Isolation of a novel Pseudomonas sp from soil that can efficiently degrade polyethylene succinate

Purpose

Polyethylene succinate (PES) is a biodegradable synthetic polymer and therefore widely used as a base material in plastic industry to circumvent the environmental problems related with the non-biodegradability of other polymers like polyethylene. Till date only few organisms have been reported to have the ability to degrade PES. Therefore for better management of PES-related environmental waste, the present study is targeted towards isolating mesophilic organism(s) capable of more efficient degradation of PES.

Results

Strain AKS2 was isolated from soil based on survival on a selection plate wherein PES was used as sole carbon source. Ribotyping and biochemical tests revealed that AKS2 is a new strain of Pseudomonas. Scanning electron and atomic force microscopic analysis of the PES films obtained after incubation with AKS2 confirmed PES-degradation ability of AKS2, wherein an alteration in surface topology was observed. The kinetics of PES weight loss showed that AKS2 degrades PES maximally during its logarithmic growth phase at a rate of 1.65?mg/day. This degradation is mediated by esterase activity and may also involve cell-surface hydrophobicity. It has also been observed that AKS2 is able to degrade PES considerably even in the presence of glucose, which is likely to increase the bioremediation potential of this isolate.

Conclusion

A new strain of Pseudomonas has been isolated from soil that is able to adhere to PES and degrade this polymer efficiently. This organism has the potential to be implemented as a useful tool for bioremediation of PES-derived materials.     

Low-density polyethylene degradation by Pseudomonas sp. AKS2 biofilm

Polyethylene materials are a serious environmental concern as their nondegradable nature allows them to persist in the environment. Recent studies have shown that polyethylene can be degraded by microbes at a very slow rate, whereby detectable changes are evident after several years. In the present study, we report the degradation of low-density polyethylene by Pseudomonas sp. AKS2. Unlike the previous reports, degradation by Pseudomonas sp. AKS2 is relatively fast as it can degrade 5?±?1 % of the starting material in 45 days without prior oxidation. This degradation can be altered by agents that modulate hydrophobic interaction between polythene and the microbe. As mineral oil promotes hydrophobic interactions, it enhances bacterial attachment to the polymer surface. This enhanced attachment results in increased biofilm formation and enhanced polymer degradation. In contrast, Tween 80 reduces bacterial attachment to the polymer surface by lowering hydrophobic interactions and thereby reduces polymer degradation. Thus, this study establishes a correlation between hydrophobic interaction and polymer degradation and also relates the biofilm formation ability of bacteria to polymer degrading potential.     

Bioaugmentation of polyethylene succinate-contaminated soil with Pseudomonas sp. AKS2 results in increased microbial activity and better polymer degradation

Pseudomonas sp. AKS2 isolated from soil degrades polyethylene succinate (PES) efficiently in the laboratory. However, this organism may not be able to degrade PES with similar efficiency in a natural habitat. Since in situ remediation is preferred for the effective removal of recalcitrant materials like plastic, in the current study, bioaugmentation potential of this organism was investigated. To investigate the potential of the AKS2 strain to bioaugment the PES-contaminated soil, a microcosm-based study was carried out wherein naturally attenuated, biostimulated, and AKS2-inoculated (bioaugmented) soil samples were examined for their ability to degrade PES. The results showed better degradation of PES by bioaugmented soil than other microcosms. Consistent with it, a higher number of PES-degrading organisms were found in the bioaugmented microcosm. The bioaugmented microcosm also exhibited a higher level of average well color development in BiOLOG ECO plate assay than the other two. The corresponding Shannon–Weaver index and Gini coefficient revealed a higher soil microbial diversity of bioaugmented microcosm than the others. This was further supported by community-level physiological profile of three different microcosms wherein we have observed better utilization of different carbon sources by bioaugmented microcosms. Collectively, these results demonstrate that bioaugmentation of PES-contaminated soil with AKS2 not only enhances polymer degradation but also increases microbial diversity. Bioaugmentation of soil with AKS2 enhances PES degradation without causing damage to soil ecology. Thus, Pseudomonas sp. AKS2 has the potential to be implemented as a useful tool for in situ bioremediation of PES.     

Fractionation of heavy metals and assessment of contamination of the sediments of Lake Titicaca

Chemical weathering is one of the major geochemical processes that control the mobilization of heavy metals. The present study provides the first report on heavy metal fractionation in sediments (8–156 m) of Lake Titicaca (3,820 m a.s.l.), which is shared by the Republic of Peru and the Plurinational State of Bolivia. Both contents of total Cu, Fe, Ni, Co, Mn, Cd, Pb, and Zn and also the fractionation of these heavy metals associated with four different fractions have been determined following the BCR scheme. The principal component analysis suggests that Co, Ni, and Cd can be attributed to natural sources related to the mineralized geological formations. Moreover, the sources of Cu, Fe, and Mn are effluents and wastes generated from mining activities, while Pb and Zn also suggest that their common source is associated to mining activities. According to the Risk Assessment Code, there is a moderate to high risk related to Zn, Pb, Cd, Mn, Co, and Ni mobilization and/or remobilization from the bottom sediment to the water column. Furthermore, the Geoaccumulation Index and the Enrichment Factor reveal that Zn, Pb, and Cd are enriched in the sediments. The results suggest that the effluents from various traditional mining waste sites in both countries are the main source of heavy metal contamination in the sediments of Lake Titicaca.     

Arsenic-induced health crisis in peri-urban Moyna and Ardebok villages, West Bengal, India: an exposure assessment study

Drinking of arsenic (As)-contaminated groundwater has adverse effects on health of millions of people worldwide. This study aimed to determine the degree of severity of As exposure from drinking water in peri-urban Moyna and Ardebok villages, West Bengal, India. Arsenic concentrations in hair, nail and urine samp les of the individuals were determined. Arsenical dermatosis, keratosis and melanosis were investigated through medical evaluation. We have evaluated the association between As exposure from drinking water, and keratosis and melanosis outcomes. The results showed that 82.7?% of the sampled tube wells contain As concentrations above 10?μg/L, while 57.7?% contain As concentrations above 50?μg/L. The hair, nail and urine As concentrations were positively correlated with As concentrations in drinking water. In our study population, we observed a strong association between As concentrations ranging 51-99?μg/L and keratosis and melanosis outcomes, although the probability decreases at higher concentration ranges perhaps due to switching away from the use of As-contaminated tube wells for drinking and cooking purposes. High As concentrations in hair, nail and urine were observed to be associated with the age of the study population. The level of As concentrations in hair, nail and urine samples of the study population indicated the degree of severity of As exposure in the study region.     

Treatment of metal (loid) contaminated solutions using iron-peat as sorbent: is landfilling a suitable management option for the spent sorbent?

Environmental Science and Pollution Research - This study firstly aimed to investigate the potential of simultaneous metal (loid) removal from metal (oid) solution through adsorption on iron-peat,...     

Women and community water supply programmes: An analysis from a socio-cultural perspective

Community water supply programmes are seen as instrumental in achieving the goal of ‘safe’ water for all. Women, a principal target group of these programmes, are to be benefited with greater convenience, enhanced socio‐cultural opportunities and better health for themselves and their families, provided through improved water facilities. Water supply programmes largely consist of three essential components, namely: technology, people and institutions. Although such programmes are intended to benefit women members of local communities, scant attention is paid to the impacts of the socio‐cultural context of the community on these programmes. This article explores the influence of social and cultural intricacies on the implementation of community water supply programmes, and assesses their effectiveness. The article offers important lessons for the design and implementation of this type of programme. It concludes that the local socio‐cultural context sets the stage for programme implementation, being a dynamic factor that determines actual access to water sources, more so than mere physical availability, which is often used as a criterion for programme performance. The article stresses the urgent need to integrate socio‐cultural factors as a fourth dimension in designing community water supply programmes, and suggests practical measures for enhancing the effectiveness of such programmes.     

Arsenic uptake by plants and possible phytoremediation applications: a brief overview

This review focuses the behaviour of arsenic in plant?Csoil and plant?Cwater systems, arsenic?Cplant cell interactions, phytoremediation, and biosorption. Arsenate and arsenite uptake by plants varies in different environment conditions. An eco-friendly and low-cost method for arsenic removal from soil?Cwater system is phytoremediation, in which living plants are used to remove arsenic from the environment or to render it less toxic. Several factors such as soil redox conditions, arsenic speciation in soils, and the presence of phosphates play a major role. Translocation factor is the important feature for categorising plants for their remediation ability. Phytoremediation techniques often do not take into account the biosorption processes of living plants and plant litter. In biosorption techniques, contaminants can be removed by a biological substrate, as a sorbent, bacteria, fungi, algae, or vascular plants surfaces based on passive binding of arsenic or other contaminants on cell wall surfaces containing special active functional groups. Evaluation of the current literature suggests that understanding molecular level processes, and kinetic aspects in phytoremediation using advanced analytical techniques are essential for designing phytoremediation technologies with improved, predictable remedial success. Hence, more efforts are needed on addressing the molecular level behaviour of arsenic in plants, kinetics of uptake, and transfer of arsenic in plants with flowing waters, remobilisation through decay, possible methylation, and volatilisation.     

Targeting arsenic-safe aquifers for drinking water supplies

At present, 70 countries worldwide are affected by groundwater contamination by arsenic (As) released from predominantly geogenic sources. Consequently, the As problem is becoming a global issue. The option to target As-safe aquifers, which uses geological, geochemical, hydrogeological, morphological and climatic similarities to delimit As-safe aquifers, appears as a sustainable mitigation option. Two pilot areas, Meghna Flood Plain in Matlab Upazila, representative of Bengal Delta in Bangladesh, and Río Dulce Alluvial Cone, representing a typical aquifer setting in the Chaco-Pampean Plain in Argentina groundwater As occurrence, were compared. In rural Bangladesh, As removal techniques have been provided to the population, but with low social acceptance. In contrast, “targeting As-safe aquifers” was socially accepted in Bangladesh, where sediment color could be used to identify As-safe aquifer zones and to install safe wells. The investigation in Argentina is more complex because of very different conditions and sources of As. Targeting As-safe aquifers could be a sustainable option for many rural areas and isolated peri-urban areas.