V. Murugan

Bio: V. Murugan is an academic researcher from Bhabha Atomic Research Centre. The author has contributed to research in topics: Desalination & Reverse osmosis. The author has an hindex of 2, co-authored 4 publications receiving 55 citations.

Bacterial lipid modification of proteins for novel protein engineering applications.

Abstract: Functioning of proteins efficiently at the solid-liquid interface is critical to not only biological but also modern man-made systems such as ELISA, liposomes and biosensors. Anchoring hydrophilic proteins poses a major challenge in this regard. Lipid modification, N-acyl-S-diacylglyceryl-Cys, providing an N-terminal hydrophobic membrane anchor is a viable solution that bacteria have successfully evolved but remains unexploited. Based on the current understanding of this ubiquitous and unique bacterial lipid modification it is possible to use Escherichia coli, the popular recombinant protein expression host, for converting a non-lipoprotein to a lipoprotein with a hydrophobic anchor at the N-terminal end. We report two strategies applicable to non-lipoproteins (with or without signal sequences) employing minimal sequence change. Taking periplasmic Shigella apyrase as an example, its signal sequence was engineered to include a lipobox, an essential determinant for lipid modification, or its mature sequence was fused to the signal sequence of abundant outer membrane lipoprotein, Lpp. Lipid modification was proved by membrane localization, electrophoretic mobility shift and mass spectrometric analysis. Substrate specificity and specific activity measurements indicated functional integrity after modification. In conclusion, a convenient protein engineering strategy for converting non-lipoprotein to lipoprotein for commercial application has been devised and tested successfully.

Fouling and cleaning of seawater reverse osmosis membranes in Kalpakkam nuclear desalination plant

Abstract: A seawater reverse osmosis plant of 1800 m³/day capacity is part of the 6300 ³/day capacity nuclear desalination demonstration project at Kalpakkam. The plant was commissioned in October 2002 and is in continuous operation. This paper deals with types of foulants, membrane cleaning procedures and the improvement in the reverse osmosis system after cleaning. This paper also describes the analysis of foulants, which may consist of adsorbed organic compounds, particulate matter, micro-organisms and metallic oxides, and describes the chemical cleaning procedure to be adopted, which is specific the seawater used because the membrane foulants are very specific with respect to the seawater constituents. The cleaning of the membranes in the Kalpakkam nuclear desalination plant was taken up because the quality of the permeate had deteriorated and the differential pressure across the membrane had gone up. This paper essentially deals with the selection of cleaning chemicals, the experience gained with the cleaning procedure adopted and the effects of cleaning on the membrane system.

Techno-economic feasibility study of providing variable frequency drive for high pressure pump, SWRO plant at NDDP, Kalpakkam

Abstract: The cost of product water is a key factor in determination of acceptability of any desalination system and plant. In case of Sea Water Reverse Osmosis plants, most of the energy consumed is in the form of electricity. The High Pressure Pump (HPP) is the single major energy consuming equipment with a share of above 75%. Hence reduction in energy consumed by HPP will have a substantial effect on the overall energy consumption. The high starting torque requirement of high pressure pump results in increased acceleration time of the motor which subsequently increases the strain on the upstream electrical system from motor feeder to transformer. Provision of a Variable Frequency Drive can be a solution for both the above problems. This paper studies the techno-economic feasibility of providing variable frequency drive for HPP motor at NDDP, Kalpakkam.

Experiences with the conventional pretreatment system in the seawater reverse osmosis plant at Kalpakkam

Abstract: A 1800 m³/day Seawater Reverse Osmosis (SWRO) plant was commissioned in October 2002 at Kalpakkam, India, as part of the Nuclear Desalination Demonstration Project (NDDP). The conventional pretreatment scheme was adopted consisting of a lamella clarifier, pressurised sand filter, activated carbon filter and cartridge filter. The dosing of pretreatment chemicals, ferrous sulphate and polyelectrolytes was done at optimum levels to keep the Silt Density Index (SDI) value between 3 and 4. Experimental trials indicated that the dosing of chemicals may not be necessary below a particular turbidity level. Similarly, the dosing of proprietary antiscalant chemicals instead of sodium hexametaphosphate to control the sulphate scaling did not affect the process performance. Rather it helped the operation, as the antiscalant is in liquid form and the addition of hydrochloric acid could be eliminated. The overall cost per unit water production was also reduced.

Lipoproteins of Bacterial Pathogens

Abstract: Bacterial lipoproteins are a set of membrane proteins with many different functions. Due to this broad-ranging functionality, these proteins have a considerable significance in many phenomena, from cellular physiology through cell division and virulence. Here we give a general overview of lipoprotein biogenesis and highlight examples of the roles of lipoproteins in bacterial disease caused by a selection of medically relevant Gram-negative and Gram-positive pathogens: Mycobacterium tuberculosis, Streptococcus pneumoniae, Borrelia burgdorferi, and Neisseria meningitidis. Lipoproteins have been shown to play key roles in adhesion to host cells, modulation of inflammatory processes, and translocation of virulence factors into host cells. As such, a number of lipoproteins have been shown to be potential vaccines. This review provides a summary of some of the reported roles of lipoproteins and of how this knowledge has been exploited in some cases for the generation of novel countermeasures to bacterial diseases.

A database of bacterial lipoproteins (DOLOP) with functional assignments to predicted lipoproteins

Abstract: Lipid modification of the N-terminal Cys residue (N-acyl-S-diacylglyceryl-Cys) has been found to be an essential, ubiquitous, and unique bacterial posttranslational modification. Such a modification allows anchoring of even highly hydrophilic proteins to the membrane which carry out a variety of functions important for bacteria, including pathogenesis. Hence, being able to identify such proteins is of great value. To this end, we have created a comprehensive database of bacterial lipoproteins, called DOLOP, which contains information and links to molecular details for about 278 distinct lipoproteins and predicted lipoproteins from 234 completely sequenced bacterial genomes. The website also features a tool that applies a predictive algorithm to identify the presence or absence of the lipoprotein signal sequence in a user-given sequence. The experimentally verified lipoproteins have been classified into different functional classes and more importantly functional domain assignments using hidden Markov models from the SUPERFAMILY database that have been provided for the predicted lipoproteins. Other features include the following: primary sequence analysis, signal sequence analysis, and search facility and information exchange facility to allow researchers to exchange results on newly characterized lipoproteins. The website, along with additional information on the biosynthetic pathway, statistics on predicted lipoproteins, and related figures, is available at http://www.mrc-lmb.cam.ac.uk/genomes /dolop/.

A short review on reverse osmosis pretreatment technologies

Abstract: Recent research reports have underlined reverse osmosis (RO) as the most optimized technology for water desalination related applications. However, implementing this technology to seawater desalination is facing challenges of membrane fouling. This includes membrane biofouling, organic and inorganic fouling which adversely affect the process performance and overall treatment cost. To overcome these issues, pretreatment units ahead of the RO system are necessary to reduce RO membrane fouling and enhance its operational efficiency. This article aimed at reviewing the literature and summarizing relevant methods, mechanisms and novel developments which improve the performance of the RO systems when coupled with either conventional or non-conventional pretreatment units. Several studies suggested that the non-conventional pretreatment units were more efficient than the conventional systems for producing better water quality and minimizing the overall treatment cost. Ultrafiltration appeared to be a cost effective and efficient method of removing suspended solids (SS) and bacteria. The advent of nanostructured membranes nanofiltration has the potential of becoming preferred non-conventional desalination pretreatment over a wide range of salinity, total dissolved solids (TDS), inorganics, viruses, etc.

Radioactive decontamination of water by membrane processes - A review

Abstract: The recent accident at the Fukushima Daiichi Nuclear Power Plant caused by the Great East Japan Earthquake of March 11, 2012 reminded us vividly of the serious hazards of radioactive substances spread over a wide range of the affected region. Currently, there is a great concern over the effect of contaminated soil and water on the health and safety of the inhabitants of the region. Hence, the advancement in the technologies of nuclear waste treatment is of vital importance if we decide to live with nuclear power to maintain our modern civilization. Among various separation technologies used, membrane technologies have been chosen in this article since they are considered as one of the emerging technologies with many advantages over the conventional processes. In this review the membrane technology is classified into different processes and, for each process, progress made since the onset of this millennium in the radioactive decontamination of water is shown. The new directions are shown by considering the progress made in membrane manufacturing and membrane processes. Thus, the combined efforts of the researchers who are engaged in membrane and membrane process design with those who are engaged in nuclear waste treatment near the plant sites were highlighted.

Engineering Signal Transduction Pathways

Abstract: Cells respond to their environment by sensing signals and translating them into changes in gene expression. In recent years, synthetic networks have been designed in both prokaryotic and eukaryotic systems to create new functionalities and for specific applications. In this review, we discuss the challenges associated with engineering signal transduction pathways. Furthermore, we address advantages and disadvantages of engineering signaling pathways in prokaryotic and eukaryotic cells, highlighting recent examples, and discuss how progress in synthetic biology might impact biotechnology and biomedicine.