Effect of tween series on growth and Cis-9, trans-11 conjugated linoleic acid production of Lactobacillus acidophilus F0221 in the presence of bile salts.

Cis-9, trans-11 conjugated linoleic acid (c9, t11 CLA) producing bacteria have attracted much attention as novel probiotics which have shown beneficial effects on host health. However, bile salts are able to inhibit bacterial growth and c9, t11 CLA production. For recovering growth and c9, t11 CLA production of Lactobacillus acidophilus F0221 in the presence of bile salts, Tween series (Tween 20, Tween 40, Tween 60 and Tween 80) were added in growth culture containing 0.3% oxgall. Results showed that the viable counts were significantly (P < 0.05) recovered to 8.58-8.75 log CFU/mL in the presence of all Tween treatments. However, recovery of c9, t11 CLA production was only demonstrated in the presence of Tween 80 (72.89 µg/mL). Stepwise increasing oxgall in a concentrations range from 0.1% to 0.9% according to human intestinal physiological environments, Tween 80 still showed significant (P < 0.05) recovery ability on growth (8.91-8.04 log CFU/mL) and c9, t11 CLA (69.22-34.27 µg/mL) production. The effect of Tween 80 on growth and production was also investigated in the presence of different types of bile salts (sodium salts of cholic acid (CA), deoxycholic acid (DCA), chendeoxycholic acid (CDCA), glycocholic acid (GCA) and taurocholic acid (TCA)). Results showed that Tween 80 could significantly (P < 0.05) recover c9, t11 CLA production in the presence of all types of bile salts, but the Tween 80 could only significantly (P < 0.05) recover viable counts of the strain in the presence of CA, DCA and CDCA. This recovery ability could be attributed to the protection of leakage of intracellular material. Additionally, although bile salts inhibited growth and c9, t11 CLA production by the growing cell, it promoted the c9, t11 CLA production by the resting cell.

[Using of selective marker gene in transgenic plants and its removal].

Selective marker gene is usually used to select transformed cells or tissue during gene transfer. However,the use of selective marker gene,especially antibiotic-resistant gene, is harmful to environment, plant development and affects multi-transformation. A new strategy that offers a approach for the elimination of those disadvantages caused by the selectable marker gene is developed. We summarized correlative marker genes used in transgenic plants and some methods of its removal.