Enlightening the characteristics of bioflocculant of endophytic actinomycetes from marine algae and its biosorption of heavy metal removal

Biodegradation and antimicrobial capability-induced heavy metal resistance of the marine-derived actinomycetes Nocardia harenae JJB5 and Amycolatopsis marina JJB11

Currently, heavy metal-resistant (HMR) marine actinomycetes have attracted much attention worldwide due to their unique capabilities. In this study, 27 marine-derived actinomycetes were isolated from coastal beaches in the Arabian Gulf of Al-Jubail in Saudi Arabia and screened for resistance to 100 mg/L of the heavy metals Cd2+, Cr6+, Cu2+, Fe2+, Pb2+, and Ni2+ using different assay techniques. Six isolates were selected as HMRs, of which two isolates, JJB5 and JJB11, exhibited the highest maximum tolerance concentrations (200- > 300 mg/L). Both isolates were the highest among six-HMR screened for their biodegradation potential of plastics low-density polyethylene, polystyrene, and polyvinyl chloride, recording the highest weight loss (15 ± 1.22 - 65 ± 1.2%) in their thin films. They also showed the highest biodegradability of the pesticides acetamiprid, chlordane, hexachlorocyclohexane, indoxacarb and lindane, indicating promising removal capacities (95.70-100%) for acetamiprid and indoxacarb using HPLC analysis. Additionally, the cell-free filtrate (CFF) of both isolates displayed the highest antimicrobial activity among the six-HMR screened against a variety of microbial test strains, recording the highest inhibition zone diameters (13.76 ± 0.66 - 26.0 ± 1.13 mm). GC‒MS analyses of the ethyl acetate extract of their CFFs revealed the presence of diverse chemical compounds with a multitude of remarkable biological activities. Based on their spore morphology and wall-chemotype, they were assigned to the nocardioform-actinomycetes. Furthermore, their phenotypic characteristics, together with 16S rRNA gene sequencing (OR121525-OR121526), revealed them as Nocardia harenae JJB5 and Amycolatopsis marina JJB11. Our results suggest that marine HMR actinomycetes are promising candidates for various biotechnological applications.

Low-Cost Greywater Treatment Using Polyculture Microalgae-Microalgal Growth, Organics, and Nutrient Removal Subject to pH and Temperature Variations During the Treatment

Organics and nutrient removal studies are rarely done using polyculture microalgae, and that too in outdoor conditions, as they are often not deemed effective for wastewater treatment purposes. This study examined the organics and nutrient removal efficiency of polyculture microalgae cultivated in greywater. The reactor was operated in outdoor conditions. Hence, it was subjected to natural pH and temperature variations. A growth rate of 0.05 g L-1 day-1 was observed for temperatures up to 37 °C, beyond which the growth rate declined by 0.07 g L-1 day-1. During the treatment, the pH of the system was observed to be between 7.4 and 8.4. However, the growth rate would again pick up (0.05 g L-1 day-1) when the pH and temperature moved towards the optimum range, indicating that the polycultures adapt very quickly to their environment. The maximum biomass concentration reached 0.82 gL-1. The highest removal efficiency of organic carbon, ammonia, and phosphate was 80.7, 61.9, and 58.4%, respectively. Nitrate and nitrite concentrations remained ≤ 1.3 mgL-1 and ≤ 2 mgL-1, respectively, indicating the absence of nitrification/denitrification and ammonia volatilization. The mass balance of microalgae indicated that the primary removal mechanism of nitrogen and phosphorus removal was assimilation by the microalgae. The study proved polyculture microalgae to be as effective as some monoculture species in wastewater treatment, which require costlier controlled growth conditions. The high organics and nutrient removal by polycultures in outdoor conditions could pave the way to reducing wastewater treatment costs.

Metagenomic assembled genomes indicated the potential application of hypersaline microbiome for plant growth promotion and stress alleviation in salinized soils

Climate change is causing unpredictable seasonal variations globally. Due to the continuously increasing earth's surface temperature, the rate of water evaporation is enhanced, conceiving a problem of soil salinization, especially in arid and semi-arid regions. The accumulation of salt degrades soil quality, impairs plant growth, and reduces agricultural yields. Salt-tolerant, plant-growth-promoting microorganisms may offer a solution, enhancing crop productivity and soil fertility in salinized areas. In the current study, genome-resolved metagenomic analysis has been performed to investigate the salt-tolerating and plant growth-promoting potential of two hypersaline ecosystems, Sambhar Lake and Drang Mine. The samples were co-assembled independently by Megahit, MetaSpades, and IDBA-UD tools. A total of 67 metagenomic assembled genomes (MAGs) were reconstructed following the binning process, including 15 from Megahit, 26 from MetaSpades, and 26 from IDBA_UD assembly tools. As compared to other assemblers, the MAGs obtained by MetaSpades were of superior quality, with a completeness range of 12.95%-96.56% and a contamination range of 0%-8.65%. The medium and high-quality MAGs from MetaSpades, upon functional annotation, revealed properties such as salt tolerance (91.3%), heavy metal tolerance (95.6%), exopolysaccharide (95.6%), and antioxidant (60.86%) biosynthesis. Several plant growth-promoting attributes, including phosphate solubilization and indole-3-acetic acid (IAA) production, were consistently identified across all obtained MAGs. Conversely, characteristics such as iron acquisition and potassium solubilization were observed in a substantial majority, specifically 91.3%, of the MAGs. The present study indicates that hypersaline microflora can be used as bio-fertilizing agents for agricultural practices in salinized areas by alleviating prevalent stresses.

IMPORTANCE

The strategic implementation of metagenomic assembled genomes (MAGs) in exploring the properties and harnessing microorganisms from ecosystems like hypersaline niches has transformative potential in agriculture. This approach promises to redefine our comprehension of microbial diversity and its ecosystem roles. Recovery and decoding of MAGs unlock genetic resources, enabling the development of new solutions for agricultural challenges. Enhanced understanding of these microbial communities can lead to more efficient nutrient cycling, pest control, and soil health maintenance. Consequently, traditional agricultural practices can be improved, resulting in increased yields, reduced environmental impacts, and heightened sustainability. MAGs offer a promising avenue for sustainable agriculture, bridging the gap between cutting-edge genomics and practical field applications.

Production of bioflocculant from Klebsiella pneumoniae: evaluation of fish waste extract as substrate and flocculation performance

The bioflocculant producing bacterial strain - UKD24 was isolated from the domestic sewage treatment plant. The isolated strain was identified as Klebsiella pneumoniae by using 16S rRNA gene sequencing. The K. pneumoniae UKD24 showed remarkable flocculation rates when grown with the carbon sources namely glucose, sucrose and lactose, and many commercial nitrogen sources. Furthermore, the fish waste extract (FE) was used to enhance the productivity of the bioflocculant as a nitrogen supplement and it showed a significant level of flocculation rate similar to the commercial nitrogen sources. The Box-Behnken experiments were designed to predict the optimal conditions for bioflocculant production and it suggested that glucose - 3.247 g L-1, FE - 0.5 g L-1 and inoculum size - 1% are the suitable levels for bioflocculant production. The FTIR analysis of the bioflocculant showed the functional groups related to the polysaccharides and the EEM analysis showed the fluorescence components related to the proteins and humic acids. The biochemical composition of the bioflocculant was identified as polysaccharides (24.36 ± 1.5%) and protein (12.15 ± 0.2%). The tested optimum conditions of the bioflocculant to induce flocculation were tested in the kaolin wastewater and it showed that the optimum dosage of the flocculant was 5 mg L-1 and the pH range was broad as 5-10. The cation dependency tests revealed that the monovalent and divalent cations are highly suitable for flocculation while the trivalent cations showed moderate flocculation. The Cr(VI) removal efficiency of the bioflocculant showed that ∼35% of heavy metal is trapped into flocks during the flocculation.

Natural Products and Biological Activity from Actinomycetes Associated with Marine Algae

Marine natural products have been recognized as the most promising source of bioactive substances for drug discovery research. This review illustrates the diversity of culturable actinobacteria associated with marine algae, their bioactivity and metabolites, and approaches to their isolation and determination of their biological properties. Furthermore, actinobacteria associated with marine algae are presented as a new subject for an extensive investigation to find novel and active natural products, which make them a potentially rich and innovative source for new drug development deserving more attention and exploration.

Changes in the bacterial communities in chromium-contaminated soils

Introduction

Hexavalent chromium or Cr(VI) is essential to various industries, such as leather manufacturing and stainless steel production. Given that inevitable leakage from industries pollutes the soil and thereby affects the soil environment. Microbial communities could improve the quality of the soil. Abundant bacterial communities would significantly enhance the soil richness and resist external pressure, benefiting agriculture. But the pollution of heavy metal broke the balance and decrease the abundance of bacterial communities, which weak the self-adjust ability of soil. This study aimed to explore changes in the diversity of soil bacterial communities and to identify the influences of soil bacterial communities on enzymes in soil polluted by Cr(VI).

Methods

The target soils were sampled quickly and aseptically. Their chromium content was detected through inductively coupled plasma-mass spectrometry, and bacterial microbiome communities were explored through MiSeq high-throughput sequencing. Then, the content of nitrite reductase and catalases were investigated through enzyme-linked immunosorbent assay (ELISA).

Results

Chromium content in polluted soils was higher than that in the control soils at all depths. Sobs, Chao1, Ace, and Shannon diversity estimators in the control were higher, whereas Simpson's diversity estimators in the control soils were lower than those of contaminated samples at all depths. Contaminants affected the composition of the bacterial community. The soil microbial species were relatively single and inhomogeneous in the polluted soils. The bacterial phyla in polluted and controlled soils include Proteobacteria, Actinobacteria, Chloroflexi, and Acidobacteria, which differ markedly in abundance.

Discussion

The results of these observations provide insights into the ecotoxicological effects of Cr(VI) exposure to soil microorganisms. To sum up these results are critical for evaluating the stabilized state of microbial community structures, contributing to the assessment of the potential risk of metal accumulation in soils.

A bioflocculant from Corynebacterium glutamicum and its application in acid mine wastewater treatment

Although many microorganisms have been found to produce bioflocculants, and bioflocculants have been considered as attractive alternatives to chemical flocculants in wastewater treatment, there are few reports on bioflocculants from the safe strain C. glutamicum, and the application of bioflocculants in acid wastewater treatment is also rare attributed to the high content of metal ions and high acidity of the water. In this study, a novel bioflocculant produced by Corynebacterium glutamicum Cg1-P30 was investigated. An optimal production of this bioflocculant with a yield of 0.52 g/L was achieved by Box-Behnken design, using 12.20 g/L glucose, 4.00 g/L corn steep liquor and 3.60 g/L urea as carbon and nitrogen source. The structural characterization revealed that the bioflocculant was mainly composed of 37.50% neutral sugar, 10.03% uronic acid, 6.32% aminosugar and 16.51% protein. Carboxyl, amine and hydroxyl groups were the functional groups in flocculation. The biofocculant was thermally stable and dependent on metal ions and acidic pH, showing a good flocculating activity of 91.92% at the dosage of 25 mg/L by aid of 1.0 mM Fe³⁺ at pH 2.0. Due to these unique properties, the bioflocculant could efficiently remove metal ions such as Fe, Al, Zn, and Pb from the real acid mine wastewater sample without pH adjustment, and meanwhile made the acid mine wastewater solution become clear with an increased neutral pH. These findings suggested the great potential application of the non-toxic bioflocculant from C. glutamicum Cg1-P30 in acid mine wastewater treatment.

Integrated approaches to mitigate threats from emerging potentially toxic elements: A way forward for sustainable environmental management

Potentially toxic elements (PTEs) such as toxic metal (loid)s and other emerging hazardous contaminants, exist in the environment and poses a serious threat. A large amount of wastewater containing PTEs such as cadmium, chromium, copper, nickel, arsenic, lead, zinc, etc. Release from industries during production process. Besides these, chemical-based fertilizers used in soils during crop production have become one of the crucial sources of PTEs. Various techniques are being employed for the mitigation of PTEs like chemical precipitation, ion exchange, coagulation, activated carbon, adsorption, membrane filtration, and bioremediation. Among these mitigation strategies, biological processes such as bioremediation, phytoremediation etc. Are extensively used, as they are economic have high-efficiency rate and are eco-friendly. This review intends to provide information on PTEs contamination through various sources; along with the toxicity of metal (loid)s with respect to their patterns of transmission and risks in the changing environment. Various remediation methods for the management of these pollutants along with their techno-economic perspective are also summarized in this review.

Laccase producing bacteria influenced the high decolorization of textile azo dyes with advanced study

Recent year, bacterial laccases are increasing interest in the field of industry and environmental applications especially decolorization of azo dyes. In industry, the dyes are present in stable nature including chemicals and lights. Due to these defects, the novel approaches are needed to removal of dyes before discharging into the environment. Among the various technologies, biological treatment methods and their strategies are very important, because of the decolorization and detoxification. Consecutively, biological mediated dyes removal are emerged with high potential especially microbes. Microbial laccases creates up new opportunities for their commercial applications. In this study, laccases were produced from Bacillus cereus (B. Cereus) and Pseudomonas parafulva (P. parafulva) by sub merged fermentation. For immobilization, the produced laccases were subjected to purify using 80% saturated ammonium sulphate and followed by dialysis. Then, crude laccases were immobilized through copper-alginate entrapment method. The maximum immobilized enzyme activity of the immobilized laccases were shown pH 8 at 50 °C and pH 7 at 40 °C for B. Cereus and P. parafulva respectively. In contrast, the normal enzyme activity was pH 10 at 40 °C and pH 8 at 40 °C were indicated for Bacillus cereus and P. parafulva respectively. Next, the free and immobilized laccases were performed the decolorization of three azo dyes T-blue, yellow GR and orange 3R, and exhibited that the 91.69 and 89.21% of Orange 3R were completely decolorized by both the B. Cereus and P. parafulva laccases when compared with free laccases enzymes. The confirmation of decolorization was monitored by UV-vis spectroscopy and FTIR spectroscopy, which clearly confirm the changes of peaks when compared with normal laccases. Finally, we have concluded that the B. Cereus and P. parafulva laccases are very important in azo dye decolorization and these used in future biological treatment of dyeing effluents.

Sustainable and efficient technologies for removal and recovery of toxic and valuable metals from wastewater: Recent progress, challenges, and future perspectives

Due to their numerous effects on human health and the natural environment, water contamination with heavy metals and metalloids, caused by their extensive use in various technologies and industrial applications, continues to be a huge ecological issue that needs to be urgently tackled. Additionally, within the circular economy management framework, the recovery and recycling of metals-based waste as high value-added products (VAPs) is of great interest, owing to their high cost and the continuous depletion of their reserves and natural sources. This paper reviews the state-of-the-art technologies developed for the removal and recovery of metal pollutants from wastewater by providing an in-depth understanding of their remediation mechanisms, while analyzing and critically discussing the recent key advances regarding these treatment methods, their practical implementation and integration, as well as evaluating their advantages and remaining limitations. Herein, various treatment techniques are covered, including adsorption, reduction/oxidation, ion exchange, membrane separation technologies, solvents extraction, chemical precipitation/co-precipitation, coagulation-flocculation, flotation, and bioremediation. A particular emphasis is placed on full recovery of the captured metal pollutants in various reusable forms as metal-based VAPs, mainly as solid precipitates, which is a powerful tool that offers substantial enhancement of the remediation processes' sustainability and cost-effectiveness. At the end, we have identified some prospective research directions for future work on this topic, while presenting some recommendations that can promote sustainability and economic feasibility of the existing treatment technologies.

Effective removal of heavy metals in industrial wastewater with novel bioactive catalyst enabling hybrid approach

Recent years, heavy metal reduction of contaminated atmosphere using microbes is heightened worldwide. In this context, the current study was focused on heavy metal resistant actinomycete strains were screened from effluent mixed contaminated soil samples. Based on the phenotypic and molecular identification, the high metal resistant actinomycete strain was named as Nocardiopsis dassonvillei (MH900216). The highest bioflocculent and exopolysaccharide productions of Nocardiopsis dassonvillei (MH900216) was confirmed by various invitro experiments result. The heavy metal degrading substances was characterized and effectively confirmed by Fourier transform infrared spectroscopy (FT-IR), X-Ray Diffraction (XRD), Scanning electron microscope (SEM). Further, the heavy metal sorption ability of actinomycete substances bioflocculent was exhibited 85.20%, 89.40%, 75.60%, and 51.40% against Cd, Cr, Pb and Hg respectively. Altogether, the bioflocculent produced actinomycete Nocardiopsis dassonvillei (MH900216) as an excellent biological source for heavy metal reduction in waste water, and it is an alternative method for effective removal of heavy metals towards sustainable environmental management.