INTRODUCTION:

The industry today manufactures on a commercial scale compound that would otherwise have been difficult, if not impossible, to produce in large enough quantities to meet the needs of the sick population. This article attempts to give the reader an overview of the techniques available for downstream purification of biotechnology products¹. Proteins represent the most useful and diverse class of biopolymers. They are important as foods and food supplements, industrial catalysts, cleaning agents and pharmaceuticals. When one considers the heterogeneity of sources from which proteins are derived, their intended uses and their diversity, the need for a tremendous variety of recovery processes becomes obvious. The variety and specificity of protein recovery methods makes it difficult to outline a single flowchart represent all downstream processes. If such a flowchart were devised it would not be linear but arboreal, with several recovery options available at each step. In part, this is because many unit operations are used for more than one purpose, and more than one operation can be used for the same purpose. For example, ultrafiltration can be used for both concentration and purification, as can some types of chromatography⁶.

REVIEW OF LITERATURE:

This review is based on various studies of different methods of downstream processing of proteins. The primary consideration during downstream processing is the purity and another is the speed of the process development, overall yield and process throughput. A variety of methods such as liquid –liquid extraction, chromatography, metal affinity separation have been reviewed. This review emphasized recent advances in protein recovery operations. This review described some of the essential elements of downstream process for large scale production of protein products. This review is just a general study of different processes under the heading of downstream processing. This gives a general idea of the steps being followed for the recovery of proteins. On the basis of study of methods, most recent advances in this field which directs to a promising future can be determined. Here, the metal-affinity separation technique finds to be the new dimension for the protein processing in biotechnology with number of advantages.

According to Buyel J.F., Twyman R.M, Fischer R-Extraction and downstream processing of plant derived recombinant proteins, 2015 Elsevier Inc², Biopharmaceutical proteins are almost universally manufactured using animal cells or microbes cultivated in fermenters, and an entire industry has evolved based on the standardization, optimization and regulation of these platforms. Economical downstream processing relies on the use of standardized unit operations that have been developed to dovetail with upstream production using fermenters. The adaption of downstream processing to plan based systems has therefore been easiest when plant cell suspension cultures are used for production, because the upstream processes are analogous to those used with microbes and animal cells. Both these systems are game-changers in terms of DSP because plants have unique DSP-relevant attributes that are not shared with fermenter-based systems. Such challenges will need to be addressed because plant-derived biopharmaceuticals are likely to emerge as market leaders in the next few decades, particularly in developing countries where the offer not only increased access to medicines but also to the production technology itself via socially responsible licensing.

According to S. Hari Krishna, N.D. Srinivas, K.S.M.S. Raghavarao, N.G. Karanth-Reverse Micellar Extraction for Downstream Processing of Proteins/Enzymes Advances in Biochemical Engineering, Biotechnology 2002⁴, In recent years there have been tremendous efforts by research and industrial community for the production of biochemicals through application of fermentation technology and cell culture. However, the technology for downstream processing (DSP) of biological products from the media/broth has not kept pace with the advances in upstream operations involving bioreactors, despite the fact that in many cases DSP contributes major share of the final product cost. The separation of many biochemical from the product stream is still performed by batch mode small-scale processes such as column chromatography, salt and solvent precipitation and electrophoresis for which scale-up poses considerable problems, making them uneconomical unless the product is of high value. Affinity-based chromatographic separations though have excellent selectivity and have been carried out on a large scale; for the most part such systems operate discontinuously and the economy of scale has not often been realized. Therefore,current research in the area of DSP is directed towards efficient and scalable alternative bioseparation processes with potential for continuous operation. Liquid-liquid extraction (LLE) is a traditional chemical engineering unit operation for which the design and scale-up of both batch as well as continuous processes are already accomplished.

According to Sebastian Schmidt, Dirk Havkcost, Klaus Kaiser, JorgKauling, Hans JurgenHenzler- Crystallization for the downstream processing of proteins, Eng. Life. Sci. 2005⁶, Unlike affinity chromatography and precipitation, LLE is well known to operate continuously on a large scale with high throughputs, ease of operation, and high flexibility in its mode of operation. LLE using organic/aqueous phase has been employed in many chemical industries. However, this technique with all its advantages has not gained wide industrial recognition in the field of biotechnology, mainly due to the poor solubility of proteins in organic solvents and the tendency of organic solvents to denature the proteins. In recent years LLE using the aqueous twophase systems (ATPS) has been recognized as a superior and versatile technique for DSP of biomolecules, and a wealth of information has been reported in the literature on various aspects of aqueous two-phase extraction (ATPE) for the isolation and concentration of proteins, enzymes, and other biological materials. The major advantages of ATPE include high capacity, biocompatible environment, low interfacial tension, high yield, lower process time and energy, and high selectivity. Further, it offers ease of scale-up, continuous operation, and, most importantly, allows easy adaptation of the equipment and the methods of conventional organicaqueous phase extraction used in the chemical industry. Reverse micellar extraction (RME) is another attractive LLE method for DSP of biological products, as many biochemicals including amino acids, proteins, enzymes, and nucleic acids can be solubilized within and recovered from such solutions without loss of native function/activity.

According to Abhinav A. Shukla, Brian Hubbard, Tim Tressel, Sam Guhan, Duncan Low- Downstream Processing of monoclonal antibodies – Application of platform approaches, 2006 Elsevier⁵, Protein crystallization is a technique which is usually used to determine the three-dimensional structure of a protein. Like low molecular weight crystallization this method can be regarded as a cost effective alternative for purification (e.g. as a substitute for chromatographic process step.

STAGES OF DOWNSTREAM PROCESSING:

Processes for purification of proteins may be divided into five stages⁸

1. Disruption of cells.

2. Removal of cell debris.

3. Concentration and enrichment.

4. High resolution purification.

5. Concentration and finishing

Many useful proteins are intracellular and therefore recovery requires cell disruption followed by extraction of homogenate. This can be done by several mechanical (milling, high pressure homogenization, ultrasonication and freeze thawing) and chemical or enzymatic methods (dessication, high Ph, osmotic shock, detergents, antibiotics, cellwall hydrolytic enzymes). Disruption not only releases the entire contents into the homogenates but also generates sub-cellular fragments which due to smaller size are difficult to remove. Removal can be carried out by centrifugation, filteration, microfilteration, differencial sedimentation, precipitation and solid-liquid filteration⁶.

Methods studied under downstream processing of protein:

A.Methods used for separation of particulates and precipitates:

1. Precipitation:

Differential precipitation is the oldest method of protein purification dating back to the last century. The commonly used method for precipitation including salting out, addition of high molecular weight polymers, addition of organic solvents, metal ion complex formation and pH and isoelectric precipitation. However, this must be carefully executed to minimize irreversible denaturation of desired protein and coprecipitation of undesired species⁶.

2. Centrifugation:

It is an important method for feedstock clarification and recovery of solid. A wide variety of centrifuge designs such as tubular bowl, multichamber disc, scroll discharge, perforated bowl have been reviewed⁶.

3. Solid-liquid Filteration:

Filteration has been long term regarded as an economical and easily scaled alternative to centrifugation for the clarification of process fluids. This is more effective when the particles fall in the range of 0.5 to 5 microns. Problems arise when substantial proportion of particles is smaller than this range which is most often the result of excessive homogenization.

4. Cross-flow Microfilteration:

The most promising alternative for smaller size range particles are a relatively new technique called cross flow microfiltration which is an extension of tangential flow ultrafilteration. Although this technique is in its infancy and many improvements can be expected. have successfully applied the method to three different types of process clarifications: fermentation harvesting, separation of proteins from a mammalian tissue homogenate, and clarification of cheese whey. This have been tested on two bacterial homogenates known to be poorly clarified by centrifugation and were able to obtain clear permeates with high enzyme yields.

B. Separation by chromatography:

Most of the research reports in protein purification have been in the area of chromatography.

Ion-exchange. affinity and gel filtration chromatography have found many new applications in protein purification.

C. Separation in solution: Ultrafilteration, Electrophoresis, Liquid-liquid extraction, Ultra centrifugation.

D. Purification: Crystallization, Two phase system, Metal affinity seperations.

E. E. Finishing operation: Drying

DISCUSSION:

This review gives the recent advances in the study of downstream processing of proteins. The methods mentioned in this review paper have already been optimized in several processes and have ensured best possible analysis results. This review attempts to give the readers an overview of techniques available for downstream processing of proteins¹. It will be seen that the method has high potential and is already used industrially⁸. While advances have occurred bin every area, the greatest diversity of innovation has taken place in the fields of chromatography and tangential flow filtration⁶. The concept of metal-affinity separation was first exploited by Porath for the selective adsorption of proteins only 15 years ago. This includes promising developments in this field in future. This method have quickly become and important and widely used tool in analytical and preparative protein processing⁵.

CONCLUSIONS:

The recovery and downstream purification of proteins is a combination of diverse purification methods¹. Well-developed processes at the research bench scale are carefully scaled up to the production level, always being bearing in mind that fewer the steps used, higher is the eventual yield. This is because even if a particular step loses only 5% of the product, the losses add up when the product goes through multistep procedure for eventually providing a product of desired level of purity¹. Therefore, it is concluded that recent advances in the processes have ultimately lead to the increase in the product yield and the advanced products have been summarized in the reiew paper.

REFERENCES:

1. Manohar Kalyanpur, Downstream processing in Biotechnology Industry-Review. 2002; 22,.

2. Buyel J.F., Twyman R.M, Fischer R-Extraction and downstream processing of plant derived recombinant proteins, 2015 Elsevier Inc.

3. Abhinav A. Shukla, Brian Hubbard, Tim Tressel, Sam Guhan, Duncan Low- Downstream Processing of monoclonal antibodies – Application of platform approaches, 2006 Elsevier.

4. S. Hari Krishna, N.D. Srinivas, K.S.M.S. Raghavarao, N.G. Karanth-Reverse Micellar Extraction for Downstream Processing of Proteins/Enzymes Advances in Biochemical Engineering/ Biotechnology, Vol. 75 Managing Editor: Th. Scheper © Springer-Verlag Berlin Heidelberg 2002

5. Sebastian Schmidt, Dirk Havkcost, Klaus Kaiser, Jorg Kauling, Hans Jurgen-Henzler- Crystallization for the downstream processing of proteins, Eng. Life. Sci. 2005. 5. No. 3.

6. Todd Becker, Iohn R. Ogez and Stuart E. Builder- Downstream processing of proteins, Genentech. Inc. 460 Pt. Son Bruno Blvd., South San Francisco. Ca//fornM 94080 USA.

7. Frances H. Arnold- Metal-affinity separation- a new dimension in protein processing, Division of Chemistry and Chemical Engineering. 210-41, California institute of technology. Pasadena, California 91125

8. H. Hustedt, K. H. Kroner, U. Menge and M-R. Kula-Protein recovery using two-phase systems, © Elsevier Science Publishers B.V., Amsterdam 0166 94301851502~0, Trends in Biotechnology, Vol. 3, No. 6, 1985.

Received on 26.06.2025 Revised on 15.07.2025

Accepted on 31.07.2025 Published on 08.08.2025

Available online from August 14, 2025

Research J. Science and Tech. 2025; 17(3):245-248.

DOI: 10.52711/2349-2988.2025.00034

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