Lactobacillus crispatus L1: high cell density cultivation and exopolysaccharide structure characterization to highlight potentially beneficial effects against vaginal pathogens
1 Department of Experimental Medicine, Section of Biotechnology and Molecular Biology, Second University of Naples, via De Crecchio n°7, Naples 80138, Italy
2 Department of Experimental Medicine, Section of Microbiology and Clinical Microbiology, Second University of Naples, via De Crecchio n°7, Naples 80138, Italy
3 Department of Chemical Sciences, University of Naples Federico II, via Cinthia 4, Naples 80126, Italy
BMC Microbiology 2014, 14:137 doi:10.1186/1471-2180-14-137Published: 30 May 2014
Vaginal lactic acid bacteria defend the host against pathogens through a combination of competitive exclusion, competition for nutrients, production of antimicrobial substances and through the activation of the immune system. A new human isolate named Lactobacillus crispatus L1 was characterized in this work, and a preliminary evaluation of its probiotic potential is described together with a process to obtain a high productivity of viable biomass.
In a simulated digestion process 1.8⋅1010 cells∙ml−1 survived the gastric environment with 80% viability, without being affected by small intestine juices. Experiments on six different C sources were performed to analyze growth and organic acids production and, glucose, provided the best performances. A microfiltration strategy was exploited to improve the cellular yield in 2 L-fermentation processes, reaching 27 g · l−1 of dry biomass. Moreover, L. crispatus L1 demonstrated a greater stability to high concentrations of lactic acid, compared to other lactobacilli. The specific L. crispatus L1 exopolysaccharide was purified from the fermentation broth and characterized by NMR showing structural features and similarity to exopolysaccharides produced by pathogenic strains. Live L. crispatus L1 cells strongly reduced adhesion of a yeast pathogenic strain, Candida albicans in particular, in adherence assays. Interestingly a higher expression of the human defensin HBD-2 was also observed in vaginal cells treated with the purified exopolysaccharide, indicating a possible correlation with C. albicans growth inhibition.
The paper describes the evaluation of L. crispatus L1 as potential vaginal probiotic and the fermentation processes to obtain high concentrations of viable cells.