Purification of a bacterial pullulanase on a fluidized bed of calcium alginate beads

Applications of Alginate in Bioseparation of Proteins

Alginate is a polysaccharide that is a block polymer consisting of block units of guluronic acid and mannuronic acid. It shows inherent biological affinity for a variety of enzymes such as pectinase, lipase, phospholipase D, a and ss amylases and glucoamylase. Taking advantage of its precipitation with Ca2+ and the above-mentioned property, alginate has been used for purification of these enzymes by affinity precipitation, aqueous two phase separation, macroaffinity ligand facilitated three phase partitioning, immobilized metal affinity chromatography and expanded bed affinity chromatography. Thus, this versatile marine resource has tremendous potential in bioseparation of proteins.

Leveraging protein purification strategies in proteomics

The proteomic studies, although, tend to be analytical in nature, yet many strategies of preparative protein purification can be usefully employed in such studies. This review points out the importance of purification techniques which are capable of dealing with samples which are suspensions rather than clear solution, e.g. aqueous two phase partitioning, three phase partitioning, expanded bed chromatography, etc. The review also outlines the potential of non-chromatographic techniques in dealing with fractionation of proteomes. Separation protocols which can deal with post-translationally modified (PTM) proteins are also considered.

Purification of phospholipase D by two-phase affinity extraction

An aqueous two-phase system of polyethylene glycol (PEG)-salt was used for purification of phospholipase D (PLD) from peanuts and carrots. Alginate, a known macroaffinity ligand for PLD, was incorporated in the PEG phase and resulted in 91 and 93% of the enzyme activity (from peanuts and carrots, respectively) getting partitioned in the PEG phase. The elution of the enzyme from alginate was facilitated by exploiting the fact that the latter can be reversibly precipitated in the presence of Ca2+. The enzyme was eluted from the polymer by using 0.5 M NaCl. Peanuts and carrots PLD could be purified 78- and 17-fold with 82 and 85% activity recovery, respectively. The purified enzyme from both sources gave a single band on sodium dodecyl sulfate-polyacrylamide gel (SDS-PAGE) electrophoresis.

kappa-Carrageenan as a new smart macroaffinity ligand for the purification of pullulanase

kappa-Carrageenan is a polysaccharide from red seaweed which gets precipitated by K+ ions and dissolves again in water. This smart, K(+)-responsive polymer was found to selectively bind pullulanase activity from Bacillus acidopullulyticus. Gel filtration on Sephadex G-200 showed the formation of the polymer-pullulanase complex at the pre-precipitation stage. On the other hand, phospholipase D, an enzyme which did not co-precipitate with kappa-carrageenan, did not form any complex with the polymer. Thus, K+ ions could be used to selectively precipitate the pullulanase activity. Then, 92% enzyme activity could be eluted with 1 M maltose solution. The single step protocol resulted in 50-fold purification, with a single band on sodium dodecylsulfate-polyacrylamide gel electrophoresis.