S. Satheesh Kumar

Bio: S. Satheesh Kumar is an academic researcher from VIT University. The author has contributed to research in topic(s): Single event upset & Flip-flop. The author has an hindex of 2, co-authored 7 publication(s) receiving 30 citation(s).

Isolation and characterization of tyrosinase produced by marine actinobacteria and its application in the removal of phenol from aqueous environment

Abstract: The present study was focused on screening and characterization of tyrosinase enzyme produced by marine actinobacteria and its application in phenolic compounds removal from aqueous solution. A total of 20 strains were isolated from marine sediment sample and screened for tyrosinase production by using skimmed milk agar medium. Among 20 isolates, two isolates LK-4 and LK-20 showed zone of hydrolysis and these were taken for secondary screening by using tyrosine agar medium. Based on the result of secondary screening LK-4 was selected for further analysis, such as tyrosinase assay, protein content and specific activity of the enzyme. The tyrosinase enzyme was produced in a SS medium and was partially purified by ammonium sulfate precipitation, dialysis and SDS PAGE. The isolate (LK-4) was identified as Streptomyces espinosus using 16S rRNA gene sequencing and named as “Streptomyces espinosus strain LK4 (KF806735)”. The tyrosinase enzyme was immobilized in sodium alginate which was applied to remove phenolic compounds from water. The enzyme efficiently removed the phenolic compounds from aqueous solution within few hours which indicated that tyrosinase enzyme produced by Streptomyces espinosus strain LK-4 can be potently used for the removal of phenol and phenolic compounds from wastewater in industries.

Fault Tolerant Cloud Systems

Abstract: Cloud computing refers to a model for accessing computing resource like networks, servers, storage, applications, and services remotely. Cloud computing offers these resources as a service, namely infrastructure-as-a-service, platform-as-a-service, and software-as-a-service. To use these services, two roles involved: the cloud provider offers the service and the cloud customer consumes the service. These resources are efficiently shared and utilized by customers and it is called workload. The requirement of workload depends on customer demands that vary from higher to lower. Based on the customer demand, cloud provider makes the resource available efficiently. In the context of cloud, the workload is based on web-based service or jobs processed in batch mode. The arrival process of jobs in the cloud is not often deterministic. The irregular increase or decrease in workload has a vital impact on resource provision. Monitoring the resources helps in measuring the performance of the cloud so that the resource can be provisioned to customers efficiently.

A SEU Hardened Dual Dynamic Node Pulsed Hybrid Flip-Flop with an Embedded Logic Module

Abstract: In this paper we study the operation and working of a Dual Dynamic node hybrid flip-flop (DDFF-ELM) with an embedded logic module. It is one of the most efficient D-Flip-flops in terms of power and delay as compared to other dynamic flip flops. A double exponential current pulse is passed to the sensitive nodes of the circuit to model a radiation particle strike in the circuit. The faulty output is then corrected using a radiation hardening by design technique. All the circuits are implemented using Cadence 90 nm technology and a comparison is made between the power and delay of already implemented D- flip-flops.

Design and analysis of 8T SRAM with assist schemes (UDVS) in 45nm CMOS

Abstract: In modern ICs designing, the process of integrating more on-chip memories on a chip leads SRAMs to reason for a huge amount of total power and area of a chip. Therefore, memory designing with dynamic voltage scaling (DVS) capability is necessary. However, optimizing circuit operation over a wide range of voltage is not easy due to trade-offs of transistor characteristics in low-voltage and high-voltage. Ultra Dynamic Voltage Scaling (UDVS) techniques are used in low voltage levels to minimize the power consumption. Designing memories with DVS capability is gaining more importance since active as well as leakage power can be reduced by voltage scaling. UDVS is to scale the supply voltage by using assists circuits for different modes of the cell operation. In this paper three write assist circuits for reduction in power and 8T cell circuits have been designed. First one is Capacitive W-AC approach to reduce the level of cell supply voltage. Second scheme is Transient Negative Bit-line Voltage write assist scheme for write operation without using any on-chip or off-chip voltage sources and third one is transient negative bit line scheme in which write operation is performed by increasing the strength of SRAM pass transistor. Read operation for reading the data from the cell without altering (destructive read operation) the cell data with low power consumption. In this paper at last 8T SRAM cell in 45nm technology is implemented with operating voltage 1V.

Low Power and High Reliable Triple Modular Redundancy Latch for Single and Multi-node Upset Mitigation

Abstract: CMOS based circuits are more susceptible to the radiation environment as the critical charge (Qcrit) decreases with technology scaling. A single ionizing radiation particle is more likely to upset the sensitive nodes of the circuit and causes Single Event Upset (SEU). Subsequently, hardening latches to transient faults at control inputs due to either single or multi-nodes is progressively important. This paper proposes a Fully Robust Triple Modular Redundancy (FRTMR) latch. In FRTMR latch, a novel majority voter circuit is proposed with a minimum number of sensitive nodes. It is highly immune to single and multi-node upsets. The proposed latch is implemented using CMOS 45 nm process and is simulated in cadence spectre environment. Results demonstrate that the proposed latch achieves 17.83 % low power and 13.88 % low area compared to existing Triple Modular Redundant (TMR) latch. The current induced due to transient fault occurrence at various sensitive nodes are exhibited with a double exponential current source for circuit simulation with a minimum threshold current value of 40 µA.

Emerging contaminants of high concern and their enzyme-assisted biodegradation - A review.

Abstract: The widespread occurrence and adverse environmental and health-related impacts of various types of emerging contaminants (ECs) have become an issue of high concern. With ever increasing scientific knowledge, socio-economic awareness, health-related problems and ecological apprehensions, people are more concerned about the widespread ECs, around the globe. Among ECs, biologically active compounds from pharmaceutical, cosmeceutical, biomedical, personal care products (PPCPs), endocrine-disrupting chemicals (EDCs), and flame-retardants are of paramount concern. The presence and persistence of ECs in water bodies are of continued and burning interest, worldwide. Various types of ECs are being discharged knowingly/unknowingly with/without partial treatments into the aquatic environments that pose serious health issues and affects the entire living ecosystem. So far, various approaches have been developed for ECs degradation and removal to diminish their adverse impact. Many previous and/or ongoing studies have focused on contaminants degradation and efficient removal via numerous treatment strategies, i.e. (1) physical, (2) chemical and (3) biological. However, the experimental evidence is lacking to enable specific predictions about ECs mechanistic degradation and removal fate across various in-practice systems. In this context, the deployment oxidoreductases such as peroxidases (lignin peroxidases, manganese-dependent peroxidases, and horseradish peroxidase), aromatic dioxygenases, various oxygenases, laccases, and tyrosinases have received considerable research attention. Immobilization is highlighted as a promising approach to improve enzyme catalytic performance and stabilization, as well as, to protect the three-dimensional structure of the enzyme against the undesirable consequences of harsh reaction environment. This work overviews the current and state-of-the-art critical aspect related to hazardous pollutants at large and ECs in particular by the immobilized oxidoreductase enzymes. The first part of the review focuses on the occurrence, physiochemical behavior, potent sources and significant routes of ECs. Following that, environmentally-related adverse impacts and health-related issues of ECs are discussed in the second part. In the third part, biodegradation and removal strategies with a comparative overview of several conventional vs. non-conventional methods are presented briefly. The fourth part majorly focuses on operational modes of different oxidoreductase enzyme-based biocatalytic processes for the biodegradation and biotransformation of a wide array of harmful environmental contaminants. Finally, the left behind research gaps, concluding remarks as well as future trends and recommendations in the use of carrier-immobilized oxidoreductases for environmental perspective are also discussed.

Recent developments in the use of tyrosinase and laccase in environmental applications

Abstract: Our current global environmental challenges include the reduction of harmful chemicals and their derivatives. Bioremediation has been a key strategy to control the massive presence of chemicals in the environment. Enzymes including the phenoloxidases, laccases and tyrosinases, are increasingly being investigated as “green products” in the removal of many chemical contaminants in waters and soils. Both phenoloxidases are widespread in nature and attractive biocatalysts due to their ability to use readily available molecular oxygen as sole cofactor for their catalytic elimination of a large number of chemicals. Taking advantage of their catalytic potentials, remarkable advances have been made in the engineering of laccases to produce suitable biocatalysts in environmental applications. Studies about novel strategies of laccase immobilization and insolubilization for the treatment of chemical contaminants were provided. Likewise, tyrosinases are gaining increasing interest in environmental applicatio...

Streptomyces spp. in the biocatalysis toolbox.

Abstract: About 20,100 research publications dated 2000-2017 were recovered searching the PubMed and Web of Science databases for Streptomyces, which are the richest known source of bioactive molecules. However, these bacteria with versatile metabolism are powerful suppliers of biocatalytic tools (enzymes) for advanced biotechnological applications such as green chemical transformations and biopharmaceutical and biofuel production. The recent technological advances, especially in DNA sequencing coupled with computational tools for protein functional and structural prediction, and the improved access to microbial diversity enabled the easier access to enzymes and the ability to engineer them to suit a wider range of biotechnological processes. The major driver behind a dramatic increase in the utilization of biocatalysis is sustainable development and the shift toward bioeconomy that will, in accordance to the UN policy agenda "Bioeconomy to 2030," become a global effort in the near future. Streptomyces spp. already play a significant role among industrial microorganisms. The intention of this minireview is to highlight the presence of Streptomyces in the toolbox of biocatalysis and to give an overview of the most important advances in novel biocatalyst discovery and applications. Judging by the steady increase in a number of recent references (228 for the 2000-2017 period), it is clear that biocatalysts from Streptomyces spp. hold promises in terms of valuable properties and applicative industrial potential.

Biotechnological Potential of Oxidative Enzymes from Actinobacteria

Abstract: Oxidative enzymes are often considered for use in industrial processes because of the variety of reactions they are able to catalyse. In the past, most of these oxidative en‐ zymes were obtained from fungi. However, in recent years, it has become evident that these enzymes are also produced by bacteria, including actinobacterial strains, which can therefore be considered as an underexploited resource of oxidative enzymes with potential for application in various industries. This chapter will focus on selected oxi‐ dative enzymes found in actinobacteria, their potential for application in industrial processes and how we can access and improve these enzymes to suit the required bio‐ process conditions.

Enzymatic reactors for the removal of recalcitrant compounds in wastewater

Abstract: Enzymatic treatments based on oxidative enzymes, such as peroxidases, laccases and tyrosinases, have been proposed as an alternative to conventional methods to remove a broad range of contaminants present in wastewater. The aim of this study is to discuss existing technologies for the removal of pollutants based on the use of oxidative enzymes, including a discussion on the most important factors affecting the efficiency of the proposed systems. Factors involved in the catalytic cycle of the enzyme (biocatalyst, substrates and mediators), the addition of certain components to the reaction medium (additives, surfactants or solvents) as well as operational parameters (temperature, pH or agitation) will be discussed. Finally, two types of reactors: one-stage and two-stage enzymatic membrane reactors, especially designed for the treatment of micropollutants present in secondary effluents, will be described in detail.