Partitioning of thermostable glucoamylase in polyethyleneglycol/salt aqueous two-phase system

Background: A major challenge in downstream processing is the separation and purification of a target biomolecule from the fermentation broth which is a cocktail of various biomolecules as impurities. Aqueous two phase system (ATPS) can address this issue to a great extent so that the separation and partial purification of a target biomolecule can be integrated into a single step. In the food industry, starch production is carried out using thermostable glucoamylase. Humicola grisea serves as an attractive source for extracellular production of glucoamylase. Results: In the present investigation, the possibility of using polyethylene glycol (PEG)/salt-based ATPS for the partitioning of glucoamylase from H. grisea was investigated for the first time. Experiments were conducted based on one variable at a time approach in which independent parameters like PEG molecular weight, type of phase-forming salt, tie line length, phase volume ratio, and neutral salt concentration were optimized. It has been found that the PEG 4000/potassium phosphate system was suitable for the extraction of glucoamylase from the fermentation broth. From the results, it was observed that, at a phase composition of 22 % w/w PEG 4000 and 12 % w/w phosphate in the presence of 2 % w/w NaCl and at pH 8, glucoamylase was partitioned into the salt-rich phase with a maximum yield of 85.81 %. Conclusions: A range of parameters had a significant influence on aqueous two-phase extraction of glucoamylase from H. grisea. The feasibility of using aqueous two-phase extraction (ATPE) as a preliminary step for the partial purification of glucoamylase was clearly proven.