Influence of Nutritional Factors on the Nature, Yield, and Composition of Exopolysaccharides Produced by Gluconacetobacter xylinus I-2281

Abstract

The influence of substrate composition on the yield, nature, and composition of exopolysaccharides (EPS) produced by the food-grade strain Gluconacetobacter xylinus I-2281 was investigated during controlled cultivations on mixed substrates containing acetate and either glucose, sucrose, or fructose. Enzymatic activity analysis and acid hydrolysis revealed that two EPS, gluconacetan and levan, were produced by G. xylinus. In contrast to other acetic acid strains, no exocellulose formation has been measured. Considerable differences in metabolite yields have been observed with regard to the carbohydrate source. It was shown that glucose was inadequate for EPS production since most of this substrate (0.84 C-mol/C-mol) was oxidized into gluconic acid, 2-ketogluconic acid, and 5-ketogluconic acid. In contrast, sucrose and fructose supported a 0.35 C-mol/C-mol gluconacetan yield. In addition, growing G. xylinus on sucrose produced a 0.07 C-mol/C-mol levan yield. The composition of EPS remained unchanged during the course of the fermentations. Levan sucrase activity was found to be mainly membrane associated. In addition to levan production, an analysis of levan sucrase's activity also explained the formation of glucose oxides during fermentation on sucrose through the release of glucose. The biosynthetic pathway of gluconacetan synthesis has also been explored. Although the activity of key enzymes showed large differences to be a function of the carbon source, the ratio of their activities remained similar from one carbon source to another and corresponded to the ratio of precursor needs as deduced from the gluconacetan composition.

Optimization of Carbon and Nitrogen Sources for Extracellular Polymeric Substances Production by Chryseobacterium indologenes MUT.2

“…The results obtained in the present study are in agreement with the general concept expressed in the early studies (15,16) which have reported the highest exopolysaccharides yield using fructose, sucrose, and glucose as carbon sources. Recently, Zhang et al (17), studied the production of gellan exopolysaccharide by growing strains of Sphingomonas paucimobilis QHZJ UJW in the medium containing various carbon sources such as glucose, sucrose, maltose, malt extract powder, and vegetable oil.…”

Structural Analysis of the Water-soluble Carbohydrate from Asaia bogorensis by NMR Spectroscopy

“…Until now, the production of levan has been reported for other acetic acid bacteria, Acetobacter diazotrophicus 7) and G. xylinus; 4,8) however, there have no reports describing the production of levan in A. bogorensis. It seems that A. bogorensis synthesized levan from sucrose by levansucrase associated with the cell surface.…”

A repeated batch process for cultivation of Bifidobacterium longum

“…The carbon sources (glucose or lactose), lactic acid and acetic acid in the culture broth were analyzed by HPLC under the following conditions: column, Supelcogel H (300 ·7.8 mm); mobile phase, 0.1 N H 2 SO 4 ; detector, a Waters 410 RI detector; temperature, 30°C [5]. Cell concentration was determined by measuring the optical density at 600 nm (OD 600 ).…”