Interaction between Galactomyces geotrichum KL20B, Lactobacillus plantarum LAT3 and Enterococcus faecalis KE06 during Milk Fermentation.

Microbial interactions are fundamental during milk fermentation, determining the product final characteristics. Galactomyces geotrichum, Lactobacillus plant arum and Enterococcus faecalis are among the most common microorganisms in the Colombian Kumis. The aim of the research was to evaluate the yeast–bacteria interactions in milk fermentation at 28 C. UHT (Ultra-High Temperature) milk was inoculated with single- or multiple-strains associations and analysed periodically to determine the microbial counts, organic acids and total free amino acids (FAA). The results evidenced different growth performance of the strains in single or co-culture, with a positive effect of G. geotrichum KL20B on the lactic acid bacteria (LAB) growth performance. All the strains consumed citric acid after 6 h of incubation with E. faecalis KE06 as the major consumer; however, all the co-cultures showed an early metabolism of citrate but with a low intake rate. In addition,the interaction between G. geotrichum KL20B and E. faecalis KE06 led to a low accumulation of acetic acid. Formic acid fluctuated during fermentation. The strains interaction also led to an increase in ethanol content and a lower accumulation of FAA. In conclusion, the three strains co-culture enhances the LAB viability, with high production of lactic acid and ethanol, as a consequence of adaptation to the environment and substrate exploitation. To our knowledge, this is the first time in which it is showed that G. geotrichum KL20B could be used to compensate for the slow acid-producing ability of Lb. plant arum and E. faecalis in milk, underlining that this consortium applies some mechanisms to regulate the growth and milk composition in acids and ethanol content.