The influence of substrate source on the growth of Ralstonia eutropha, aiming at the production of polyhydroxyalkanoate

Abstract

With the aim of producing polyhydroxyalkanoates, a study of the influence of culture conditions (nitrogen and carbon sources and temperature) on the growth of Ralstonia eutropha in stirred flasks was carried out and the use of some low-cost sources (hydrolyzed lactose, inverted sugar and corn steep liquor) as evaluated. The best specific growth rate was obtained when inverted sugar was utilized as the substrate (mmax = 0.26 h-1). Two different phases in the assimilation of the carbon source were observed when hydrolyzed lactose was present, suggesting the assimilation first of glucose and then of galactose. To confirm the growth of Ralstonia eutropha using galactose as the only carbon source, experiments were carried out and the results showed that this bacterium is able to grow in the presence of this sugar at a growth rate of 0.13 h-1. The use of galactose by Ralstonia eutropha for its growth has not been reported in the literature until now. Corn steep liquor was found to be a viable alternative nitrogen source to ammonium sulfate. The results of experiments carried out at 30°C and 34°C were similar.