Comparison of melibiose and trehalose as stabilising excipients for spray-dried β-galactosidase formulations

Spray-dried protein formulations commonly require stabilising excipients to prevent protein degradation during processing and storage, and trehalose has been commonly used. The purpose of this work was to evaluate melibiose in spray-dried protein formulations in comparison to trehalose. The protein-activity-preserving efficacy, process behaviour and storage stability were studied. Spray drying of β-galactosidase was carried out using different process temperature, drying air flow and feed liquid atomisation settings. Both melibiose and trehalose reduced protein activity loss during drying. A decrease in activities was observed when the process temperature exceeded a threshold temperature. During storage (30 days at 18% RH and 20 or 40 °C), the formulations dried below this threshold temperature showed no further activity loss, and the stabilising efficacy of the two disaccharides was equal. With higher process temperatures, the remaining protein activities after storage trended higher with melibiose formulations. All formulations remained amorphous. The powder yields of melibiose formulations were similar to trehalose. There was a difference in residual moisture contents, with melibiose formulations giving drier products. In conclusion, protein formulations with melibiose could be spray dried into amorphous powders that were physically stable, contained lower moisture contents and protected protein activity at least as well as trehalose formulations.