Microbial amensalism in Lactobacillus casei and Pseudomonas taetrolens mixed culture.

Pseudomonas taetrolens has recently been revealed as an effective microbial producer of lactobionic acid from carbohydrates contained in dairy byproducts. In terms of food industrial applications, the implementation of lactobionic acid biosynthesis coupled with the classic bacterial production of lactic acid appears an important goal. This research paper studies the simultaneous fermentation of residual cheese whey by P. taetrolens and Lactobacillus casei to co-produce lactic and lactobionic acids. Experimental data showed the importance of the interactions established between the two microorganisms. Changes in physiology, viability, growth, and productive capacity were tested experimentally. Lactobacillus was not seen to suffer any appreciable stress, but considerable variations were observed in the Pseudomonas behavior presumably owing to inhibitory lactic metabolites, interaction that can be classified as microbial amensalism. As to production, lactic acid remained without significant changes in mixed fermentations, whereas the production of lactobionic acid decreased sharply due to the competitive exclusion of Pseudomonas.