Potential application of 2D nano-layered MXene in analysing and remediating endocrine disruptor compounds and heavy metals in water.

With the advancement of technologies and growth of the economy, it is inevitable that more complex processes are deployed, producing more heterogeneous wastewater that comes from biomedical, biochemical and various biotechnological industries. While the conventional way of wastewater treatment could effectively reduce the chemical oxygen demand, pH and turbidity of wastewater, trace pollutants, specifically the endocrine disruptor compounds (EDCs) that exist in µg L-1 or ng L-1 have further hardened the detection and removal of these biochemical pollutants. Even in small amounts, EDC could interfere human's hormone, causing severe implications on human body. Hence, this review elucidates the recent insights regarding the effectiveness of an advanced 2D material based on titanium carbide (Ti3C2Tx), also known as MXene, in detecting and removing EDCs. MXene's highly tunable feature also allows its surface chemistry to be adjusted by adding chemicals with different functional groups to adsorb different kinds of EDCs for biochemical pollution mitigation. At the same time, the incorporation of MXene into sample matrices also further eases the analysis of trace pollutants down to ng L-1 levels, thereby making way for a more cleaner and comprehensive wastewater treatment. In that sense, this review also highlights the progress in synthesizing MXene from the conventional method to the more modern approaches, together with their respective key parameters. To further understand and attest to the efficacy of MXene, the limitations and current gaps of this potential agent are also accentuated, targeting to seek resolutions for a more sustainable application.

Environmental impact assessment via life cycle analysis on ultrafiltration membrane fabricated from polyethylene terephthalate waste to treat microalgal cultivation wastewater for reusability.

The current study had conducted the life cycle analysis (LCA) to assess the environmental impact of microalgal wastewater treatment via an integrated membrane bioreactor. The functional unit selected for this analysis was 1 kg of treated microalgal wastewater with contaminants eliminated by ultrafiltration membrane fabricated from recycled polyethylene terephthalate waste. Meanwhile, the applied system boundary in this study was distinguished based on two scenarios, namely, cradle-to-gate encompassed wastewater treatment only and cradle-to-cradle which included the reutilization of treated wastewater to cultivate microalgae again. The environmental impacts and hotspots associated with the different stages of the wastewater treatment process had clearly elucidated that membrane treatment had ensued the highest impact, followed by microalgal harvesting, and finally cultivation. Among the environmental impact categories, water-related impact was found to be prominent in the following series: freshwater ecotoxicity, freshwater eutrophication and marine ecotoxicity. Notably, the key performance indicator of all environmental impact, i.e., the global warming potential was found to be very much lower at 2.94 × 10-4 kg CO2 eq as opposed to other literatures reported on the LCA of wastewater treatments using membranes. Overall, this study had proffered insights into the environmental impact of microalgal wastewater treatment and its stimulus for sustainable wastewater management. The findings of this study can be instrumental in making informed decision for optimizing microalgal wastewater treatment and reutilization assisted by membrane technology with an ultimate goal of enhancing sustainability.

Modelling photoperiod in enhancing hydrogen production from Chlorella vulgaris sp. while bioremediating ammonium and organic pollutants in municipal wastewater.

Municipal wastewater is ubiquitously laden with myriad pollutants discharged primarily from a combination of domestic and industrial activities. These heterogeneous pollutants are threating the natural environments when the traditional activated sludge system fails sporadically to reduce the pollutants' toxicities. Besides, the activated sludge system is very energy intensive, bringing conundrums for decarbonization. This research endeavoured to employ Chlorella vulgaris sp. In converting pollutants from municipal wastewater into hydrogen via alternate light and dark fermentative process. The microalgae in attached form onto 1 cm3 of polyurethane foam cubes were adopted in optimizing light intensity and photoperiod during the light exposure duration. The highest hydrogen production was recorded at 52 mL amidst the synergistic light intensity and photoperiod of 200 µmolm-2s-1 and 12:12 h (light:dark h), respectively. At this lighting condition, the removals of chemical oxygen demand (COD) and ammoniacal nitrogen were both achieved at about 80%. The sustainability of microalgal fermentative performances was verified in recyclability study using similar immobilization support material. There were negligible diminishments of hydrogen production as well as both COD and ammoniacal nitrogen removals after five cycles, heralding inconsequential microalgal cells' washout from the polyurethane support when replacing the municipal wastewater medium at each cycle. The collected dataset was finally modelled into enhanced Monod equation aided by Python software tool of machine learning. The derived model was capable to predict the performances of microalgae to execute the fermentative process in producing hydrogen while subsisting municipal wastewater at arbitrary photoperiod. The enhanced model had a best fitting of R2 of 0.9857 as validated using an independent dataset. Concisely, the outcomes had contributed towards the advancement of municipal wastewater treatment via microalgal fermentative process in producing green hydrogen as a clean energy source to decarbonize the wastewater treatment facilities.

Fundamental alteration of cellular biochemicals from attached microalgae onto palm kernel expeller waste upon optimizing the growth environment in forming adhesion complex.

Changing the growth environment for microalgae can overall lead to the fundamental alteration in cellular biochemicals whilst attaching onto palm kernel expeller (PKE) waste to form adhesion complex in easing harvesting at stationary growth phase. This study had initially optimized the PKE dosage, light intensity and photoperiod in maximizing the attached microalgal productivity being attained at 0.72 g/g day. Lipid content increased progressively from pH 3 to pH 11, with the highest value observed at pH 11. Meanwhile, in terms of protein and carbohydrate contents, the highest values were obtained by cultivation medium of pH 5 with 9.92 g and 17.72 g, respectively followed by pH 7 with 9.16 g and 16.36 g, respectively. Moreover, the findings also suggested that the low pH mediums utilized polar interactions in the formation of complexes between PKE and microalgae, whereas at higher pH levels, the non-polar interactions became more significant. The work of attachment was thermodynamically favourable towards the attachment formation with values greater than zero which was also aligned with the microscopic surface topography, i.e., revealing a clustering pattern of microalgae colonizing the PKE surface. These findings contribute to comprehensive understanding of optimizing growth condition and harvesting strategy of attached microalgae in attaining the cellular biochemical components, facilitating the development of efficient and sustainable bioresource utilization.

Biopreservative technologies of food: an alternative to chemical preservation and recent developments.

Despite centuries of developing strategies to prevent food-associated illnesses, food safety remains a significant concern, even with multiple technological advancements. Consumers increasingly seek less processed and naturally preserved food options. One promising approach is food biopreservation, which uses natural antimicrobials found in food with a long history of safe consumption and can help reduce the reliance on chemically synthesized food preservatives. The hurdle technology method that combines multiple antimicrobial strategies is often used to improve the effectiveness of food biopreservation. This review attempts to provide a research summary on the utilization of lactic acid bacteria, bacteriocins, endolysins, bacteriophages, and biopolymers helps in the improvement of the shelf-life of food and lower the risk of food-borne pathogens throughout the food supply chain. This review also aims to evaluate current technologies that successfully employ the aforementioned preservatives to address obstacles in food biopreservation.

Interspecies microbial interactions in bioelectrochemical system and biodegradation: A state of the art review.

Microbial mutualistic interaction or synthetic microbiology evolves closely from the concept of cell-cell relations in a complex microbial community, which plays a crucial role in waste degradation, bioremediation, and bioenergy generation. Recently, the application of synthetic microbial consortia has renewed attention in the field of bioelectrochemistry. In the past few years, the influence of microbial mutualistic interaction has been extensively studied in bioelectrochemical systems (BES), especially in microbial fuel cells (MFCs). Nevertheless, synthetic microbial consortia were found to exhibit superior bioremediation performance compared to single strains of microbes for polycyclic aromatic hydrocarbons, synthetic dyes, polychlorinated biphenyls, and other organic pollutants compared to the respective single microbial species. However, a comprehensive understanding of intermicrobial interactions, specifically the metabolic pathways in a mixed-cultured microbial community system, is still lacking. In this study, we have comprehensively reviewed the possible pathways for executing intermicrobial communication within a complex microbial community consortium with various underlying pathways. The influence of mutualistic interactions on the power generation of MFCs and wastewater biodegradation has been widely reviewed. We argue that this study would motivate the design and construction of potential synthetic microbial consortia to stimulate the extraction of bioelectricity and the biodegradation of contaminants.

An overview on human exposure, toxicity, solid-phase microextraction and adsorptive removal of perfluoroalkyl carboxylic acids (PFCAs) from water matrices.

Perfluoroalkyl carboxylic acids (PFCAs) are sub-class of perfluoroalkyl substances commonly detected in water matrices. They are persistent in the environment, hence highly toxic to living organisms. Their occurrence at trace amount, complex nature and prone to matrix interference make their extraction and detection a challenge. This study consolidates current advancements in solid-phase extraction (SPE) techniques for the trace-level analysis of PFCAs from water matrices. The advantages of the methods in terms of ease of applications, low-cost, robustness, low solvents consumption, high pre-concentration factors, better extraction efficiency, good selectivity and recovery of the analytes have been emphasized. The article also demonstrated effectiveness of some porous materials for the adsorptive removal of the PFCAs from the water matrices. Mechanisms of the SPE/adsorption techniques have been discussed. The success and limitations of the processes have been elucidated.

Antimicrobial peptides: Promising alternatives over conventional capture ligands for biosensor-based detection of pathogenic bacteria.

The detection of pathogenic bacteria using biosensing techniques could be a potential alternative to traditional culture based methods. However, the low specificity and sensitivity of conventional biosensors, critically related to the choice of bio-recognition elements, limit their practical applicability. Mammalian antibodies have been widely investigated as biorecognition ligands due to high specificity and technological advancement in antibody production. However, antibody-based biosensors are not considered as an efficient approach due to the batch-to-batch inconsistencies as well as low stability. In recent years, antimicrobial peptides (AMPs) have been increasingly investigated as ligands as they have demonstrated high stability and possessed multiple sites for capturing bacteria. The conjugation of chemo-selective groups with AMPs has allowed effective immobilization of peptides on biosensor surface. However, the specificity of AMPs is a major concern for consideration as an efficient ligand. In this article, we have reviewed the advances and concerns, particularly the selectivity of AMPs for specific detection of pathogenic bacteria. This review also focuses the state-of-the-art mechanisms, challenges and prospects for designing potential AMP conjugated biosensors. The application of AMP in different biosensing transducers such as electrochemical, optical and piezoelectric varieties has been widely discussed. We argue that this review would provide insights to design and construct AMP conjugated biosensors for the pathogenic bacteria detection.

Bio-electrochemical power generation in petrochemical wastewater fed microbial fuel cell.

The petrochemical wastewater (PCW) from acrylic acid plants possesses a very high chemical oxygen demand (COD) due to the presence of acrylic acid along with other organic acids. The treatment of PCW by conventional aerobic and anaerobic methods is energy intensive. Therefore, the treatment of PCW with concurrent power generation by employing microbial fuel cell (MFC) could be a potential alternative to solve the energy and environmental issues. This study demonstrates the potentiality of PCW from acrylic acid plant with an initial COD of 45,000 mg L-1 generating maximum power density of 850 mW m-2 at a current density of 1500 mA m-2 using acclimatized anaerobic sludge (AS) as biocatalyst. The predominant microbes present in acclimatized AS were identified using Biolog GEN III analysis, which include the electrogenic genera namely Pseudomonas spp. and Bacillus spp. along with methanogenic archea Methanobacterium spp. The mechanism of electron transfer was elucidated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) which clearly demonstrated the natural metabolite-based electron transfer across the electrode/biofilm/solution interface. The abundance of the electron shuttle metabolites was increased with the microbial growth in the bulk solution as well as in the biofilm leading to a high power generation. The COD removal efficiency and the coulombic efficiency (CE) were found to be 40% and 21%, respectively after 11 days of operation using initial COD of 45,000 mg L-1. The low COD removal efficiency could drastically be increased to 82% when the initial COD of PCW was 5000 mg L-1 generating a power density of 150 mW m-2. The current work proves the feasibility of the MFC for the treatment of acrylic acid plant PCW using acclimatized anaerobic sludge (AS) as a biocatalyst.

Optimization of co-culture inoculated microbial fuel cell performance using response surface methodology.

Microbial fuel cells (MFCs) are considered as promising technology to achieve simultaneous wastewater treatment and electricity generation. However, operational and technological developments are still required to make it as a sustainable technology. In the present study, response surface methodology (RSM) was used to evaluate the effects of substrate concentration, co-culture composition, pH and time on the performance of co-culture (Klebsiella variicola and Pseudomonas aeruginosa) inoculated double chamber MFC. From the statistical analysis, it can be seen that the performance of MFC was not influenced by the interaction between the initial COD and time, pH and time, pH and initial COD, time and initial COD. However, the interaction between the inoculum composition and time, pH and the inoculum composition, initial COD and inoculum composition significantly influenced the performance of MFC. Based on the RSM results, best performance (power density and COD removal efficiency) was obtained when the inoculum composition, initial COD, pH and time were about 1:1, 26.690 mg/L, 7.21 and 15.50 days, respectively. The predictions from the model were in close agreement with the experimental results suggesting that the proposed model could adequately represent the actual relationships between the independent variables generating electricity and the COD removal efficiency.