Potential capacity of Beauveria bassiana and Metarhizium anisopliae in the biosorption of Cd2+ and Pb2+

Copper biosorption by Bacillus pumilus OQ931870 and Bacillus subtilis OQ931871 isolated from Wadi Nakheil, Red Sea, Egypt

BACKGROUND

Despite being necessary, copper is a toxic heavy metal that, at high concentrations, harms the life system. The parameters that affect the bioreduction and biosorption of copper are highly copper-resistant bacteria.

RESULTS

In this work, the ability of the bacterial biomass, isolated from black shale, Wadi Nakheil, Red Sea, Egypt, for Cu2+ attachment, was investigated. Two Cu2+ resistance Bacillus species were isolated; Bacillus pumilus OQ931870 and Bacillus subtilis OQ931871. The most tolerant bacterial isolate to Cu2+ was B. pumilus. Different factors on Cu2+ biosorption were analyzed to estimate the maximum conditions for Cu biosorption. The qmax for Cu2+ by B. pumilus and B. subtilis determined from the Langmuir adsorption isotherm was 11.876 and 19.88 mg. g-1, respectively. According to r2, the biosorption equilibrium isotherms close-fitting with Langmuir and Freundlich model isotherm. Temkin isotherm fitted better to the equilibrium data of B. pumilus and B. subtilis adsorption. Additionally, the Dubinin-Radushkevich (D-R) isotherm suggested that adsorption mechanism of Cu2+ is predominately physisorption.

CONCLUSION

Therefore, the present work indicated that the biomass of two bacterial strains is an effective adsorbent for Cu2+ removal from aqueous solutions.

Bacillus and microalgae biofertilizers improved quality and biomass of Salvia miltiorrhiza by altering microbial communities

Objective

Biofertilizers are reliable alternatives to chemical fertilizers due to various advantages. However, the effect of biofertilizers on Salvia miltiorrhiza yield and quality and the possible mechanisms remain little known. Here, an experiment was conducted in S. miltiorrhiza field treated with two kinds of biofertilizers including Bacillus and microalgae.

Methods

A field experiment was conducted on S. miltiorrhiza of one year old. The biofertilizers were applied at six treatments: (i) control check, CK; (ii) microalgae, VZ; (iii) Bacillus, TTB; (iv) microalgae + Bacillus (1:1), VTA; (v) microalgae + Bacillus (0.5:1), VTB; (vi) microalgae + Bacillus (1:0.5), VTC. Here, high-throughput sequencing, ICP-MS and UPLC were employed to systematically characterize changes of microbial diversity and structure composition, heavy metals content and bioactive compounds, respectively.

Results

Compared to CK, root biomass increased by 29.31%-60.39% (P < 0.001). Meanwhile, bioactive compounds were higher than CK after the application of the biofertilizers, peculiarly in TTB and VTB. However, the content of Pb contents in roots significantly reduced by 46.03% and 37.58% respectively in VTC and TTB (P < 0.05). VTA application notably increased the available nitrogen content by 53.03% (P < 0.05), indicating the improvement of soil fertility. Significantly, bacterial and fungal Chao I diversity indices showed an increasing trend with biofertilizer application (P < 0.05), and biofertilizer amendment enriched the rhizosphere soil with beneficial microorganisms that have abilities on promoting plant growth (Achromobacter and Penicillium), adsorbing heavy metal (Achromobacter and Beauveria), controlling plant pathogen (Plectosphaerella, Lechevalieria, Sorangium, Phlebiopsis and Beauveria) and promoting the accumulation of metabolites (Beauveria and Phoma).

Conclusion

Bacillus and microalgae biofertilizers improved the quality and biomass of S. miltiorrhiza by altering microbial communities in soil.

Consequences of Arsenic Contamination on Plants and Mycoremediation-Mediated Arsenic Stress Tolerance for Sustainable Agriculture

Arsenic contamination in water and soil is becoming a severe problem. It is toxic to the environment and human health. It is usually found in small quantities in rock, soil, air, and water which increase due to natural and anthropogenic activities. Arsenic exposure leads to several diseases such as vascular disease, including stroke, ischemic heart disease, and peripheral vascular disease, and also increases the risk of liver, lungs, kidneys, and bladder tumors. Arsenic leads to oxidative stress that causes an imbalance in the redox system. Mycoremediation approaches can potentially reduce the As level near the contaminated sites and are procuring popularity as being eco-friendly and cost-effective. Many fungi have specific metal-binding metallothionein proteins, which are used for immobilizing the As concentration from the soil, thereby removing the accumulated As in crops. Some fungi also have other mechanisms to reduce the As contamination, such as biosynthesis of glutathione, cell surface precipitation, bioaugmentation, biostimulation, biosorption, bioaccumulation, biovolatilization, methylation, and chelation of As. Arsenic-resistant fungi and recombinant yeast have a significant potential for better elimination of As from contaminated areas. This review discusses the relationship between As exposure, oxidative stress, and signaling pathways. We also explain how to overcome the detrimental effects of As contamination through mycoremediation, unraveling the mechanism of As-induced toxicity.

Statistical Analysis and Optimization of the Brilliant Red HE-3B Dye Biosorption onto a Biosorbent Based on Residual Biomass

Using various techniques, natural polymers can be successfully used as a matrix to immobilize a residual microbial biomass in a form that is easy to handle, namely biosorbents, and which is capable of retaining chemical species from polluted aqueous media. The biosorption process of reactive Brilliant Red HE-3B dye on a new type of biosorbent, based on a residual microbial biomass of Saccharomyces pastorianus immobilized in sodium alginate, was studied using mathematical modeling of experimental data obtained under certain conditions. Different methods, such as computer-assisted statistical analysis, were applied, considering all independent and dependent variables involved in the reactive dye biosorption process. The optimal values achieved were compared, and the experimental data supported the possibility of using the immobilized residual biomass as a biosorbent for the studied reference dye. The results were sufficient to perform dye removals higher than 70-85% in an aqueous solution containing around 45-50 mg/L of reactive dye, and working with more than 20-22 g/L of prepared immobilized microbial biosorbent for more than 9.5-10 h. Furthermore, the proposed models agreed with the experimental data and permitted the prediction of the dye biosorption behavior in the experimental variation field of each independent variable.

Metarhizium robertsii as a promising microbial agent for rice in situ cadmium reduction and plant growth promotion

The toxic chemical element cadmium (Cd) in paddy fields triggered increasing problems of growth inhibition and food security in rice consistently. In this study, we found Metarhizium robertsii, which is widely used as a bioinsecticide and biofertilizer in agriculture and recently found to be resistant to Cd, developed intraradical and extraradical symbiotic hyphae in rice seedlings, and successfully colonized in the rice rhizosphere soil to more than 10³ CFUs g^-1 soil at harvesting. M. robertsii colonization significantly reduced Cd accumulations in both hydroponically cultured seedlings and the matured rice cultured in Cd contaminated potting soil (2 ppm). Notably, Cd accumulation reduction of the roots, stems, leaves, husks and grains of the matured rice induced by the fungus were 44.3%, 32.1%, 35.3%, 31.9% and 24.7%, respectively. It was caused by the M. robertsii-induced suppression of Cd intake transporter gene osNramp5 in the rice roots, and the chemical stabilizing of Cd to the residual fraction in the rhizosphere soil. In addition, the colonization of M. robertsii significantly promoted the growth characters and the photosynthesis of the rice plants. This is achieved by the increase of endogenous hormone levels of indole-3-acetic, gibberellin A₃ and brassinolide induced by M. robertsii. Furthermore, the fungus enhanced the antioxidative capacities via increasing enzyme activities of catalase, peroxidase and the production of glutathione, ascorbic acid, proline in the rice plants. Our work provides theoretical basis for expanding the use of M. robertsii as in situ Cd accumulation reduction and detoxification agents for rice in contaminated paddy fields.

Enhanced Cd efflux capacity and physiological stress resistance: The beneficial modulations of Metarhizium robertsii on plants under cadmium stress

Due to the high migration capacity in agricultural soil-crop systems, cadmium (Cd) is accumulated in various crops and severely inhibits plant growth. In this study, we showed that, under Cd stress, the plant-symbiotic fungus Metarhizium robertsii reduced Cd accumulation in Arabidopsis thaliana shoots and roots by 21.8 % and 23.8 %, respectively. This is achieved by M. robertsii colonization-induced elevation of Cd efflux capacity via upregulation of three PCR genes, which is confirmed by the fact that the extent to which M. robertsii reduced Cd accumulation in the WT plants was greater than the inactivating mutants of the PCR genes. M. robertsii also alleviated Cd-induced leaf etiolation in A. thaliana by increasing the chlorophyll amount and modified plant physiological status to increase Cd stress tolerance via increasing production of catalase, peroxidase and glutathione and upregulating multiple HIPP proteins involved in sequestration of Cd. Notably, consistent with that in A. thaliana, the colonization of M. robertsii also reduced the Cd accumulation in Oryza sativa seedlings by upregulating the PCR gene OsPCR1, and increased chlorophyll amount and alleviated oxidative stress. Therefore, M. robertsii colonization reduced Cd accumulation in plants, and promoted plant growth and health by elevating Cd efflux capacity and modifying physiological status.

A novel yeast strain Geotrichum sp. CS-67 capable of accumulating heavy metal ions

Bioremediation, which has several advantages over traditional methods, represents an alternative means of dealing with heavy metal pollution. We screened for microorganisms showing heavy metal tolerance in polluted mangrove soils. A novel yeast, Geotrichum sp. CS-67, was discovered and tested for tolerance of Cu²⁺, Zn²⁺, and Ni²⁺. Zn²⁺ was the most efficiently sequestered by Geotrichum sp. CS-67 followed by Ni²⁺ and Cu²⁺. Zn²⁺ and Ni²⁺ were actively taken up into the cell, while Cu²⁺ was adsorbed to the cell wall. We used RNA-Seq to show that a large number of genes involved in the physiological and biochemical processing of heavy metals were differentially expressed in this yeast when it was subjected to Zn²⁺ and Ni²⁺ stress. From this panel, we selected the SED1, GDI1 and ZRT1 genes for validation by qRT-PCR and discovered that, during Zn²⁺ and Ni²⁺ stress, SED1 and GDI1 were upregulated, while ZRT1 was downregulated, which was consistent with the RNA-Seq results and the biochemical function of these genes. In conclusion, the novel yeast Geotrichum sp. CS-67 has a marked ability to accumulate heavy metal ions, making it of great interest as a possible microbial agent for heavy metal pollution remediation in the future.

CuO, ZnO, and γ-Fe2O3 nanoparticles modified the underground biomass and rhizosphere microbial community of Salvia miltiorrhiza (Bge.) after 165-day exposure

To investigate whether metal oxide nanoparticles exhibit toxicity or positive effects on medicinal plants, CuO, ZnO, and γ-Fe₂O₃ nanoparticles (NPs), at concentrations of 100 and 700 mg kg^-1_, were introduced into the cultivation of Salvia miltiorrhiza (Bge.). Metal elemental contents, chemical constituents, biomass and the structure of the rhizosphere microbial community was used to estimate this effect. The results indicated CuO NPs increased the Cu content and ZnO NPs increased the Zn content significantly as exposure increased, γ-Fe₂O₃ NPs had no significant effect on Fe content in S. miltiorrhiza roots, while 100 mg kg^-1 ZnO and CuO NPs significantly decreased the Fe content in roots. Additionally, ZnO and γ-Fe₂O₃ NPs increased the underground biomass, and diameter of S. miltiorrhiza roots. However, these three metal oxide nanoparticles had no significant effect on total tanshinones, while the 700 mg kg^-1 γ-Fe₂O₃ NPs treatment increased salvianolic acid B content by 36.46%. High-throughput sequencing indicated at 700 mg kg^-1 ZnO NPs, the relative abundance of Humicola (Zn superoxide dismutase producer), was notably increased by 97.46%, and that of Arenimonas, Thiobacillus and Methylobacillus (taxa related to heavy metal tolerance) was significantly increased by 297.14%, 220.26% and 107.00%. The 700 mg kg^-1 CuO NPs exposure caused a significant increase in the relative abundances of Sphingomonas (a copper-resistant and N₂-fixing genus) and Flavisolibacter (stripe rust biocontrol bacteria) by 127.32% and 118.33%. To our best knowledge, this is the first study to examine the potential impact of NPs on the growth and rhizosphere microorganisms of S. miltiorrhiza.

Biological treatment of hazardous heavy metals by Streptomyces rochei ANH for sustainable water management in agriculture

Microbial bioremediation of heavy metals-polluted industrial effluents has been adopted as one of the most effective eco-friendly tool to cope up with the harmful effects of metals. This study was designed to investigate the biosorption potential of marine actinomycetes isolated from the Alexandrian Mediterranean Seacoast, Egypt, with their potential use in metal remediation of industrial effluents. Among the nine marine actinomycetes isolates, Streptomyces rochei ANH showed the highest versatile metal resistance capability with MIC values of 125 mg/l for Cr⁶⁺ and 60 mg/l for both Cd²⁺ and Pb²⁺. Additionally, scanning electron micrographs showed complete disintegration of Cr⁶⁺-treated biomass compared with the control ones where spores remained intact and connected in long chains. The study also aimed to improve the percentage of Cr⁶⁺ biosorption by S. rochei ANH biomass using the statistical designs of Plackett–Burman and Box-Behnken where up to 85% of Cr⁶⁺ removal was recorded under the following conditions: pH (5), incubation temperature (30 °C), contact time (3 h), agitation speed (90 rpm), initial Cr⁶⁺ concentration (50 mg/l) and living biomass concentration (10 mg/ml). The results also showed that the percentage of Cr⁶⁺ biosorption by S. rochei ANH decreased gradually beyond these values. Moreover, the results revealed that the use of the biomass of S. rochei ANH is an effective biotechnological agent for the biological treatment of heavy metal-contaminated tannery effluent where the percentages of metal removal were in the following order: Ni²⁺ (100%) ≥ Cu²⁺  ≥ Mn²⁺  ≥ Fe²⁺  > Pb²⁺ (95%) ≥ Cd²⁺  > Cr⁶⁺ (86%). Furthermore, the treated effluent exhibited a stimulating effect on the germination process of Lepidium sativum seeds. Therefore, the present study implies that S. rochei ANH can be considered a powerful candidate to mitigate hazardous heavy metals pollution from industrial effluents and improve the water quality for agricultural purposes.

Metarhizium: jack of all trades, master of many

The genus Metarhizium and Pochonia chlamydosporia comprise a monophyletic clade of highly abundant globally distributed fungi that can transition between long-term beneficial associations with plants to transitory pathogenic associations with frequently encountered protozoans, nematodes or insects. Some very common 'specialist generalist' species are adapted to particular soil and plant ecologies, but can overpower a wide spectrum of insects with numerous enzymes and toxins that result from extensive gene duplications made possible by loss of meiosis and associated genome defence mechanisms. These species use parasexuality instead of sex to combine beneficial mutations from separate clonal individuals into one genome (Vicar of Bray dynamics). More weakly endophytic species which kill a narrow range of insects retain sexuality to facilitate host-pathogen coevolution (Red Queen dynamics). Metarhizium species can fit into numerous environments because they are very flexible at the genetic, physiological and ecological levels, providing tractable models to address how new mechanisms for econutritional heterogeneity, host switching and virulence are acquired and relate to diverse sexual life histories and speciation. Many new molecules and functions have been discovered that underpin Metarhizium associations, and have furthered our understanding of the crucial ecology of these fungi in multiple habitats.

Enhanced removal of trichlorfon and Cd(II) from aqueous solution by magnetically separable chitosan beads immobilized Aspergillus sydowii

Simultaneous removal of heavy metals and organics from wastewater has always been an environmental problem with great concern. In this study, a novel ecofriendly bioborbent, magnetic chitosan beads immobilized Aspergillus sydowii (MCBAs) were synthesized and used to simultaneously remove trichlorfon (TCF) and Cd(II) from aqueous solution. MCBAs showed an increased special surface area (55.38 m²·g^-1) through immobilizing A. sydowii and its saturation magnetization reached 14.62 emu·g^-1. The equilibrium removal capacities of TCF and Cd(II) were 135.43 mg·g^-1 and 56.40 mg·g^-1 in the co-system with 200 mg·L^-1 TCF and 50 mg·L^-1 Cd(II), respectively. The removal capacities of TCF and Cd(II) were strongly depended on the immobilized A. sydowii spore concentration, initial concentrations of TCF and Cd(II), and MCBAs dose. TCF biodegradation intermediates were identified by gas chromatography-mass spectrometry system. Fourier transform infrared spectra displayed that -OH and -NH groups on MCBAs mainly participated in the Cd(II) sequestration and the CO stretching vibration was possibly related to the degradation intermediates of TCF. MCBAs exhibited excellent recyclability upto four cycles. Therefore, MCBAs are suitable and effective for the simultaneous removal of TCF and Cd(II) from wastewater.

Application of Beauveria bassiana spore waste as adsorbent to uptake acid red 97 dye from aqueous medium

The adsorption of acid red 97 dye (RED 97) by the waste of the filamentous fungus Beauveria bassiana was analyzed. The adsorbent was obtained as a waste of a fermentative process, and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffractometry (XRD), and specific surface area (BET). After the characterization, adsorption tests were carried out to determine the ideal conditions of pH, adsorbent mass, and contact time for the process. Adsorption isotherms, thermodynamic studies, and the treatment of textile effluent were also investigated. The adsorbent characterization allowed the visualization of its amorphous structure, with irregular and heterogeneous particles. The pore diameter was 51.9 nm and the surface area was 0.247 m² g^-1. 1.2 g L^-1 of the adsorbent and pH of 2.0 were the ideal conditions for RED 97 adsorption. The pseudo-second-order kinetic model was the most appropriate to represent the experimental data, being the equilibrium reached in about 110 min. The Langmuir model was the most suitable to represent the equilibrium data, with maximum adsorption capacity of 194.1 mg g^-1 at 45 °C. The adsorption processes was thermodynamically spontaneous, favorable, and exothermic. In the treatment of a real textile effluent, 5 g L^-1 of the spores was capable to decolorize 70% of the solution. Therefore, spore wastes of Beauveria bassiana were promising for RED 97 adsorption.

Potentiality of Neopestalotiopsis clavispora ASU1 in biosorption of cadmium and zinc

In this study, a fungal isolate was isolated from avocado fruit collected from a market in Makkah city, Saudi Arabia, and identified as Neopestalotiopsis clavispora ASU1. The biomass of Neopestalotiopsis clavispora ASU1 was used as a natural bio-sorbent for removal of Cd(II) and Zn(II) from aqueous solutions. Characterization of fungal biomass was performed using Fourier transform infrared spectroscopy, X-ray Diffractometer, and BET surface area. Different factors on Cd(II) and Zn(II) biosorption were studied to evaluate the maximum conditions for metals biosorption. The (q_max) for Cd(II) and Zn (II) by N. clavispora ASU1 calculated from the Langmuir adsorption isotherm was 185.3 ± 0.25 and 153.8 ± 0.21 mg/g, respectively. Based on r², the equilibrium biosorption isotherms fitted well with Langmuir model than Freundlich isotherm. The adsorption kinetics was studied, and the biosorption followed to the pseudo-second-order model. Thus, the current study indicated that the biomass of N. clavispora ASU1 is an effective adsorbent for the removal of heavy metals from aqueous solutions.

Isolation, identification and characterization of arsenic transforming exogenous endophytic Citrobacter sp. RPT from roots of Pteris vittata

The aim of the present study was to assess the arsenic (As) transformation potential of endophytic bacteria isolated from roots of Pteris vittata plant. The endophytic bacterium was tested for minimal inhibitory concentration (MIC) against As. The endophytic strain RPT exhibited the highest resistance to As(V) (400 mg/l). Phylogenetic analysis of the 16S rRNA sequence suggested that strain RPT was a member of genus Citrobacter. The As transformation assay revealed As(III) oxidation and As(V) reduction potential of Citrobacter sp. RPT. The As resistance mechanism was further confirmed by amplification of arsC and aoxB genes. The growth kinetics of strain RPT was altered slightly in the presence of different concentration (100-400 mg/l) of As stress. Temperature and pH influenced the As removal rate. The maximum As removal was observed at pH 7.0 (74%) and 37 °C (70.9%). The results suggest that strain RPT can survive under the As stress and has been identified as a potential candidate for application in bioremediation of As in contaminated environments.

Bioremediation of heavy metals using an endophytic bacterium Paenibacillus sp. RM isolated from the roots of Tridax procumbens

The aim of the present study was to assess the bioremediation potential of endophytic bacteria isolated from roots of Tridax procumbens plant. Five bacterial endophytes were isolated and subsequently tested for minimal inhibitory concentration (MIC) against different heavy metals. Amongst the five isolates, strain RM exhibited the highest resistance to copper (750 mg/l), followed by zinc (500 mg/l), lead (450 mg/l), and arsenic (400 mg/l). Phylogenetic analysis of the 16S rDNA sequence suggested that strain RM was a member of genus Paneibacillus. Strain RM also had the capacity to produce secondary metabolites, indole acetic acid, siderophores, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and biosurfactant and solubilize phosphate. The growth kinetics of strain RM was altered slightly in the presence of metal stress. Temperature and pH influenced the metal removal rate. The results suggest that strain RM can survive under the high concentration of heavy metals and has been identified as a potential candidate for application in bioremediation of heavy metals in contaminated environments.

Multiple heavy metal removal using an entomopathogenic fungi Beauveria bassiana

Towards the development of a potential remediation technology for multiple heavy metals [Zn(II), Cu(II), Cd(II), Cr(VI) and Ni(II)] from contaminated water, present study examined the growth kinetics and heavy metal removal ability of Beauveria bassiana in individual and multi metals. The specific growth rate of B. bassiana varied from 0.025h(-1) to 0.039h(-1) in presence of individual/multi heavy metals. FTIR analysis indicated the involvement of different surface functional groups in biosorption of different metals, while cellular changes in fungus was reflected by various microscopic (SEM, AFM and TEM) analysis. TEM studies proved removal of heavy metals via sorption and accumulation processes, whereas AFM studies revealed increase in cell surface roughness in fungal cells exposed to heavy metals. Present study delivers first report on the mechanism of bioremediation of heavy metals when present individually as well as multi metal mixture by entomopathogenic fungi.