Papers by Pogaku Ravindra
Renewable & Sustainable Energy Reviews, 2011
Contemporary industrial developments and rapid pace of urbanization have called for an environ-me... more Contemporary industrial developments and rapid pace of urbanization have called for an environ-mentally sustainable energy sources. Ethanol made from biomass provides unique environmental, economic strategic benefits and can be considered as a safe and cleanest ...
Journal of Commercial Biotechnology, 2007
1 has an MSc and is currently pursuing a PhD in biotechnology at the Jawaharlal Nehru Technologic... more 1 has an MSc and is currently pursuing a PhD in biotechnology at the Jawaharlal Nehru Technological University. He is also working with Celestial Labs Ltd, Hyderabad, as a project consultant in establishing the enzymes production facility. He previously worked for Dalas Biotech Ltd, Bhiwadi, ...
International Journal of Chemical Engineering, 2010
Critical Reviews in Biotechnology, 2010
The discrepancy of the existing literature data on the surface tension values of biopolymer solut... more The discrepancy of the existing literature data on the surface tension values of biopolymer solutions could be affected by the measurement technique. The aim of the study was to compare the surface tension values of biopolymer solutions, measured using the du Nouy ring method and the drop weight methods (Harkins-Brown correction factors method and the LCP coefficient method). Four biopolymers were chosen (sodium alginate, carboxymethyl cellulose, xanthan gum and pectin) and the surface tensions of the solutions were measured as a function of biopolymer concentration. The surface tension was found to increase with biopolymer concentration when measured using the du Nouy ring method. On the other hand, the drop weight methods gave an opposite trend. The results verified the discrepancy of the existing literature data. The error may be caused by the correction factors calculation and the solution viscosity when the du Nouy ring method was used. The LCP coefficient method which is independent of correction factors and liquid properties is proposed for measurement of the surface tension of viscous biopolymer solutions.
Journal of Colloid and Interface Science, 2009
The aim of this work was to develop prediction models for shape and size of ca-alginate macrobead... more The aim of this work was to develop prediction models for shape and size of ca-alginate macrobeads produced through extrusion-dripping method. The relationship between the process variables on the shape and size of the alginate drops before and after gelation was established with the aid of image analysis. The results show that a critical Ohnersorge number (Oh) > 0.24 was required to form spherical beads. The shape transition of ca-alginate beads could be typically distinguished into three phases along the collecting distance and it was affected by the combined influence of the solution properties, the collecting distance and the drop size. Mathematical equations and a master shape diagram were developed to reveal a clear operating region and the overall process limits within which spherical ca-alginate beads could be formed. In terms of bead size, the overall size correction factor (K) which accounted for the liquid loss factor (k LF ) and the shrinkage factor (k SF ), varied between 0.73 and 0.85 under the experimental conditions. The size prediction model correlated well with the experimental data. The approach and the outcome could be used as a model to develop prediction tools for similar bead production systems.
A comparative study on the stability and potential of alginate and pectin based beads for product... more A comparative study on the stability and potential of alginate and pectin based beads for production of poultry probiotic cells using MRS medium in repeated batch fermentation was conducted. The bead cores, made of three types of materials, i.e. ca-alginate, ca-pectinate and ca-alginate/pectinate, were compared. The effect of single and double layer coatings using chitosan and core material, respectively, on the bead stability and cell production were also studied. The pectin based beads were found to be more stable than that of the alginate beads and their stability was further improved by coating with chitosan. The cell concentration in pectin based beads was comparable to that in the alginate beads. On the other hand, pectin based beads gave significantly lower cell concentration in the growth medium for the initial fermentation cycles when compared to the alginate beads. In conclusion, pectin was found to be potential encapsulation material for probiotic cell production owing to its stability and favourable microenvironment for cell growth.
Renewable & Sustainable Energy Reviews, 2009
Food and Bioproducts Processing, 2010
Encapsulation of herbal aqueous extract through absorption with ca-alginate hydrogel beads was st... more Encapsulation of herbal aqueous extract through absorption with ca-alginate hydrogel beads was studied. A model herbal aqueous extract, Piper sarmentosum, was used in this study. The effect of process variables (i.e. alginate M/G ratio, alginate concentration, extract concentration, bead size and bead water content) on encapsulation efficiency and biochemical compounds stability were studied. The stability of biochemical compounds was evaluated by using mass balance analysis and FT-IR spectroscopy. The results show that the encapsulation efficiency was mainly affected by alginate M/G ratio and bead water content. In general, ca-alginate beads made of higher alginate M/G ratio or dried to a lower water content were found to absorb significantly more aqueous extract. However, the beads made of higher M/G ratio were less rigid after the absorption process. Besides, the mass balance analysis reveals that the encapsulation process and material did not degrade the bioactive compounds, as the total antioxidant content remained unchanged. This is well supported by the FT-IR analysis where the characteristic bands of chemical groups remained unaltered. Interestingly, the beads made of lower alginate M/G ratio were found to have higher antioxidant affinity. In conclusion, this study demonstrates the potential of using absorption process and hydrogel material for encapsulation of herbal aqueous extract.
The main objective of this work is to improve the physical properties of lyophilized calcium (Ca)... more The main objective of this work is to improve the physical properties of lyophilized calcium (Ca)-alginate beads as a carrier material for the stabilization of encapsulated living cells. Improvements in the sphericity, flowability and mechanical strength of the dried beads were attributed to the filler, which provided structure and reinforcement to the Ca-alginate hydrogel networks, as verified by X-ray microtomography and scanning electron microscopy. A quantitative analysis of the micro-images revealed the less porous nature of the alginate-starch beads compared to the control. The beads with filler were also found to be less hygroscopic. The results also show that the cells encapsulated within the beads with reduced porosity and hygroscopicity were clearly more stable during lyophilization and storage than the control. In conclusion, the qualities of the alginate beads were improved by incorporating the solid filler, and the filler had a significant influence on cell viability during lyophilization and storage.
Colloids and Surfaces A-physicochemical and Engineering Aspects, 2009
The validity of the existing drop weight analyses for determining surface tension could be influe... more The validity of the existing drop weight analyses for determining surface tension could be influenced by the liquid properties. This study aimed to verify the validity of the Harkins-Brown correction factors and the Bond number correlation, as well as to develop a new drop weight analysis that is insensitive to liquid properties. The liquid samples of known surface tension and viscosity were chosen and classified into six different groups. Validation was done by comparing the data compiled in this study with the existing correlations as well as by dimensionless analysis. Results show that the existing drop weight analyses are valid for most liquid groups provided that the surface tension number (N ) exceeds 10 −1 or the Ohnersorge number (Oh) is below 10 2 . This, however, confirms the influence of liquid properties on the validity of the analyses. The LCP coefficient method was developed to eliminate this problem by using the drop weight results generated from multiple tips of different sizes. The surface tension could then be calculated by using a semi-empirical linear correlation. Error analysis shows that the LCP coefficient method gives the best reliability and accuracy among various drop weight analyses.
Journal of Renewable and Sustainable Energy, 2009
In this study, an eco-friendly immobilized lipase was designed for biodiesel production process. ... more In this study, an eco-friendly immobilized lipase was designed for biodiesel production process. Lipase enzyme was encapsulated in -carrageenan by coextrusion technique. The various parameters, such as catalytic activity, stability, reusability, shape, and size of the ...
Critical Reviews in Biotechnology, 2008
International Journal of Food Sciences and Nutrition, 2007
Extensive studies have been carried out on the effect of temperature and salt concentration on th... more Extensive studies have been carried out on the effect of temperature and salt concentration on the theological behavior of whey proteins and different starches individually, but not on mixed dispersions of whey protein isolates and starches. In the present studies, the rheological behavior of cross-linked waxy maize starch and whey protein isolate mixed dispersions during heating at 60-85 degrees C was investigated. Further, the effect of CaCl2 (25-100 mM ionic strengths) on the gelatinization of these dispersions was determined. It was found that at a 2:3 ratio and a 3:2 ratio of cross-linked waxy maize starch to whey protein isolate mixed gels form a compatible networkmM concentration the solution viscosity was higher.
Applied Microbiology and Biotechnology, 2010
The aim of this work was to develop a standard quantitative method to measure the acid tolerance ... more The aim of this work was to develop a standard quantitative method to measure the acid tolerance of probiotic cells when exposed to a simulated gastric fluid. Three model strains of different cell concentrations were exposed to a standard simulated gastric fluid of fixed volume. The fluid pH ranged from pH 1.5 to 2.5. In general, the death kinetics followed an exponential trend. The overall death constant, k d, for all strains was found to be in a power relationship with the pH value and the initial cell concentration, and it can be expressed as $$ {k_{\text{d}}}{\text{ = }}{k_{\text{AII}}}\left( {{\text{p}}{{\text{H}}^{ - {\text{9}}.0}}{N_0}^{ - 0.{\text{19}}}} \right) $$ where k AII is defined as the acid intolerance indicator and N 0 is the initial cell concentration (CFU/ml). This equation was validated with the experimental data with an average R 2 of 0.98. The acid intolerance of cells can be quantitatively expressed by the k AII values, where higher value indicates higher intolerance. In conclusion, a standard quantitative method has been developed to measure the acid tolerance of probiotic cells. This could facilitate the selection of probiotic strains and processing technologies.
Journal of Applied Sciences, 2011
Journal of Applied Sciences, 2010
Fuel, 2010
This work deals with the enzymatic transesterification of palm oil with methanol in a solvent-fre... more This work deals with the enzymatic transesterification of palm oil with methanol in a solvent-free system. Among the five lipases tested in the initial screening, lipase PS from Burkholderia cepacia resulted in the highest triglyceride conversion. Lipase PS was further investigated in a novel immobilized form by encapsulating within a biopolymer, j-carrageenan. Using the immobilized lipase the production parameters of biodiesel from palm oil were optimized. The optimal conditions for processing 10 g of palm oil was: 30°C, 1:7 oil/methanol molar ratio, 1 g water, 5.25 g immobilized lipase, 72 h reaction time and 23.7g relative centrifugal force. At the optimal conditions, triglyceride conversion of up to 100% could be obtained. The immobilized lipase was stable and retained 82% relative transesterification activity after five cycles. Liquid core lipase encapsulated in j-carrageenan could be a potential immobilized catalyst for eco-friendly production of biodiesel.
Journal of Molecular Catalysis B-enzymatic, 2009
In this work, a novel approach for lipase immobilization was exploited. Lipase from Burkholderia ... more In this work, a novel approach for lipase immobilization was exploited. Lipase from Burkholderia cepacia was encapsulated into -carrageenan by co-extrusion method to form a liquid core capsule. The diameter of the encapsulated lipase was found to be in the range of 1.3-1.8 mm with an average membrane thickness of 200 m and 5% coefficient of variance. The encapsulation efficiency was 42.6% and 97% moisture content respectively. The encapsulated lipase was stable between pH 6 and 9 and temperature until 50 • C. The encapsulated lipase was stable until disintegration of the carrier when stored at 27 • C and retained 72.3% of its original activity after 6 cycles of hydrolysis of p-NPP. The encapsulated lipase was stable in various organic solvents including methanol, ethanol, iso-propanol, n-hexane and n-heptane. Kinetic parameters K m and V max were found to be 0.22 mM and 0.06 mol/min for free lipase and 0.25 mM and 0.05 mol/min for encapsulated lipase respectively.
Chemical Engineering Communications, 2008
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Papers by Pogaku Ravindra