Tony Gutierrez, Gordon Morris, David H. Green
In this study, we investigated the yield and physicochemical properties of the high molecular weight extracellular polymeric substance (HMW–EPS) produced by Halomonas sp. strain TG39 when grown on different types and ratios of substrates. Glucose (1% w/v) and a peptone/yeast extract ratio of 5.1 (0.6% w/v final concentration) yielded an EPS fraction (HMW-glucose) exhibiting the highest anionic activity (20.5) and specific emulsifying activity (EI24¼100%) compared to EPS produced by cells grown on mannitol, sucrose, malt extract or no carbon source. The HMW–EPS fractions were capable of binding 255–464 mg of methylene blue (MB) per gram of EPS, which represents the highest reported binding of MB by a bacterial EPS. A comparative evaluation of these properties to those of commercial hydrocolloids indicated that the combined effect of protein and anionic residues of the HMW–EPS contributed to its ability to emulsify n-hexadecane. Liquid chromatography revealed the HMW-glucose EPS to be a heterogeneous polymer with a polydispersity index of 1.8. This work presents evidence of a correlation between the anionic nature and protein content of bacterial EPS with its emulsifying qualities, and identifies EPS produced by strain TG39 as a high MB-binding bacterial sorbant with potential biotechnological application.
Biotechnol. Bioeng. 2009;103: 207–216. 2008 Wiley Periodicals, Inc.