Use of Poly(ethylene glycol)s To Regulate Poly(3-hydroxybutyrate) Molecular Weight during Alcaligenes eutrophus Cultivations

The ability of poly(ethylene glycol)s, PEGs, to control poly(3-hydroxybutyrate), P3HB, molecular weight in a microbial fermentation polymerization process was studied using Alcaligenes eutrophus with fructose as the sole carbon source. PEGs varying in molecular weight and end group functionality were added to the cultivation medium subsequent to cell growth, and their effects on polymer formation were evaluated. In general, A. eutrophus showed substantial tolerance for PEGs. This was illustrated by similar viable cell concentrations for the medium without PEG, 10% (w/v) PEG-10 000 and 2% PEG-200. Furthermore, detrimental effects on polymer yields were not observed for concentrations of 5% PEG-106 and 10% PEG-10 000. The greatest reductions in molecular weight were obtained when relatively low molecular weight PEG was added to the medium. PEG-106 was most effective in that only 0.25% was required to reduce the number average molecular weight (Mn) by 74%. The largest decrease in P3HB Mn (from 455 000 to 19 ...