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Wastewater treatment plants (WWTPs) have been implicated as direct key reservoir of both antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) associated with human infection, as high concentrations of ARBs and ARGs have been detected in recycled hospital wastewater. Among the ARBs, the carbapenem-resistant Acinetobacter baumannii has been ranked as priority 1 (critical) pathogen by the World Health Organization (WHO), due to its overwhelming burden on public health. Therefore, this study is aimed at investigating non-thermal plasma (NTP) technology as an alternative disinfection step to inactivate this bacterium and its ARGs. Culture-based method and PCR were employed in confirming the carbapenem resistance gene blaNDM-1 in A. baumannii (BAA 1605). Suspension of carbapenem-resistant A. baumannii (24 h culture) was prepared from the confirmed isolate and subjected to plasma treatment at varying time intervals (3 min, 6 min, 9 min, 12 min, and 15 min) in triplicates. The plasma-treated samples were evaluated for re-growth and the presence of the resistance gene. The treatment resulted in a 1.13 log reduction after 3 min and the highest log reduction of ≥ 8 after 15 min, and the results also showed that NTP was able to inactivate the blaNDM-1 gene. The log reduction and gel image results suggest that plasma disinfection has a great potential to be an efficient tertiary treatment step for WWTPs.

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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.

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Natural water sources are habitually marred by insidious anthropogenic practices and municipal wastewater discharges that contain either of xenobiotic pollutants and their sometimes more toxic degradation products, or both. Although wastewater is considered as both a resource and a problem, as explained in this review, it is however daunting that, while the global village is still struggling to decipher the mode of proper handling, subsequent discharge and regulation of already established aromatic contaminants in wastewater, there emanates some more aggressive, stealth and sinister groups of compounds. It is quite ironic that majority of these compounds are the 'go through' consumables in our present society and have been suspected to pose several health risks to the aquatic ecosystem, eliciting unfavourable clinical manifestations in aquatic animals and humans, which has heightened the uncertainties conferred on freshwater use and consumption of some aquatic foods. This review therefore serves to give a brief account on the metamorphosis of approach in detection of aromatic pollutants and ultimately their implications along the trophic chains in the community.

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The aim of this present study was to investigate the environmental proficiency of two laccase producing bacterial strains, Hb16c and Berl11b2. Here, laccases, which were secreted in media containing environmental wastes, were characterized for biochemical and kinetic novelty and applied in the decolourization of some synthetic dyes and subsequently, denim bleaching. The laccases exhibited enhanced pH-, thermo-, psychro-, metal-, halo-, and surfacto-tolerance, eliciting residual activities of at least ca. 71%. Thereafter, the enzymes were able to decolourize novel high concentrations of synthetic dyes (0.2% w v-1) at 56 h of incubation, and also elicit a mediator-assisted perpetual wash up and decolourization of indigo pigment from fabric under 6 h. The outcomes observed in this study therefore warrant the adoption of these isolates for applications toward a sustainable and total environment through production of fine biochemicals, and the minimization of environmental wastes.

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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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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.

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Agroindustrial residual lignocellulosic biomaterial provides an economical and renewable natural bioresource for the large-scale, gainful biofuel production, as well as the production of fine bulk chemicals, which may include industrial biocatalysts. To this end, the laccase-inducing aptitude of some agroindustrial, lignocellulosic residues were appraised in submerged fermentation batch culture of two woodland betaproteobacteria (Hb9c; Achromobacter xylosoxidans HWN16, Hb16c; Bordetella bronchiseptica HSO16). Significant fermentation factors for laccase production were identified following a one-variable-at-a-time: OVAT screening method, levels of significant factors were optimized using response surface methodology: RSM. Mandarin peelings: MP and wheat bran: WB were suitable substrates for laccase production in Hb9c; 29.4 U/mL and Hb16c; 28.2 U/mL, respectively. However, the numerical optimization of significant factors for laccase production in both isolates presented an overall maximum laccase output encountered throughout the study (Hb9c; 169.39 U/mL, Hb16c; 45.22 U/mL), albeit the simulated conditions of the statistical model were outside the design space of the algorithm such as pH 5, 0.5 g MP, 100 rpm, 0.25 g NaNO3 for Hb9c and pH 3, 2.5 g WB, 50 rpm, 0.05 g yeast extract for Hb16c. Furthermore, a record 17.5 and 15.54 fold increase in laccase turnover depicts the astuteness of the statistical method in the valorization of these lignocellulosic residues for enhanced laccase production, hence, the incorporation of these outcomes at industrial scales might yield tremendous outputs.

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