Bacillus subtilis has become an increasingly popular host for recombinant protein expression. With its ability to secrete protein directly into culture media, amenability to medium- and large-scale fermentation, lack of codon bias, and designation by the U.S. Food and Drug Administration as an organism that is Generally Regarded As Safe (GRAS), it's no wonder that the majority of industrially-produced enzymes are expressed in Bacillus species such as B. subtilis. Optimization of secretion, however, may be required to achieve optimal yield. To address this concern, the B. subtilis Secretory Protein Expression System from Takara Bio allows rapid development of a B. subtilis clone library, with each clone bearing a pBE-S construct in which the ORF of your protein of interest is fused with 173 different sequences for unique signal peptides. By performing a downstream assay to identify and select the clone that secretes the highest amount of functional protein, you can quickly identify which signal peptide results in the most efficient expression of your desired secreted protein.