PhD Theses (Environment)


Recent Submissions

Now showing 1 - 20 of 49
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    Comprehensive Investigation of the gut microbial community of Antheraea assamensis Helfer through Meta-omic Approach
    (2023) Saikia, Dharitri
    Antheraea assamensis Helfer, commonly known as the Muga silkworm, is an endemic, economically important Lepidopteran species explicitly found in the northeastern part of India and its neighbouring areas. This semi-domesticated, multivoltine, polyphagous, edible insect produces an economically important, lustrous golden-coloured silk with high tensile strength and durability. The cultivation of Muga silkworm for silk production has been in practice for ages in Assam, a state of India. Due to its extreme durability, magnificent colour and lustre, Muga silk is considered one of the most expensive natural fibers in the world. The fibroin part of the Muga silk is also a promising material for tissue engineering. Unlike mulberry-feeding silkworms, A. assamensis is semi-domesticated and can be grown only in outdoor conditions. Lack of genetic variation and low adaptability to changing environmental conditions and limited knowledge of its host plants are the key bottlenecks towards its domestication. The role of gut microbiota in host metabolism, growth, development, nutrition and immune regulation is becoming increasingly evident in humans and other organisms. To date, the gut microbiota of A. assamensis has remained largely unexplored. The present work aims to comprehensively identify and characterize the gut microbial community of A. assamensis through a culture-independent approach. The gene expression analysis of the gut microbial community was studied through metatranscriptome analysis. The influence of the host leaf–associated microbiota on larval gut microbial composition and its variation to changes in host plants was also investigated. The results have indicated that the 5th instar larva of A. assamensis contains a highly diverse gut microbial community dominated by Proteobacteria, Patescibacteria, Planctomycetota, Chloroflexi, Acidobacteriota and Actinobacteriota. Functional analysis of A. assamensis gut microbiome through shotgun metagenomics and metatranscriptomics revealed key associations between the insect and its gut microbial community including host leaf digestion, metabolite detoxification, chitinase production and fat body metabolism. The host leaf-associated microbiota was found to occupy a major portion of the total larval gut microbiota. However, the diversity of the larval gut microbiota was greater than the host leaf-associated microbiota. The findings of this study will illustrate the structure of the gut microbial community of A. assamensis, their key interactions with the host organism and the role of host leaf-associated microbiota on the holobiont. The thesis also describes the global metabolome of the host plant leaf, larval gut and silk gland of 5th instar larvae of A. assamensis and how the change in the host plant affects the gut and silk gland metabolite composition. For this, larvae reared on Som and Mejankari plants were considered. The results of this experiment identified hundreds of metabolites from the larval gut, silk gland and host plant leaf of A. assamensis larvae reared on the two host plants. The identified metabolites can be clustered into different categories like amino acids, sugars, fatty acids, alkaloids, secondary metabolites, pigments vitamins and others. Change in the host plant was found to change the metabolite composition of the larval gut and the silk gland. The findings of this study will help to extend our knowledge of the global metabolomes of the studied samples.
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    Synthesis of TiO2-Based Nano-Photocatalysts for Organic Synthesis, Wastewater Treatment and Antibacterial Photocatalytic Therapy
    (2023) Sinha, Sayantan
    The dissertation entitled “Synthesis of TiO2-Based Nano-Photocatalysts for Organic Synthesis, Wastewater Treatment, and Antibacterial Photocatalytic Therapy” consists of a total of five chapters. Chapter 1 is a review chapter focusing on the application of TiO2-based heterogeneous photocatalysts in photocatalytic organic synthesis and wastewater treatment. Also, this chapter discusses in detail the basic understanding of heterogeneous photocatalysis and the exclusive properties of TiO2 that is necessary to modify the crystal structure and bandgap orientation of TiO2 for synthesizing new catalysts.
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    Advanced treatment methods of melanoidin for the effective remediation of distillery spentwash
    (2023) Verma, Rahul
    The melanoidin-containing wastewater, particularly distillery spentwash possesses very high loads of chemical oxygen demand (COD) and other organic and inorganic pollutants. The discharge of this dark brown colour wastewater to water bodies results in eutrophication, reduction of dissolved oxygen level, obstruction of sunlight penetration, inhibition of photosynthesis of aquatic plants and groundwater contamination. The treatment efficacies of the conventional methods are quite low due to the poor biodegradability of melanoidin. In this regard, the present study explores adsorption, advanced oxidation process, and photocatalysis to remove melanoidin from wastewater. In addition, the bioprocessing of molasses to produce alternative metabolite biosurfactants has been investigated to decrease the pollution load of wastewater. Chapter 1 and chapter 2 demonstrate the introduction and literature review on melanoidin removal in distillery spentwash.
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    Evidence based Assessment of Environmental Toxicity due to Pesticides & Nanomaterials Exposure
    (2022) Mosahari, Ponnala Vimal
    The pesticide and nanomaterials induced environmental toxicity is problematic and is responsible for various kinds of diseases today. Under these circumstances evidence based assessment of pesticide and nanomaterials induced toxicity and evidence synthesis for the same is very much needed. The present study explores the evidence synthesis techniques like Systematic Review and Scoping Review in organophosphate and nanomaterials induced environmental toxicity. A systematic review of the organophosphate exposure induced health impact has been done, based on the data from multiple databases covering both human and in-vivo studies. The study indicated that susceptibility to OP pesticide toxicity can be determine by two exonic polymorphisms viz. PON1L55M and PON1Q192R SNPs in human population. The mechanism of OP pesticide toxicity is attributed to the inhibition of acetylcholinesterase (AChE). Scoping review for nanomaterials induced environmental neurotoxicity was carried out to find the link between various neurodegenerative diseases and nanomaterials. It was found that there are limited number of longitudinal or observational studies regarding environmental nanomaterials induced neurotoxicity. Most of the reviews considered for scoping review were based on in-vivo and in-vitro models, and few based on epidemiological studies. No observational studies for the pre-defined period were found. Most of the reviews emphasized on the neurotoxicity mechanisms and route of exposure.
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    Utilization of Steel Industry LD-slag for Environmental Applications
    (2024) Samanta, Niladri Shekhar
    Steel slag is an industrial byproduct of the steel-making process. It is created in enormous amounts during steel production using electric arc furnaces. LD-slag, also known as LD (Linz-Donawitz) converter slag, is a byproduct of steelmaking in a basic oxygen furnace. This kind of slag is typically created during the steelmaking process from iron ore. The LD-slag comprised several hazardous metallic oxides therefore, dumping such waste may cause several detrimental effects on the environment. The global output of LD-Slag is around 47 MT per year. As a result, there is a strong case to be made for making extensive use of LD-slag, either through conversion into useable material or recycling as process material. Taking all these above issues into consideration, the main objectives of this work are divided into four sections. The first section deals with wastewater treatment by different zeolites derived from LD-slag of the steel industry. The second section deals with the preparation of zeolites A and X and their physico-chemical study.
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    Development of novel sulfonium containing drug carriers with inherent antimicrobial activities to combat drug resistance
    (2023) Patel, Anjali
    This Thesis title “Development of novel sulfonium containing drug carriers with inherent antimicrobial activities to combat drug resistance” deals with the study of sulfonium containing liposome and polymers which contains membrane directed bactericidal activity and hence it can counteract different drug resistance mechanism of the drug resistance due to efflux transporter, reduced number of porins, metabolic drug inactivation and hence it can rejuvenate the activity of the clinically proven antibiotics against drug resistant bacterial strains
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    Developing Ecofriendly Nano-Particulate Adsorbents using lron-Plant Polyphenols, Understanding the Molecular Properties and their Environmental Applications
    (2022) Aktar, Jinat
    Removing pollutants using adsorbents made from natural ingredients is an exciting proposition from the standpoint of their cost-effectiveness and safety. Polyphenols are a class of chemicals widely distributed in leaves, seeds, and other parts of plants. They are known for their health benefits and antioxidant properties. Two iron(lll) based new materials were synthesized from tannic acid (tttlat-1) and guava leaf extract (Mat-2) in -10 g scale under identical conditions. The physical properties, surface properties, and chemical properties of all three materials were analyzed using FESEM, FETEM, DLS, BET, pHzpc, CHNS analysis, Magnetic susceptibilities, EPR, XPS, Mass analysis, TGA, PXRD, FTIR. The results of FESEM and TEM showed the materials as clusters of nano-sized particles. The adsorbent properties of the materials were tested with anionic fluoride and cationic dyes. The biosafety of Mat-1 and Mat-2 was checked on mung beans (Vrgna radiata) and on a number of bacteria.
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    Tools and Techniques for Assessing Recovery Potential of Aerobic Sludge Biomass Stressed with Copper(II), Amoxicillin IV, Chlorpyrifos, and Piggery Wastewater
    (2022) Kumar, Rajneesh
    The biological processes are widely used for domestic and industrial wastewater treatment to remove the organic matter before its discharge to the natural environment. Various human and industrial activities add undesirable organic and inorganic pollutants (such as heavy metals, pharmaceuticals, agrochemicals, and others) to wastewater, which find their way to the sewage treatment plants. Microorganisms play an essential role in the biological process of sewage treatment. It degrades organic matter present in sewage and utilizes the energy for synthesis of new cells. The undesirable pollutants in wastewater are likely to impart detrimental effects to microorganisms resulting in hindrance in treatment efficiency or sometimes even shut down the operation. Therefore, studies are required to evaluate the behavior, characteristics, and activity of aerobic sludge biomass in presence of undesirable pollutants — such as a heavy metal, an antibiotic, a pesticide, and piggery wastewater. The three fold objective of this experimental investigation are to (i) assess impact of stress imposed by undesirable pollutant on aerobic sludge biomass, (ii) assess the recovery potential of stressed aerobic sludge biomass after discontinuation of stress-causing undesirable pollutant, and (iii) identify the tools and techniques suitable for field application in assessing the health status of aerobic sludge biomass
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    Studies on the Green Synthesis of Silver Nanoparticles and their Utilization on the Development of Polymer Nanocomposites for Water Disinfection and Wound Healing Applications
    (2022) Bora, Anupama
    The thesis contains embodiment of research aimed towards (a) Synthesis, optimization and characterization of silver nanoparticles (AgNPs) via the green route using ‘Bhimkol’ (Musa balbisiana Colla) peel extracts; (b) Study of the phytochemical properties of Bhimkol (Musa balbisiana Colla) peels and the antibacterial activities of both bhimkol peel extract and green synthesized AgNPs; (c) Synthesis and characterization of Silver Nanoparticle via green route using Sechium edule aqueous extract, study of their antimicrobial as well as catalytic activity; (d) Characterization and development of polystyrene nanocomposites (PS-AgNPs) from waste thermocol and green synthesized AgNPs for water disinfection application and (e) Characterization and development of PVA/Gelatin/AgNPs based polymer nanocomposite hydrogel for wound dressing application.
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    Synthesis and Modification of Aniline-Formaldehyde Condensate and Chitosan Schiff Base Polymers for Application in Cr(VI) and Hg(II) Binding
    (2022) Dutta, Tanmay
    This thesis represents the effort to use principles of coordination chemistry in polymeric systems to address problems related to heavy metal removal from wastewater. In the present research, emphasis was given to understanding amine polymers and increasing their adsorption capacities by modifying their current forms or introducing new functional groups to the monomeric units to increase site accessibility for better metal adsorption.
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    Benzylic Organosulfides and Analogues: Greener Synthesis, Anti-cancer Activities and the Feasibilities of H2S Donation
    (2023) Bhattacherjee, Debojit
    The thesis comprises four chapters. Chapter 1 highlights the general introduction of H2S and its role in biological systems. This chapter briefly discusses the production, metabolism, and biochemical pathways of H2S regulation and its detection techniques. Additionally, a brief and concise review has been made on the reported synthetic and natural donors of H2S and their biological implications in different diseases, notably cancer. In chapter 2, we presented a series of 4-substituted benzylic derivatives of DADS as well as their diselenide analogues for detailed structure-activity relationship (SAR) studies regarding their anti-cancer properties against ER+ breast cancer cell lines (MCF-7) and other organ-specific cancer cells. The SAR study revealed that the anti-cancer activity of the benzylic disulfides/diselenides could be enhanced significantly upon the incorporation of 4-cyano group on the benzene ring. Further investigations revealed the notable increase in intracellular ROS level upon the administration of diselenides towards MCF-7 cells correlating with their anti-proliferative activity. Treatment of 4-cyanobenzyl diselenide in MCF-7 cells induced prominent nuclear fragmentation and induced the apoptosis pathway, confirmed by evaluating the expression level of several oncogenic marker proteins (Bcl2, Survivin, and Procaspase 3). In chapter 3, we described a very simple and convenient method for the selective synthesis of garlic-derived allyl sulfides and related derivatives utilizing a wide variety of alkyl, alkenyl, and benzyl halides as precursors under a greener and catalyst-free condition. We show for the first time that, the selectivity among symmetrical trisulfides, disulfides, and monosulfides could be achieved by variation of several reaction parameters. Our study further revealed that the reaction temperature and solvent were two crucial parameters for an effective selectivity toward trisulfides over disulfides. The detailed mechanistic studies by experimental and computational methods indicated that the co-formation of disulfides along with trisulfides is due to the formation of sodium sulfite (Na2SO3) as a by-product that interfere in the reaction. Furthermore, results from the preliminary anti-proliferative activities by trisulfides towards MCF-7 revealed potent anti-cancer activities of most of the trisulfides in general. Importantly, the 4-methyl substituted trisulfide exhibited the highest anti-proliferative activity in MCF-7 cells and it was capable of donating H2S in a sustained manner in the presence of biothiols. The mechanistic investigations on the potent anti-proliferative activity of the benzylic organotrisulfide (3,5-dimethoxybenzyl) against the highly aggressive triple-negative breast cancer cells (MDA-MB-231) was carried out in chapter 4. From the pool of different substituted benzylic organotrisulfides, 3,5-dimethoxybenzyl trisulfide (4.0) exhibited highest selectivity towards the MDA-MB-231 over the normal cells (HEK-293). The selected trisulfide compound further studied the detailed mechanistic aspects for evaluating its anti-proliferative activity. Trisulfide 4.0 exhibited the anti-cancer activity mainly by targeting and suppressing the Wnt/β-catenin signaling pathway. The detailed mechanistic studies revealed that compound 4.0 facilitated the GSK-3β-induced phosphorylation of β-catenin and subsequent proteasomal degradation, which was supported by the G2/M phase arrest of the cell cycle and the significant down-regulation of downstream signaling genes such as Cyclin D1 and c-Myc. Unlike the disulfide and monosulfide moieties, the presence of a trisulfide functionality facilitated the release of H2S, which was found to be important for the desired inactivation of β-catenin expression. Surprisingly, combination with DATS and our synthesized sustained donor 4.0 exhibited cytoprotective effect due to the optimum level of H2S donation. Moreover compound 4.0 or the released H2S induced down-regulation of the p53 protein, possibly through S-sulfhydration process observed by western blot experiment.
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    Treatment of Blast Furnace Wastewater and Utilization of LD Slag from Steel Industry
    (2022) Deepti
    Steel industries are one among the major industries which contribute to the world's economic growth. However, waste generation.within the industry is enormous due to its high production rates. Large quantity of water is used in the steel industry for different processes like cooling operations, dust scrubbing and descaling. Nanofiltration (NF) is been used as a tertiary treatment system for the blast furnace (BF) wastewater in TATA Steel Ltd., India. The volume of the reject stream varies between 20-30 % of feed steam. This membrane reject stream contain concentrated monovalent and divalent ions (3- 4 times of feed). Available technologies for the treatment of NF reject are not efficient and economically viable due to high energy and space requirement (eg. Solar concentrator). Therefore, there is an urge for a more efficient, economical and facile technique for the treatment of membrane reject stream. Similarly, around 2 - 4 tontres of waste per tonne of steel are being generated within the industry. Linz Donawitz (LD) slag is one among the wastes in integrated steel industry. Globally, production of LD Slag is around 47 MT per annum. Hence there is a need for use of the LD slag in much persuading way through either conversion of slag into useful material or recycling as process material. Taking all these issues into considerations, the main objectives of this work are divided into two sections. First section deals with the treatment of highly saline wastewater from blast furnace unit of steel industry. And the second section deals with the utilization of LD slag which is a by-product of steel industry.
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    Treatment of Hydrocarbon-rich and Complex Refinery Wastewater in Aerobic Granular Reactors (AGR) with Polyhydroxyalkanoates (PHA) Biopolymer Production
    (2021) Ghosh, Sayanti
    The modern era of bioremediation has been practicing aerobic granulation technology since last three decades in various recalcitrant industrial wastewater treatments. Compact granular structure, excellent settling property, presence of numerous pollutant degrading microbes and high tolerance to toxicity made granulation a promising biotechnology. Petroleum industries are the producers of toxic and poorly-biodegradable hydrocarbon polluted wastewater. Our first study provides extensive information about oily wastewater treatment in aerobic granular reactors (AGR) using three different inocula from sewage, refinery and brewery. In emulsified diesel exposure, previous oil adaptation helped the refinery sludge granules to achieve maximum granule size of 3.49±0.01 mm and extracellular polymeric substances (EPS: 404 mg/g volatile suspended solids (VSS)) with maximum 67.39±0.15% oil removal efficiency. Brevibacterium paucivorans strain SG001, Micrococcus aloeverae strain SG002 and Staphylococcus hominis strain SG003 were identified as the major pollutant degraders isolated from sewage, refinery and brewery granules. Micrococcus aloeverae exhibited maximum hydrocarbon removal efficiencies (oil: 61.34±0.85%) among the three species. Re-addition of sodium acetate reconstructed broken granules. We further checked the impacts of hydraulic retention time (HRT) on granule characteristics, hydrocarbon removal efficiency and removal mechanism while treating emulsified diesel wastewater in AGRs. AGR with shortest HRT (12 h) achieved maximum 4.72±0.05 mm granule size, 400.31±0.01 mg/g VSS of EPS among the AGRs. But longest HRT (48 h) played major role providing longer reaction time for 90.31±0.26% hydrocarbon removal. Degradation of short and long chain alkanes (C6-C7, C9-C10, C11-C13, C15-C18, C27) were observed in the AGRs which further produced fatty acids as metabolites. About 24-48 h HRT with 0.125-0.25 kg/ hydrocarbon loadings providing below 77 mg/L effluent hydrocarbon was recommended for AGRs to avoid phytotoxicity after effluent disposal. Rapid granulation of oil degrader Micrococcus aloeverae strain SG002 was conducted with investigation of its most efficient approach of bioaugmentation in AGRs to reduce granule rupture and enhance pollutant removal in multiple hydrocarbon laden refinery wastewater treatment. Highly settleable Micrococcus granules with 0.5±0.02 mm size formed in 15 days achieving 80% organics removal. In control AGR, recalcitrant hydrocarbons deteriorated size and stability of aerobic granules. About 2 doses of 10% (w/w) granular augmentation of Micrococcus facilitated cocci abundant granule microstructure with 404.65±1.45 mg/g VSS of EPS content ensuring simultaneous 99% phenolics removal and 19% nitrification in AGR. Degradation of C8-C15 n-alkanes followed partial fatty acid conversion in control reactor and C6-C36 removal was observed indicating β-oxidation of fatty acids in bioaugmented AGRs. Thereafter, accumulation of polyhydroxyalkanoates (PHA) biopolymers was observed in aerobic granules having mixed sludge and pure strain inoculum. Small sized (0.71±0.04 mm) Micrococcus granules achieved 81.40±0.2% hydrocarbon removal efficiency accumulating 0.47±0.01 mg PHA/mg cell dry weight (CDW) due to cocci populated strong microbial structure. Changing organic loading (0.6-1.8 kg COD/ and high C/N (8-24) ratio stimulated 0.71±0.04 mg PHA/mg CDW yield in the refinery granules with 90% hydrocarbon removal. Long and short chain nalkanes (C16-C36, C6-C10) were mostly biotransformed into PHA. Granule extracted PHA was characterized as copolymer P(3HB-co-3HV) having 3.5-4.5 of butyrates and valerates (PHB:PHV) ratios . At last, a batch scale study was conducted to produce salt tolerant aerobic granules of Brevibacterium paucivorans, Staphylococcus hominis and Micrococcus aloeverae evaluating organics removal and nitrification efficiencies in refinery wastewater treatment. Each strain separately formed granules in 20-25 days. In Brevibacterium, granule rupture took place at 20 g/L NaCl influence. Refinery sludge origin and thick layer of 226 mg/g VSS EPS prevented 35 g/L NaCl saline inhibition in Micrococcus granules improving nitrification up to 28% with 93% hydrocarbon removal in 12 h of batch operation.
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    lnfluence of Green Corridor and Bridge Piers on River turbulence by Experimental and Numerical investigation
    (2021) Suresh, Modalavalasa
    Most of the lndian peninsular rivers are generally low sinuous rivers. The three-dimensional flow structures in curved channels control the hydrodynamic and morphological adjustments of the river system. ln addition, physiohydrological characteristics of the river, engineering interventions and river corridor vegetation alter the flow structure in these rivers. ln this thesis, to study the hydraulic behavior of the low sinuous river by quantifying the turbulence parameters such as turbulence intensity, Reynold's stress and turbulent kinetic energy. Further, the impact of floodplain vegetation on flow structure into the mainstream and the variability of velocity profiles under different flow conditions and vegetation densities has been studied, These findings provide better understanding of turbulence and altering of velocity distribution. The understanding of flow and floodplain vegetation interaction is extended to study the hydrodynamic response of the sinuous river subjected to combined effect of bridge piers and vegetation cover over the floodplain. ln this research, an inter-comparison study is carried out between numerical model simulations and experimental results for evaluating the performance of CFD model in predicting the hydrodynamics structure with the influence of flood-plain vegetation in the sinuous channel. For this study, vegetation cover and bridge piers are incorporated in the FLOW3D CFD model, and hydrodynamic simulations are carried out for the turbulence characteristics. The study of vegetation- bridge pier-flow response can be extended further by monitoring the process at field scale for river corridor management. The present thesis work provides a comprehensive understanding on the effect of floodplain vegetation of various scenarios on main channel turbulent characteristics of sinuous rivers.
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    Refinery wastewater treatment and value addition using Rhodococcus opacus- a hydrocarbonoclastic oleaginous bacterium
    (2021) Paul, Tanushree
    Bio-fuels for energy generation are one of the alternatives, which require integration with wastewater treatment to keep the economics of the production process low. The present study focused on treating raw refinery wastewater by Rhodococcus opacus for converting it into bio-oil by hydrothermal liquefaction process. For treating the raw refinery wastewater, different operating modes using a continuous stirred tank bioreactor were investigated. Continuous mode with cell recycle proved efficient in terms of complete removal of chemical oxygen demand (COD) (99%) and high lipid production (86%, w/w) at a hydraulic retention time (HRT) of 16 h (dilution rate of 0.06 h-1). Toxicity assessment of the permeate water was carried out following different methods which established the reuse potential of the treated wastewater. Furthermore, a novel strategy involving two-stage submerged tubular membrane bioreactor (STMBR) system with the reactors connected in series was effectively employed for treating the refinery wastewater which yielded complete COD removal along with 2.98 g L-1 biomass growth and 2.3 g L-1 lipid concentration. The lipid-rich bacterial biomass obtained by treating the wastewater was converted to bio-oil by hydrothermal liquefaction (HTL) which revealed its excellent potential for bio-fuel applications. A maximum bio-oil yield of 25.53% w/w was obtained at the optimum HTL conditions of 215 °C temperature, 125 min treatment time, and 0.25 biomass/water ratio. Overall, this study demonstrated a sustainable zero waste strategy along with a closed loop integrated approach using the hydrocarbonoclastic oleaginous bacterium R. opacus for refinery wastewater treatment with provisions for resource recovery.
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    Novel bioprocessing strategy for polyhydroxybutyrate production from agro-industrial effluents: A waste biorefinery
    (2022) Jayakrishnan, U
    Effective waste management is still a burning issue in the modern world due to the generation of more waste than that can be properly disposed off. In this scenario, waste biorefinery has shown tremendous potential to drive improved waste disposal through income generation. The research work presented in the thesis investigates bioprocessing strategies to recover a value-added product, polyhydroxybutyrate (PHB), from agro-industrial effluents under the waste biorefinery approach. Initially, the volatile fatty acid (VFA) production from rice mill effluent (RME) and brewery effluent (BE) was influenced by gobar gas plant sludge (GPS) and brewery anaerobic sludge (BAS) in an untreated state and pretreated under cyclic heat and acid shock regime to convert the effluent streams into media suitable for PHB production using acidogenic fermentation. The acidification of RME with pretreated gobar gas plant sludge at the optimized feed to microbe ratio led to enhanced total VFA content (TVFA) and degree of acidification of 2437±0.03 mg/L and 86±0.13 % compared to all other combinations. Acetate and butyrate were the major VFAs produced after the pretreatment of GPS, along with stable COD and acidic pH profiles. However, the fermentation of RME with pretreated BAS had an enhanced even to odd ratio of 20.97±0.08 mg/mg along with the highest acetate and butyrate yield compared to all other combinations. The improvement can positively affect polymer composition and property. Meanwhile, the untreated system had the upper hand regarding TVFA concentration compared to the pretreated system due to the negative effect of the pretreatment regime on different microbial communities in BAS. Therefore, pretreatment of anaerobic inoculum inhibited carbon sinks and enhanced even-numbered VFA production from RME, indicating its potential implications as a fermentation media for improved PHB production.
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    Study of sequence dependent in-situ peptide cyclization and its applications as biomolecules
    (2021) Ghosh, Nibedita
    The peptides are gaining escalating recognition due to its progress in the area of biotechnology and bioengineering. The work presented in the thesis mainly centred on the design and synthesize of side chain modified peptides which can form cyclic peptide in situ at the physiological condition without the need for any external reagents in-vitro. Further, the cyclization concept has been applied to release bioactive molecules and also to inhibit the protein aggregation. Peptides are early leading for the realistic design to deliver bioactive molecules as they can provide target specificity, potency, resistance towards chemical or enzymatic hydrolysis and longer resident times for more effective duration of action to improve biological efficacy and minimize side effects. In the second chapter, a quick conversion of a smartly designed linear tri-peptide (RXE, X= P/ A/ G) into the cyclic one has been demonstrated to release the bioactive molecules in a controlled manner in-vitro. This method may be a new direction to design peptide-drug conjugates where no external stimuli will be needed to release the drug. On the other hand, an increasing number of human diseases seem to be associated with protein aggregation, which directly contributes to or modulates the associated pathology. Amyloids are insoluble protein aggregates with highly ordered -sheet conformations that differ from its native states conformation. Misfolding and aggregation of the amyloid (A) peptide into fibrillar aggregates is a cause of Alzheimer's disease (AD) which is a progressive neurodegenerative disorder and the most common form of dementia. Various strategies are being developed for the treatment of Alzheimer's disease though there is no cure available till date. In the third and fourth chapters, in situ side chain peptide cyclization has been introduced as a -sheet breaker strategy, and this is a promising therapeutic approach against AD and related disorders. In the fifth chapter, inspiring from the concept of aspartimide formation; NN and ON acyl migration have been applied to release the bioactive molecules in-vitro.
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    Bioinspired Engineering of Nanomaterials for Electrocatalytic Sensing of Heavy Metals and Organic Analytes
    (2021) Dash, Smruti Ranjan
    This work focuses on the bioinspired synthesis of various spherical and tailor-made nanoparticles using reducing and capping agents present in the leaves extract of the Psidium guajava (guava) plant. These bioinspired synthesized nanoparticles were used in the modification of graphite paste electrodes (GPEs) and glassy carbon electrodes (GCEs) by drop-casting method for electrochemical sensing of different organic analytes like ascorbic acid, dipyrone (drug), chlorpyrifos (organophosphate pesticide), and inorganic analytes (heavy metal ions). The mass spectra analysis of the bio-extract revealed the presence of various antioxidants and polyphenols like ascorbic acid, quercetin, chlorogenic acid, caffeic acid, naringenin, and rutin. These components could successfully reduce metal precursors like silver nitrate and chloroplatinic acid to produce stable silver, platinum, and tailor-made bimetallic core-shell Ag@Pt nanoparticles. The biomass residue generated during bio-extract preparation was also used to synthesize carbon dots for electrocatalytic sensing of chlorpyrifos. The fabrication of a miniaturized three-electrode system was also successful for the electrochemical sensing of heavy metal ions. A portable electrochemical sensing device that can be applied for on-field monitoring of heavy metal ions was successfully developed using a fluorine-doped tin oxide based three-electrode system. Silver-coated copper nanorods (Cu@Ag) synthesized in an environmentally friendly method showed improved sensing capabilities than copper nanorods modified FTOs. Cu@AgNR/FTOs could successfully quantify Pb(II), Zn(II), Cd(II), and Hg(II) both in single metal systems and in mixed metal matrices with the detection limits in the nanomolar range. The device showed repeatability of up to 4 cycles, thus providing an alternative to the conventional screen-printed electrodes that are typically single-use devices and generate a lot of plastic wastes
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    Fabrication and Evaluation of Chemically Modified Chitosan and Silk Fibroin Derived Nanomaterials for Anti-cancer Agents
    (2021) Horo, Himali
    The thesis is compiled into seven chapters, which comprises the introduction, review of literature, experimental findings, a summary of the work and future prospects. Chapter 1 presents a brief introduction to the design and development of anti-cancer drug delivery systems based on biopolymers and their modified materials. It also showcases a brief review of biopolymer derived structures, including covalently conjugated systems, nanoparticles, and microparticles. Chapter 2 presents the development of a photocleavable nanocarrier system where 5-fluorouracil (5-FU) is covalently conjugated to low molecular weight chitosan (LMWC) via a photocleavable linker. The conjugate was designed to be cleaved explicitly under UV-A radiations of wavelength 365 nm and release the drug in a dose-dependent manner. The conjugate was found to form hydrogel and organogel. The modified biopolymer was also fabricated into nanoparticles by ionic gelation technique for better cell penetration. The drug release study from the nanoparticles was done by irradiating it under a light of wavelength 365 nm. Chapter 3 presents a method for antiproliferation of the cancer cells using a combination of 5-fluorocytosine (5-FC) loaded silver nanoparticles (AgNPs) prodrug and a non-mammalian enzyme Cytosine Deaminase (CD). 5-FC and 5-FU loaded AgNPs were synthesized using a green synthesis protocol using LMWC as the reducing and the stabilizing agent, and nanoparticles with size less than 25 nm were formed. CD activity study showed, it effectively hydrolyzes prodrug 5-FC in 5-FC loaded nanoparticles into 5-FU (active drug) but was inert to blank nanoparticles and 5-FU loaded nanoparticles, thus proving its efficiency and specificity. The investigation in MDA-MB-468 cell lines manifested potent cytotoxicity for 5-FU nanoparticles compared to the 5-FC loaded nanoparticles without CD, thus showing the prodrug nature of 5-FC loaded nanoparticles. Chapter 4 presents the synthesis of gold nanoparticles using LMWC, loaded with a model anti-cancer drug, doxorubicin (DOX), which was further coated with folic acid (FA) and fluorescein (FL) conjugated silk fibroin (SF). The SF coating helps in the sustained release of the drug and provides a binding domain for FA attachment to facilitate cell-targeting. The drug release from both the coated and uncoated nanoparticles was studied, where the coated one showed slow and sustained release compared to the uncoated ones. The cytotoxicity of coated nanoparticles in HeLa cell lines showed a maximum dose-dependent decrease in cell viability than the uncoated ones. The cellular uptake of coated and uncoated nanoparticles, as studied by confocal microscopy, showed increased uptake efficacy of the coated nanoparticles by the cells. Chapter 5 presents the formulation of microparticles/beads from the synthesized DOX loaded gold nanoparticles in the previous chapter. Here, the beads were coated with FL coated SF for sustained drug release. The beads were synthesized by the ionic gelation technique using TPP, as the cross-linking agent. The drug release study from the coated beads showed slow and sustained release compared to the uncoated ones. Chapter 6 presents the synthesis of biotin conjugated LMWC-SF based carbon dots (CS-dots) for targeted delivery of anti-cancer drugs and cell imaging. 5-FU is loaded to the conjugate as the model anti-cancer drug. LMWC and SF based Cdots possess a large number of free amino groups that can be utilized for functionalization. The LMWC-SF mixture based Cdots were 3±1.5 nm sized and showed increased fluorescence intensity and relative quantum yield compared to the pure LMWC and SF based Cdots. Biotin covalently conjugated to the free amino group of Cdots can provide target specificity to the nanocarrier. Chapter 7 consists of the summary and the future prospects of the thesis work.
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    Indigenous Biosurfactant Producing Strains for Potential Applications in Enhanced Oil Recovery
    (2021) Datta, Poulami
    The isolation, screening and identification of potential indigenous biosurfactant-producing and oil-utilizing bacterial strains were carried out from the formation water as well as soil sample of the Assam oil reservoir. Among the isolated strains from the indigenous sources, Bacillus subtilis MG495086 and Bacillus tequilensis MK 729017 showed better surface-active properties as they lowered the surface tension (ST) to 30 ± 2 mN/m along with a high emulsification index (EI) of 70 ± 2 %. Their growth kinetics and stability studies were also performed. The produced biosurfactants were chemically identified using NMR, FTIR, LC-MS and HPLC and proved to be lipopeptide, Surfactin with very low critical micelle concentration (CMC) value. Response surface methodology based on the central composite design (RSM-CCD) experiments aimed to optimize the suitable carbon source percentage and the environmental parameters to maximize the biosurfactant (Surfactin) production in terms of surface tension (ST) reduction and biosurfactant concentration which was reduced to 29.85 mN/m and the maximum Surfactin concentration was determined to be 7.46 ± 0.39 g/L, respectively. The potential of the biosurfactants in oil degradation was also analyzed with their subsequent biosurfactant production capacity which was found to be very significant. Bacillus subtilis MG 495086 and Bacillus tequilensis MK 729017 were able to degrade the hydrophobic substrate (light paraffin oil and glycerol) almost completely within 96 hours during the course of Surfactin production. Moreover, the isolated Bacillus strains were established to be suitable for both ex-situ and in-situ enhanced oil recovery (EOR) applications. Surfactants can reduce interfacial tension (IFT) between water and residual oil, which improves the oil recovery factor. But one of the challenges of surfactant flooding is the adsorption phenomenon of surfactant onto the solid surfaces, which decreases its effectiveness in lowering the IFT for EOR application and leaves a negative impact on the process economics. Therefore, the adsorption behavior of Surfactin onto the model sand (silica) sample was discussed. HPLC was used to quantify the amount of surfactant before and after the course of adsorption. The rock mineralogy along with the impact of aqueous media salinity and the experimental temperature was the major variables. EDX, XRD and BET analyses have been carried out to characterize sandstone samples. Both the kinetics and equilibrium adsorption data were obtained from the batch mode studies. Among alternate models, the Freundlich isotherm model, Elovich kinetics and intraparticle diffusion kinetics fit well to represent applied biosurfactant adsorption characteristics. Effect of contact time and temperature on the adsorption process was also analyzed. The thermodynamic feasibility of the adsorption process was studied to verify the spontaneity of the process as well. These findings provided newer insights into real-time biosurfactant adsorption characteristics, which are often ignored in conventional approaches and methodologies. The suitability of the biosurfactant for core flooding studies and subsequent microbial enhanced oil recovery (MEOR) purpose was evaluated in terms of its oil washing efficiency, stability (thermal and halophilic) studies, interfacial activities and wettability alteration capability. The oil washing efficiency (80 ± 2 %) of the produced Surfactin was quite comparable with the commercial surfactants such as SDS, CTAB and Rhamnolipid. Surfactin improved wetting of hydrophobic rock surface from 90 ± 1 ° to 26 ± 1° and resulted in a lower interfacial tension (IFT) value of 0.32 ± 0.02 mN/m. The stability of the produced biosurfactants was studied over a wide range of temperature, pH, pressure and salinity and they were found to be stable even after their exposure for a longer period. Due to its thermal and colloidal stability, the biosurfactant was further endorsed to be employed for MEOR applications.