(512x) Utilization of Oleaginous Yeast for Sustainable Production of Biosurfactants

Surfactants are surface active compounds, which reduce interfacial tension between liquid, solids and gases. Due to its amphiphilic characteristics and emulsifying capacity, surfactants have a range of applications including cosmetics, food additives, detergents, multipurpose cleaning products and in the agricultural industry. The main classes of surfactants are glycolipids, lipoproteins, lipopeptides and free fatty acids.

As a substitute for petroleum-based synthetic surfactants, biosurfactants generated by microorganisms are gaining huge attention because of the low toxicity, stability, and biodegradability. Natural producers of biosurfactants include Bacillus spp, Lactobacillus spp, Saccharomyces cerevisie and Pseudomonas spp. Since various microorganisms naturally generate biosurfactants, strategies to achieve high titers of biosurfactants varies among species. Also, the sustainable production of biosurfactants is challenging, owing to low yields and high production costs. There are numerous studies to attain high titers of biosurfactant production via metabolic engineering techniques. However, most of these trials still require free fatty acids as a substrate starting material for the production of biosurfactants.

Oleaginous yeast species are promising candidates to provide starting materials for biosurfactant production due to the inherent ability to accumulate lipids inside their bodies by up to 70 %, mostly in the form of triacylglycerol. Their strong intolerance to toxic byproducts as well as the capability to utilize diverse sugars and/or acids as carbon sources are also highly advantageous for the economical production of starting materials for biosurfactants.

In this study, the potential of Trichosporon oleaginosus as a host to generate starting materials for biosurfactant production was investigated. Major free fatty acid species generated by T. oleaginosus was oleic acid, composing 50% (wt/wt) of total lipids, followed by palmitic acid, composing 30% (wt/wt) of total lipids. Moreover, the effect of nutrients on lipid accumulation of T. oleaginosus was examined. Glycerol was the favorable carbon source for lipid production by T. oleaginosus since the highest lipid accumulation, consisting of 42% (wt/wt), and fastest growth rate were attained with 15.5 g/L of final cell dry weights. Using glucose, a total of 37% (wt/wt) was achieved with 16 g/L of final cell dry weights. In testing of nitrogen sources, peptone resulted in the fasted growth kinetics and the highest lipid accumulation consisting of 55% (wt/wt) lipids. Using urea as a nitrogen source, only 37 % (wt/wt) lipid content was obtained. Ammonium sulfate and sodium nitrate resulted in stunted cell growth in spite of high lipid accumulation with more than 50 % (wt/wt) lipids. For economical production of lipids, glucose and urea were tested as nutrient sources at the fermenter level, and it resulted in a total of 20 g/L lipid with a lipid accumulation of 67% (wt/wt).

This study demonstrated a potential of T. oleaginosus that can be used as a starting material producer for biosurfactant manufacturing. It provided preferable nutrients for their effect on lipid production by T. oleaginosus to attain economical production and high titers of oleic acid rich lipids, which can be utilized for biosurfactant production.