteobacteria; 16.6% of ß-proteobacteria; 8.3% of α-proteobacteria), while 33.3% were of uncultured bacteria and 16.6% were of firmicutes.

Self-induced bio-potential and graphite electron accepting conditions enhances petroleum sludge degradation in bio-electrochemical system with simultaneous power generation.

Bio-electrochemical treatment (BET) documented effective degradation of real field petroleum sludge over the conventional anaerobic treatment (AnT). BET (41.08%) operation showed enhanced total petroleum hydrocarbons (TPH) removal over AnT (20.72%). Aromatic fraction visualized higher removal (75.54%) compared to other TPH fractions viz., aliphatics, asphaltenes and NSO (nitrogen, sulfur and oxygen) during BET operation. Higher ring aromatics (5-6) documented easy degradation in BET, while AnT was limited to lower ring (2-3) compounds. Voltammetric analysis evidenced simultaneous redox behavior during BET operation due to presence of graphite electrode as electron acceptor, while AnT showed extended reduction behavior only. Self-induced primary and secondary oxidation reactions and capacitive-deionization might have enhanced the degradation capability of BET. BET documented higher charge/capacitance (2810 mJ/1120 mF) than AnT (450 mJ/180 mF). Power output corroborated well with observed results supporting BET performance as fuel cell. Electrodes offer a potential alternative electron acceptor for promoting the degradation of organic contaminants.