Environmental Engineering
F.A. Febria; A. Syafrita; A. Putra; H. Hidayat; C. Febrion
Abstract
BACKGROUND AND OBJECTIVES: Low-density polyethylene is one of the dominant recalcitrant plastic pollutants in the ocean, thus causing complicated problems. Biodegradation is an efficient, environmentally friendly, and sustainable option to overcome these problems. This study aims to quantitatively and ...
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BACKGROUND AND OBJECTIVES: Low-density polyethylene is one of the dominant recalcitrant plastic pollutants in the ocean, thus causing complicated problems. Biodegradation is an efficient, environmentally friendly, and sustainable option to overcome these problems. This study aims to quantitatively and qualitatively analyze the ability of marine bacterial isolates to degrade low-density polyethylene plastic.METHODS: Bacteria were isolated from plastic samples using serial dilution technique and inoculated on media containing low-density polyethylene powder. Bacterial degradation ability was analyzed quantitatively based on weight loss percentage and energy-dispersive X-ray spectroscopy values, as well as qualitatively based on changes in physical and chemical structures using Scanning Electron Microscopy and Fourier transform infrared spectroscopy. Meanwhile, bacterial isolates were identified based on gene sequence and phylogenetic analyses.FINDINGS: Four bacterial isolates were isolated from low-density polyethylene plastic samples. Quantitative analysis found that the low-density polyethylene film experienced weight loss up to 10-15 percent during 35 days of incubation, with a maximum daily weight loss rate of 0.004 milligrams per day, meaning that the four bacterial isolates have the potential to degrade plastic. Meanwhile, qualitative analysis based on Scanning Electron Microscope observations revealed changes in the physical structure of the film surface in the form of a rough surface, formation of holes, and breakdown into clumps across the film surface. Variations in these changes were tested. In the control, no changes occurred and the film surface remained flat and smooth. Conversely, the results of the energy dispersive X-ray spectroscopy spectrum analysis showed that the low-density polyethylene film broke down into smaller fragments, characterized by a decrease in mass from 98.51 percent to 98.23 percent. Fourier transform infrared observations showed variations in transmittance and wavenumbers, indicating changes in chemical bonds or functional groups in the low-density polyethylene film which caused it to become brittle and break down into smaller fragments with a lower molecular weight, making it easier for bacteria to digest. The results of the gene sequence analysis identified four bacterial isolates, namely Lysinibacillus sp. IBP-1, Bacillus sp. IBP-2, Bacillus paramycoides IBP-3, and Bacillus cereus IBP-4. Based on the quantitative and qualitative analyses, the ability of the bacterial isolates to degrade low-density polyethylene film was shown in the following order: Bacillus paramycoides IBP-3 > Bacillus cereus IBP-4 > Lysinibacillus sp. IBP-1 > Bacillus sp. IBP-2.CONCLUSION: All four marine bacterial isolates can use low-density polyethylene as the sole carbon source. Based on quantitative and qualitative analyses, Bacillus paramycoides IBP-3 has the best potential for degrading low-density polyethylene film. This study provides information on potential bacterial isolates that can be developed to control low-density polyethylene plastic waste.
Environmental Science
G. Manjarrez Paba; R. Baldiris Ávila; D. Baena Baldiris
Abstract
BACKGROUND AND OBJECTIVES:The objective of this study isto present a description of the main characteristics of azo dyes and the different treatment methods used to remove them from water. There is a special emphasis given to the benefits associated with biological treatment, predominantly those related ...
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BACKGROUND AND OBJECTIVES:The objective of this study isto present a description of the main characteristics of azo dyes and the different treatment methods used to remove them from water. There is a special emphasis given to the benefits associated with biological treatment, predominantly those related to the use of bacteria, which has to do with its competitive advantages over other microorganisms in the dye degradation processes.METHODS: The topic to be addressed was first defined through workshops with the research group. The literature review was carried out following several inclusion/exclusion criteria: the year of publication, as the selection was limited to studies published between 2010 and 2020, the focus of the investigation, which had to be related to the efficiency of different techniques for the remediation of ecosystems contaminated with azo dyes and, lastly, that the studies also discussed the use of environmental bacteria in dye degradation processes.FINDING: The efficiency of bacteria to degrade azo dyes ranges from 63-100%, the most efficient being: Marinobacter sp, Sphingobacterium sp, Enterococcus faecalis, Enterococcus casseliflavus. The bacteria that, reportedly, have greater efficiency for simultaneously removing the dye-metal complex are Bacillus circulans and Acinetobacter junii.CONCLUSION: Traditional strategies for the treatment of effluents contaminated with azo dyes are limited to physical and chemical processes that have a high energy and economic cost. For these reasons, current challenges are focused on the use of environmental bacteria capable of transforming dyes into less toxic compounds.
