Bacillus subtilis is a gram-positive bacterium that dwells in the upper layers of soil and the rhizosphere of plants and has the ability to generate spores. Due to its clear genetic background as well as its simple and adaptable genetic manipulation methods, it is a model bacterium for investigations of bacterial physiology and metabolism. It has also been utilized extensively as a cell factory for the microbial manufacture of chemicals, enzymes, and antimicrobial agents for industry, agriculture, and medicine because of its extremely effective protein secretion system and flexible metabolism. This chapter looks at its industrial and medicinal uses. Additionally, we offer information on surface display technologies, scaling up industrial applications, environmental protection, secretion pathways, and approaches to improve the stability of secretory proteins.