Effect of some factors on exopolysaccharide production of Lactobacillus fermentum TC21 isolated from ‘tom chua’ in Hue, Vietnam

Abstract

Abstract: Exopolysaccharide biosynthesis ability of four Lactobacillus fermentum strains isolated from ‘Tom Chua’, a Hue traditional fermented shrimp was investigated. When comparison with another strains, Lactobacillus fermentum TC21 produced the highest EPS amounts. The EPS yield produced by this strain was obtained were 177.151 µg/mL in the MRS broth added 1% glucose, 2% lactose after 48 h incubation at 37 ^oC. Therefore, the effects of sugar composition, nitrogen sources, and the culture conditions (initial pH, temperature, initial cell density and time course of incubation) on EPS production by Lactobacillus fermentum TC21 were studied. With the presence 4% sugars added into MRS broth the EPS yields were obtained maximum comparing with another concetrations. The stimulation on EPS synthesis of Lactobacillus fermentum TC21 by lactose was the best (179.752 µg/mL). The replacement of coconut water containing 20% sugar for distilled water in MRS broth significantly affected the EPS production. When 50% of distilled water was replaced by coconut water the EPS yield was the highest (182.638 µg/mL). The effect of nitrogen sources such as peptone, beef extract and yeast extract) on  this strain EPS biosynthesis of this strain was also investigated by supplementating them into MRS containing 4% lactose. All of samples were incubated at 37 ^oC for 48 h. The EPS amount was 301.988 µg/mL when adding 0.8% (w/v) beef extract into medium. From all of above results, optimal medium for EPS production by Lactobacillus fermentum TC21 contains 0.8% (w/v) beef extract and 4% lactose. Under optimal medium, the EPS yield was reached the highest (405.728 mg/l) after 36 h of incubation with initial pH 6.0 and initial cell density of 10⁶ cfu/mL at 35 °C.

Keywords: coconut water, cultural conditions, exopolysaccharide, Lactobacillus fermentum, sugar

Corresponding author: Tran Thi Ai Luyen