Growth and Exopolysaccharide Production by Lactobacillus helveticus ATCC 15807 in an Adenine-Supplemented Chemically Defined Medium

TORINO, MARÍA INÉS; HÉBERT, ELVIRA MARÍA; MOZZI, FERNANDA; FONT DE VALDEZ, GRACIELA

JOURNAL OF APPLIED MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2005 vol. 99 p. 123 - 129

1364-5072

Chemically defined culture media were used for studying exopolysaccharide (EPS) production by Lactobacillus helveticus ATCC 15807. The assayed media were the following: i) Chemically Defined (CD) containing essential and non-essential bases and vitamins; ii) Simplified Chemically Defined (SCD) without non-essential bases and vitamins; and iii) supplemented SCD (SCD-S) containing individually: folic acid, cyanocobalamine, p-amino benzoic acid, orotic acid, thymine, inosine, guanine, biotin, thiamine or adenine. Adenine in SCD medium (SCD-A) stimulated cell growth and EPS production compared to SCD; moreover, polysaccharide formation was 1.2 fold higher than in CD medium. The EPS synthesis was dependent on the sugar source, lactose being the most suitable; consequently, SCD-A-lac was selected for further studies. The EPS synthesis began at the early exponential growth phase and reached the maximum value (8.0 mg/l) after 24 h; maximum cell viability (6.0 x 107 cfu/ml) was obtained after 18.5 h. Under osmotic stress conditions (NaCl or glycerol), cell growth and EPS production by L. helveticus ATCC 15807 decreased although a better EPS yield efficiency was seen when higher NaCl concentrations were present. At low culture pH values (4.5) polymer synthesis was also enhanced. The EPS monomeric composition and molecular mass were similar in all the assayed conditions