Characterization of freeze dried crude xylanase on its stability during storage at different temperatures

Abstract

Most of the enzymes are commercially available in powder form after undergoing freeze-drying process. However, such form is unstable if exposed to humidity at relatively higher temperature for a long-period of time that could affect the stability of the enzyme. Recently, crude xylanase enzyme has been produced through solid-state fermentation (SSF) and subjected to freeze-drying. The freeze-dried form of crude xylanase was characterised in terms of its stability after storage at different temperatures. Oil palm frond (OPF) is used as a substrate in a SSF to produce crude xylanase after fermentation for 18 days, then the samples of crude xylanase enzyme were extracted and analysed. Prior to centrifugation, crude xylanase solution was subjected to freeze-dry (Lyophilisation approach). In this research, storage test was conducted at various temperature points (-20°C, 4°C and 25°C), which were the common storage temperature for biological products. In addition, each sample taken was analysed in terms of xylanase activities using a standard xylanase assay. Meanwhile, qualitative structural changes of the crude xylanase were analysed using the Fourier Transform Infrared Spectroscopy (FTIR). No significant changes were observed in the peak profile in the FTIR analysis for all samples as compared to commercial xylanase. However, there were slight modifications of peak profile in the secondary structure pattern. Preliminary results showed that the freeze-dried crude xylanase was stable within the storage period of 91 days. Reduction of xylanase activities was observed after 120 days for the samples stored at 25°C. However, at temperature of -20°C and 4°C, results show that freeze-dried xylanase was stable or can be stored in a long-period of time. In conclusion, the crude xylanase can be stored in a long-period of time at -20°C, 4°C and 25°C for at least more than 3 months after freeze-drying process.