Identification of oleaginous yeast strains able to accumulate high intracellular lipids when cultivated in alkaline pretreated corn stover

Abstract

Microbial oil is a potential alternative to food/plant-derived biodiesel fuel. Our previous screening studies identified a wide range of oleaginous yeast species, using a defined laboratory medium known to stimulate lipid accumulation. In this study, the ability of these yeasts to grow and accumulate lipids was further investigated in synthetic hydrolysate (SynH) and authentic ammonia fiber expansion (AFEX™)-pretreated corn stover hydrolysate (ACSH). Most yeast strains tested were able to accumulate lipids in SynH, but only a few were able to grow and accumulate lipids in ACSH medium. Cryptococcus humicola UCDFST 10-1004 was able to accumulate as high as 15.5 g/L lipids, out of a total of 36 g/L cellular biomass when grown in ACSH, with a cellular lipid content of 40% of cell dry weight. This lipid production is among the highest reported values for oleaginous yeasts grown in authentic hydrolysate. Pre-culturing in SynH media with xylose as sole carbon source enabled yeasts to assimilate both glucose and xylose more efficiently in the subsequent hydrolysate medium. This study demonstrates that ACSH is a suitable medium for certain oleaginous yeasts to convert lignocellullosic sugars to triacylglycerols for production of biodiesel and other valuable oleochemicals.

Toward a microbial palm oil substitute: oleaginous yeasts cultured on lignocellulose

“…Boundy‐Mills et al . screened 39 yeasts on model corn stoverhydrolyzate that contained no inhibitors but did contain xylose as well as glucose . For the nine yeasts that grew well on this medium, the authors demonstrated that the yeasts consumed both glucose and xylose faster after pre‐culturing on xylose, presumably as the yeasts have already activated the metabolic pathways for catabolising xylose so the necessary enzymes are already synthesized.…”

Production of valuable compounds by molds and yeasts

“…141 Cryptococcus humicola produced 15 g l − 1 lipids in a total biomass weight of 36 g l − 1 . The strain (UCSEST 10-1004) came from the Phaff yeast collection at the University of California, Davis.…”

Production of single cell oil from Lipomyces starkeyi ATCC 56304 using biorefinery by-products

“…Oleaginous yeast have potential as a viable alternative oil-source but manufacturing for commoditybased products is cost-prohibitive mainly due to the high costs of feedstocks. Oleaginous yeast are capable of generating SCO from a variety of low-valued inedible plant-based feedstocks including corn cobs (Huang et al, 2012;Gao et al, 2014), corn residue Galafassi et al, 2012;Sitepu et al, 2014), corn fiber (Liang et al, 2014), rice straw (Huang et al, 2009), sorghum bagasse (Liang et al, 2012), sugarcane bagasse (Tsigie, 2011), and wheat straw (Yu et al, 2011). The oleaginous yeast Lipomyces starkeyi has considerable potential as a viable SCO producer due to its ability to produce high amounts of oil from hemicellulose-derived sugars including xylose (Anschau et al, 2014).…”