Comparative Analysis of L-Carnitine Production by Y. Lipolytica in Different Culture Conditions in Biofuel Waste and Fatty-Poor Medium for Commercial Purposes

Abstract

\n BackgroundYarrowia lipolytica is oleaginous yeast with the ability to grow in a variety of hydrophilic and hydrophobic substrates, including industrial wastes, in which it produces and accumulates various nutrients.MethodsThe aim of the present study was to examine the presence of free L-carnitine in the biomasses of two Yarrowia lipolytica strains (A-101 and ATCC 9793) growing in biofuel waste and YPD medium. The cultivations of Y. lipolytica were performed in aerobic conditions at different temperatures (20-30°C) and pH values (4.0-7.0) of the media with and without the addition of precursors for L-carnitine production (trimethyllysine, iron, and L-ascorbic acid) in a laboratory scale or other substances (chromium, selenite, or zinc) in a pilot plant scale.ResultsBoth tested Y. lipolytica strains grown in fatty acid-poor YPD medium at 20°C and pH 6.0 contained endogenous free L-carnitine in their biomass with a maximum of 22.85 mg/100 g of wet biomass. The addition of L-carnitine precursors to the YPD medium exerted a significant effect on L-carnitine concentration in the yeast biomass, increasing it up to 250%. In turn, the biomass of both tested Y. lipolytica strains cultivated in the biofuel waste, irrespective of the culture conditions, contained below 1 mg of L-carnitine/100 g of wet biomass. However, the supplementation of the culture media with the L-carnitine precursors significantly increased the yield of the yeast biomass by 20-30% in the non-fermentable biofuel waste cultures. Moreover, the addition of chromium (III) chloride into the biofuel waste caused an increase in the free L-carnitine concentration in the yeast biomass up to 2.24 mg/100 g of dry weight.ConclusionBiomass of Y. lipolytica grown in the fatty-poor medium contained free L-carnitine, in contrast to the biomass grown in the fat-rich biofuel waste. The very low amounts of L-carnitine in the biomass of Y. lipolytica grown in the crude biofuel waste suggest that the yeast is able to utilize almost the entire pool of free L-carnitine for growth and nutritional biomass production. However, the addition of chromium to the biofuel waste contributed to an increase in L-carnitine concentration in Y. lipolytica biomass.