Biomedical subjects

R S Barhate

Publications and source records attributed to R S Barhate.

4 recordsLinked to original sources

PubMed2004

Drop formation in aqueous two-phase systems.

Extraction using aqueous two-phase systems (ATPSs) is a versatile technique for the downstream processing of various proteins/enzymes. The study of drop formation deals with the fundamental understanding of the behavior of liquid drops under the influence of various external body as well as surface forces. These studies provide a basis for designing of the extractions in column contactors in which liquid drops play a major role. Most of the drop formation studies reported so far is restricted to aqueous-organic systems. ATPSs, differ from aqueous-organic systems in their physical properties. In view of this, an attempt was made to develop a model for drop formation in ATPSs adopting the information available on aqueous-organic systems. In order to validate the model, experiments were performed by using polyethylene glycol (PEG)/salt systems of different phase compositions at various flow rates. At low flow rates the single stage model and at high flow rates the two stage model are able to predict the drop volume during its formation from tip of capillary. The experimental results were found to agree reasonably well with those predicted by the model.

Polyethylene Glycols↗

PubMed2001

Acoustic field assisted enhanced demixing of aqueous two-phase systems.

Aqueous two-phase extraction has been recognized as a versatile downstream processing technique for the recovery of biomolecules. A major deterrent to its industrial exploitation is the slow demixing of the two aqueous phases after extraction, due to their similar physical properties. A method to decrease the demixing times of these systems, employing a travelling acoustic wave field, is reported. The effects of phase composition and microbial cells on demixing in a polyethylene glycol/potassium phosphate two-phase system are studied in detail. As phase composition increased, demixing time decreased gradually. Phase volume ratio was found to have a significant effect on demixing time at low phase compositions. However, at intermediate and high phase compositions, only a small effect on demixing time was observed. The effect of phase composition and volume ratio on demixing behavior was explained based on the droplet size of the dispersed phase, which is the resultant effect of the physical properties of the phases. At all the phase compositions studied, the acoustically assisted process decreased the demixing time by 17-60% when compared to demixing under gravity alone. Increasing the cell concentration increased the demixing time markedly in case of yeast cells. However, it remained practically constant in the case of Lactobacillus casei cells. Application of an acoustic field reduced the demixing times up to 60% and 40% in the case of yeast and L. casei cells, respectively. Visual observations indicated that ultrasonication caused mild circulation currents in the phase dispersion enhancing droplet-droplet interaction, which in turn enhanced the rate of coalescence, eventually resulting in an enhanced demixing rate.

Countercurrent Distribution↗

PubMed2001

Optimization of single-step purification of alkaline protease using different hydrophobic ligands.

The adsorption and desorption pattern of alkaline protease was studied using different aliphatic and aromatic hydrophobic ligands. Overall, higher adsorption was obtained on ligands coupled to 6% cross-linked gel than the 4% gel. The highest adsorption was obtained on butyl (94%) and phenyl (98.4%) of 6% cross-linked gel. The adsorption was dependent on concentration and nature of the ligand. In a single-step operation, almost 20-fold purification with 40% yield of the enzyme was obtained using all the optimized experimental parameters.

Adsorption↗

PubMed2000

Acoustic demixing of aqueous two-phase systems.

Aqueous two-phase systems demix slowly due to similar physical properties. This is one of the major drawbacks for their adaptation for industrial scale extraction of enzymes. In the present work, a method to accelerate the demixing rates of these systems, employing a traveling acoustic wave field is reported for the first time. Phase-demixing for three systems, viz. polyethylene glycol (PEG)/sodium sulfate, PEG/potassium phosphate and PEG/maltodextrin were studied. The acoustically assisted process decreased the demixing time significantly (about 2- to 3-fold in PEG/salt systems and about 2-fold in the PEG/maltodextrin system), compared to that in gravity alone. Ultrasonication apparently enhanced the coalescence of the dispersed phase droplets due to the mild circulation currents it caused in the dispersion. This in turn enhanced the rate of demixing due to the increased migration velocity of the larger droplets.

Acoustics↗