Bioaffinity extraction of glucoamylase in aqueous two-phase systems using starch as free bioligand

Amylase partitioning and extractive bioconversion of starch using thermoseparating aqueous two-phase systems

The effectiveness of thermoseparating polymer-based aqueous two-phase systems (ATPS) in the enzymatic hydrolysis of starch was investigated. In this work, the phase diagrams of PEO-PPO-2500/ammonium sulfate and PEO-PPO-2500/magnesium sulfate systems were determined at 25 degrees C. The partition behavior of pure alpha-amylase and amyloglucosidase in four ATPS, namely, PEO-PPO/(NH(4))(2)SO(4), PEO-PPO/MgSO(4), polyethylene glycol (PEG)/(NH(4))(2)SO(4), and PEG/MgSO(4), was evaluated. The effects of phase-forming component concentrations on the enzyme activity and partitioning were assessed. Partitioning of a recombinant, thermostable alpha-amylase (MJA1) from the hyperthermophile, Methanococcus jannaschii was also investigated. All of the studied enzymes partitioned unevenly in these polymer/salt systems. The PEO-PPO-2500/MgSO(4) system was extremely attractive for starch hydrolysis. Polymer-based starch hydrolysis experiments containing PEO-PPO-2500/MgSO(4) indicated that the use of ATPS had a significant effect on soluble starch hydrolysis. Batch starch hydrolysis experiments with PEO-PPO/salt two-phase systems resulted in higher production of maltose or glucose and exhibited remarkably faster hydrolysis. A 22% gain in maltose yield was obtained as a result of the increased productivity. This work is the first reported application of thermoseparating polymer ATPS in the processing of starches. These results reveal the potential for thermoseparating polymer-enhanced extractive bioconversion of starch as a practical technology.

Free polymeric bioligands in aqueous two-phase affinity extractions of microbial xylanases and pullulanase

Two reversibly soluble-insoluble polymers (viz. Eudragit S-100 and alginate) were used as free macroaffinity bioligands in polyethylene glycol (PEG)/salt two-phase systems for separation of enzymes. Incorporation of Eudragit S-100 and alginate in the PEG phase led to considerable selectivity in separation of microbial xylanases and pullulanase, respectively. Xylanase from Aspergillus niger was recovered 93% with 56-fold purification, whereas the enzyme from Trichoderma reesei and Bacillus amyloliquefaciens was obtained with 93% activity recovery (31-fold purification) and 90% activity recovery (32-fold purification), respectively. From Bacillus acidopullulyticus pullulanase, 85% enzyme activity recovery with 44-fold purification was obtained. The approach described here shows the potential of developing into a general approach for use of reversibly soluble-insoluble macroaffinity ligand in two-phase affinity extraction.

Reversibly soluble macroaffinity ligand in aqueous two-phase separation of enzymes

Use of alginate as a free bioligand incorporated in an aqueous two-phase system of polyethylene glycol 6000-salt resulted in considerable purification of wheat germ alpha-amylase and sweet potato beta-amylase from their crude extracts. The elution of the enzyme from the free bioligand was facilitated by exploiting the fact that alginate can be reversibly precipitated in the presence of Ca2+. alpha-Amylase could be purified 42-fold with 92% activity recovery. beta-Amylase on the other hand could be purified 43-fold with 90% recovery. Both purified enzymes showed a single band on sodium dodecylsulfate-polyacrylamide gel electrophoresis.