Kayla Topper

Document Type

Honors Project

First Advisor

Dr. Stephen Baron

Degree Award Date

Spring 2014


3-Hydroxybutyrate Dimer Hydrolase, Streptomyces sp. 5A


Environmental Microbiology and Microbial Ecology | Microbiology


Polyhydroxybutyrate (PHB) is a biodegradable, plastic-Uke polymer consisting of 3-hydroxybutyrate (3HB) monomers. Previous research has shown that degradation of PHB in the soil bacterium, Streptomyces sp. 5A, is carried out by a PHB depolymerase produced during growth on PHB. In other soil bacteria, PHB is first degraded to dimers of 3HB by a PHB depolymerase, and the dimers are then hydrolyzed to 3HB monomers by a suspected 3HB dimer hydrolase. 3HB dimer hydrolase can be assayed via its esterase activity, using an artificial substrate, p-nitrophenyl butyrate (PNPB). Streptomyces sp. 5A was cultured and the enzymes were precipitated out to be tested for activity. The two enzymes were separated on a phenyl sepharose column and fractions were tested for depolymerase and esterase activity. A distinct peak of depolymerase activity was established in late fractions. Esterase activity was found randomly throughout the fractions, leading to inconclusive results on the identity of this suspected 3HB dimer hydrolase.