Taking the waste out of dye wastewater using microbial fuel cells

Dye-containing wastewater (e.g. from textiles) is getting ever more challenging to treat partly due to its complexity but also due to tightening legislation regarding discharge standards. In India for example, they have a zero-water discharge policy which means the wastewater has to be treated to such a level that it can be reused. Treatment of the water for reuse is also of interest to water stressed countries. Conventional methods of treatment are however, either too costly (e.g. membrane systems) or produce sludges that create a secondary disposal problem (e.g. flocculation). I will explore the role that microbial fuel cells can play in overcoming some of the challenges of treating dye wastewater using conventional means. Case studies will include anodic vs cathodic decolourisation of dyes, integration of microbial fuel cells with activated sludge systems and scale up of reactors used

Recycling and the Environment: a Comparative Review Between Mineral-based Plastics and Bioplastics

Since their conception in the 1950s, mineral-based plastics have completely revolutionised our society with production reaching record highs year upon year. This cheap, and durable material has seen usage across a plethora of diverse industries and products, replacing traditional materials such as metals and wood. However, our reliance on mineral-based plastics has led to their improper disposal across the global, affecting our environments and ecosystems. As a response, different methods have been developed to help dispose of the large amounts of plastic waste produced, such as incineration or dumping in landfill sites, but these methods are not without their drawbacks including release of toxic substances into the air and leachate into the soil and waters respectively. Consequently, much interest is generated and channelled in recent years to the introduction of several types of biopolymers. These include plastics based on cellulosic esters, starch derivatives, polyhydroxybutyrate and polylactic acid. These biopolymers have been viewed as a suitable replacement for mineral-based plastics, and their production a good strategy towards sustainable development as they are mainly composed of biocompounds such as starch, cellulose and sugars. This short review article provides an overview as to whether biopolymers can rival mineral-based plastics considering properties such as mechanical strength, Young’s modulus and crystallinity and could they be regarded as a suitable material to reduce our reliance on mineral-based plastics, whilst simultaneously reducing non-renewable energy consumption and carbon dioxide emissions

Enhanced electrochemical treatment of phenanthrene-polluted soil using microbial fuel cells.

In this study, tubular microbial fuel cells (MFCs) were inserted into phenanthrene-contaminated water-logged soil in order to evaluate their treatment efficiency and overall system performance within 60 days incubation period. At day 10, phenanthrene degradation rates were found to decrease with increasing distance from the anodes from 50-55 % at 2 cm to 38-40 % at 8 cm. Bromate (used as a catholyte) removal in both MFCs was about 80-95 % on average which is significantly higher than the open circuit controls (15-40 %) over the 60 day period. Total chemical oxygen demand removal (72.8 %) in MFCs amended with surfactants was significantly higher than MFCs without surfactant (20 %). This suggests that surfactant addition may have enhanced bioavailability of not only phenanthrene, but other organic matter present in the soil. The outcomes of this work has demonstrated the simultaneous removal of phenanthrene (86%) and bromate (95%) coupled with concomitant bioelectricity generation (about 4.69 mWm-2) using MFC systems within a radius of influence (ROI) up to 8 cm. MFC technology may be used for in situ decontamination of soils due to its potential detoxification capacity and could be deployed directly as a prototype-MFC design in field applications

Prospecting for electrochemically-active hydrocarbon degrading microorganisms for use in bioelectrochemical remediation of petroleum hydrocarbons

Petroleum hydrocarbons pollution is commonplace in the environment owing to accidental spillages, leakages and indiscriminate disposal. Globally, it is estimated that between 1.7-8.8 million tonnes of oil is released into the aquatic environment annually; and from 1970-2018, 5.8 million tonnes of oil were spilled as a result of tanker incidences. Remediating these spills is a great priority due to their negative impacts on the environment e.g. irreversible habitat loss and threat to the survival of living organisms and public health e.g. genotoxic, mutagenic and/or carcinogenic effects. Work is currently underway to enrich and select electrochemically active hydrocarbon degraders for use in bioelectrochemical remediation of target petroleum hydrocarbons–benzene and phenantherene. Inocula from contaminated matrices (soil, sediment and groundwater) was taken from the Niger Delta region, Nigeria, which was highlighted by a 2011 UNEP report as being highly contaminated with petroleum hydrocarbons. Selected isolates will be identified and inoculated into microbial fuel cell as pure cultures and as microcosms to determine their hydrocarbon removal efficiencies and rates. Bioelectrochemical remediation has promise in speeding up the degradation process while reducing the amount of energy and chemicals used both of which are current impediments to conventional bioremediation processes applied to petroleum hydrocarbons

Plastics and Environment: Is There a Happy Medium?

In 2013 alone, 56 million tons of Poly(ethylene terephthalate) (PET) was produced worldwide. It’s low cost of production, coupled with desirable properties such as high durability and plasticity has led to its extensive use in many different applications, from mobile phones to medical equipment to clothing. Demand for PET is steadily increasing year by year. However, PET is mineral-based and is a non-degradable material due to its synthetic nature. It accumulates within the environment globally, and this has led to collective global efforts for developing strategies to tackle the issue using various different options. Biopolymers such as Polyhydroxyalkanoate (PHA) present themselves as a possible solution and as suitable alternative to help manage the ever-rising global demand for plastics as well as alleviating the global environmental crisis arising from non-degradable plastics. Capable to be produced in an eco-friendly manner and possessing biodegradable properties, biopolymers should be set to replace non-degradable plastics, but despite extensive research on production of biodegradable plastics, the cost of their production is too high to lend them to large-scale production. This project focuses on economic production of PHAs. In this context, several approaches are adopted. Cheaper media such as orange peel, wheat bran, and spirulina with other quality enhancing ingredients have been tried; dual polymer production has been proved a possible option, and stage-wise fermentations, appart from fed-batch have been tried. Furthermore, downstream processing strategies such as planned time of harvest have the potential to attenuate adverse effects of extraction methods for PHA extraction. A holistic approach promises positive future for biopolymer industry

The use of bio-electrochemical systems in environmental remediation of xenobiotics: a review

Summary Remediation of our environment of anthropogenic pollutants has become an imperative of the 21st century in order to sustain human activity and all life on the planet. With the current limitations of the existing technologies for this purpose, the need for innovative bioremediation technologies has become vitally important. Hitherto, electrochemically active microorganisms have only been a scientific curiosity and a platform for sustainable power production from waste material. However, recent research utilizing these electrochemically active microorganisms in Bio-electrochemical systems (BES) has revealed their promising potential for bioremediation applications. The primary research focus of BES applications up-to now has been to optimize and increase their power output. The possibility of utilizing these systems for bioremediation applications has been a new facet of this field of work. This review provides a comprehensive outlook on the utilization of BES based technologies for remediation of xenobiotic environmental pollutants

Antifungal effect of triclosan on Aspergillus fumigatus: quorum quenching role as a single agent and synergy with liposomal amphotericin-B

The purpose of this research was to determine Aspergillus fumigatus conidial viability and its biofilm formation upon treatment with triclosan and amphotericin-B loaded liposomes. A. fumigatus was treated with the antimicrobials, triclosan and liposomal amphotericin-B (L-AMB), in single and combined supplementation. To quantify the cells’ viability upon treatments, resazurin-based viability assay was performed. Confocal laser scanning microscopy was done by applying FUN-1 stain to screen the role of the agents on extracellular polymeric substances. Total A. fumigatus biomass upon treatments was estimated by using crystal violet-based assay. To study the agents’ effect on the conidial viability, flow cytometry analysis was performed. Expression levels of A. fumigatus genes encoding cell wall proteins, α-(1,3)-glucans and galactosaminogalactan were analysed by real-time polymerase chain reaction assay. A synergistic interaction occurred between triclosan and L-AMB when they were added sequentially (triclosan + L-AMB) at their sub-minimum inhibitory concentrations, the triclosan and L-AMB MICs were dropped to 0.6 and 0.2 mg/L, respectively, from 2 to 1 mg/L. Besides, L-AMB and triclosan contributed to the down-regulation of α-(1,3)-glucan and galactosaminogalactan in A. fumigatus conidia and resulted in less conidia aggregation and mycelia adhesion to the biotic/abiotic surfaces; A. fumigatus conidia-became hydrophilic upon treatment, as a result of rodlet layer being masked by a hydrophilic layer or modified by the ionic strength of the rodlet layer. In A. fumigatus, the potential mechanisms of action for L-AMB might be through killing the cells and for triclosan through interrupting the cells’ development as a consequence of quorum quenching

Fungal Enzymes as Catalytic Tools for Polyethylene Terephthalate (PET) Degradation.

The ubiquitous persistence of plastic waste in diverse forms and different environmental matrices is one of the main challenges that modern societies are facing at present. The exponential utilization and recalcitrance of synthetic plastics, including polyethylene terephthalate (PET), results in their extensive accumulation, which is a significant threat to the ecosystem. The growing amount of plastic waste ending up in landfills and oceans is alarming due to its possible adverse effects on biota. Thus, there is an urgent need to mitigate plastic waste to tackle the environmental crisis of plastic pollution. With regards to PET, there is a plethora of literature on the transportation route, ingestion, environmental fate, amount, and the adverse ecological and human health effects. Several studies have described the deployment of various microbial enzymes with much focus on bacterial-enzyme mediated removal and remediation of PET. However, there is a lack of consolidated studies on the exploitation of fungal enzymes for PET degradation. Herein, an effort has been made to cover this literature gap by spotlighting the fungi and their unique enzymes, e.g., esterases, lipases, and cutinases. These fungal enzymes have emerged as candidates for the development of biocatalytic PET degradation processes. The first half of this review is focused on fungal biocatalysts involved in the degradation of PET. The latter half explains three main aspects: (1) catalytic mechanism of PET hydrolysis in the presence of cutinases as a model fungal enzyme, (2) limitations hindering enzymatic PET biodegradation, and (3) strategies for enhancement of enzymatic PET biodegradation