5 research outputs found

    The biobleaching potential of laccase produced from mandarin peelings : impetus for a circular bio-based economy in textile biofinishing

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    The quest for circular bioeconomy has been on the rise in recent years, and it is anticipated to fulfil the environmental sustainability aspect of the sustainable development goals (SDG 2030). In this regard, our investigation attempted the biotechnological appraisal of an enzymatic derivative of bacterial (Pseudomonas sp. HRJ16) mandarin peelings (MP) fermentation as a vehicle for an environmentally benign and sustainable textile bioscouring. Production of the bacterial exudate (HRJ16 laccase) was optimized by response surface methodology (RSM), using the common low-cost agroindustrial waste (MP). HRJ16 laccase was further assessed for its advantageous biochemical and catalytic properties, and then applied in synthetic dye decolorization and denim bleaching. Results emphasized the extremotolerance of the exudate to temperature, pH, salts, cations and surfactants, when at least ca. 80 % residual activity was recollected after exposure to the different extreme operating conditions. The interesting capabilities of the HRJ16 in this study culminated in its successful bioscouring of denim fabric over 6 h and the spontaneous decolorization of the resultant effluent. This constitutive properties of HRJ16 might make it a crucial catalyst for achieving a circular bioeconomy in the textile industry.The South Africa Medical Research Council (SAMRC), the National Research Foundation and Central University of Technology, Free State.https://www.journals.elsevier.com/arabian-journal-of-chemistryhj2023Chemical Engineerin

    Inactivation of antibiotic-resistant bacteria and antibiotic-resistance genes in wastewater streams: Current challenges and future perspectives

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    The discovery of antibiotics, which was once regarded as a timely medical intervention now leaves a bitter aftertaste: antimicrobial resistance (AMR), due to the unregulated use of these compounds and the poor management receiving wastewaters before discharge into pristine environments or the recycling of such treated waters. Wastewater treatment plants (WWTPs) have been regarded a central sink for the mostly unmetabolized or partially metabolised antibiotics and is also pivotal to the incidence of antibiotic resistance bacteria (ARBs) and their resistance genes (ARGs), which consistently contribute to the global disease burden and deteriorating prophylaxis. In this regard, we highlighted WWTP-antibiotics consumption-ARBs-ARGs nexus, which might be critical to understanding the epidemiology of AMR and also guide the precise prevention and remediation of such occurrences. We also discovered the unsophistication of conventional WWTPs and treatment techniques for adequate treatment of antibiotics, ARBs and ARGs, due to their lack of compliance with environmental sustainability, then ultimately assessed the prospects of cold atmospheric plasma (CAP). Herein, we observed that CAP technologies not only has the capability to disinfect wastewater polluted with copious amounts of chemicals and biologicals, but also have a potential to augment bioelectricity generation, when integrated into bio electrochemical modules, which future WWTPs should be retrofitted to accommodate. Therefore, further research should be conducted to unveil more of the unknowns, which only a snippet has been highlighted in this study

    Recovery of laccase-producing gammaproteobacteria from wastewater

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    Wastewater environment is a rich source of microorganisms with the capability for the degradation of malicious aromatic pollutants. Although wastewater could be regarded as both a resource and a problem, we intended to elucidate its beneficial aspect in this study sourcing for laccase-producing proteobacteria. Different wastewater samples, from selected wastewater treatment plants (WWTPs), were selectively enriched with some model compounds (vanillin, lignin and potassium hydrogen phthalate) to screen out bacterial isolates that possess excellent degradation potentials. Thereafter, positive isolates were screened for the production of laccase and degradation on phenolic (guaiacol, α-naphthol and syringaldazine) and non-phenolic (ABTS; 2,2 azino-bis -(3-ethylbenzothiazoline 6 sulphonic acid) and PFC; potassium ferrocyanoferrate) substrates characteristic of laccase oxidation. Remarkable laccase producers were identified based on their 16 S rRNA sequences and their secreted enzymes were subjected to substrate specificity test, employing laccase substrates; ABTS, PFC, guaiacol, α-naphthol, 2,6-dimethoxyphenol and pyrogallol. Results showed that wastewater and selective enrichment, in tandem, produced the gammaproteobacteria Pseudomonas aeruginosa DEJ16, Pseudomonas mendocina AEN16 and Stenotrophomonas maltophila BIJ16, which preferably oxidized the non-phenolic substrates. Units of extracellular laccase activity ranging between cca. 490 and cca. 600 U/mL were recorded for ABTS whereas outputs recorded from PFC catalysis ranged from cca. 320 to cca. 430 U/mL. Stenotrophomonas maltophila BIJ16 presented an unparalleled high laccase activity and had a responsive substrate specificity to aromatic and inorganic substrates, thereby suggesting its employment for in situ biodegradation studies. In conclusion, wastewater serves as an ideal milieu for the isolation of laccase producing bacteria. Keywords: Wastewater, Selective enrichment, Biodegradation, Gammaproteobacteria, Laccas

    Aptitude of Oxidative Enzymes for Treatment of Wastewater Pollutants: A Laccase Perspective

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    Natural water sources are very often contaminated by municipal wastewater discharges which contain either of xenobiotic pollutants and their sometimes more toxic degradation products, or both, which frustrates the universal millenium development goal of provision of the relatively scarce pristine freshwater to water-scarce and -stressed communities, in order to augment their socioeconomic well-being. Seeing that both regulatory measures, as regards the discharge limits of wastewater, and the query for efficient treatment methods remain unanswered, partially, the prospects of enzymatic treatment of wastewater is advisable. Therefore, a reconsideration was assigned to the possible capacity of oxidative enzymes and the respective challenges encountered during their applications in wastewater treatment, and ultimately, the prospects of laccase, a polyphenol oxidase that oxidizes aromatic and inorganic substrates with electron-donating groups in treatment aromatic contaminants of wastewater, in real wastewater situations, since it is assumed to be a vehicle for a greener community. Furthermore, the importance of laccase-driven catalysis toward maintaining mass-energy balance, hence minimizing environmental waste, was comprehensibly elucidated, as well the strategic positioning of laccase in a model wastewater treatment facility for effective treatment of wastewater contaminants
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