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For a long time, yeasts have been used for the production of various biocompounds. New strains may exhibit a variety of benefits and applications to modern and classic biotechnological processing. Pichia kluyveri and Pseudozyma tsukubaensis were isolated from peach ( Prunus persica ) and nectarine ( P. persica var. nucipersica ) fruit, respectively, and identified through a molecular approach (D1/D2 28S rDNA) and phylogenetic analysis. The isolated yeasts were tested based on their ability to produce galactooligosaccharides from lactose using living whole cells. For both selected strains, an in vitro analysis of probiotic properties was carried out. A maximum yield of 14.01% and 15.71% (w/w) galactooligosaccharides was obtained from a lactose solution reaction (40% w/v) using P. kluyveri and P. tsukubaensis , respectively, at 30 °C, pH 7.0 and 24 h. To the best of our knowledge, this is the first study reporting the potential of P. kluyveri and P. tsukubaensis to produce galactooligosaccharides from lactose. It was shown that the P. kluyveri strain has desirable probiotic potential using the following parameters: thermotolerance, antibacterial activity against some pathogenic bacterial species and tolerance to acid and bile. [ABSTRACT FROM AUTHOR]

Abstract: The effects of production parameters on the biotransformation of sucrose in fructooligosaccharides (FOS) by osmophilic microorganisms Aureobasidium pullulans was evaluated by the RSM (Response Surface Metodology) exactly Plackett-Burman Design with 12 variables: concentration of sucrose, inoculum, yeast extract, urea, K2HPO4, (NH4)2SO4, MgSO4, ZnSO4, MnSO4. The strategy used was PB 16 with additional 3 central points, comprising 19 experiments. The levels of each variable (%) were sucrose: 20 a 40; yeast extract: 0 a 0.5; inoculum: 1 a 20; K2HPO4: 0 – 0.0435; urea: 0 – 0.015; (NH4)2SO4: 0 – 0.033; MgSO4.7H2O: 0 – 0.0245; ZnSO4: 0.0015; MnSO4.7H2O: 0 – 0.001, pH: 4.5 a 6.0; temperature (°C): 27 a 30; agitation (rpm): 150 a 250. The high yields reach values of 54.7% at 48h of reaction in treatment 9, 49.97% at 24h for treatment 4 and 49.34% in 24h for treatment 12. The variable effects were estimated for each parameter FOS Yield and total FOS concentration. The FOS Yield data showed significance at 24h the variables agitation, with negative effect -16.32 and p-value 0.016, MnSO4, with positive effect 15.33 and p-value 0.020. At 48h the agitation was the only parameter significant with negative effect - 14.94. The inoculum levels showed significance at 0h with positive effect 14.08, however it was negative at 24 and 48hours. Regarding Total FOS Concentration, sucrose levels displayed p-values of 0.0085, 0.028 and 0.046 at 24, 48 and 72h respectively. MnSO4 was the only mineral presenting stimulatory effect upon FOS concentration added. More research should be done to evaluate and optimize this process. This in turn can provide a focus for effective use of Aureobasidium pullulans to synthesize fructooligosaccharide through bioconversion using whole cells and obtaining the product by direct manner. [Copyright &y& Elsevier]

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