Hairy root induction and phytoremediation of textile dye, Reactive green 19A-HE4BD, in a halophyte, Sesuvium portulacastrum (L.) L

Contamination of textile dyes in aquatic environment: Adverse impacts on aquatic ecosystem and human health, and its management using bioremediation

Textile dyes are the burgeoning environmental contaminants across the world. They might be directly disposed of from textile industries into the aquatic bodies, which act as the direct source for the entire ecosystem, ultimately impacting the human beings. Hence, it is essential to dissect the potential adverse outcomes of textile dye exposure on aquatic plants, aquatic fauna, terrestrial entities, and humans. Analysis of appropriate literature has revealed that textile dye effluents could affect the aquatic biota by disrupting their growth and reproduction. Various aquatic organisms are targeted by textile dye effluents. In such organisms, these chemicals affect their development, behavior, and induce oxidative stress. General populations of humans are exposed to textile dyes via the food chain and drinking contaminated water. In humans, textile dyes are biotransformed into electrophilic intermediates and aromatic amines by the enzymes of the cytochrome family. Textile dyes and their biotransformed products form the DNA and protein adducts at sub-cellular moiety. Moreover, these compounds catalyze the production of free radicals and oxidative stress, and trigger the apoptotic cascades to produce lesions in multiple organs. In addition, textile dyes modulate epigenetic factors like DNA methyltransferase and histone deacetylase to promote carcinogenesis. Several bioremediation approaches involving algae, fungi, bacteria, biomembrane filtration techniques, etc., have been tested and some other hybrid systems are currently under investigation to treat textile dye effluents. However, many such approaches are at the trial stage and require further research to develop more efficient, cost-effective, and easy-to-handle techniques.

Biodegradation of furfuryl alcohol by indigenous Bacillus species of industrial effluent-contaminated sites: estimation, biokinetics and toxicity assessment of bio-transformed metabolites

Furfuryl alcohol (FA) and other furanic compounds have garnered considerable attention in the quest for sustainable alternatives. FA-based resins have been used in various sectors that entail the release of FA into the environment. Hence, to ensure sustainability in this scenario, devising a dependable approach to its degradation is imperative. Given the crucial role of bacterial strains in the biodegradation of various organic pollutants, this study investigates the microbial degradation of FA, using bacterial strains isolated from sites that are constantly exposed to industrial waste. Three potential isolates were identified as B. paramycoides, B. cereus, and B. tequilensis by 16S rRNA gene sequencing. At a concentration of 300 µg/ml, these isolates demonstrated efficient FA degradation; 60-70% (at 300 µg/ml FA) and 50-60%, (at 500 µg/ml FA). Fourier-transform infrared (FTIR) spectroscopy and High-Performance Liquid Chromatography (HPLC) analysis further supported the result that the bacterial isolates consumed FA as the carbon source. Liquid chromatography-mass spectrometry (LC-MS) facilitates the detection of the major metabolic intermediate product in which FA gets transformed. The prominent peaks at 113 and 119 m/z obtained in the MS spectra of the degraded FA samples indicated the possibility of the conversion of FA into furoic acid or levulinic acid. The phytotoxicity bioassay findings revealed the non-toxic nature of the bio-transformed products as compared to pure FA. This investigation presents the initial documentation of the FA degradative potential of Bacillus strains, thereby augmenting the understanding of the prospective implementation of Bacillus species in industrial waste treatment projects.

Induction and metabolomic analysis of hairy roots of Atractylodes lancea

Atractylodes lancea is an important source of traditional Chinese medicines. Sesquiterpenoids are the key active compounds in A. lancea, and their presence determines the quality of the material. Hairy hoot (HR) culture is a potential method to produce medicinally active compounds industrially; however, the induction and metabolic profiling of A. lancea HR have not been reported. We found that optimal induction of A. lancea HR was achieved by Agrobacterium rhizogenes strain C58C1 using the young leaves of tissue culture seedlings in the rooting stage as explants. Ultra-performance liquid chromatography-tandem mass spectrometric analyses of the chemical compositions of HR and normal root (NR) led to the annotation of 1046 metabolites. Over 200 differentially accumulated metabolites were identified, with 41 found to be up-regulated in HR relative to NR and 179 down-regulated in HR. Specifically, atractylodin levels were higher in HR, while the levels of β-eudesmol and hinesol were higher in NR. Metabolic pathway analyses showed a significant difference in metabolites of the shikimate acid pathway between HR and NR. Five A. lancea compounds are potential biomarkers for evaluation of HR and NR quality. This study provides an important reference for the application of HR for the production of medicinally active compounds. KEY POINTS: • We established an efficient protocol for the induction of HR in A. lancea • HR was found to have a significantly higher amount of atractylodin than did NRs • Metabolic pathway analyses showed a significant difference in metabolites of the shikimate acid pathway between HR and NR.

Hydroxyapatite@Mn-Fe composite as a reusable sorbent for removal of Nile blue dye and Cr(VI) from polluted water

In this study, hydroxyapatite@Mn-Fe composite was used as a novel adsorbent to eliminate Nile blue (NB) dye and hexavalent chromium ion (Cr(VI)) from aqueous media. Different analyses such as FTIR, Map, SEM, EDX, BET, and XRD were used to study the characteristics of the composite. The highest sorption efficiencies of Cr(VI) and NB at pH 2 and 10 were 97.63% and 98.83%, respectively, which are significant values. Equilibrium and kinetic studies of the sorption process showed that the Freundlich isotherm model and pseudo-second-order kinetic model can better describe the equilibrium and kinetic behavior of the sorption process. According to the Langmuir model, the maximum sorption capacities of NB dye and Cr(VI) ion using the hydroxyapatite@Mn-Fe composite were 0.259 and 0.938 mmol/g, respectively. Also, the results of the thermodynamic study showed that the sorption process is favorable (ΔS° =  - 34.2 kJ/mol·K for Cr(VI) and - 144.6 kJ/mol·K for NB), spontaneous (ΔG° < 0), and exothermic (ΔH° =  - 27.99 kJ/mol for Cr(VI) and - 64.2 kJ/mol for NB). Moreover, the desorption process of both contaminants using the hydroxyapatite@Mn-Fe composite showed that the H₂SO₄ solution with a concentration of 3 mol/L can remove both contaminants separately with the highest efficiency. Furthermore, the reusability study indicated that the composite can be used in five reuse cycles without significant decrease in its efficiency. Besides, the composite was able to eliminate color, turbidity, COD, and BOD₅ from the textile wastewater with removal efficiencies of 93.06, 81.61, 76.05, and 71.88%, respectively. To the best of our knowledge, hydroxyapatite@Mn-Fe composite was synthesized and used for the first time to remove Cr(VI) ions and NB dye. In general, the aforementioned composite is recommended for industrial wastewater treatment.

Application of In Vitro Plant Tissue Culture Techniques to Halophyte Species: A Review

Halophytes are plants able to thrive in environments characterized by severe abiotic conditions, including high salinity and high light intensity, drought/flooding, and temperature fluctuations. Several species have ethnomedicinal uses, and some are currently explored as sources of food and cosmetic ingredients. Halophytes are considered important alternative cash crops to be used in sustainable saline production systems, due to their ability to grow in saline conditions where conventional glycophyte crops cannot, such as salt-affected soils and saline irrigation water. In vitro plant tissue culture (PTC) techniques have greatly contributed to industry and agriculture in the last century by exploiting the economic potential of several commercial crop plants. The application of PTC to selected halophyte species can thus contribute for developing innovative production systems and obtaining halophyte-based bioactive products. This work aimed to put together and review for the first time the most relevant information on the application of PTC to halophytes. Several protocols were established for the micropropagation of different species. Various explant types have been used as starting materials (e.g., basal shoots and nodes, cotyledons, epicotyls, inflorescence, internodal segments, leaves, roots, rhizomes, stems, shoot tips, or zygotic embryos), involving different micropropagation techniques (e.g., node culture, direct or indirect shoot neoformation, caulogenesis, somatic embryogenesis, rooting, acclimatization, germplasm conservation and cryopreservation, and callogenesis and cell suspension cultures). In vitro systems were also used to study physiological, biochemical, and molecular processes in halophytes, such as functional and salt-tolerance studies. Thus, the application of PTC to halophytes may be used to improve their controlled multiplication and the selection of desired traits for the in vitro production of plants enriched in nutritional and functional components, as well as for the study of their resistance to salt stress.

Toxicity Mitigation of Textile Dye Reactive Blue 4 by Hairy Roots of Helianthus annuus and Testing Its Effect in In Vivo Model Systems

An anthraquinone textile dye, Reactive Blue 4 (RB4), poses environmental health hazards. In this study, remediation of RB4 (30-110 ppm) was carried out by hairy roots (HRs). UV-visible spectroscopy and FTIR analysis showed that the dye undergoes decolourization followed by degradation. In addition, toxicity and safety analyses of the bioremediated dye were performed on Allium cepa and zebrafish embryos, which revealed lesser toxicity of the bioremediated dye as compared to untreated dye. For Allium cepa, the highest concentration, i.e., 110 ppm of the treated dye, showed less chromosomal aberrations with a mitotic index of 8.5 ± 0.5, closer to control. Two-fold decrease in mortality of zebrafish embryos was observed at the highest treated dye concentration indicating toxicity mitigation. A higher level of lipid peroxidation (LPO) was recorded in the zebrafish embryo when exposed to untreated dye, suggesting a possible role of oxidative stress-inducing mortality of embryos. Further, the level of LPO was significantly normalized along with the other antioxidant enzymes in embryos after dye bioremediation. At lower concentrations, mitigated samples displayed similar antioxidant activity comparable to control underlining the fact that the dye at lesser concentration can be more easily degraded than the dye at higher concentration.

Integrated physical-biological treatment system for batik industry wastewater: A review on process selection

Batik is well known as one of the unique identifiers of the Southeast Asian region. Several countries that still preserve the batik heritage are Malaysia, Indonesia, China and India. The Batik industry holds a significant place in Malaysia's craft-based industry. In Malaysia, batik motifs and patterns are mostly hand-drawn and painted directly on fabric, therefore, each one is unique. The players in the Batik industry are mostly small businesses and cottage industries, particularly in the states of Kelantan, Terengganu, Pahang, Sabah and Sarawak. However, their market growth and contribution are not synchronized with the treatment system. The wastewater generated by this industry rarely meets standard effluent requirements and regulations, thus worrying the authorities. Batik wastewater is categorized as one of the highly polluted wastewaters. The toxicity of pollutants from batik may reduce environmental quality and pose a risk to human health. Batik wastewater needs extensive treatment, since no complete and appropriate treatment has been applied for so many years in specific batik industries. This paper reviews the batik industry in Malaysia, its wastewater generation and the available current treatment practices. It discusses integrated treatments of coagulation-flocculation and phytoremediation technology as a batik wastewater treatment process with potential utility in the batik industry. This review may become part of the guidance for the entire batik industry, especially in Malaysia.

Remediation of endosulfan-contaminated water by hairy roots: removal and phytometabolization assessment

Although many countries banned the insecticide endosulfan, it is still an environmental pollutant. Plants metabolize the two diastereomers of the formulations known as technical grade endosulfan (TGE) by two phase I pathways: hydrolysis leading to less toxic derivatives and oxidation giving endosulfan sulfate which is as toxic as endosulfan itself. We assessed the removal, bioaccumulation and phase I metabolization of TGE from water matrices using hairy root clones (HRs) of three edible species, Brassica napus, Raphanus sativus and Capsicum annuum. B. napus and C. annuum HRs removed 86% of TGE from the bioreaction media in 2 and 96 h, respectively, whereas R. sativus HRs removed 91% of TGE within 6 h of biotreatment. In the experiments with B. napus, only endosulfan sulfate was detected in both biomass and medium, whereas R. sativus and C. annuum accumulated endosulfan sulfate and endosulfan alcohol. Besides, endosulfan lactone was detected in C. annuum reaction medium. Acute ichthyotoxicity assays toward Poecilia reticulata showed that media contaminated with TGE lethal levels did not produce mortality after the phytotreatments. This research highlights the feasibility of using HRs to evaluate plant enzymatic abilities toward xenobiotics and their potential for the design of ex situ decontamination processes.

Antibacterial efficacy of poly(hexamethylene biguanide) immobilized on chitosan/dye-modified nanofiber membranes

This study aimed to develop a novel electrospun polyacrylonitrile (PAN) nanofiber membrane with the enhanced antibacterial property. The PAN nanofiber membrane was first subjected to alkaline hydrolysis treatment, and the treated membrane was subsequently grafted with chitosan (CS) to obtain a CS-modified nanofiber membrane (P-COOH-CS). The modified membrane was then coupled with different dye molecules to form P-COOH-CS-Dye membranes. Lastly, poly(hexamethylene biguanide) hydrochloride (PHMB) was immobilized on the modified membrane to produce P-COOH-CS-Dye-PHMB. Physical characterization studies were conducted on all the synthesized nanofiber membranes. The antibacterial efficacies of nanofiber membranes prepared under different synthesis conditions were evaluated systematically. Under the optimum synthesis conditions, P-COOH-CS-Dye-PHMB was highly effective in disinfecting a high concentration of Escherichia coli, with an antibacterial efficacy of approximately 100%. Additionally, the P-COOH-CS-Dye-PHMB exhibited an outstanding wash durability as its antibacterial efficacy was only reduced in the range of 5%-7% even after 5 repeated cycles of treatment. Overall, the experimental results of this study suggested that the P-COOH-CS-Dye-PHMB is a promising antibacterial nanofiber membrane that can be adopted in the food, pharmaceutical, and textile industries.

Role of Salvinia molesta in biodecolorization of methyl orange dye from water

In the present study, the potential of Salvinia molesta for biodecolorization of methyl orange (MO) dye from water was examined. Six glass vessels were filled with 4 L of water contaminated with MO with three concentrations (5, 15, and 25 mg/L), three with plants and another three without plant as contaminant control. The influence of operational parameters, including initial dye concentration, pH, temperature, and plant growth, on the efficacy of the biodecolorization process by S. molesta was determined. Temperature and pH was in the range of 25-26 °C and 6.3 to 7.3, respectively. Phytotransformation was monitored after 10 days through Fourier transform infrared (FTIR) spectroscopy, and a significant variation in the peak positions was demonstrated when compared to the control plant spectrum, indicating the adsorption of MO. The highest biodecolorization was 42% in a 5 mg/L MO dye concentration at pH 7.3 and at 27 °C. According to the FTIR results, a potential method for the biodecolourization of MO dye by S. molesta was proven. Salvinia molesta can be successfully used for upcoming eco-friendly phytoremediation purposes for dye removal.

Biotransformation of xenobiotics by hairy roots

The exponential industrial growth we see today rides on the back of large scale production of chemicals, explosives and pharmaceutical products. However, the effluents getting released from their manufacturing units are greatly compromising the sustainability of our environment. With greater awareness of the imperative for environmental clean-up, a promising approach that is attracting increasing research interests is biodegradation of xenobiotics. In this approach, biotransformation has proven to be one of the most effective tools. While many different model frameworks have been used to study different aspects of biotransformation, hairy roots (HRs) have been found to be exceptionally valuable. HR cultures are preferred over other in-vitro model systems due to their biochemical stability and hormone-autotrophy. In addition, the multi-enzyme biosynthetic potential of HRs which is similar to the parent plant and their relatively low-cost cultural requirements further characterize their suitability for biotransformation. The recent progress observed in scale-up of HR cultures and understanding of functional genomics has opened up new dimensions providing valuable insights for industrial application. This review article summarizes the potential of HR cultures in the biotransformation of xenobiotics, their limitations in the application on a large scale and current strategies to alleviate them. Advancement in bioreactors engineering enabling large scale cultivation and modern gene technologies improving biotransformation efficiency promises to extend laboratory results to industrial applications.

Targeting Acr3 from Ensifer medicae to the plasma membrane or to the tonoplast of tobacco hairy roots allows arsenic extrusion or improved accumulation. Effect of acr3 expression on the root transcriptome

Transgenic tobacco hairy roots expressing the bacterial arsenite efflux pump Acr3 from Ensifer medicae were generated. The gene product was targeted either to the plasma membrane (ACR3 lines) or to the tonoplast by fusing the ACR3 protein to the tonoplast integral protein TIP1.1 (TIP-ACR3 lines). Roots expressing Acr3 at the tonoplast showed greater biomass than those expressing Acr3 at the plasma membrane. Furthermore, higher contents of malondialdehyde (MDA) and RNA degradation in ACR3 lines were indicative of higher oxidative stress. The determination of ROS-scavenging enzymes depicted the transient role of peroxidases in ROS detoxification, followed by the action of superoxide dismutase during both short- and medium-term exposure periods. Regarding As accumulation, ACR3 lines accumulated up to 20-30% less As, whereas TIP-ACR3 achieved a 2-fold increase in As accumulation in comparison to control hairy roots. Strategies that presumably induce As uptake, such as phosphate deprivation or dehydration followed by rehydration in the presence of As, fostered As accumulation up to 10 800 μg g-1. Finally, the effects of the heterologous expression of acr3 on the root transcriptome were assessed. Expression at the plasma membrane induced drastic changes in gene expression, with outstanding overexpression of genes related to electron transport, ATP synthesis and ATPases, suggesting that As efflux is the main detoxification mechanism in these lines. In addition, genes encoding heat shock proteins and those related to proline synthesis and drought tolerance were activated. On the other hand, TIP-ACR3 lines showed a similar gene expression profile to that of control roots, with overexpression of the glutathione and phytochelatin synthesis pathways, together with secondary metabolism pathways as the most important resistance mechanisms in TIP-ACR3, for which As allocation into the vacuole allowed better growth and stress management. Our results suggest that modulation of As accumulation can be achieved by subcellular targeting of Acr3: expression at the tonoplast enhances As accumulation in roots, whereas expression at the plasma membrane could promote As efflux. Thus, both approaches open the possibilities for developing safer crops when grown on As-polluted paddy soils, but expression at the tonoplast leads to better growth and less stressed roots, since the high energy cost of As efflux likely compromises growth in ACR3 lines.

Phytoremediation of Palm Oil Mill Effluent (POME) Using Eichhornia crassipes

It is inevitable that the manufacturing process of palm oil is accompanied by the generation of a massive amount of high strength wastewater, namely palm oil mill effluent (POME), which could pose serious threat to the aquatic environment. POME which contains high organic compounds originating from biodegradable materials causes water pollution if not properly managed. Palm oil industries are facing the challenges to make ends meet in the aspects of natural assurance, financial reasonability and development sustainability. It is therefore crucial to seek a practical solution to achieve the goal of environmental protection while continuing the economic sustainability. Phytoremediation has been proven as a potential method for removal or degradation of various hazardous contaminants. However, research on phytoremediation of POME using Eichhornia crassipes (E. crassipes) is still limited. This study aims to determine the feasibility of applying phytoremediation technique using E. crassipes for POME treatment. The effects of pH, plant:POME ratio and retention time on the biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solid (TSS) of POME were investigated. The highest BOD removal of 92.6% was achieved after 21 days retention time at pH 4 with plant:POME ratio of 1:20 kg/L. The highest COD removal of 20.7% was achieved after 14 days retention time at pH 6 with plant:POME ratio of 1:20 kg/L. Phytoremediation using E. crassipes was shown to be a promising eco-friendly technique for POME treatment, and is therefore recommended as a good alternative treatment solution for this industrial effluent.

Effect of light on the kinetics and equilibrium of the textile dye (Reactive Red 120) adsorption by Helianthus annuus hairy roots

The study demonstrates for the first time that light influences the adsorption equilibrium and kinetics of a dye by root culture system. The azo dye (Reactive Red 120) adsorption by the hairy roots of H. annuus followed a pseudo first-order kinetic model and the adsorption equilibrium parameters were best estimated using Langmuir isotherm. The maximum dye adsorption capacity of the roots increased 6-fold, from 0.26 mg g^-1 under complete dark conditions to 1.51 mg g^-1 under 16/8 h light/dark photoperiod. Similarly, adsorption rate of the dye and removal (%) also increased in the presence of light, irrespective of the initial concentration of the dye (20-110 mg L^-1). The degradation of the azo dye upon adsorption by the hairy roots of H. annuus was also confirmed. In addition, a strategy for simultaneous dye removal and increased alpha-tocopherol (industrially relevant) production by H. annuus hairy root cultures has been proposed and demonstrated.

Concurrent uptake and metabolism of dyestuffs through bio-assisted phytoremediation: a symbiotic approach

Manipulation of bio-technological processes in treatment of dyestuffs has attracted considerable attention, because a large proportion of these synthetic dyes enter into natural environment during synthesis and dyeing operations that contaminates different ecosystems. Moreover, these dyestuffs are toxic and difficult to degrade because of their synthetic origin, durability, and complex aromatic molecular structures. Hence, bio-assisted phytoremediation has recently emerged as an innovative cleanup approach in which microorganisms and plants work together to transform xenobiotic dyestuffs into nontoxic or less harmful products. This manuscript will focus on competence and potential of plant-microbe synergistic systems for treatment of dyestuffs, their mixtures and real textile effluents, and effects of symbiotic relationship on plant performances during remediation process and will highlight their metabolic activities during bio-assisted phytodegradation and detoxification.

Enhanced production of an anti-malarial compound artesunate by hairy root cultures and phytochemical analysis of Artemisia pallens Wall

Artemisinin and its derivatives are still one of the most effective drugs for the treatment of malaria. Artemisia pallens commonly known as Dhavanam, is an aromatic herb belonging to the family Asteraceae. Increasing the artemisinin content of A. pallens by genetic engineering would improve the availability of this much needed drug. In the present study, Agrobacterium rhizogenes (strain NCIM 5140) mediated genetic transformation of Artemisia pallens were carried out for hairy root induction. The effect of different media (Half MS, MS, MS along with BAP 0.5 mg/l and MS along with Kinetin 0.5 mg/l) and type of explants (leaf and stem) on hairy root induction and culture were also studied. Maximum transformation efficiency (70.0 %) was observed in case of stem explants when it was co-cultivated with Agrobacterium rhizogenes and kept on half strength MS media. Artesunate is a derivative of artemisinin, was quantified using HPLC from dried aerial extract and hairy roots. The content of artesunate in hairy roots was increased up to twofold as compared to aerial part of Artemisia pallens. The maximum amount of artesunate found in hairy roots was 5.62 ± 0.16 μg/g of dry weight. Apart from artesunate the other phytochemicals like alkaloids, polyphenols, and flavonoids are important because they impart the medicinal properties in this plant. Therefore, we have also quantified total alkaloids, flavonoids and polyphenolic content in the aerial part of the plants. The total alkaloids and flavonoids content were found 1.72 ± 0.00 mg/g dry weight in aqueous extract and 3.8 ± 0.00 mg/g in methanolic extract in terms of colchicine and rutin equivalents, respectively. Similarly, total phenolic content is 3.70 ± 0.01 mg/g in ethanolic extract in terms of tannic acid equivalent.