RESUMEN
The yeast Pichia kudriavzevii N77-4 was isolated from the Korean traditional fermentation starter nuruk. In this study, fermentation performance and stress resistance ability of N77-4 was analyzed. N77-4 displayed superior thermotolerance (up to 44°C) in addition to enhanced acetic acid resistance compared to Saccharomyces cerevisiae. Moreover, N77-4 produced 7.4 g/L of ethanol with an overall production yield of 0.37 g/g glucose in 20 g/L glucose medium. However, in 250 g/L glucose medium the growth of N77-4 slowed down when the concentration of ethanol reached 14 g/L or more and ethanol production yield also decreased to 0.30 g/g glucose. An ethanol sensitivity test indicated that N77-4 was sensitive to the presence of 1% ethanol, which was not the case for S. cerevisiae. Furthermore, N77-4 displayed a severe growth defect in the presence of 6% ethanol. Because inositol biosynthesis is critical for ethanol resistance, expression levels of the PkINO1 encoding a key enzyme for inositol biosynthesis was analyzed under ethanol stress conditions. We found that ethanol stress clearly repressed PkINO1 expression in a dose-dependent manner and overexpression of PkINO1 improved the growth of N77-4 by 19% in the presence of 6% ethanol. Furthermore, inositol supplementation also enhanced the growth by 13% under 6% ethanol condition. These findings indicate that preventing downregulation in PkINO1 expression caused by ethanol stress improves ethanol resistance and enhances the utility of P. kudriavzevii N77-4 in brewing and fermentation biotechnology.
Asunto(s)
Reactores Biológicos , Farmacorresistencia Fúngica/genética , Etanol/toxicidad , Fermentación/genética , Monoéster Fosfórico Hidrolasas/genética , Pichia , Ácido Acético/metabolismo , Etanol/metabolismo , Glucosa/metabolismo , Ingeniería Metabólica/métodos , Organismos Modificados Genéticamente , Monoéster Fosfórico Hidrolasas/metabolismo , Pichia/genética , Pichia/metabolismo , República de Corea , Termotolerancia/genética , Regulación hacia Arriba/genéticaRESUMEN
This study introduces a facile method to hybridize metal nanoparticles with lipid vesicles, which allows us to control over their membrane micro-fluidity. We have fabricated these hybrid liposomes by directly hybridizing metal nanoparticles with lipid bilayers solely consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC). For this, we have used the dehydration and rehydration method. Characterizing their morphology and micro-fluidity, in which we have used electron microscopy and fluorescence anisotropy spectroscopy, enables us to demonstrate that metal nanoparticles with different surface properties create interactions with either phosphorus end groups or hydrophobic tails of DPPC, thereby resulting in decrease in micro-fluidity of the assembled lipid membranes, especially for the hydrophobic layers. Our approach to hybridize metal nanoparticles in between lipid layers offers a flexible means that allows us to obtain a liposome system with more controllable membrane properties.