Optimization of lipid production by the oleaginous yeast Lipomyces starkeyi by random mutagenesis coupled to cerulenin screening

Abstract

In this work we performed assays for the genetic improvement of the oleaginous yeast Lipomyces starkeyi DSM 70296 focusing on its utilization for lipid biosynthesis from renewable sources. The genetic optimization was carried out by random mutagenesis by ultraviolet irradiation and mutant selection by cerulenin, a compound displaying inhibitory effects on lipid biosynthesis. Mutants demonstrating normal growth in presence of cerulenin were considered as good candidates for further studies. Using this strategy, we selected 6 mutants for further studies, in which their productivities were evaluated by fermentation in shaken flasks and bioreactor. The evaluation of the fermentative performance of mutants was carried out using xylose as sole carbon source; the fermentation of wild-type strain was used as reference. Using this strategy it was possible to identify one mutant (termed A1) presenting a significant increase in the productivity rates of both biomass and lipid in comparison to wild-type strain. A1 mutant was further studied in bioreactor using the same fermentation parameters optimized for L. starkeyi lipid production from a mixed carbon source (xylose:glucose), as previously determined by other studies in our laboratory. A1 presented a productivity increase of 15.1% in biomass and 30.7% in lipid productivity when compared to the wild-type strain with a similar fatty acid composition, despite a slight increase (approx. 7%) on the unsaturated fraction. Our work demonstrates the feasibility of the random mutagenesis strategy coupled with mutant selection based on cerulenin screening for the genetic improvement of the oleaginous yeast L. starkeyi.

Microbial oil production by Rhodotorula glutinis CICC 31643 using sugar cane molasses

“…27,28 The results in this study also indicated that the fatty acid composition of R. glutinis was similar to that of other oleaginous yeast. When microbial oils come to biodiesel production, only those with a high content of stearic and oleic acid are potential targets of interest.…”

Effects of medium composition on the growth and lipid production of microplasmodia of Physarum polycephalum

“…produced approximately 2.5 g/L of dry biomass after 20 days, but the lipid content ranged from 30 to 40% . Some oleaginous yeasts such as Lipomyces starkeyi (wild type) reached the maximal values of DCW and lipid content of 12.3 g/L and 35.02%, respectively, after 7 days . However, it should be noted that in contrast to other microorganisms, microplasmodia have no cell walls.…”

“…The cetane number (CN) is widely used as diesel fuel quality parameter related to the ignition delay time and combustion quality . The CN decreases with decreasing chain length, increased branching, and increased saturation of the fatty acid chain .…”

“…Therefore, the best time for biomass harvest is between 4 and respectively, after 7 days. 24 However, it should be noted that in contrast to other microorganisms, microplasmodia have no cell walls. As such, lipid extraction from their biomass or direct transesterification of the biomass is much easier.…”

Development of continuous cultivation process for oil production through bioconversion of minimally treated waste streams from second‐generation bioethanol production

“…Second-generation bioethanol (2G ethanol) from lignocellulosic biomass (LCBs) is expected to be commercially available within a few years with several of the upcoming technologies reaching maturity. In an alternate pathway these waste streams can be assimilated into lipids by oleaginous yeasts such as Rhodotorula 3 , Lipomyces, 4 Yarrowia 5 and Trichosporon. 1 Acid pretreatment prior to the ethanol fermentation process results in pentose-rich waste streams containing a broad range of inhibitors such as furfural, hydroxymethyl furfural, acetic acid and formic acid.…”