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

A Strategy for Dual Biopolymer Production of P(3HB) and γ-PGA

BACKGROUND Production of biopolymers has gained considerable attention because of their biodegradability, biocompatibility, and as suitable replacements for mineral-based polymers. Despite advances in production process, a notable drawback still exists due to high production cost. The aim of this paper is to provide a production strategy for cost reduction. The suggested process may be adopted to other polymers, useable to wide audience in biopolymer research. RESULTS Dual production of two commercially important biopolymers, P(3HB) and γ-PGA, in a single batch from cheap substrates was studied, as proof of concept, for a feasible low cost dual biopolymer production. The dual production from a single batch yielded 1 g/L P(3HB) and 0.4 g/L γ-PGA using Bacillus subtilis OK2 (B. subtilis OK2). When orange peel was substituted as a cheap carbon source for dual production, coupled pH and dissolved oxygen control proved to be essential to overcome the inhibition imposed by the non-sugar components of the substrate. The cell lysis and release of P(3HB) granules in the dual production medium can be exploited of as a new approach for separation of this polymer. CONCLUSION This proof of concept study provides a new approach from upstream to downstream processing for low cost production of dual biopolymers

Agro-Industrial Waste Materials as Substrates for the Production of Poly(3-Hydroxybutyric Acid)

Accumulation of recalcitrant plastics in the environment has become a world-wide problem in today’s societies. Rapid depletion of natural resources for synthetic plastics along with environmental concerns has directed research towards finding alternatives to petroleum-based polymers. Poly(3-hydroxybutyric acid) P(3HB), as one of these alternatives, have attracted much attention in recent years due to their varied mechanical properties, biocompatibility and iodegradability. The aim of this study was to identify an agro-industrial waste resource economically suitable for large-scale production of P(3HB), to optimize the production using Response Surface Methodology in small-scale and subsequently, to test the production in a continuously stirred tank reactor. Among a range of agro-industrial waste, orange peel was selected as the most suitable for P(3HB) production. P(3HB) concentration of 1.24 g P(3HB)/L culture broth with 41% P(3HB)/dcw yield was obtained using orange peel as the sole carbon source in optimized medium with a modified strain of Bacillus subtilis (B. subtilis OK2)

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

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

Repeated batch for dye degradation in an airlift bioreactor by laccase entrapped in copper alginate

A repeated batch of synthetic dye decolorization was efficiently demonstrated in a 5 L airlift bioreactor. A laccase from Ganoderma sp. KU-Alk4, degrading commercial aromatic dyes was selected. The crude enzyme extract expressed laccase activity, and was immobilized under optimal conditions in copper-alginate beads, 3 IU/bead. The immobilized enzyme showed high efficiency in degrading various synthetic dyes under non-buffered conditions, in particular the indigoid dye Indigo Carmine. The immobilized laccase also showed marked increase in stability toward temperature and pH when compared with free enzyme preparation. Immobilization enhanced its temperature stability to maintain initial activity up to 55 °C, ten degrees higher than the free enzyme. The immobilized laccase was stable in the alkaline region up to pH 10.0. The dye decolorization system in 5 L airlift bioreactor was demonstrated with 25 mg/L Indigo Carmine dissolved in tap water and a total immobilized laccase activity of 6 × 104 IU. Airflow rate was the most important factor affecting the number of batch runs and the time for 100% dye degradation. An optimal airflow rate was of 4 L/min. Fourteen batch runs of complete dye degradation were successfully completed with only a single enzyme supplementation, and this could be a feasible system for operation in industry. Total dye degraded by this repeated process at 4 L/min airflow rate was 1.8 g. Isatin sulfonic acid was a metabolic product of Indigo Carmine degradation catalyzed by the immobilized laccase. This development of an effective repeatable bioprocess using enzymes for the treatment of dye-contaminated effluent has potential for implementation on an industrial scale