Invertase immobilised on montmorillonite: reusability enhancement and reduction in leaching

Invertase was immobilised on microporous montmorillonite K-10 via adsorption and covalent binding. The immobilised enzymes were tested for sucrose hydrolysis activity in a batch reactor. Km for immobilised systems was greater than free enzyme. The immobilised forms could be reused for 15 continuous cycles without any loss in activity. After 25 cycles, 85% initial activity was retained. A study on leaching of enzymes showed that 100% enzyme was retained even after 15 cycles of reuse. Leaching increased with reaction temperature. Covalent binding resisted leaching even at temperatures of 70 °C.

Design of Cyclophanes: Synthesis and Study of Photophysical and Biomolecular Recognition Properties

Development of organic molecules that exhibit selective interactions with different biomolecules has immense significance in biochemical and medicinal applications. In this context, our main objective has been to design a few novel functionaIized molecules that can selectively bind and recognize nucleotides and DNA in the aqueous medium through non-covalent interactions. Our strategy was to design novel cycIophane receptor systems based on the anthracene chromophore linked through different bridging moieties and spacer groups. It was proposed that such systems would have a rigid structure with well defined cavity, wherein the aromatic chromophore can undergo pi-stacking interactions with the guest molecules. The viologen and imidazolium moieties have been chosen as bridging units, since such groups, can in principle, could enhance the solubility of these derivatives in the aqueous medium as well as stabilize the inclusion complexes through electrostatic interactions.We synthesized a series of water soluble novel functionalized cyclophanes and have investigated their interactions with nucleotides, DNA and oligonucIeotides through photophysical. chiroptical, electrochemical and NMR techniques. Results indicate that these systems have favorable photophysical properties and exhibit selective interactions with ATP, GTP and DNA involving electrostatic. hydrophobic and pi-stacking interactions inside the cavity and hence can have potential use as probes in biology.

Development of nitrifying and photosynthetic sulfur bacteria based bioaugmentation systems for the bioremediation of ammonia and hydrogen sulphide in shrimp culture

This thesis entitled Development of nitrifying ans photosynthetic sulfur bacteria based bioaugmentation systems for the bioremediation of ammonia and hydregen sulphide in shrimp culture. the thesis is to propose a sustainable, low cost option for the mitigation of toxic ammonia and hydrogen sulphide in shrimp culture systems. Use of ‘bioaugmentors’ as pond additives is an emerging field in aquaculture. Understanding the role of organisms involved in the ‘bioaugmentor’ will obviously help to optimize conditions for their activity.The thesis describes the use of wood powder immobilization of nitrifying consortia.Shrimp grow out systems are specialized and highly dynamic aquaculture production units which when operated under zero exchange mode require bioremediation of ammonia, nitrite nitrogen and hydrogen sulphide to protect the crop. The research conducted here is to develop an economically viable and user friendly technology for addressing the above problem. The nitrifying bacterial consortia (NBC) generated earlier (Achuthan et al., 2006) were used for developing the technology.Clear demonstration of better quality of immobilized nitrifiers generated in this study for field application.

Growth and characterisation of tin dichalcogenide crystals

During the past few decades, a wide spread interest in the structural, optical, electrical and other physical properties of the transition metal dichalcogenide layer compounds has evolved. The members of this family of compounds can be regarded as strongly bonded two dimensional chalcogen-metal~chalcogen layers which are loosely coupled to one another by the weak ven der Waal's forces. Because of this type of bonding, the crystals are easily cleavable along the basal plane and show highly anisotropic properties. This thesis contains the growth and the study of the physical properties of certain tin dichalcogenide crystals (SnS2 and SnSe2). Tin disulphide and tin diselenide crystallize in the hexagonal CdI2 type crystal structure. This structure consists of layers of tin atoms sandwiched between two layers of chalcogen atoms. A tin atom is surrounded by six chalcogen atoms octahedrally.In the layers the atoms are held together by covalent bonding and in between the layers there is van der Waal's bonding.

Growth and characterisation of tin dichalcogenide crystals

During the past few decades, a wide spread interest in the structural, optical, electrical and other physical properties of the transition metal dichalcogenide layer compounds has evolved. The members of this family of compounds can be regarded as stronglybonded two dimensional chalcogen-metal-chalcogen layers which are loosely coupled to one another by the weak van der Waal's forces. Because of this type of bonding, the crystals are easily cleavable along the basal plane and show highly anisotropic properties. This thesis contains the growth and the study of the physical properties of certain tin dichalcogenide crystals (SnS2 and Snsea). Tin disulphide and tin diselenide crystallize in the hexagonal CdI2 type crystalstructure. This structure consists of layers of tin atoms sandwiched between two layers of chalcogen atoms. Aitin atom is surrounded by six chalcogen atoms octahedrally. In the layers the atoms are held together by covalent bonding and in between the layers there is van der Waal's bonding.

Crystal Structures and Spectral Investigation of Aroylhydrazones and their Mixed Ligand Metal Chelates

Supra molecular architectures of coordination complexes of liydrazones through non covalent interactions have been explored. Molecular self—assernbly driven by weak interactions such as hydrogen— bonding, K '”T[, C-1-I‘ "TE, van der Waals interactions, and so forth are currently of tremendous research interest in the fields of molecule based materials. The directional properties of the hydrogembonding interaction associate discrete molecules into aggregate structures that are sufficiently stable to be considered as independent chemical species. Chemistry can borrow nature’s strategy to utilize hydrogen-bonding as Well as other noncovalent interactions as found in secondary and tertiary structures of proteins such as the double helix folding of DNA, hydrophobic selflorganization of phospholipids in cell membrane etc. In supramolecular chemistry hydrogen bonding plays an important role in forming a variety of architectures. Thus, the wise modulation and tuning of the complementary sites responsible for hydrogen—bond formation have led to its application in supramolecular electronics, host-guest chemistry, self-assembly of molecular capsules, nanotubes etc. The work presented in this thesis describes the synthesis and characterization of metal complexes derived from some substituted aroylhydrazones. The thesis is divided into seven chapters.

Studies on L-glutamic acid Production using Brevibacterium sp.

The thesis comprises a set of experiments mainly focused on the improvement of L-glutamic acid fennentation. Much attention has been given to use of locally available raw materials, culturing the organism on inert solid substrates and also immobilization of the bacterial cells from the view point of long term utilization of biocatalyst and continuous operation of the stabilized system. Studies were also carried out for the down stream processing for the extraction and purification of L-glutamic acid. An attempt was made to study the morphological features of the microorganism including the cell premeability. In relation with the accumulation of glutamic acid within the cells an approach was made to study the behaviour of the Brevibacterium cells when they are exposed to hyper osmotic environment. Attempts were also made to study the requirement of iron and production of siderophores by this microbial strain. The search for a suitable nitrogen source for glutamate fermentation ended with a promising result that they got a potent urease activity and it can be utilized for many biotransfonnation studies. The entire thesis is presented in three sections, viz. introductory section, experimental section and the concluding section

Electronic structure and magnetic interactions of the spin-chain compounds Ca2CuO3 and Sr2CuO3

The results are presented of a combined periodic and cluster model approach to the electronic structure and magnetic interactions in the spin-chain compounds Ca2CuO3 and Sr2CuO3. An extended t-J model is presented that includes in-chain and interchain hopping and magnetic interaction processes with parameters extracted from ab initio calculations. For both compounds, the in-chain magnetic interaction is found to be around -240 meV, larger than in any of the other cuprates reported in the literature. The interchain magnetic coupling is found to be weakly antiferromagnetic, -1 meV. The effective in-chain hopping parameters are estimated to be ~650 meV for both compounds, whereas the value of the interchain hopping parameter is 30 meV for Sr2CuO3 and 40 meV for Ca2CuO3, in line with the larger interchain distance in the former compound. These effective parameters are shown to be consistent with expressions recently suggested for the Néel temperature and the magnetic moments, and with relations that emerge from the t-J model Hamiltonian. Next, we investigate the physical nature of the band gap. Periodic calculations indicate that an interpretation in terms of a charge-transfer insulator is the most appropriate one, in contrast to the suggestion of a covalent correlated insulator recently reported in the literature.

Lipase Production by Candida rugosa

Strain improvement is one of the major objectives for maximizing the microbial production of industrially significant primary and secondary metabolites. This goal can be achieved by judicious tuning of the organisms by monitoring its growth parameters and optimizing adequate supply of micro and macro nutrients, inducers, pH, temperature and other factors which control fermentation. Though C. rugosa has been under extensive studies for lipases, maximum world production is only 36 units. In fact, in India, enhanced production conditions for lipases have not yet been initiated. C. rugosa has been cultivated in diverse environments like liquid, semi-solid, solid—state and immobilized conditions, though major emphasis is on SmF or suspension culture. Hence the present investigations mainly focused on increasing the yield by adjusting the physico-chemical growth parameters and to characterize the lipase isoforms secreted by C. rugosa in the culture medium. Maximum possible improved methods were investigated to achieve these objectives. Within this under-optimised background, enhancement of lipase production and its characterization were investigated, employing modified liquid, semi-solid, solid—state and immobilized fermentation strategies

Fermentation Of Rice And Related Products By Bacillus Sp.

Recently’ recognition cnf immobilization ‘technology for the rapid conversion of several substrates into metabolites and repeated reuse of the biocatalysts have drawn the attention of the fermentation scientists and technologists to try these new technologies for the rapid production of pnxkmt and enhancement of the efficiencies of the systems Hence in the present study rice was selected,as a substrate since it is a rich source of starch, available and cultivated throughout the year almost in all part of our country. Rice although known for its use as a staple food in many forms as rice, idli, dosai etc., has not been used in industry extensively. However, it ii; a potential resource for’ the production of alcohol, high protein food anui for sugar and sugar syrups as it is evidenced by the few reports mentioned in the review of literature. Of the several microorganisms available, Bacillus sp, is a known candidate for the production of amylases. Hence in the present study Bacillus sp, was desired for its known efficiencies in starch conversion

Studies On In Vitfio Production Of Secondary Metabolites From Medicinal Plants

In the light of the very huge demand for natural ephedrine and pseudoephidrine, a search for an angiosperm plant containing the alkaloid ephedrine was made and could locate Sida spp. of malvaceae family. Sida is a large genus of, herbs and shrubs distributed throughout the tropics. About a dozen species occur in India. The medicinally important species known are S.rhombrfolia S.cordata and S.spinosa (Anon, 1972). Among the various species, S.rh0mbIfolia is the most widely used one in the traditional system of medicine. An attempt was made in the present study to develop an ideal bioprocess for the in vitro production of ephedrine from the cell culture system of Sida rhombrfolia Linn. ssp. retusa. The callus and suspension culture were initiated and attempts were made to enhance the yield positively by employing various strategies like mutagenesis, immobilization and addition of precursors, elicitors and penneabilizing agents.

Activated packed bed bioreactor for rapid nitrification in brackish water hatchery systems

A packed bed bioreactor (PBBR) was developed for rapid establishment of nitrification in brackish water hatchery systems in the tropics. The reactors were activated by immobilizing ammonia-oxidizing (AMONPCU- 1) and nitrite-oxidizing (NIONPCU-1) bacterial consortia on polystyrene and low-density polyethylene beads, respectively. Fluorescence in situ hybridization demonstrated the presence of autotrophic nitrifiers belong to Nitrosococcus mobilis, lineage of b ammonia oxidizers and nitrite oxidizer Nitrobacter sp. in the consortia. The activated reactors upon integration to the hatchery system resulted in significant ammonia removal (P\0.01) culminating to its undetectable levels. Consequently, a significantly higher percent survival of larvae was observed in the larval production systems. With spent water the reactors could establish nitrification with high percentage removal of ammonia (78%), nitrite (79%) and BOD (56%) within 7 days of initiation of the process. PBBR is configured in such a way to minimize the energy requirements for continuous operation by limiting the energy inputs to a single stage pumping of water and aeration to the aeration cells. The PBBR shall enable hatchery systems to operate under closed recirculating mode and pave the way for better water management in the aquaculture industry.

Stringed bed suspended bioreactors (SBSBR)for in situ nitrification in penaeid and non-penaeid hatchery systems

For establishing nitrification in prawn (non-penaeid, salinity 10–15 ppt) and shrimp (penaeid, salinity 30–35 ppt) larval production systems, a stringed bed suspended bioreactor (SBSBR) was designed, fabricated, and validated. It was fabricated with 5 mm polystyrene and low density polyethylene beads as the substrata for ammonia and nitrite oxidizing bacterial consortia, respectively, with an overall surface area of 684 cm2. The reactors were activated in a prototype activator and were transported in polythene bags to the site of testing. Performance of the reactors activated with the nitrifying bacterial consortia AMONPCU-1 (ammonia oxidizers for non-penaeid culture) and NIONPCU-1 (nitrite oxidizers for non-penaeid culture) was evaluated in a Macrobrachium rosenbergii larval rearing system and those activated with AMOPCU-1 (ammonia oxidizers for penaeid culture) and NIOPCU-1 (nitrite oxidizers for penaeid culture) in a Penaeus monodon seed production system. Rapid setting up of nitrification could be observed in both the static systems which resulted in a higher relative per cent survival of larvae

Continuous production of L-glutaminase by an immobilized marine Pseudomonas sp BTMS-51 in a packed bed reactor

A marine Pseudomonas sp BTMS-51, immobilized by Ca-alginate gel entrapment was used for the production of extracellular Lglutaminase under repeated batch process and continuous process employing a packed bed reactor (PBR). Immobilized cells could produce an average of 25 U/ml of enzyme over 20 cycles of repeated batch operation and did not show any decline in production upon reuse. The enzyme yield correlated well with the biomass content in the beads. Continuous production of the enzyme in PBR was studied at different substrate concentrations and dilution rates. In general, the volumetric productivity increased with increased dilution rate and substrate concentrations and the substrate conversion efficiency declined. The PBR operated under conditions giving maximal substrate conversion efficiency gave an average yield of 21.07 U/ml and an average productivity of 13.49 U/ml/h. The system could be operated for 120 h without any decline in productivity