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Three Metschnikowia strains marketed as bioprotection yeasts were studied to compare their antimicrobial effect on a mixture of two Hanseniaspora yeast strains in synthetic must at 12 °C, mimicking pre-fermentative maceration by combining different approaches. The growth of the different strains was monitored, their nitrogen and oxygen requirements were characterised, and their metabolomic footprint in single and co-cultures studied. Only the M. fructicola strain and one M. pulcherrima strains colonised the must and induced the rapid decline of Hanseniaspora. The efficiency of these two strains followed different inhibition kinetics. Furthermore, the initial ratio between Metschnikowia and Hanseniaspora was an important factor to ensure optimal bioprotection. Nutrient consumption kinetics showed that apiculate yeasts competed with Metschnikowia strains for nutrient accessibility. However, this competition did not explain the observed bioprotective effect, because of the considerable nitrogen content remaining on the single and co-cultures. The antagonistic effect of Metschnikowia on Hanseniaspora probably implied another form of amensalism. For the first time, metabolomic analyses of the interaction in a bioprotection context were performed after the pre-fermentative maceration step. A specific footprint of the interaction was observed, showing the strong impact of the interaction on the metabolic modulation of the yeasts, especially on the nitrogen and vitamin pathways. [ABSTRACT FROM AUTHOR]

In order to develop a cheap and efficient culture system of Lactobacillus rhamnosus, walnut pulp was used to replace the nitrogen source in MRS medium. Taking cell growth as the indicator, the cultivation system was optimized in aspects of walnut pulp particle size, solid-liquid ratio, dosage, lipid removing treatment, and the shaking speed during the cultivation of Lactobacillus rhamnosus. The antibacterial activity and antioxidant activity of cell-free culture supernatant were also tested in all conditions. The obtained cells were also subjected to selenium enrichment treatment and then fed to mice for 3 d before they were exposed to simulated low-pressure hypoxia condition (altitude 5000 m) for 6 h to evaluate their anti-hypoxia potential. As results, complete replacement of the nitrogen source (beef extract and peptone) of MRS medium with the lipid-free walnut pulp filtered by 120 mesh screen at the solid-liquid ratio of 1:10 (g/mL) could reduce the cost of MRS medium by 70% and increase the cell yield by 2.5 times (from 2.6×109 to 7.6×109 CFU/mL), but did not affect the antibacterial activity and antioxidant activity of the fermentation broth (P>0.05). Continuous oral administration of selenium enriched bacteria for 3 days could significantly increase the hemoglobin content of mice when they were exposed to low-pressure hypoxia for 6 h (P

Three Metschnikowia strains marketed as bioprotection yeasts were studied to compare their antimicrobial effect on a mixture of two Hanseniaspora yeast strains in synthetic must at 12 °C, mimicking pre-fermentative maceration by combining different approaches. The growth of the different strains was monitored, their nitrogen and oxygen requirements were characterised, and their metabolomic footprint in single and co-cultures studied. Only the M. fructicola strain and one M. pulcherrima strains colonised the must and induced the rapid decline of Hanseniaspora. The efficiency of these two strains followed different inhibition kinetics. Furthermore, the initial ratio between Metschnikowia and Hanseniaspora was an important factor to ensure optimal bioprotection. Nutrient consumption kinetics showed that apiculate yeasts competed with Metschnikowia strains for nutrient accessibility. However, this competition did not explain the observed bioprotective effect, because of the considerable nitrogen content remaining on the single and co-cultures. The antagonistic effect of Metschnikowia on Hanseniaspora probably implied another form of amensalism. For the first time, metabolomic analyses of the interaction in a bioprotection context were performed after the pre-fermentative maceration step. A specific footprint of the interaction was observed, showing the strong impact of the interaction on the metabolic modulation of the yeasts, especially on the nitrogen and vitamin pathways.