**Abstract**

Spray drying is an economical drying method for converting aqueous solutions into stable dry powders. This one-step continuous process generates a sustainable solution for long-term storage of various protein formulations. This study focuses on recombinant growth factors produced in a barley seed host. The retained bioactivity of the growth factor in the final solid form suggests that co-purified host components may have preserving effects throughout the optimized spray drying process. To identify the critical spray drying parameters, a customized response surface design of experiment was applied. The defined input spray drying parameters: feed flow rate, spray gas flow rate, and outlet temperature, as well as their interactions, were discovered to be the most critical in terms of product quality and yield. The best operating parameters were chosen after considering potential reduction in energy consumption of the process. Cell proliferation assay results, which show the bioactivity of the growth factors, reveal that the native host components seem to act as proper stabilizing agents that protect the fragile growth factors against various stresses during the drying procedure. This unique matrix composition therefore surpasses the timeconsuming process optimization with excipients, allowing for a fully continuous process from purification to the final formulated powder.

**Keywords:** spray drying, design of experiment, optimization, preservation matrix, bioactive growth factors, barley proteins, economical drying, continuous system
