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Applied and Environmental Microbiology, December 2006, p. 7495-7502, Vol. 72, No. 12
0099-2240/06/$08.00+0     doi:10.1128/AEM.01078-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Culture Conditions Determine the Balance between Two Different Exopolysaccharides Produced by Lactobacillus pentosus LPS26{triangledown}

Jorge-Ignacio Sánchez,1 Beatriz Martínez,1 Rafael Guillén,2 Rufino Jiménez-Díaz,2 and Ana Rodríguez1*

Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Spain,1 Instituto de la Grasa (IG-CSIC), Departamento de Biotecnología de Alimentos, Apartado 1078, 41012 Seville, Spain2

Received 10 May 2006/ Accepted 19 September 2006

Lactobacillus pentosus LPS26, isolated from a natural fermentation of green olives, produces a capsular polymer constituted of two exopolysaccharides (EPS): EPS A, a high-molecular-weight (high-Mw) polysaccharide (1.9 x 106 Da) composed of glucose and rhamnose (3:1), and EPS B, a low-Mw polysaccharide (3.3 x 104 Da) composed of glucose and mannose (3:1). Fermentation experiments in a chemically semidefined medium with different carbon sources (glucose, fructose, mannitol, and lactose) showed that all of them except fructose supported EPS A production rather than EPS B production. The influence of temperature and pH was further analyzed. As the temperature dropped, increased synthesis of both EPS was detected. The control of pH especially enhanced EPS B production. With regard to this, the maximum total EPS production (514 mg liter–1) was achieved at a suboptimal growth temperature (20°C) and pH 6.0. Continuous cultures showed that EPS A, synthesized mainly at low dilution rates, is clearly dependent on the growth rate, whereas EPS B synthesis was hardly affected. EPS production was also detected in supplemented skimmed milk, but no increase on the viscosity of the fermented milk was recorded. This could be linked to the high proportion of the low-Mw polysaccharide produced in these conditions in contrast to that observed in culture media. Overall, the present study shows that culture conditions have a clear impact on the type and concentration of EPS produced by strain LPS26, and consequently, these conditions should be carefully selected for optimization and application studies. Finally, it should be noted that this is, to our knowledge, the first report on EPS production by L. pentosus.

* Corresponding author. Mailing address: Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Ctra. Infiesto s/n, 33300 Villaviciosa, Spain. Phone: 34 985892131. Fax: 34 985892233. E-mail: anarguez{at}ipla.csic.es.

{triangledown} Published ahead of print on 29 September 2006.

Applied and Environmental Microbiology, December 2006, p. 7495-7502, Vol. 72, No. 12
0099-2240/06/$08.00+0     doi:10.1128/AEM.01078-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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