A mutant Bacillus subtilis, which does not express a functional KASIIIA and/or KASIIIB, and method of making; a mutant Rhodospirillum rubrum, which does not express a functional PhaC1, PhaC2, and/or PhaC3, and method of making; method of characterizing substrate specificity of KASIII; method of making mutant KASIII with altered substrate specificity and/or altered level of activity and nucleic acid, vector, host cell/organism, and mutant KASIII; an in vitro, high-throughput spectrophotometric method of assaying KASIII activity; and materials and methods for using KASIII for production of bi-functional fatty acids and the materials so produced.