Biomedical subjects

V Loha

Publications and source records attributed to V Loha.

8 recordsLinked to original sources

PubMed2000

Sonic wave separation of invertase from a dilute solution to generated droplets.

It has previously been shown that a droplet fractionation process, simulated by shaking a separatory funnel containing a dilute protein solution, can generate droplets richer in protein than present in the original dilute solution. In this article, we describe an alternative method that can increase the amount of protein transferred to the droplets. The new method uses ultrasonic waves, enhanced by a bubble gas stream to create the droplets. The amount of protein in these droplets increases by about 50%. In this method, the top layer of the dilute protein solution (of the solution-air interface) becomes enriched in protein when air is bubbled into the solution. This concentrating procedure is called bubble fractionation. Once the protein has passed through the initial buildup, this enriched protein layer is transferred into droplets with the aid of a vacuum above the solution at the same time that ultrasonic waves are introduced. The droplets are then carried over to a condenser and coalesced. We found that this new method provides an easier way to remove the protein-enriched top layer of the dilute solution and generates more droplets within a shorter period than the separatory funnel droplet generation method. The added air creates the bubbles and carries the droplets, and the vacuum helps remove the effluent airstream from the condenser. The maximum partition coefficient, the ratio of the protein concentration in the droplets to that in the residual solution (approx 8.5), occurred at pH 5.0.

Glycoside Hydrolases↗

PubMed2000

Modeling a protein foam fractionation process.

A simple staged model for the protein foam fractionation process is proposed in this article. This simplified model does not detail the complex foam structure and gas-liquid hydrodynamics in the foam phase but, rather, is built on the conventional theoretical stage concept considering upward bubbles with entrained liquid and downward liquid (drainage) as counter-current flows. To simulate the protein concentration distribution in the liquid along the column by the model, the bubble size and liquid hold-up with respect to the position must be known, as well as the adsorption isotherm of the protein being considered. The model is evaluated for one stage by data from the semibatch foam fractionation of egg albumin and data from the continuous foam fractionation of bovine serum albumin. The effect of two significant variables (superficial gas velocity and feed protein concentration) on enrichment is well predicted by the model, especially for continuous operation and semibatch operation when initial concentration is high.

Adsorption↗

PubMed2000

Effect of shear on human insulin in zinc suspension.

Human insulin in zinc suspension was used as a model protein to test the effect of shear on the settling rate of proteins, a possible inference for protein denaturation. The rate of settling was determined directly in a spectrophotometer. Shear effects are important in retaining the activity of proteins and are present in bubble, foam, and droplet protein fractionation processes. A simple test, such as that conducted here, may even be useful for monitoring changes in protein structure caused by commercial shipping of the protein. The settling rate for insulin was continuously monitored in the original bottle by spectrophotometric absorbance changes as a function of time. A settling curve was determined following each shear experiment, which included shaking the "worked" insulin solution in a vortex mixer for different lengths of time. It was determined, when comparing long shaking times with short ones, that the initial settling rate was less for the long-term shaking of the insulin samples and greater for the short-term shaking. The secondary effects of light and heat, along with shaking, apparently did not produce differences from shaking alone.

Drug Stability↗

PubMed2000

Effect of protein denaturation on void fraction in foam separation column.

Foam fractionation is a cost-effective process that uses air to extract protein from a liquid (in this case "crude" dilute egg-albumin solution). This article deals with how the void fraction (fraction of air in the aerated solution) of foam is affected by heat denaturation of the protein. A 2-mm glass tube was used to sample the foam-liquid interface fluid in a 35-mm-diameter column in order to detect small changes in void fraction and foam production, which are not easily detected directly from the bulk foam. The main control variable in this study was the protein solution preheating time. As the preheating time increased, the initial void fraction in the column decreased. The initial void fraction of the undenatured solution ranged from about 0.73 to 0.80, and the void fraction for significant preheating times of 5 min ranged from approx 0.68 to 0.72. Furthermore, the period of foam production increased from 5 to 7 min for undenatured proteins in solution to as long 15 min for 5-min preheated solutions. Side-port sampling through a small capillary tube has the potential to be used as a rapid and inexpensive way to determine the level of protein denaturation by directly determining the void fraction and then estimating the effect of denaturation from a protein denaturation calibration curve of the void fraction.

Biotechnology↗

PubMed1999

Partitioning invertase between a dilute water solution and generated droplets.

Water droplets or mist occur naturally in the air at seashores. These water droplets carry inorganic and organic substances from the sea to the land via the air, creating fertile land in sandy coastal areas (1). The same phenomenon occurs in an air-fluidized bed bioreactor (2). In an air-fluidized bed reactor, proteins can be transferred from the bioreactor semisolid bulk phase to an enriched droplet phase. This protein transfer process (droplet fractionation) can be experimentally simulated by shaking a separatory funnel containing a dilute solution of a given protein, which can be an enzyme like invertase. The created droplets become richer in invertase (protein) than that of the original dilute solution. The droplets can then be coalesced by trapping them and recovering the concentrated protein in the new liquid phase. Typically, in such a droplet fractionation process a collected enzyme can be degraded in its ability to catalyze a chemical reaction. In this article, we explore whether the initial solution pH control variable can be adjusted to minimize the decrease of enzyme activity in this process. The protein droplet recovery problem is one in which the recovered amount of desired protein (enzyme) in the droplet is maximized, subject to the minimization of the enzyme activity loss. The partition coefficient, which is the ratio between the protein concentration in the droplets and the residual solution, is maximized at approx 4.8 and occurs at pH 3.0. Here, the partition coefficient for invertase decreases as the initial solution pH increases, between pH 3.0 and 8.0. Interestingly, the initial solution surface tension seems to be inversely proportional to the partition coefficient. The partition coefficient reaches a maximum value at a surface tension value of approx 63 mN/m at pH 3.0. The enzymatic activity of the initial, the residual, and the droplet solutions all decrease as the bulk solution pH increases. A decrease of enzymatic activity was observed in the residual bulk solution when compared with that in the initial bulk solution at all pH levels. Also, up to 90% of the invertase activity was lost in the droplets when compared to the initial bulk solution.

Journal Article↗

PubMed1999

Preserving the activity of cellulase in a batch foam fractionation process.

Foam fractionation is one of the low operating-cost techniques for removing proteins from a dilute solution. The initial bulk solution pH and air superficial velocity play an important role in the foam-fractionation process. Denaturation of proteins (enzymes) can occur, however, during the foam-fractionation process from the shear forces resulting from bursting air bubbles. At the extreme bulk solution pHs (lower than 3.0 and higher than 10.0), the enzymatic activity of cellulase in the foamate phase drops significantly. Within these two pH bounds an increase in the air superficial velocity, V0, and a decrease in the bulk solution pH leads to a decrease in the separation ratio (SR), defined as the ratio of the protein concentration in the foamate to the protein concentration in the residue. On the other hand, an increase in V0 provides a higher foamate-protein recovery. The process efficiency is defined as the product of foamate-protein recovery times the SR times the cellulase activity. The optimal operating condition of the cellulase foam-fractionation process is taken into account at the maximum value of the process efficiency. In this study, that optimal condition is at an air superficial velocity of 32 cm/min and a bulk-solution pH of 10.0. At this condition, the recovered foamate is about 80% of the original protein mass, the SR is about 12, and the enzymatic activity is about 60% of the original cellulase activity.

Journal Article↗

PubMed1998

Batch foam recovery of sporamin from sweet potato.

The major sweet potato root protein, sporamin (which comprises about 80-90% of the total protein mass in the sweet potato) easily foams in a bubble/foam-fractionation column using air as the carrier gas. Control of that foam fractionation process is readily achieved by adjusting two variables: bulk solution pH and gas superficial velocity. Varying these parameters has an important role in the recovery of sporamin in the foam. Changes in the pH of the bulk solution can control the partitioning of sporamin in the foam phase from that in the bulk phase. A change in pH will also affect the amount of foam generated. The pH varied between 2.0 and 10.0 and the air superficial velocities (V0) ranged between 1.5 and 4.3 cm/s. It was observed in these ranges that, as the pH increased, the total foamate volume decreased, but the foamate protein (mainly sporamin) concentration increased. On the other hand, the total foamate volume increased significantly as the air superficial velocity increased, but the foamate concentration decreased slightly. The minimum residual protein concentration occurred at pH 3.0 and V0 = 1.5 cm/s. On the other hand, the maximum protein mass recovery occurred at pH 3.0 and at V0 = 4.3 cm/s.

Chemical Fractionation↗

PubMed1998

Batch foam fractionation of kudzu (Pueraria lobata) vine retting solution.

The aqueous protein solution from kudzu (Pueraria lobata) vine retting broth, without the addition of other surfactants, was foam-fractionated in a vertical tubular column with multiple sampling ports. Time-varying trajectories of the total protein levels were determined to describe the protein behavior at six positions along the 1-m column. The lowest two trajectories of this batch process represented a loss of proteins from the bulk liquid and tended to merge and decay together in time; the other trajectories displayed a gain in proteins in the foam phase. These upper column port protein concentration trajectories generally increased in time up to 45 mm, followed by a decrease, reflecting the removal of proteins from the column ports. The foam became dryer as it passed up the column to the top port. The protein concentration was about 5-8x higher in the top port foam than in the initial bulk solution, mainly as a result of liquid drainage from the foam along the column axis. This concentration increase in the collected foam was dependent on the initial pH of the bulk solution. The mol-wt profile of the proteins in the concentrated foam effluent was determined by one-dimensional gel electrophoresis. An analysis of the gel electropherograms indicated that the most abundant proteins could be cellulases and pectinases.

Aspergillus niger↗