Probiotic Properties and Safety Evaluation in the Invertebrate Model Host Galleria mellonella of the Pichia kudriavzevii YGM091 Strain Isolated from Fermented Goat Milk.

Abstract

Potential probiotic yeast strains isolated from fermented food need to meet safe and beneficial conditions for the host's health. The Pichia kudriavzevii YGM091 strain isolated from fermented goat milk has outstanding probiotic characteristics, including: the high survival percentage in digestive system conditions (reaching up 247.13 ± 0.12 and 145.03 ± 0.06% at pH 3.0 and bile salt 0.5%, respectively); good tolerance to temperature, salt, phenol, ethanol; good surface properties such as high hydrophobicity percentage (> 60%), the high auto-aggregation percentage rate (66.56 ± 1.45% after 45min of incubation) and the high co-aggregation percentage rate with pathogenic bacteria in a short time (> 40% after 2h of incubation); biofilm forming after 24h of incubation on abiotic surfaces; antioxidant activity reached excellent level after only 24h of incubation (The percentage free radical scavenging and the Trolox equivalent reaching up 79.86 ± 0.70% and 92.09 ± 0.75µg/mL after 72h of incubation); extracellular enzymes production protease and cellulase with high activity, amylase and pectinase with moderate activity and non-lipase activity. Simultaneously, the YGM091 strain is the in vitro safety yeast: insensitive to antibiotics and fluconazole, negative for gelatinase, phospholipase, coagulase, and non-hemolysis activities. Furthermore, this strain is in vivo safety yeast with the dosages below 106CFU/larva in the Galleria mellonella model with over 90% survival larvae and the yeast density reduced to just 102-103CFU/larva after 72h post-injection. Research results have demonstrated that the Pichia kudriavzevii YGM091 strain is a safe potential probiotic yeast and could become a candidate probiotic food to be used in the future.