Abstract: The present disclosure relates to biocatalytic methods or processes for the synthesis of acrylic acid and its derivatives, or other carboxylic acid compounds of the formula R—CO2H, wherein R is a carbon chain of 5 carbons or fewer, such as methacrylic acid or 3-hydroxypropionic acid. More specifically, the disclosure relates to methods of using an acyl-CoA hydrolase (such as a thioesterase) as a biocatalyst for the hydrolysis (and removal of the CoA moiety) of a substrate acyl-CoA compound to produce the corresponding carboxylic acid compound, such as acrylic acid. In some embodiments, the disclosure provides non-naturally occurring microorganisms that have been transformed with a heterologous acyl-CoA hydrolase, such as a thioesterase, that is capable of hydrolyzing an acyl-CoA produced in a pathway of the microorganism and produce the corresponding carboxylic acid compound, thereby allowing methods for the direct fermentative production of the compound.