Abstract

Three yeast strains were isolated from decaying wood in the Chilean Valdivian forest and their ability to produce lipids from lignocellulosic monosaccharides was studied. This subject is of high interest for biotechnology and chemical industry (1). The yeasts, identified as Scheffersomyces coipomensis, Sugiyamaella paludigena and Meyerozyma guilliermondii (GenBank code: KX609756, KX609757 and KX609758, respectively), were grown in model media containing lignocellulosic carbon sources, such as glucose, xylose or mannose (at 40 g/L) or a mixture of them (at 40 g/L each, in total 120 g/L). The above monosaccharides are the major monomers released after acid hydrolysis of lignocellulosic biomass derived from Pinus spp. and Eucalyptus spp. (2, 3). The yeast biomass and lipids production were evaluated in two different incubation temperatures (i.e. 20 ºC and 28 ºC) during 160 h. The experimental data showed significant differences in biomass production (X, g/L) and in substrate consumption rate (qs, h-1), ranging from 5.3 to 14 g/L and from 0.0288 to 0.0765 h-1, respectively. Higher biomass yield (YX/S) values (i.e. ~0.4 g/g) were observed in S. coipomensis and S. paludigena cultivated on mannose at 20 ºC. Besides, the three strains were able to consume the three monosaccharides simultaneously, though a repression of mannose and xylose metabolism by glucose was observed. The strains cultivated on glucose and mannose presented high lipid yields (YL/S) at 28 ºC than 20 ºC. The higher value was presented by S. coipomensis on mannose (0.09 g/g). Lipids were accumulated in yeast cells in various percentages ranging from 6.9% (w/w), for the yeast S. paludigena cultivated on xylose at 20 ºC, to 24.7% (w/w), for the yeast S. coipomensis cultivated on mannose at 28 ºC. The fatty acid composition of the lipids produced was similar in the three yeasts, with oleic acid (ranging from 43.1 to 70.7% w/w) as the most abundant fatty acid obtained in all experimental conditions. It was concluded that the above newly isolated strains, especially S. coipomensis could be employed in the future for converting lignocellulosic biomass to lipids with different applications, such as biofuels, animal nutrition, pharmaceutical, among others.