Effects of Spray Drying Temperature and Additives on the Stability of Serine Alkaline Protease Powders

Abstract

In this study, after production by recombinant Bacillus subtilis (BGSC-1A751), carrying pHV1431::subc gene in the complex medium and separation of solids from the fermentation broth, serine alkaline protease (SAP) was dried in order to investigate the stabilization during spray drying and subsequent storage. The effect of air inlet temperature of the spray dryer between T = 70 and 130°C and the effect of protective additives, glucose and maltodextrin, at 0–2% (w/v) on SAP activity during spray drying and storage stability of obtained SAP powders at 4°C for a long period (6 months) were evaluated. Increasing drying air inlet temperature generally resulted in an increase in activity loss; moreover, higher absorbance peaks observed at wave number 1061 cm⁻¹ of the IR spectrums when drying temperature is increased indicates the structural change in the SAP molecule. In most cases presence of additives provided higher activities both after drying and during storage period compared to no additive case. Drying the enzyme with 1% (w/v) glucose at T = 110°C resulted in the highest enzyme activity after drying and storage processes.

Keywords:

• Activity loss
• Protective additives
• Serine alkaline protease
• Spray drying
• Storage stability

ACKNOWLEDGEMENTS

This work was supported by METU Research Fund (BAP-2004-07-02-00-87). The authors acknowledge the gracious willingness of Professor Tunçer H. Özdamar and Dr. Sema Salgιn at Ankara University Biochemical Reaction Engineering Lab in obtaining FTIR data in Fig. 4.