Biomedical subjects

Gautam Lal Baruah

Publications and source records attributed to Gautam Lal Baruah.

5 recordsLinked to original sources

PubMed2006

Purification of monoclonal antibodies derived from transgenic goat milk by ultrafiltration.

With the goal of recovering heterologous immunoglobulin (IgG), which comprises 10-15% of the total proteins, from transgenic goat milk at 80% yield and 80% purity, we have developed and tested a two-step membrane isolation and purification process. In the first step, reported earlier by Baruah and Belfort, microfiltration was used to fractionate the milk proteins and recover > 90% of the original IgG at a purity of about 15-20% in the permeate stream. Here, we focus on ultrafiltration (UF) to increase the purity of the target protein to 80%, while maintaining a relatively high IgG yield (80%). Tangential flow UF experiments in diafiltration mode were conducted with 100 kDa cellulosic membranes to evaluate the optimal pH, ionic strength, and uniform transmembrane pressure (TMP). The TMP was kept uniform by permeate circulation in co-flow mode. The traditional approach of conducting the UF process close to the pI of the predominant whey proteins (15-40 kDa, pI 5.2), to transmit these proteins while retaining heterologous IgG (155 kDa), could not be applied here because of precipitation of residual casein at pH values lower than 8.5. Instead, the packing characteristics of the cake layer on the membrane wall, as elucidated in the Aggregate Transport Model presented by Baruah et al. was utilized to achieve a selectivity of > 15, which was sufficient to meet the stated goals of purity and yield for this difficult separation. This combined process is expected to reduce the load on subsequent purification and polishing steps for eventual therapeutic use.

Animals↗

PubMed2004

Optimized recovery of monoclonal antibodies from transgenic goat milk by microfiltration.

The Predictive Aggregate Transport Model for microfiltration is used in combination with optimum fluid mechanics and electrostatics to maximize recovery of a heterologous immunoglobulin (IgG) from transgenic goat milk. The optimization algorithm involved varying pH (6.8-9), transmembrane pressure (2-4.5 psi), milk feed concentration (1-2X), membrane module type (linear vs. helical design), and axial velocity (Reynolds number: 830-1170). Operation in the pressure-dependent regime at low uniform transmembrane pressures (approximately 2 psi) using permeate circulation in co-flow, at the pI of the protein (9 in this case) was used to increase IgG recovery from less than 1% to over 95%. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and attenuated total reflection Fourier transform infrared spectroscopy of the microfiltration permeate samples confirmed that all the fat globules and most of the casein micelles were retained in the MF membrane whereas a large amount of the target IgG was transported through the membrane. Transmembrane pressure and hence permeation flux was kept low (approximately 15 lmh) to maximize IgG membrane transport and thus recovery, due to a sparse deposit on the membrane which facilitated high solute transport. Next, an analytical method was used to optimize the diafiltration process using the aggregate transport model, experimental target protein sieving coefficients and permeation flux (Baruah and Belfort, 2003). The methodology reported here should be generalizable to the recovery of target proteins found in other complex suspensions of biological origin using the microfiltration process.

Algorithms↗

PubMedDate not supplied

A predictive aggregate transport model for microfiltration of combined macromolecular solutions and poly-disperse suspensions: model development.

A methodology, called the aggregate transport model, is presented that can a priori predict both the pressure-independent permeation flux and yield of target species for the microfiltration of poly-disperse solutions. The model captures the phenomenon of critical shear rate. Beyond the critical shear rate (expressed as a ratio of shear rate to permeation flux), the transmission of proteins drops sharply as a result of cake classification. The widely reported benefits of operating at uniform transmembrane pressure and constant wall concentration follow from this method. The methodology is general in nature and can be used predictively to obtain an optimal balance between flux and yield of target species during the microfiltration of many commercial poly-disperse suspensions. In the accompanying paper we test this model for microfiltration of transgenic whole goat milk.

Complex Mixtures↗

PubMedDate not supplied

A predictive aggregate transport model for microfiltration of combined macromolecular solutions and poly-disperse suspensions: testing model with transgenic goat milk.

To meet the technical challenge of recovering human IgG fusion protein from transgenic whole goat milk at reasonable cost with high purity and yield, a predictive aggregate transport model for microfiltration has been developed (Baruah and Belfort, 2003). Here, to test the model's predictability of permeate flux and mass transport, a comprehensive series of experiments with varying wall shear rate, feed temperature, feed concentration, and module design are presented. A very good fit was obtained between the model predictions and measurements for a wide variety of experimental conditions. For microfiltration module design comparison, a linear hollow fiber module (representing current commercial technologies) gave lower permeation flux and higher yield than a helical hollow fiber module (representing the latest self-cleaning methodology). These results are easily explained with the model that is now being used to define operating conditions for maximizing performance. The procedure described by the model is generalizable and can be used to obtain optimal filtration performance for applications other than milk.

Animals↗

PubMedDate not supplied

Global model for optimizing crossflow microfiltration and ultrafiltration processes: a new predictive and design tool.

A global model and algorithm that predicts the performance of crossflow MF and UF process individually or in combination in the laminar flow regime is presented and successfully tested. The model accounts for solute polydispersity, ionic environment, electrostatics, membrane properties and operating conditions. Computer programs were written in Fortran 77 for different versions of the model algorithm that can optimize MF/UF processes rapidly in terms of yield, purity, selectivity, or processing time. The model is validated successfully with three test cases: separation of bovine serum albumin (BSA) from hemoglobin (Hb), capture of immunoglobulin (IgG) from transgenic goat milk by MF, and separation of BSA from IgG by UF. These comparisons demonstrate the capability of the global model to conduct realistic in silico simulations of MF and UF processes. This model and algorithm should prove to be an invaluable technique to rapidly design new or optimize existing MF and UF processes separately or in combination in both pressure-dependent and pressure-independent regimes.

Algorithms↗