Abstract: Immobilized Lactobacillus helveticus L7 was used for biosynthesizing c9,t11-CLA from linoleic acid. The immobilization conditions were optimized by response surface methodology. The optimal conditions for the preparation of immobilized cells required 1.78 g/100 mL sodium alginate, 3.13 g/100 mL calcium chloride and 30 min immobilization time. The fermentation of immobilized cells under the optimal conditions could result in the highest accumulation of c9,t11-CLA up to 561 μg/mL. Meanwhile, the immobilized strain displayed good transformation properties. No obvious change in the activity of the immobilized strain was observed after reuse for five times, and the yield of c9,t11-CLA remained up to 549 μg/mL. Examined by scanning electron microscope (ESEM), the internal structure and surface of immobilized bead were observed, and were suitable for the mass transfer. Therefore, sodium alginate-immobilized cells had a good performance in improving the recycling rate of cells, reducing the production costs of c9,t11-CLA, and improving economic efficiency of enterprises.

Key words: Lactobacillus helveticus L7, immobilization, biosynthesis, conjugated linoleic acid, response surface methodology