| 摘要: | The aim of this work was to examine the ropiness of Lactobacillus helveticus BCRC14030, L. helveticus BCRC14076, and Streptococcus thermophilus BCRC14085, and evaluate the effect of fermentation time on exopolysaccharides (EPS) production by the ropy strain. Each of the three strains was inoculated in skim milk medium and incubated in a fermenter for 0-84 h at pH 5, 37 degrees C. The fermented samples, containing a net volume of 300 ml skim milk, were withdrawn at intervals of 0, 12, 16, 24, 32, 36, 48, 60, 72, and 84 It for determinations of ropy condition, EPS yield, and molecular mass. EPS with ropiness values of 11.3-21.0 nun, produced from L. helveticus BCRC14030 at 32-60 h demonstrated the ropy nature of the strain. Those EPS were composed of high molecular mass of 26,500 kDa. The highest EPS yield of 0.73 g l(-1) from this strain was observed (P < 0.05) at less favourable fermentation condition of 60 h. In addition, a relationship between the presence of high molecular mass and the ropiness of EPS from L. helveticus BCRC14030 was revealed. (c) 2005 Elsevier Ltd. All rights reserved. |
