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A two-stage selection process was applied to eight oleaginous yeast strains from the Lipomyces genera. In the primary selection stage, a nitrogen-limited mineral medium (-NMM) that contained a mixture of glucose and xylose as a carbon source was used to evaluate the lipid-accumulating abilities of the yeast strains. The strains L. doorenjongii , L. orientalis , and L. starkeyi were selected as the potential strains in the primary selection. These three strains exhibited a remarkable ability to simultaneously assimilate glucose and xylose and achieved a cell biomass of more than 30 g/L. The values for lipid content in the selected strains were 57.89 ± 1.92, 56.38 ± 1.93, and 77.14 ± 1.55% for L. doorenjongii , L. orientalis , and L. starkeyi , respectively. In the secondary selection, when the -NMM medium contained an inhibitory chemical compound (ICC), the selected strains showed a different tolerance level against each of the typical inhibitor compounds. However, L. starkeyi accumulated the highest lipid content and yield at 68.24 ± 2.48% and 0.19 ± 0.00 (w/w), respectively. L. starkeyi accumulated high levels of intracellular lipid and tolerated the ICC. The composition of fatty acid methyl esters (FAMEs) was unaltered by the presence of ICC and the major FAMEs consisted of oleic, palmitic, stearic, palmitoleic and linoleic acids. [ABSTRACT FROM AUTHOR]

Oleaginous microbes can convert substrates such as carbon dioxide, sugars, and organic acids to single-cell oils (SCOs). Among the oleaginous microorganisms, Lipomyces starkeyi is a particularly well-suited host given its impressive native abilities, including the capability to utilize a wide variety of carbon sources. In this work, the potential of L. starkeyi NBRC10381 to produce SCOs in a synthetically nitrogen-limited mineral medium (-NMM) was investigated by differing the inoculum size using glucose and/or xylose as a carbon source. Fermentation using glucose and xylose as mixed carbon sources generated the highest production of biomass at 40.8 g/L, and achieved a lipid content of 84.9% (w/w). When either glucose or xylose was used separately, the totals for achieved lipid content were 79.6% (w/w) and 85.1% (w/w), respectively. However, biomass production was higher for glucose than for xylose (30.3 vs. 28.7 g/L, respectively). This study describes the first simultaneous achievement of higher levels of cell mass and lipid production using glucose and/or xylose as the carbon sources in different inoculum sizes. [ABSTRACT FROM AUTHOR]

• The fermentation of Ls-D35 was carried out at low initial C/N ratio (17.9). • The fermentation of Ls-D35 was optimum at pH 5 for cell and lipid productions. • The highest lipid yield was achieved by using single xylose feeding. Oleaginous microorganisms such as oleaginous yeasts are well known for the ability to accumulate intracelular lipid more than 20% w/w in certain conditions. Lipomyces starkeyi D35 (Ls-D35 strain) is one of promising oleaginous yeast for lipid production. The purpose of this research is to establish the optimum condition for cell and lipid production of Ls-D35 strain under low C/N ratio (17.9) by high cell density cultivation. The optimum pH for cell and lipid production was achieved at pH 5 by using batch cultivation. Four different feeding strategies were conducted to observe the cell and lipid production of Ls-D35 strain. The highest cell yield was achieved by mixed glucose and xylose as substrates (0.15 w/w substrate) after 96 h and the highest lipid yield was achieved by single xylose feeding (0.13 w/w substrate) after 120 h. Meanwhile, the two most fatty acids content were C18:1 and C16:0 which are similar to the content of vegetable oil. These results showed that Ls-D35 strain could produce high cell and optimum lipid under low initial C/N ratio medium which can be an alternative for biodiesel production and other industrial products. [ABSTRACT FROM AUTHOR]