Browsing by Author "Raval, K."

Now showing 1 - 20 of 53

A marine chitinase from Bacillus aryabhattai with antifungal activity and broad specificity toward crystalline chitin degradation
(Taylor and Francis Ltd., 2022) Subramani, A.K.; Raval, R.; Sundareshan, S.; Sivasengh, R.; Raval, K.
Chitinases convert chitin into chitin oligomers and are also known antifungal agents. Chitin oligomers have numerous industrial applications. However, chitin’s crystalline nature requires pretreatment before breakdown into oligomers. In the study, a novel marine bacterium Bacillus aryabhattai is isolated from the Arabian Sea. Bacterial growth in different crystalline chitin substrates like chitin powder, chitin flakes, and colloidal chitin confirmed the chitinase presence in bacterium could act upon insoluble crystalline chitin with the fractional release of oligomers. The domain architecture analysis of the chitinase confirmed the presence of two N-terminal LysM domains which help enzyme action on crystalline chitin. Statistical optimization of media and Process parameters revealed glycerol, yeast extract, magnesium chloride, and manganese sulfate as significant media components along with colloidal chitin. The optimum process parameters such as pH 7, temperature 40 °C, inoculum size 12.5% (v/v), and inoculum age 20 hours enhanced the specific enzyme activity to ±146.2 U/mL, ±114.9 U/mL and ±175.4 U/mL against chitin powder, chitin flakes and colloidal chitin respectively, which is five to six times higher than basal level activity. The antifungal activity of chitinase against plant pathogenic fungi like Candida albicans and Fusarium oxysporum revealed a zone of inhibition with 14 mm diameter. © 2022 Taylor & Francis Group, LLC.
A perspective of advanced biosensors for environmental monitoring
(Elsevier, 2019) Mohan Balakrishnan, R.M.; Uddandarao, U.; Raval, K.; Raval, R.
Biosensor technology has developed in leaps and bounds due to multidisciplinary approach between biotechnology and nanotechnology. This synergy provided much needed characteristic features, such as sensitivity and selectivity to the biosensor technology. Biosensors are venerated as superior entities for electrochemical, optical, and calorimetric-based sensing because of their exceptional size properties. They are the potential tools, which exhibited the feasibility and potential in detecting various biological, physical, chemical, radiological contaminants in water. This book chapter outlines the overview of various types of sensors, especially on chalcogen-based semiconductor nanoparticles. In this scenario, green route nanoparticles which employ PbSe quantum dots synthesis via marine Aspergillus terreus and ZnS/PbS nanoparticles via an endophytic fungus Aspergillus flavus are focused in this chapter. The book chapter also discusses about highly selective biogenic nanosensors which play a significant role in improving the capacity of biosensors due to their size tuneable quantum confinement effects. Potential applications of these biosensors for environmental monitoring are discussed. © 2019 Elsevier Inc. All rights reserved.
A sustainable bioprocess for lipase production using seawater and the byproduct obtained from coconut oil industries
(CRC Press/Balkema, 2019) Raval, R.; Verma, A.; Raval, K.
Globally lipases are the most attractive source of research, as it has numerous applications in various industries like food industry, paper and pulp industry, preparation of beverages etc. A lipase producing bacterium, Pseudomonas stutzeri, was isolated from sea water. The bacterial culture was introduced to the physical and chemical mutagens and then allowed to grow on the solid media. A number of mutated clones were produced which were further followed by examining their lipase activity. There was a significant increase in the extracellular lipase activity i.e. 13, 56 and 14 folds increase in the case of UV mutation, sodium azide, and NTG respectively. Further, the mutants were subcultured and stability was observed in NTG mutants. The lipase production from the NTG mutants was optimized using Response Surface Methodology (RSM). The maximum lipase activity of 1132.6 U/ml was obtained which was about 7 folds higher than the parent strain using the process which utilized the residual coconut cake, a byprtoduct of coconut oil industries and the sea water which makes the process sustainable. Â© 2020 Taylor & Francis Group, London, ISBN 978-0-367-33737-7
Adsorptive removal of trivalent and pentavalent arsenic from aqueous solutions using iron and copper impregnated melanin extracted from the marine bacterium Pseudomonas stutzeri
(2020) Manirethan, V.; Raval, K.; Raj Mohan, Balakrishnan
The metalloid arsenic is one of the most conspicuous groundwater contaminants in the Indian subcontinent and its removal from aqueous medium is the main focus of this study. The study aims at functionalising melanin using iron and copper for the efficient removal of arsenic and rendering water fit for consumption. Melanin obtained from the marine bacteria Pseudomonas stutzeri was functionalised by iron impregnation (Fe-melanin) and copper impregnation (Cu-melanin). Morphological studies using FESEM portrayed the impregnated iron and copper granules on the surface of melanin, while XRD analysis confirmed the presence of Fe2O3 and CuO on melanin. Adsorption studies on As (V) and As (III) were conducted using Fe-melanin and Cu-melanin for different operating variables like pH, temperature and contact time. More than 99% per cent of As (III) and As (V) from water was removed at a pH range between 4 and 6 within 50 min in the case of Fe-melanin and 80 min for Cu-melanin. Adsorption equilibrium studies showed better fit with Langmuir adsorption isotherm and had good agreement with Redlich-Peterson's three-parameter model. The maximum adsorption capacities of Fe-melanin and Cu-melanin obtained from Langmuir adsorption model are 50.12 and 20.39 mg/g, respectively, for As (V) and similarly 39.98 and 19.52 mg/g, respectively, for As (III). Arsenic-binding to the functionalised melanin was confirmed using FT-IR and the XPS analysis. Reuse of the adsorbent was effectively done by desorbing the iron and copper together with the bound As (III) and As (V) and further re-impregnation of iron and copper in melanin. Re-functionalised melanin showed 99% adsorption efficiency up to four cycles of adsorption/desorption. A novel iron and copper impregnated melanin was synthesized to remove As (III) and As (V) from groundwater and the adsorption process was optimized. 2019 Elsevier Ltd
Adsorptive removal of trivalent and pentavalent arsenic from aqueous solutions using iron and copper impregnated melanin extracted from the marine bacterium Pseudomonas stutzeri
(Elsevier Ltd, 2020) Manirethan, V.; Raval, K.; Mohan Balakrishnan, R.M.
The metalloid arsenic is one of the most conspicuous groundwater contaminants in the Indian subcontinent and its removal from aqueous medium is the main focus of this study. The study aims at functionalising melanin using iron and copper for the efficient removal of arsenic and rendering water fit for consumption. Melanin obtained from the marine bacteria Pseudomonas stutzeri was functionalised by iron impregnation (Fe-melanin) and copper impregnation (Cu-melanin). Morphological studies using FESEM portrayed the impregnated iron and copper granules on the surface of melanin, while XRD analysis confirmed the presence of Fe2O3 and CuO on melanin. Adsorption studies on As (V) and As (III) were conducted using Fe-melanin and Cu-melanin for different operating variables like pH, temperature and contact time. More than 99% per cent of As (III) and As (V) from water was removed at a pH range between 4 and 6 within 50 min in the case of Fe-melanin and 80 min for Cu-melanin. Adsorption equilibrium studies showed better fit with Langmuir adsorption isotherm and had good agreement with Redlich-Peterson's three-parameter model. The maximum adsorption capacities of Fe-melanin and Cu-melanin obtained from Langmuir adsorption model are 50.12 and 20.39 mg/g, respectively, for As (V) and similarly 39.98 and 19.52 mg/g, respectively, for As (III). Arsenic-binding to the functionalised melanin was confirmed using FT-IR and the XPS analysis. Reuse of the adsorbent was effectively done by desorbing the iron and copper together with the bound As (III) and As (V) and further re-impregnation of iron and copper in melanin. Re-functionalised melanin showed 99% adsorption efficiency up to four cycles of adsorption/desorption. A novel iron and copper impregnated melanin was synthesized to remove As (III) and As (V) from groundwater and the adsorption process was optimized. © 2019 Elsevier Ltd
Batch and continuous studies on the removal of heavy metals from aqueous solution using biosynthesised melanin-coated PVDF membranes
(2019) Manirethan, V.; Gupta, N.; Raj Mohan, Balakrishnan; Raval, K.
Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up. 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
Batch and continuous studies on the removal of heavy metals from aqueous solution using biosynthesised melanin-coated PVDF membranes
(Springer, 2020) Manirethan, V.; Gupta, N.; Mohan Balakrishnan, R.M.; Raval, K.
Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon–Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
Bioethanol: A New Synergy between Marine Chitinases from Bacillus haynesii and Ethanol Production by Mucor circinelloides
(MDPI, 2023) Govindaraj, V.; Subramani, A.K.; Gopalakrishnan, R.; Kim, S.-K.; Raval, R.; Raval, K.
The fourth generation of bioethanol production is on a lookout for non-lignocellulosic biomass waste. One such candidate is chitin, the second most abundant biopolymer on earth. However, the crystalline nature of chitin hinders its application potential for bioethanol production. This limitation can be circumvented by hydrolysing this polymer into oligomers using chitinases. We used this hypothesis and isolated a Bacillus haynesii, a marine bacterium that utilizes colloidal chitin as a substrate and produces chitin oligosaccharides. Further, we utilized Mucor circinelloides to produce bioethanol using the chitin oligosaccharides in the shake flask. We investigated the effect of inoculum age, filling volume, different substrates, and substrate concentration on bioethanol production using Mucor circinelloides from Bacillus haynesii-produced chitin oligosaccharides. Bacillus haynesii demonstrated a maximum chitinase activity of 3.08 U/mL with specific activity of 96 U/mg at the 90th h. Chitin oligosaccharides produced by Bacillus haynesii were confirmed using mass spectrometry. Bioethanol concentration was determined using dichromate oxidation assay as well as gas chromatography. The research resulted in 7.4 g/L of ethanol from 30 g/L of chitin oligosaccharides, with a maximum ethanol yield of 0.25 g of ethanol/g substrate at the 55th h with 48 h inoculum in 80 mL of fermentation medium. Results suggest that chitin oligosaccharides from Bacillus haynesii are an effective and renewable substrate for bioethanol production. © 2023 by the authors.
Characterization of heat transfer of large orbitally shaken cylindrical bioreactors
(2014) Raval, K.; Kato, Y.; Buechs, J.
Disposable shaking bioreactors are a promising alternative to other disposable bioreactors owing to their ease of operation, flexibility, defined hydrodynamics and characterization. Shaken bioreactors of sizes 20. L and 50. L are characterized in terms of heat transfer characteristics in this research work. Water and an 80% glycerol-water system were used as fluid. Results indicated large heat generation due to shake mixing which was observed by temperature difference between the fluid inside the vessel and the surrounding air outside the vessel. Maximum temperature difference of ca. 30. K was encountered for a 50. L vessel, at 300. rpm and 20. L filling volume. Outside heat transfer rate was governing the overall heat transfer process. Lateral air flow did increase heat transfer rates to large extent. An empirical correlation of overall heat transfer coefficient was obtained in terms of filling volume, rotational speed and lateral air flow rate. However, as the vessel thickness increased, the overall heat transfer process was limited by vessel wall resistance. 2014 Elsevier B.V.
Characterization of heat transfer of large orbitally shaken cylindrical bioreactors
(Elsevier, 2014) Raval, K.; Kato, Y.; Büchs, J.
Disposable shaking bioreactors are a promising alternative to other disposable bioreactors owing to their ease of operation, flexibility, defined hydrodynamics and characterization. Shaken bioreactors of sizes 20. L and 50. L are characterized in terms of heat transfer characteristics in this research work. Water and an 80% glycerol-water system were used as fluid. Results indicated large heat generation due to shake mixing which was observed by temperature difference between the fluid inside the vessel and the surrounding air outside the vessel. Maximum temperature difference of ca. 30. K was encountered for a 50. L vessel, at 300. rpm and 20. L filling volume. Outside heat transfer rate was governing the overall heat transfer process. Lateral air flow did increase heat transfer rates to large extent. An empirical correlation of overall heat transfer coefficient was obtained in terms of filling volume, rotational speed and lateral air flow rate. However, as the vessel thickness increased, the overall heat transfer process was limited by vessel wall resistance. © 2014 Elsevier B.V.
Cloning, expression, purification and characterization of chitin deacetylase extremozyme from halophilic Bacillus aryabhattai B8W22
(Springer Science and Business Media Deutschland GmbH, 2021) Pawaskar, G.M.; Raval, K.; Rohit, P.; Shenoy, R.P.; Raval, R.
Chitin deacetylase (CDA) (EC 3.5.1.41) is a hydrolytic enzyme that belongs to carbohydrate esterase family 4 as per the CAZY database. The CDA enzyme deacetylates chitin into chitosan. As the marine ecosystem is a rich source of chitin, it would also hold the unexplored extremophiles. In this study, an organism was isolated from 40 m sea sediment under halophilic condition and identified as Bacillus aryabhattai B8W22 by 16S rRNA sequencing. The CDA gene from the isolate was cloned and overexpressed in E. coli Rosetta pLysS and purified using a Ni–NTA affinity chromatography. The enzyme was found active on both ethylene glycol chitin (EGC) and chitooligosaccharides (COS). The enzyme characterization study revealed, maximum enzyme velocity at one hour, optimum pH at 7 with 50 mM Tris–HCl buffer, optimum reaction temperature of 30 ºC in standard assay conditions. The co-factor screening affirmed enhancement in the enzyme activity by 142.43 ± 7.13% and 146.88 ± 4.09% with substrate EGC and COS, respectively, in the presence of 2 mM Mg2+. This activity was decreased with the inclusion of EDTA and acetate in the assay solutions. The enzyme was found to be halotolerant; the relative activity increased to 116.98 ± 3.87% and 118.70 ± 0.98% with EGC and COS as substrates in the presence of 1 M NaCl. The enzyme also demonstrated thermo-stability, retaining 87.27 ± 2.85% and 94.08 ± 0.92% activity with substrate EGC and COS, respectively, upon treatment at 50 ºC for 24 h. The kinetic parameters Km, Vmax, and Kcat were 3.06E?05 µg mL?1, 3.06E + 01 µM mg?1 min?1 and 3.27E + 04 s?1, respectively, with EGC as the substrate and 7.14E?07 µg mL?1, 7.14E + 01 µM mg?1 min?1 and 1.40E + 06 s?1, respectively, with COS as the substrate. The enzyme was found to be following Michaelis–Menten kinetics with both the polymeric and oligomeric substrates. In recent years, enzymatic conversion of chitosan is gaining importance due to its known pattern of deacetylation and reproducibility. Thus, this BaCDA extremozyme could be used for industrial production of chitosan polymer as well as chitosan oligosaccharides for biomedical application. © 2021, The Author(s).
Duration of dry and humidified incubation of single-step embryo culture medium and oxygen tension during sham culture do not alter medium composition.
(F1000 Research Ltd, 2022) Adiga, S.K.; Cheredath, A.; Uppangala, S.; Asampille, G.; Lakshmi, V.; Joseph, D.; Raval, K.; Gowda, N.; Kalthur, G.
Background: The extended embryo culture using single-step medium gained popularity in clinical in vitro fertilisation (IVF). However, there are concerns about the degradation of unstable medium components and their negative effects on the developing embryos. Further, dry-incubation can increase osmolality, which can in-turn enhance the concentration of constituents of the media and their stability. Hence, this study was conducted to understand the immediate changes in the culture media constituents in relation to clinically comparable situations such as single-step extended embryo culture and use of dry and humidified-incubation in two-different gaseous conditions. Methods: Commercially available single-step medium was sham-cultured in droplets under oil in two different conditions viz. dry (37°C; 6%CO 2; 5%O 2) and humidified (37°C; 6% CO 2; atmospheric O 2) for 0h, 72h, and 120h intervals. Droplets were subjected to the sensitivity-enhanced nuclear magnetic resonance (NMR)-based profiling using 800 MHz NMR equipped with a cryogenically cooled micro-coil (1.7mm) probe. NMR profile of the embryo culture medium between the two groups were comprehensively assessed. Results: A total of ten amino acids and four energy substrates were identified from the culture medium. The medium constituents identified showed a non-significant increase in the dry-incubation group at 72h and then declined at 120h. Humidified incubation had no effects on the level of the identified medium constituents until 120h. No significant differences in the levels of medium constituents identified were observed between the dry and humidified-groups at various time-points tested. Conclusions: A non-significant variation in the levels of medium constituents observed in the dry-incubation of single-step medium most unlikely to influence a clinical outcome. However, the impact of these subtle changes on the (epi)genetic integrity of the embryos in a clinical set-up to be addressed. © 2022 Cheredath A et al.
Duration of dry and humidified incubation of single-step embryo culture medium and oxygen tension during sham culture do not alter metabolomics signature
(NLM (Medline), 2022) Cheredath, A.; Uppangala, S.; Asampille, G.; Lakshmi, V.; Joseph, D.; Raval, K.; Gowda G A, N.; Kalthur, G.; Adiga, S.K.
Background: The extended embryo culture using single-step medium gained popularity in clinical in vitro fertilisation (IVF). However, there are concerns about the degradation of unstable medium components and their negative effects on the developing embryos. Further, dry-incubation can increase osmolality, which can in-turn enhance the concentration of constituents of the media and their stability. Hence, this study was conducted to understand the immediate changes in the culture media metabolites in relation to clinically comparable situations such as single-step extended embryo culture and use of dry and humidified-incubation in two-different gaseous conditions. Methods: Commercially available single-step medium was sham-cultured in droplets under oil in two different conditions viz. dry (37°C; 6%CO 2; 5%O 2) and humidified (37°C; 6% CO 2; atmospheric O 2) for 0h, 72h, and 120h intervals. Droplets were subjected to the sensitivity-enhanced nuclear magnetic resonance (NMR)-based profiling using 800 MHz NMR equipped with a cryogenically cooled micro-coil (1.7mm) probe. Metabolomic signatures between the two groups were comprehensively assessed. Results: A total of ten amino acids and four energy substrates were identified from the culture medium. Metabolite levels showed a non-significant increase in the dry-incubation group at 72h and then declined at 120h. Humidified incubation had no effects on the level of the metabolite until 120h. No significant differences in the levels of metabolites were observed between the dry and humidified-groups at various time-points tested. Conclusions: A non-significant variation in the levels of metabolites observed in the dry-incubation of single-step medium most unlikely to influence a clinical outcome. However, the impact of these subtle changes on the (epi)genetic integrity of the embryos in a clinical set-up to be addressed. ©: © 2022 Cheredath A et al.
Engineering a recombinant chitinase from the marine bacterium Bacillus aryabhattai with targeted activity on insoluble crystalline chitin for chitin oligomer production
(Elsevier B.V., 2024) Subramani, A.K.; Ramachandra, R.; Thote, S.; Govindaraj, V.; Vanzara, P.; Raval, R.; Raval, K.
Chitin, an abundant polysaccharide in India, is primary by-product of the seafood industry. Efficiently converting chitin into valuable products is crucial. Chitinase, transforms chitin into chitin oligomers, holds significant industrial potential. However, the crystalline and insoluble nature of chitin makes the conversion process challenging. In this study, a recombinant chitinase from marine bacteria Bacillus aryabhattai was developed. This enzyme exhibits activity against insoluble chitin substrates, chitin powder and flakes. The chitinase gene was cloned into the pET 23a plasmid and transformed into E. coli Rosetta pLysS. IPTG induction was employed to express chitinase, and purification using Ni-NTA affinity chromatography. Optimal chitinase activity against colloidal chitin was observed in Tris buffer at pH 8, temperature 55°C, with the presence of 400 mM sodium chloride. Enzyme kinetics studies revealed a Vmax of 2000 μmole min−1 and a Km of 4.6 mg mL−1. The highest chitinase activity against insoluble chitin powder and flakes reached 875 U mg−1 and 625 U mg−1, respectively. The chitinase demonstrated inhibition of Candida albicans, Fusarium solani, and Penicillium chrysogenum growth. Thin Layer Chromatography (TLC) and LC-MS analysis confirmed the production of chitin oligomers, chitin trimer, tetramer, pentamer, and hexamer, from chitin powder and flakes using recombinant chitinase. © 2024 Elsevier B.V.
Enhanced degradation of azo dye using mixed cultures of white-rot fungi in a modified rotating packed disc bioreactor and reuse of treated water
(Elsevier Ltd, 2023) Kalnake, R.P.; Raval, R.; Murthy, D.V.R.; Vanzara, P.B.; Raval, K.
Reactive azo dyes are toxic and carcinogenic. In this study, mixed cultures of white-rot fungi (WRF) are used to treat synthetic reactive black 5 (RB-5) wastewater in a modified rotating packed disc bioreactor (RPDB). The continuous degradation studies were carried out for 25 days under the influence of the recycle stream in which 3665 L of synthetic effluent was treated. The dye wastewater was completely decolorized with more than 93 % chemical oxygen demand (COD) reduction using the mixed fungal culture. During the continuous operation, the COD of influent reduced more than 85 % for successive 25 days of continuous operation at hydraulic retention time of 10.8 h. The dry biomass loading was about 0.14 g/g GAC at the end of the continuous process. The rate of COD removal followed first order kinetics with a rate constant of 0.026 per hour. The treated water was reused to produce melanin from microbial culture. © 2023 Elsevier Ltd
Enhancement of a Novel Extracellular Uricase Production by Media Optimization and Partial Purification by Aqueous Three-Phase System
(2015) Ram, S.K.; Raval, K.; Jagadeeshbabu, P.E.
Uricase (urate: oxygen oxidoreductase, EC 1.7.3.3), an enzyme belonging to the class of oxidoreductases, catalyzes the enzymatic oxidation of uric acid to allantoin and finds a wide variety of application as therapeutic and clinical reagent. In this study, uricase production ability of the bacterial strains isolated from deep litter poultry soil is investigated. The strain with maximum extracellular uricase production capability was identified as Xanthomonas fuscans subsp. aurantifolii based on 16S rRNA sequencing. Effect of various carbon and nitrogen sources on uricase productivity was investigated. The uricase production for this strain was optimized using statistically based experimental designs and resulted in uricase activity of 306 U/L, which is 2 times higher than initial uricase activity. Two-step purification, such as ammonium sulfate precipitation and aqueous two-phase system, was carried out and a twofold increase in yield and specific activity was observed. 2015 Taylor and Francis Group, LLC.
Enhancement of a Novel Extracellular Uricase Production by Media Optimization and Partial Purification by Aqueous Three-Phase System
(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2015) Ram, S.K.; Raval, K.; JagadeeshBabu, P.E.
Uricase (urate: oxygen oxidoreductase, EC 1.7.3.3), an enzyme belonging to the class of oxidoreductases, catalyzes the enzymatic oxidation of uric acid to allantoin and finds a wide variety of application as therapeutic and clinical reagent. In this study, uricase production ability of the bacterial strains isolated from deep litter poultry soil is investigated. The strain with maximum extracellular uricase production capability was identified as Xanthomonas fuscans subsp. aurantifolii based on 16S rRNA sequencing. Effect of various carbon and nitrogen sources on uricase productivity was investigated. The uricase production for this strain was optimized using statistically based experimental designs and resulted in uricase activity of 306 U/L, which is 2 times higher than initial uricase activity. Two-step purification, such as ammonium sulfate precipitation and aqueous two-phase system, was carried out and a twofold increase in yield and specific activity was observed. © 2015 Taylor and Francis Group, LLC.
Evaluation of Chitosan and Its Derivatives in Immunomodulating Blood Sentinel Cells
(Apple Academic Press, 2024) Subramani, A.K.; Raval, K.; Raval, R.
Opportunistic pathogens can invade and thus cause infections in the body. However, in most instances, the body mounts an immune response to counter the infection. Sentinel cells are the body’s second line of defense, which act against invading microbes. An important part of the innate system, these sentinel cells include macrophages, neutrophils, and dendritic cells. The plethora of pattern recognition receptors helps them to combat the invading pathogen from colonizing the body. They do so by inducing inflammation and oxidative stress or by the adaptive immune cells releasing chemokines. However, a paradigm shift of unrestrained inflammation or oxidative stress can also lead to a hypersensitivity reaction, sepsis, or autoimmune disorder. On the other extreme, an under-responsive sentinel cell might lead to frequent infections. Immunomodulators like chitosan can assist the sentinel cells in the titrated priming of the pathogen, thereby reducing chronic inflammation conditions. Chitosan, the amorphous derivative of chitin is the second largest abundant polymer after cellulose. The physicochemical properties of chitosan and COS depend on molecular weight, degree of polymerization 52(DP), and degree of deacetylation (DD). Thus, the modulation of these properties can impart chitosan and its oligosaccharides (COS) for various biomedical applications. In the present chapter, an overview of the innate responses of the sentinel cells and the synergistic roles played by chitosan and its derivatives to regularize various responses. © 2024 Apple Academic Press, Inc.
Experimentally Induced Hyperglycemia in Prepubertal Phase Impairs Oocyte Quality and Functionality in Adult Mice
(Endocrine Society, 2022) Predheepan, D.; Daddangadi, A.; Uppangala, S.; Koulmane Laxminarayana, S.L.K.; Raval, K.; Kalthur, G.; Kovaĉiĉ, B.; Kumar Adiga, S.
Reproductive abnormalities in women with a history of childhood diabetes are believed to be partially attributed to hyperglycemia. Prolonged hyperglycemia can negatively affect ovarian function and fertility during reproductive life. To address this in an experimental setting, the present study used streptozotocin-induced hyperglycemic prepubertal mouse model. The impact of prolonged hyperglycemic exposure during prepubertal life on ovarian function, oocyte quality, and functional competence was assessed in adult mice. The ovarian reserve was not significantly altered; however, the in vitro maturation potential (P<0.001), mitochondrial integrity (P<0.01), and meiotic spindle assembly (P<0.05-0.001) in oocytes were significantly affected in hyperglycemic animals in comparison to control groups. The results from the study suggest that prepubertal hyperglycemia can have adverse effects on the oocyte functional competence and spindle integrity during the reproductive phase of life. Because these changes can have a significant impact on the genetic integrity and developmental potential of the embryos and fetus, the observation warrants further research both in experimental and clinical settings. © 2022 The Author(s). Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved.
Expression of Bacillus licheniformis chitin deacetylase in E. coli pLysS: Sustainable production, purification and characterisation
(2019) Bhat, P.; Pawaskar, G.-M.; Raval, R.; Cord-Landwehr, S.; Moerschbacher, B.; Raval, K.
Chitosan obtained by enzymatic deacetylation of chitin using chitin deacetylase (CDA) holds promise primarily due to the possibility to yield chitosan with non-random patterns of acetylation and more environmentally friendly process compared to chemical deacetylation. In the present study, a sustainable bioprocess is reported for over-expression of a bacterial CDA in E. coli pLysS cells. A Bacillus licheniformis CDA gene is identified in the genome of the bacterium, cloned, and expressed, yielding enzymatically active recombinant protein. For enzyme production, a growth medium is formulated using carbon and nitrogen sources, which do not compete with the human food chain. The maximum enzyme activity of 320 20 U/mL is achieved under optimized conditions. The CDA productivity is improved by about 23 times in shake flask culture by optimizing operating conditions and medium components. The CDA is purified and the enzyme kinetic values i.e. K m , V max and K cat are reported. Also the effect of cofactors, temperature, and pH on the enzyme activity is reported. Further, economic yield is proposed for production of CDA through this bioprocess. 2019 Elsevier B.V.