Faculty Publications
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Item Bacillus Subtilis Immobilised Areca Fibre Mortar for Robust Self-healing(Springer Science and Business Media Deutschland GmbH, 2024) Sai Teja, A.; Palanisamy, T.; Anoop, P.P.; Gopal, M.This study focuses on developing a bacteria-based self-healing mortar by immobilizing bacteria with Areca Nut Husk Fibre (ANHF). ANHF is an agricultural waste that is eco-friendly, lightweight, renewable, and sustainable construction material. The objectives of this study include determining the optimal ANHF percentage, self-healing potential, mechanical properties, and durability performance of developed mortar. The type of carrier material significantly influences the viability of bacteria and their calcite precipitation ability in self-healing concrete. The present study examined the possible application of natural fiber, ANHF and to carry bacterial spores that maximize-healing potential while maintaining structural integrity in concrete. Along with Bacillus subtilis VEB4 bacteria, calcium lactate pentahydrate and, urea are used as organic nutrients. The study examined the effect of adding ANHF at different volumes of mortar (0, 0.25, 0.50, 0.75, and 1%).The mortars showed the maximum mechanical strength at an ANHF content of 0.75%. The fiber-reinforced bacteria-immobilized mortars exhibited 100% healing. A maximum crack width of 0.813 mm was healed after 56 days, while controlled specimens healed partially. SEM, FTIR and, XRD tests on Fibre bacterial mix revealed that calcite is the predominant mineral substance with a few microbial imprints on the crystalline surface. Mechanical property analysis includes compressive and flexural strength evaluations. The research assesses the material’s durability through resistance to alkaline and acid substances. The findings aim to contribute to sustainable construction materials by offering an eco-friendly solution to concrete deterioration. The optimized microbial mortar, with improved self-healing, robust mechanical properties, and durability, holds promise for applications in civil engineering, promoting resilient and long-lasting concrete structures. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.Item Biological sulfide oxidation using autotrophic Thiobacillus sp.: Evaluation of different immobilization methods and bioreactors(2009) Ravichandra, P.; Gopal, M.; Jetty, A.Aims: Evaluation of various immobilization methods and bioreactors for sulfide oxidation using Thiobacillus sp. was studied. Methods and Results: Ca-alginate, K-carrageenan and agar gel matrices (entrapment) and polyurethane foam and granular activated carbon (adsorption) efficacy was tested for the sulfide oxidation and biomass leakage using immobilized Thiobacillus sp. Maximum sulfide oxidation of 96% was achieved with alginate matrix followed by K-carrageenan (88%). Different parameters viz. alginate concentration (1%, 2%, 3%, 4% and 5%), CaCl2 concentration (1%, 2%, 3%, 4% and 5%), bead diameter (1, 2, 3, 4 and 5 mm), and curing time (1, 3, 6, 12 and 18 h) were studied for optimal immobilization conditions. Repeated batch experiments were carried out to test reusability of Ca-alginate immobilized beads for sulfide oxidation in stirred tank reactor and fluidized bed reactor (FBR) at different sulfide concentrations. Conclusions: The results proved to be promising for sulfide oxidation using Ca-alginate gel matrix immobilized Thiobacillus sp. for better sulfide oxidation with less biomass leakage. Significance and Impact of the Study: Biological sulfide oxidation is gaining more importance because of its simple operation. Present investigations will help in successful design and operation of pilot and industrial level FBR for sulfide oxidation. © 2009 The Society for Applied Microbiology.Item Production of novel cell-associated tannase from newly isolated Serratia ficaria DTC(2010) Belur, P.D.; Gopal, M.; Nirmala, K.R.; Nainegali, N.Five strains of tannic acid degrading bacteria were isolated and identified by phenotypic characterization. All the five isolates showed cell-associated activity, whereas only three showed extracellular activity. Serratia ficaria DTC, showing the highest cell-associated activity (0.29 U/l), was selected for further shake-flask studies. Tannase synthesis was growth associated and reached the peak in the late stationary phase of growth. Organic nitrogen sources enhanced the tannase production. Peak tannase production of 0.56 U/l was recorded in the medium having the initial pH of 6. The pH and temperature optima of the enzyme were found to be 8.9 and 35°C, respectively. This is the first report of cell-associated activity in the case of bacterial tannase. Cell-associated tannase of Serratia ficaria DTC could be industrially important from the perspective of its activity at broad temperature and pH ranges, and its unusually high activity at pH 8.9. © The Korean Society for Microbiology and Biotechnology.Item Experimental evaluation of the synergistic effect of calcium precursor dosage and bacterial strain interactions on the biogenic healing potential of self-healing cement mortar(Taylor and Francis Ltd., 2024) Baby, B.; Palanisamy, T.; Gupta, A.; Gopal, M.This study investigates the microbially induced calcium carbonate precipitation (MICP) in repair mortar, focusing on the impact of calcium precursor dosage and bacterial strain selection. C6H10CaO6·xH2O and (CH3COO)2Ca·xH2O were used as calcium precursors at dosages of 0.1, 0.25, and 0.4 M with Bacillus subtilis VEB4, Priestia megaterium TSB16, and Halobacillus halophilus MCC2188 microbes. Quantitative assessment of precipitate and optimization of precursor dosages were conducted before making mortar cube specimens of size 70.6 × 70.6 × 70.6 mm with bacterial spores and nutrients immobilized in Modified Expanded Perlite. Cracked cube specimens underwent automated wet-dry cycles of 12 h daily for 60 days to induce healing. Comparative analysis of biomortar specimens showed P. megaterium as the most effective in compressive strength recovery (up to 89.33%) and crack healing with a maximum healed crack width of 0.64 mm, followed by B. subtilis with significant CSR improvements. H. halophilus, less efficient in non-saline conditions, healed cracks up to 0.48 mm. Calcium lactate was considered the better calcium source choice for B. subtilis and P. megaterium strains, whereas calcium acetate improved MICP by H. halophilus. Microstructural analysis of healed precipitates collected from cracked cubes identified distinct morphology of MICP and the presence of polymorphs viz, calcite, aragonite, and vaterite. Tailored selection and dosage of calcium precursors for each strain significantly enhanced MICP and improved the quality of healing products in cracks, advancing the understanding of self-healing construction biomaterials. © 2024 Informa UK Limited, trading as Taylor & Francis Group.Item Long-lasting Bacillus safensis CG1 and Bacillus cereus DKBovi-5 based coconut shell biochar spore composites as self-healing additives for bio-mortar production(Elsevier B.V., 2024) Anoop, P.P.; Palanisamy, T.; Gupta, A.; Gopal, M.The major challenge in the production of bio-mortar lies in the effective storage of immobilised bacterial carriers. This study explores the effective storage and use of coconut shell biochar as a carrier for bacterial spores. Bacillus safensis CG1 and Bacillus cereus DKBovi-5 were immobilised in biochar and stored at 4 °C and 25 °C for 120 days. The storage at 4 °C showed enhanced viability, and Field Emission Gun Scanning Electron Microscopy studies revealed the firm adherence of bacterial spores within the biochar pores, attributed to the secretion of extracellular polymeric substances. Biochar-based spore composites stored at 4 °C were subsequently added as self-healing additives in mortar. Mechanical, self-healing, and microstructural evaluations demonstrated that the biochar with Bacillus cereus DKBovi-5 exhibited superior results. Cracks up to 0.888 mm were healed within 56 days, indicating enhanced healing efficiency, as supported by higher ultrasonic pulse velocity and a lower resistivity ratio. Brunauer-Emmett-Teller 20-point adsorption-desorption analysis showed that biochar with Bacillus cereus DKBovi-5 mix possessed the smallest pore width of 3.086 nm. Additionally, Field Emission Gun Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy, X-ray Diffraction, and Fourier Transform Infrared Spectroscopy analyses confirmed the formation of biogenic calcium carbonate in the healed regions. Overall, the biochar composite with Bacillus cereus DKBovi-5 showed significantly improved performance compared to Bacillus safensis CG1 and is recommended as a long-lasting self-healing additive for large-scale construction applications. © 2024 Elsevier B.V.Item Unified Convergence Analysis of Certain At Least Fifth Order Methods(SINUS Association, 2025) Sadananda, R.; Gopal, M.; George, S.; Argyros, I.K.A class of iterative methods was developed by Xiao and Yin in 2015 and obtained convergence order five using Taylor expansion. They had imposed the conditions on the derivatives of the involved operator of order at least up to four. In this paper, the order of convergence is achieved by imposing conditions only on the first two derivatives of the operator involved. The assumptions under consideration are weaker and the analysis is done in the more general setting of Banach spaces without using Taylor series expansion. The semi-local convergence analysis is also given. Further, the theory is justified by numerical examples. © 2024, SINUS Association. All rights reserved.Item Macro and microstructure evaluation of self-healing cement mortar enhanced with microbe-immobilized hemp fiber(Elsevier Ltd, 2025) Chaudhary, P.; Palanisamy, T.; Gupta, A.; Gopal, M.Sustainable construction materials are gaining attention in structural engineering to improve performance and reduce environmental impact. This study presents an eco-friendly composite of hemp fiber-reinforced cement mortar with self-healing bacteria, aimed at improving mechanical properties and crack repair efficiency. Microbe immobilized fiber enhanced (MIFE) cement mortar was developed by incorporating dormant bacterial spores of Priestia megaterium and Bacillus licheniformis through the mixing water, with hemp fibers serving as carrier medium. The MIFE mortar was tested at various fiber content levels, specifically 0 %, 0.5 %, 1 %, and 1.5 % by weight of cement, to evaluate its structural efficacy through comprehensive compressive strength tests, strength regain assessments, water absorption analysis, and detailed microstructural evaluations. The results revealed a significant 22 % increase in compressive strength with 1 % hemp fiber content, attributed to enhanced particle cohesion and reduced microstructural voids. The fiber's ability as a carrier to uniformly facilitate calcite precipitation also led to a notable 4.31 % reduction in water absorption. Morphological studies of CaCO3 from healed cracks in biomortar specimens demonstrated that the bio-environment and microbial interactions significantly influenced calcite polymorph formation, with vaterite crystals showing improved mechanical integrity and reduced chemical reactivity. The present study underscores the potential of microbe-immobilized hemp fibers as a green reinforcement option in cementitious materials, offering improved mechanical performance, self-healing capabilities, and environmental sustainability. These findings also align with the increasing focus on bio-based composites in the evolution of structural engineering, complementing the industry's shift toward sustainable construction materials. © 2025 Institution of Structural EngineersItem A procedure for increasing the convergence order of iterative methods from p to 5p for solving nonlinear system(Academic Press Inc., 2025) George, S.; M, M.; Gopal, M.; Godavarma, C.; Argyros, I.K.In this paper, we propose a procedure to obtain an iterative method that increases its convergence order from p to 5p for solving nonlinear systems. Our analysis is given in more general Banach space settings and uses assumptions on the derivative of the involved operator only up to order max?{k,2}. Here, k is the order of the highest derivative used in the convergence analysis of the iterative method with convergence order p. A particular case of our analysis includes an existing fifth-order method and improves its applicability to more problems than the problems covered by the method's analysis in earlier study. © 2024Item Improved convergence analysis for an at least fourth and at least sixth order parametric family of iterative methods for nonlinear system(Springer-Verlag Italia s.r.l., 2025) George, S.; Gopal, M.; M, M.Hueso et al. (2015) introduced a new family of iterative methods for solving non-linear systems. However, the convergence analysis is based on Taylor series expansion, which requires the existence of derivatives of the involved operator up to the fifth and seventh orders, respectively, for the method with at least fourth-order convergence and the method with sixth-order convergence. In this paper, we obtain at least fourth- and sixth-order convergence for the respective methods by assuming derivatives only up to the third order. We also provide the semi-local convergence analysis (which is not given in Hueso et al. (2015)) in a more general Banach space form. Moreover, our semi-local and local convergence analyses are based on the same set of assumptions, unlike existing studies, where the authors typically use one set of assumptions for semi-local convergence analysis and another set of assumptions for local convergence analysis. Numerical examples and dynamics of the methods are also provided in this study. © The Author(s), under exclusive licence to Springer-Verlag Italia S.r.l., part of Springer Nature 2025.Item An Improved Convergence Analysis of a Multi-Step Method with High-Efficiency Indices(Multidisciplinary Digital Publishing Institute (MDPI), 2025) George, S.; Gopal, M.; Bhide, S.; Argyros, I.K.A multi-step method introduced by Raziyeh and Masoud for solving nonlinear systems with convergence order five has been considered in this paper. The convergence of the method was studied using Taylor series expansion, which requires the function to be six times differentiable. However, our convergence study does not depend on the Taylor series. We use the derivative of F up to two only in our convergence analysis, which is presented in a more general Banach space setting. Semi-local analysis is also discussed, which was not given in earlier studies. Unlike in earlier studies (where two sets of assumptions were used), we used the same set of assumptions for semi-local analysis and local convergence analysis. We discussed the dynamics of the method and also gave some numerical examples to illustrate theoretical findings. © 2025 by the authors.