Improved gymnemic acid production in the suspension cultures of Gymnema sylvestre through biotic elicitation

Bhuvaneswari Chodisetti,Kiranmayee Rao,Suryakala Gandi,Archana Giri 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.4

Enhancement of secondary metabolite accumulation in cultured plant cells through biotic and abiotic elicitation has been recognised as an important biotechnological strategy. Gymnema sylvestre is a rich source of triterpenoid saponins—gymnemic acids used mainly in the treatment of diabetes I and II. The cell suspension cultures initiated from the leaves and stalks of in vitro-grown plantlets have shown to accumulate large amounts of gymnemic acid. The cell-free extracts of Aspergillus niger, Saccharomyces cerevisiae, Agrobacterium rhizogenes, Bacillus subtilis and Escherichia coli were employed as sources of biotic elicitors to study the effect on secondary metabolite production. All the elicitors have shown a positive response in terms of gymnemic acid, with the highest response induced by A. niger [98.65 ± 0.93 mg/gramdry cell weight (gDCW)], 11.2-fold, and the lowest by E. coli (33.25 ± 1.38 mg/gDCW), 3.8-fold, in comparison to the untreated cultures (8.79 ± 0.82 mg/ gDCW). The suspension cultures of G. sylvestre can serve as a continuous source of gymnemic acids throughout the year, irrespective of the climatic and geographical barriers.

Three-Phase Hybrid Shunt Filters for Power Quality Improvement

Bhuvaneswari, G.,G.Nair, Manjula The Korean Institute of Power Electronics 2007 JOURNAL OF POWER ELECTRONICS Vol.7 No.3

Active power filters can be cost-effective for use in practical systems with the insertion of a few passive elements in shunt or series configuration. The resulting hybrid filters can be designed to provide dominant lower order harmonic elimination and reactive power support by the passive elements so that the burden on the active filter counterpart is reduced. In this paper, the rate reduction in the shunt active filter is estimated when it is connected in parallel with suitable passive tuned harmonic filters. The active filtering system is based on an appropriate control scheme. The simulation and the experimental results of the shunt active filter, along with the estimated value of reduction in rating, show that the hybrid shunt filtering system is quite effective in compensating for the harmonics and reactive power, in addition to being cost-effective.

Modeling of a Switched Reluctance Motor in Sensorless and 'With Sensor' Modes

Bhuvaneswari G.,Thakurta Sarit Guha,Rao P. Srinivasa,Murthy S.S. The Korean Institute of Power Electronics 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.4

Switched Reluctance Motors (SRM) have emerged as viable alternatives to other adjustable speed drives such as vector controlled induction motors (VCIM) and permanent magnet brush-less (PMBL) motors due to their simple construction, ease of control, low inertia and higher operating speeds. However, the indispensability of the rotor position sensor in an SRM for its successful operation increases its cost, apart from causing other problems like decreasing its reliability and inability to operate in adverse environmental conditions. In this paper, a new sensorless control scheme for the SRM is advocated. The required fundamental data is obtained by analyzing the SRM using the Finite Elements (FE) package MAXWELL. The drive is studied in both 'with sensor' and 'sensorless' modes and a comparison of the performances, in both cases, is presented for various operating conditions.

Improved gymnemic acid production in the suspension cultures of Gymnema sylvestre through biotic elicitation

Chodisetti, Bhuvaneswari,Rao, Kiranmayee,Gandi, Suryakala,Giri, Archana 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.4

Enhancement of secondary metabolite accumulation in cultured plant cells through biotic and abiotic elicitation has been recognised as an important biotechnological strategy. Gymnema sylvestre is a rich source of triterpenoid saponins-gymnemic acids used mainly in the treatment of diabetes I and II. The cell suspension cultures initiated from the leaves and stalks of in vitro-grown plantlets have shown to accumulate large amounts of gymnemic acid. The cell-free extracts of Aspergillus niger, Saccharomyces cerevisiae, Agrobacterium rhizogenes, Bacillus subtilis and Escherichia coli were employed as sources of biotic elicitors to study the effect on secondary metabolite production. All the elicitors have shown a positive response in terms of gymnemic acid, with the highest response induced by A. niger [$98.65{\pm}0.93$ mg/gramdry cell weight (gDCW)], 11.2-fold, and the lowest by E. coli ($33.25{\pm}1.38$ mg/gDCW), 3.8-fold, in comparison to the untreated cultures ($8.79{\pm}0.82$ mg/gDCW). The suspension cultures of G. sylvestre can serve as a continuous source of gymnemic acids throughout the year, irrespective of the climatic and geographical barriers.

Three-Phase Hybrid Shunt Filters for Power Quality Improvement

G. Bhuvaneswari,Manjula G.Nair 전력전자학회 2007 JOURNAL OF POWER ELECTRONICS Vol.7 No.3

Active power filters can be cost-effective for use in practical systems with the insertion of a few passive elements in shunt or series configuration. The resulting hybrid filters can be designed to provide dominant lower order harmonic elimination and reactive power support by the passive elements so that the burden on the active filter counterpart is reduced. In this paper, the rate reduction in the shunt active filter is estimated when it is connected in parallel with suitable passive tuned harmonic filters. The active filtering system is based on an appropriate control scheme. The simulation and the experimental results of the shunt active filter, along with the estimated value of reduction in rating, show that the hybrid shunt filtering system is quite effective in compensating for the harmonics and reactive power, in addition to being cost-effective.

Modeling of a Switched Reluctance Motor in Sensorless and “With Sensor” Modes

G. Bhuvaneswari,Sarit Guha Thakurta,P. Srinivasa Rao,S. S. Murthy 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.4

Switched Reluctance Motors (SRM) have emerged as viable alternatives to other adjustable speed drives such as vector controlled induction motors (VCIM) and permanent magnet brush-less (PMBL) motors due to their simple construction, ease of control, low inertia and higher operating speeds. However, the indispensability of the rotor position sensor in an SRM for its successful operation increases its cost, apart from causing other problems like decreasing its reliability and inability to operate in adverse environmental conditions. In this paper, a new sensorless control scheme for the SRM is advocated. The required fundamental data is obtained by analyzing the SRM using the Finite Elements (FE) package MAXWELL. The drive is studied in both “with sensor” and “sensorless” modes and a comparison of the performances, in both cases, is presented for various operating conditions.

Reduced Rating T-Connected Autotransformer Based Thirty-Pulse AC-DC Converter for Vector Controlled Induction Motor Drives

Singh Bhim,Bhuvaneswari G.,Garg Vipin The Korean Institute of Power Electronics 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.3

The design and performance analysis of a reduced rating autotransformer based thirty-pulse AC-DC converter is carried out for feeding a vector controlled induction motor drive (VCIMD). The configuration of the proposed autotransformer consists of only two single phase transformers, with their windings connected in a T-shape, resulting in simplicity in design, manufacturing and in a reduction in magnetics rating. The design procedure of the autotransformer along with the newly designed interphase transformer is presented. The proposed configuration has flexibility in varying the transformer output voltage ratios as required. The design of the autotransformer can be modified for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The proposed thirty-pulse AC-DC converter is capable of suppressing less than $29^{th}$ harmonics in the supply current. The power factor is also improved to near unity in the wide operating range of the drive. A comparison of different power quality indices at AC mains and DC bus is demonstrated in a conventional 6-pulse AC-DC converter and the proposed AC-DC converter feeding a VCIMD. A laboratory prototype of the proposed autotransformer based 30-pulse AC-DC converter was developed with test results validating the proposed design and system.

An Input Current Waveshaping AC-DC Converter for Rectifier Loads

Singh, Bhim,Garg, Vipin,Bhuvaneswari, G. The Korean Institute of Power Electronics 2008 JOURNAL OF POWER ELECTRONICS Vol.8 No.1

This paper presents the design and analysis of a new input AC current wave shaping AC-DC converter for cost effective harmonic mitigation under varying loads. The proposed converter consists of a delta-polygon connected autotransformer based twelve-pulse AC-DC converter and a small rating passive shunt filter tuned at $11^{th}$ harmonic frequency. The proposed AC-DC converter eliminates the most dominant $5^{th},\;7^{th}$ and $11^{th}$ harmonics and reduces higher order harmonics; thereby, resulting in an improved power quality at AC mains. Moreover, the design of the autotransformer is modified to make it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. To validate the proposed approach, various power quality indices are presented under varying loads. Experimental results obtained on the developed converter are given to validate the model and design of the proposed converter.

Optimization of Laccase Production from Bacillus sp. PK4 through Statistical Design of Experiments

( Murugesan Rajeswari ),( Vembu Bhuvaneswari ) 한국미생물생명공학회(구 한국산업미생물학회) 2017 한국미생물·생명공학회지 Vol.45 No.4

Statistical design of experiments was employed to optimize the media composition for the production of laccase from Bacillus sp. PK4. In order to find the key ingredients for the best yield of enzyme production from the selected eleven variables viz yeast extract, glucose, zinc sulphate, copper sulphate, potassium chloride, magnesium sulphate, calcium chloride, ferrous sulphate, sodium chloride, potassium dihydrogen phosphate (KH₂PO₄) and dipotassium hydrogen phosphate (K₂HPO₄), Plackett-Burman design was applied. The MgSO₄, FeSO₄, and CuSO₄ showed positive estimate, and their concentration optimized further. The steepest ascent method and Box-Behnken method revealed that 1.5 mM MgSO₄, 0.33 g/l FeSO₄ and 1.41 mM CuSO₄ were optimal for the laccase production by Bacillus sp. PK4. This optimization strategy leads to enhancement of laccase production from 2.13 U/ml to 40.79 U/ml. Agro-wastes residues replace the carbon source glucose in the optimized media namely sugarcane bagasse, wheat bran, rice husk, and groundnut shell, among these groundnut shells (117 U/ml) was found to enhance the laccase production significantly. The laccase produced by Bacillus sp. PK4 was found to have the potential to degrade persistent organic pollutant benzo[a]pyrene.

Reduced Rating T-Connected Autotransformer Based Thirty-Pulse AC-DC Converter for Vector Controlled Induction Motor Drives

Bhim Singh,G.Bhuvaneswari,Vipin Garg 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.3

The design and performance analysis of a reduced rating autotransformer based thirty-pulse AC-DC converter is carried out for feeding a vector controlled induction motor drive (VCIMD). The configuration of the proposed autotransformer consists of only two single phase transformers, with their windings connected in a T-shape, resulting in simplicity in design, manufacturing and in a reduction in magnetics rating. The design procedure of the autotransformer along with the newly designed interphase transformer is presented. The proposed configuration has flexibility in varying the transformer output voltage ratios as required. The design of the autotransformer can be modified for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The proposed thirty-pulse AC-DC converter is capable of suppressing less than 29<SUP>th</SUP> harmonics in the supply current. The power factor is also improved to near unity in the wide operating range of the drive. A comparison of different power quality indices at AC mains and DC bus is demonstrated in a conventional 6-pulse AC-DC converter and the proposed AC-DC converter feeding a VCIMD. A laboratory prototype of the proposed autotransformer based 30-pulse AC-DC converter was developed with test results validating the proposed design and system.