Lipid production by Lipomyces starkeyi using sap squeezed from felled old oil palm trunks.

The ability of oleaginous yeast Lipomyces starkeyi to efficiently produce lipids when cultivated on sap extracted from felled oil palm trunk (OPT) as a novel inexpensive renewable carbon source was evaluated. OPT sap was found to contain approximately 98 g/L glucose and 32 g/L fructose. Batch fermentations were performed using three different OPT sap medium conditions: regular sap, enriched sap, and enriched sap at pH 5.0. Under all sap medium conditions, the cell biomass and lipid production achieved were approximately 30 g/L and 60% (w/w), respectively. L. starkeyi tolerated acidified medium (initial pH ≈ 3) and produced considerable amounts of ethanol as well as xylitol as by-products. The fatty acid profile of L. starkeyi was remarkably similar to that of palm oil, one of the most common vegetable oil feedstock used in biodiesel production with oleic acid as the major fatty acid followed by palmitic, stearic and linoleic acids.

Effect of inoculum size on single-cell oil production from glucose and xylose using oleaginous yeast Lipomyces starkeyi.

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.

Glutathione production from mannan-based bioresource by mannanase/mannosidase expressing Saccharomyces cerevisiae.

This work aims to produce glutathione directly from mannan-based bioresources using engineered Saccharomyces cerevisiae. Mannan proved to be a valuable carbon source for glutathione production by this organism. Mannan-hydrolyzing S. cerevisiae was developed by heterologous expression of mannanase/mannosidase on its cell surface. This strain efficiently produced glutathione from mannose polysaccharide, ß-1,4-mannan. Furthermore, it produced glutathione from locust bean gum (LBG), a highly dense and inexpensive mannan-based bioresource, as sole carbon source. Glutathione productivity from LBG was enhanced by engineering the glutathione metabolism of mannan-hydrolyzing S. cerevisiae. Expression of extracellular mannanase/mannosidase protein combined with intracellular metabolic engineering is potentially applicable to the efficient, environmentally friendly bioproduction of targeted products from mannan-based bioresources.