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COVID-19 (Coronavirus disease of 2019) pandemic is one of the largest health threats the planet has faced in recent decades. Efforts are being continuously made to design a viable drug or a vaccine. Several natural and synthetic molecules are under study for their potency to inhibit viral replication. In order to emphasize the importance of microbial-based natural components in antiviral drug discovery, an attempt has been made through this study to find potential inhibitors for SARS-CoV-2 Papain-Like protease (PLpro) molecule from microbial sources. PLpro, with its multifunctional roles like viral polypeptide proteolysis and suppression of the host's innate immune response, is acting as a potential drug target. The X-ray crystal structure of PLpro and ligand molecules were retrieved from the protein structure database and Npatlas database, respectively. The molecules were screened based on drug likeliness and the pharmacophore model created in reference to a known potent PLpro inhibitor GRL0617. Totally 3272 molecules have undergone the docking process and the complexes of top hits were subjected to 100 ns molecular dynamic simulation. The results showed that Holyrine B, Dihydroarcyriarubin C, Baraphenazine C and 3-hydroxy-3'-N-acetylholyrine A had formed a stable complex in the active site of the PLpro with significant interaction efficiency. Earlier studies showed that Holyrine B could also be a possible inhibitor of the Main protease of SARS-CoV-2, which increases its significance in the process of COVID-19 drug development. In conclusion, these microbial compounds can be considered as possible SARS-CoV-2 inhibitors for further in vitro studies. Communicated by Ramaswamy H. Sarma.

Worldwide ever-augmenting urbanization, modernization, and industrialization have contributed to the release of pernicious compounds and a variety of pollutants into the environment. The pollutants discharged due to industrialization are of global concern. Industrial waste and effluent are comprised of hazardous organic and inorganic chemicals including heavy metals which pose a significant threat to the environment and may bring about numerous diseases or abnormalities in human beings. This brings on greater urgency for remediation of these polluted soil and water using sustainable approaches and mechanisms. In the present research, a multi-metal-resistant, gram-positive, non-virulent bacterial strain Bacillus sp. GH-s29 was isolated from contaminated groundwater of Bhojpur district, Bihar, India. The strain had the potential to develop a biofilm that was able to remediate different heavy metals [arsenic, cadmium, and chromium] from individual and multi-heavy metal solutions. Maximum removal for As (V), Cd (II), and Cr (VI) from individual-metal and the multi-metal solution was observed to be 73.65%, 57.37%, 61.62%, and 48.92%, 28.7%, and 35.46%, respectively. SEM-EDX analysis revealed the sequestration of multi-heavy metals by bacterial biofilm. Further characterization by FTIR analysis ensured that the presence of negatively charged functional groups on the biofilm-EPS such as hydroxyl, phosphate, sulfate, and carboxyl helps in binding to the positively charged metal ions. Thus, Bacillus sp. GH-s29 proved to be an effective and economical alternative for different heavy metal remediation from contaminated sites.

Nanoparticles have excellent catalytic, adsorptive, and reactive properties, which led to their application for wastewater treatment. The current study focuses on silver nanoparticle synthesis using neem leaf and banana peel extract and its application as an antimicrobial and dye degrading agent for wastewater treatment. The use of these extracts led to a rapid, simple, and environment-friendly method for the biosynthesis of silver nanoparticles (AgNPs). UV-Vis spectroscopy showed absorption bands at 473 and 423 nm for AgNPs synthesized from neem leaf and banana peel extracts, respectively. The AgNPs were further characterized using XRD, FTIR, ESEM, EDX, and DLS methods. XRD data confirmed the crystalline nature of the synthesized AgNPs. ESEM images revealed the synthesized nanoparticles were spherical. From DLS analysis the average diameter of the AgNPs was found to be 168.7 nm from banana peel and 206.4 nm from neem leaf extract. Antibacterial activity of synthesized nanoparticles at 0.025 mg/ml concentration was tested against Escherichia coli (E.coli), Bacillus subtilis (B.subtilis), Staphylococcus aureus (S.aureus), and Klebsiella sp. using disk diffusion method and the zone of inhibitions observed were 10-13, 3-4, 2-3, and 1-3 nm respectively. 99% degradation of model dye malachite green was observed using banana peels-derived nanoparticles at a concentration of 0.06 mg/ml within 4.5 h. This study provides an eco-friendly and economic approach to AgNP synthesis and its potential application in the removal of hazardous dye from wastewater.

Biosorption is an environment-friendly and economic technique to remediate heavy metals from aqueous systems. In the present study, Artocarpus heterophyllus seed powder was used as a biosorbent material to remove different heavy metals. The batch adsorption studies confirmed the higher removal percentage of the Artocarpus heterophyllus (jackfruit) seed powder for arsenic (As

Ethanol has gained its importance as one of the highly demanded biofuels and is being produced from different food crops or food crop wastes after vigorous pretreatment compelling the production process economically incompatible to some extent. The process also becomes non-ecofriendly as the pretreatment process generally produces acid fumes and toxic effluents as well as consumes high energy. In this current study, the potential of the banana peel as a probable substrate for ethanol production was evaluated with the help of logical prediction. Moreover, a single-step ethanol production process was investigated to eliminate hazardous pretreatment processes. A potential bacterial strain SWET4 was isolated from a sewage treatment pond and was identified as a member of the Klebsiella genus by partial sequencing of the 16S rRNA gene. The isolated strain showed ethanol tolerance up to 12% and exhibited its potential as a cellulolytic strain. The bacterial strain SWET4 was found able to ferment banana peel in MSM broth without any other carbon source with a comparatively prolonged lag phase of cellular growth. Trace of ethanol in banana peel fermentation broth of SWET4 was confirmed by high-pressure liquid chromatography. The optimization study for ethanol production enlightened the fact that high temperature and pH supported higher ethanol production. However, due to the growth restriction of the bacterial cell at higher temperatures and pH, only 40 °C and pH 8 were considered optimum. At the optimum substrate concentration (40 g l−1), ethanol concentration was found to be 5.48 g l−1 after 5 days of incubation which summed as a total yield of 0.137 g of ethanol per g of dried banana peel. This current study evaluates the potential of banana peel as a probable substrate for ethanol production and emphasizes on a new possibility of single-step ethanol production without any pretreatment, although metabolic optimization of the strain SWET4 is required to make the process industrially feasible.

Dry powder of fruit wastes including pomegranate, grapes, lime, apple, and papaya was used to examine their pigment extraction capability. Solvent combination of hexane and acetone (1:1) produced the maximum extraction for lime waste with a yield of 1.65%. Gas Chromatography and Mass Spectrometry analysis of the crude pigment of lime exhibited the abundance of compounds like chlorogenic acid, caffeic acid, and coumaric acid. Three major bands were obtained in Thin Layer Chromatography. Column Chromatographic purification using ethyl acetate and hexane mixture as eluting phase showed a retention factor of 0.62 for the major band. Nuclear Magnetic Resonance revealed the final structure of the compound as chlorogenic acid. Slight inhibition was exhibited by the compound against Escherichia coli. Adsorption of arsenate by residual fruit waste revealed the highest adsorption in grapes with 92% efficiency. This study enlightens an alternative approach of fruit waste management with the production of value-added products and its utilization of residue as bioadsorbent.

Ethanol tolerant strains were isolated from the marine waters of Digha and Shankarpur of West Bengal, India and screened for ethanol production using several domestic wastes including, paper, kitchen, garden, and fruit wastes. Strain E4 was found to be the most efficient in ethanol production through fermentation of kitchen and fruit waste. Phylogenetic analysis of the 16S rRNA gene of strain E4 showed its closeness to Citrobacter sp. Production of 2.96 g/l of ethanol was obtained using fruit waste using High-Performance Liquid Chromatography (HPLC) analysis. The yield of ethanol production was obtained as 0.13 g of ethanol/g of reducing sugar present in fruit waste. Although after optimization of fermentation condition, the yield was improved to 0.30 in batch scale. The production was optimized using Central Composite Design. The production was scaled up to 4 l culture volume in the stirred tank bioreactor. Finally, a distillation of fermentation broth resulted in 16.10 ml of product with a yield of 0.30 g of ethanol from 1 g of fruit waste. Thus the isolated marine strain Citrobacter sp. E4 could be potentially used for ethanol production from fruit wastes without any pretreatment in a cost-effective and eco-friendly way.

Synthetic dyes are established colorants in the pharmaceutical industries for the coating and coloration of tablets, capsules, etc. to mark the specific formulation and dosage, improve the stability, and esthetic value. The pharmaceuticals manufacturing process releases large volumes of dye-containing wastewaters, contributing to eco-toxic concerns related to different health risks. In this study, biodegradation of amaranth, sunset yellow, tartrazine, indigo carmine, and quinoline yellow dyes was investigated in the mixed environment. Initially, 24 tolerant bacterial strains were isolated from pharmaceutical wastewater samples, among which 19 strains were found to be non-virulent. Five different consortia were constructed by considering the 19 strains among which C1 consisting of strains DY7, 10, 11, and 18 was found to be the most potential consortium with an overall efficiency of 96.65% dye degradation in the presence of glucose after 15 days. The strains DY7, 10, 11, and 18 were identified as members of the Klebsiella genus by 16S rRNA partial sequencing. The cell wall structure, carbohydrate utilization profile, and metabolic characterization were conducted on the selected strains of C1. Among the 25 different antibiotics, DY7 and DY11 exhibited the highest zone of growth inhibition in the presence of cefixime, and DY10 was restricted by chloramphenicol whereas DY18 was found sensitive to ceftazidime/tazobactam.

Pigment-producing bacteria were isolated from kitchen wastewaters of the National Institute of Technology, Rourkela. A pink non-virulent bacterial strain PWN1 was selected based on the India Ink Broth and Coomassie Brilliant Blue (R-250) dye assay. According to morphological and biochemical characterization, the strain PWN1was a Gram-negative, rod-shaped, motile, non-coliform bacterium and could utilize only glucose and adonitol as sole carbon source. The pigment was found to be a growth-associated product, and the pigment production was accelerated after 40 h of bacterial culture. Further, 16S rRNA gene-based molecular identification showed its similarity with Enterobacter sp. The pigments were extracted by the solvent extraction method using chloroform and ethanol (3:1). The extracted pigments were then purified through thin-layer chromatography and column chromatography. To maximize pigment production, the culture condition was optimized for maximum biomass production using statistical software Design Expert v13. A quadratic model was structured describing the process efficiently and it suggested a moderate temperature, pH, and a high inoculum concentration which generated biomass of 3.81 ± 0.02 g/L. At optimized condition, 1 L of cell culture produced 3.77 g of biomass which produced a crude pigment of 0.234 g after solvent extraction and 0.131 g after column chromatography, implying a yield of 6.2% for crude pigment and 3.47% for purified pigment from biomass. The yield of the obtained pigment was high enough to draw interest for industrial production, although the application of the pigment is considerable for further study.

The rhizosphere is a composite ecosystem which supports multiple bacterial populations that nourishes the terrestrial biosphere and plays a crucial role in the continuous recycling of minerals, nutrients, and organic matter through the soil. Diverse varieties of molecular tools based on immediate isolation and analysis of various compounds from environmental samples such as lipids, nucleic acids, and peptides have been discovered which have provided structural and functional data about microbial communities present in rhizospheric soil. With the advent of next-generation sequencing technologies (NGS), it has become possible to delve deeper into the rhizosphere microbiome to understand the unknown aspects of it. This has resulted in a shift from traditional approaches to the modern omics-based approach based on NGS sequencing technologies for discovering and distinguishing the vast microbial diversity to understand their interactions with different environmental factors. The major objective of this chapter is to provide insights on structural and functional rhizospheric microbial diversity analysis by the application of cutting-edge biotechnological tools. We have first glanced through the basic concepts of rhizosphere and its importance in plant system, the common rhizospheric microbial population, and looked at the plant–microbe interactions which are of prime importance in the rhizosphere ecosystem. Next, we come to the molecular tools used for rhizospheric microscopic diversity analysis—a detailed view into a few of the traditional approaches used for diversity approaches before proceeding to the rapidly emerging and more popular omics-based approaches used for rhizosphere microbial diversity analysis. We have also identified the merits and demerits, future opportunities of omics-based approaches in rhizosphere microbiology.

Metals are extensively used by many industries such as real estate, mining, construction, and transport. These heavy metals are detrimental to the environment as most of the heavy metals are carcinogenic. Without treatment of heavy metal-containing wastewater, these may accumulate in the fishes and other aquatic flora and fauna. Upon human consumption of those fishes, it may cause carcinogenic or mutagenic conditions such as skin irritation, allergies, or dermatitis. Adsorption and other existing waste treatment technologies are unable to remove heavy metals efficiently. Conventional remediation techniques are expensive and not eco-friendly. Microbial fuel cell (MFC) is a promising technology where electroactive bacteria can be used for removal of heavy metals with simultaneous electricity generation. Heavy metals can be removed via bioelectrochemical reduction at cathode chamber using the reduction capabilities of bacteria. This chapter highlighted the principle of MFCs for heavy metal removal, microbes associated with heavy metal reduction, catabolic pathway responsible for microbial oxidation of substrate, and heavy metal reduction. The different types of heavy metals, their structure, and effects along with the advantages and disadvantages of the heavy metals removal methods of MFC compared to other existing methods. This chapter discussed different case studies for heavy metal removal from groundwater using MFCs, the factors affecting metal recovery, and challenges in MFC operation during metal reduction at the cathode. The present chapter will help the readers to understand the fundamentals of microbial electrochemical heavy metal recovery.

Advancement in technology and the industrial sector has led to major pollution concerns all over the world. In many industries. for example. pharmaceutical, rubber, textile, and other dyes are used, which is a major cause of pollution. Tons of dyes are released into the environment yearly and this leads to water pollution. Various physical, chemical, and biological methods have been utilized for dye degradation but these methods are not economical and environmentally friendly. Metallic nanoparticles are of great importance as they have a range of applications in different fields, which also includes catalysis. Thus, nanoparticles are now being utilized for photocatalytic degradation of toxic dyes. Nanoparticle synthesis can be done by chemical and physical methods, but the green synthesis of nanoparticles has gained much importance as this method is ecofriendly and less toxic. Various plant parts or plant wastes have been utilized for nanoparticle synthesis. These materials are not costly and are easily available. Different nanoparticles such as Au, Ag, Pd, ZnO, TiO2, Pt, and others have been used for photocatalytic degradation. This chapter will focus on the green biosynthesis of nanoparticles and their role in photocatalytic dye degradation.

Water pollution arising from the presence of heavy metals including arsenic, cadmium, chromium, lead, and mercury above their permissible limits set by the World Health Organization and Environmental Protection Agency has affected agriculture, human health, and aquatic life widely across the world. The toxic nature of heavy metals is due to their nonbiodegradable nature; hence they accumulate in living cells affecting their normal functions, therefore their removal from water is of the utmost importance. Natural polysaccharides originating from different bacteria, fungi, algae, and plant materials provide an efficient alternative to conventional techniques for the treatment of wastewater contaminated by heavy metals. This chapter describes various natural polysaccharides and their composites which can be used as efficient biosorbents for the removal of various heavy metals from wastewater and industrial effluent.

Biosorption is an ingenious technique that uses biological materials to acquire trace metal ions from wastewater. In the present study, the ability of Colocasia esculenta stem biomass was explored for the biosorption of toxic trace metals. The maximum removal was observed for arsenate (As5+) with 58.63%, followed by chromium (Cr6+) with 56.56%, and cadmium (Cd2+) with 41.2%. However, for copper (Cu2+), nickel (Ni2+), and zinc (Zn2+), low adsorption was observed. Batch sorption tests revealed that adsorbent dosage of 0.5g, 0.5g, and 0.3g; time of 10 h, 4 h, and 10 h; room temperature range of 25–30°C; pH range of 7.0–4.5; and initial concentration of 30 μg/L, 20 mg/L, and 30 mg/L were the optimum conditions for the removal of As5+, Cr6+, and Cd2+, respectively. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDX) analysis of Colocasia esculenta stem biomass before and after adsorption revealed that the trace metals successfully get adsorbed on the surface of the biosorbent. The equilibrium data fitted well with the adsorption isotherm model of Langmuir (for As5+, Cr6+, and Cd2+), Dubinin-Radushkevich (for As5+ and Cr6+), and Flory-Huggins (for Cd2+), and the kinetic data of As5+, Cr6+, and Cd2+ biosorption were best described by pseudo-second-order kinetic model. Thermodynamic studies revealed that the adsorption process for all concerned trace metals acts in a spontaneous manner and is endothermic in nature. Thus, the use of Colocasia esculenta stem biomass proved to be an efficient and economical alternative for the treatment of effluents contaminated with these trace metals.

A superior arsenite [As (III)] oxidizing strain was isolated by enrichment technique from a shallow aquifer of Bhojpur district, Bihar, India. Along with high As (III) and arsenate [As (V)] resistance [up to 70 mM of As (III) and 1000 mM of As (V), respectively], it showed high resistance to multi-metals and a superior ability to utilize a wide range of carbon sources. The gram-negative rod-shaped strain of Delftia spp. BAs29 was characterized thoroughly for its As (III) oxidation ability. The strain showed mixed growth associated, facultative chemolithotrophic As (III) oxidation process, releasing-67 kJ/reaction of free energy in an exergonic reaction. Testing of cost-effective and natural bio-sorbents showed efficient As (V) removal from the contaminated water. Moringa oleifera showed the maximum As (V) removal capacity of 57.89% among the tested bio-sorbents. This study revealed a two-step approach for arsenic removal with 98.77% efficiency from groundwater using an indigenous As (III) oxidizing strain combined with a natural bio-sorbent.

Groundwater arsenic contamination represents a global threat to human health. Among the proposed bioremediation applications, microbial transformation of arsenite (As (III)) seems to be the most favorable approach as it can be easily coupled with several adsorption techniques, without producing lethal by-products or demanding chemical addition. This study highlights the potential contribution of a highly efficient As (III) transforming bacteria Delftia sp. BAs29 followed by the adsorption of transformed arsenate (As (V)) using neutralized red mud under suitable treatment conditions. Diverse experimental conditions elucidated (inflow As (III) concentrations, flow rate) the rate and oxidation efficiency to mediate the process. Red mud is a waste by-product from the Bayer's process of the alumina industry, which when neutralized aids the removal of As (V). The neutralized red mud was characterized using X-ray diffraction (XRD) microanalysis, Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) and Fourier-transform infrared spectroscopy (FTIR). Arsenate adsorption using neutralized red mud was also studied as a function of pH and time, adsorbent dosage, and initial As (V) concentration. The adsorption process was significantly affected by the solution pH, which on decreasing gradually increased the adsorption efficiency. The maximum monolayer capacity for adsorption of 274.1 mg/g As (V) was found at optimum conditions of pH 4.0 and a contact time of 30 min at a temperature of 30 °C, respectively. Furthermore, this process significantly contributed in fabricating a two-step bio-filter column for the removal of total arsenic from groundwater. Graphical abstract.

Arsenic endosmosis causes a severe threat to human health within the developing countries. This study assessed the levels of geogenic arsenic and other heavy metals affecting the release of As in the aquifers within the drinking water sources in Bhojpur district of Bihar, India. Eighteen water samples were collected in triplicates from hand-dug wells in six neighboring villages in proximity to the River Ganga namely Bakhorapur, Gaziapur, Parasrampur (or Kanhachhapara), Saraiya, Paiga and Gundiinin. The physicochemical parameters, ionic content and heavy metal analysis of the collected water samples indicated the region to be highly contaminated with arsenic, zinc, manganese and iron. The arsenic and iron concentration ranged between 24.3 and 168.07 μg/L and 0.17–1.16 mg/L respectively, indicating the excessive withdrawal of groundwater for domestic and irrigation purposes with a significant correlation between both the metals. Elevated concentration of zinc in the region attributed to the excessive application of chemical fertilizers and pesticides. Concentration of manganese was also in the higher range of 0.05–1.15 mg/L, primarily due to the urbanized industrial activities. Human health risk assessment within two population groups in the region indicated that the overall water quality is slightly contaminated but the risk associated with it is low. Water Quality Index ranged from 29 to 48, signifying the water quality to be poor. Residual sodium carbonate values indicated that few water sample sources are not suitable for irrigation purposes whereas, sodium adsorption ratio (SAR) values were within the acceptable limits to be used for irrigation.

High arsenic groundwater contamination causes serious health risks in many developing countries, particularly in India and Bangladesh. The arsenic fluxes in aquifers are primarily controlled by bacterial populations through biogeochemical cycle. In this present study, two gram-positive rod-shaped bacteria were isolated from shallow aquifers of Bhojpur district in Bihar during the early winter season, able to withstand arsenite (As