Influence of the nature of the carbon source on the characteristics of Lactobacillus plantarum strains. The objective of this work was to study the effect of a natural carbon source (wheat sourdough) and mannitol as a synthetic (heterogeneous) carbon source on the biological and technological properties of Lactobacillus plantarum strains. The experimental strains L. plantarum Lp 2 and L. plantarum Lp 14, selected from naturally fermented wheat sourdough, and L. plantarum ATCC 14917, grown with mannitol, were characterized for their ability to produce volatile organic compounds, organic acids, and hydrogen peroxide. The strains grown on mannitol produced more volatiles, especially aldehydes, than the wheat sourdough strains. The strains showed a different metabolic behavior, but the main differences were related to the production of organic acids. Results showed a significant increase of lactate production (ranging from 8% to 21%) by wheat sourdough strains compared with mannitol-grown strains. Lactobacillus plantarum Lp 2 produced the highest yield of lactic acid (15.8 +/- 0.1 g/100 g of fermentable carbohydrate) and L. plantarum Lp 14 the lowest (11.3 +/- 0.4 g/100 g of fermentable carbohydrate). The presence of heterofermentative LAB in mannitol-grown strains was supported by the presence of typical heterofermentative compounds: 2-methylbutanol and 3-methylbutanal. The volatile compounds, aldehydes, acids, and peroxide contents showed high values in wheat sourdough strains compared with mannitol-grown strains, although the pH and aw were similar. The use of mannitol as a heterofermentative carbon source might not be suitable for the selection of specific lactic acid bacteria (LAB) that are involved in the ripening of bread.