Combined “de novo” and “ex novo” lipid fermentation in a mix-medium of corncob acid hydrolysate and soybean oil by Trichosporon dermatis

Abstract

BackgroundMicrobial oil is one important bio-product for its important function in energy, chemical, and food industry. Finding suitable substrates is one key issue for its industrial application. Both hydrophilic and hydrophobic substrates can be utilized by oleaginous microorganisms with two different bio-pathways (“de novo” lipid fermentation and “ex novo” lipid fermentation). To date, most of the research on lipid fermentation has focused mainly on only one fermentation pathway and little work was carried out on both “de novo” and “ex novo” lipid fermentation simultaneously; thus, the advantages of both lipid fermentation cannot be fulfilled comprehensively.ResultsIn this study, corncob acid hydrolysate with soybean oil was used as a mix-medium for combined “de novo” and “ex novo” lipid fermentation by oleaginous yeast Trichosporon dermatis. Both hydrophilic and hydrophobic substrates (sugars and soybean oil) in the medium can be utilized simultaneously and efficiently by T. dermatis. Different fermentation modes were compared and the batch mode was the most suitable for the combined fermentation. The influence of soybean oil concentration, inoculum size, and initial pH on the lipid fermentation was evaluated and 20 g/L soybean oil, 5% inoculum size, and initial pH 6.0 were suitable for this bioprocess. By this technology, the lipid composition of extracellular hydrophobic substrate (soybean oil) can be modified. Although adding emulsifier showed little beneficial effect on lipid production, it can modify the intracellular lipid composition of T. dermatis.ConclusionsThe present study proves the potential and possibility of combined “de novo” and “ex novo” lipid fermentation. This technology can use hydrophilic and hydrophobic sustainable bio-resources to generate lipid feedstock for the production of biodiesel or other lipid-based chemical compounds and to treat some special wastes such as oil-containing wastewater.

Refined soybean oil wastewater treatment and its utilization for lipid production by the oleaginous yeast Trichosporon fermentans

“…The biomass, lipid concentration, and lipid content were determined as described by Wu [ 44 ]. The biomass was the cell dry weight per liter wastewater (g/L); the lipid concentration was the amount of lipid extracted from the cells per liter wastewater (g/L); and the lipid content was the mass percentage of lipid to biomass (% w/w) [ 45 ]. NH 4 + -N and TP were assayed with the Nessler’s reagent spectrophotometry method and ammonium molybdate spectrophotometric method, respectively [ 46 , 47 ].…”

Utilization of Clarified Butter Sediment Waste as a Feedstock for Cost-Effective Production of Biodiesel

“…Nevertheless, to enhance the contact area between hydrophobic substrates and the cell surface, some external emulsifiers are often used to reduce the size of the hydrophobic substrates [42]. For example, in one study, oleaginous yeast Trichosporon dermatis CH007 was cultivated on a soybean oil-based medium along with Tween 80, Span 80, Tween 60, and OP-10 as external emulsifiers [43]. The addition of emulsifiers had a minor negative effect on the final lipid production.…”

Oleaginicity of the yeast strain Saccharomyces cerevisiae D5A

“…The fatty acid profile of D5A differs from that of typical oleaginous yeasts. Whereas, in D5A, the fatty acids C16:0, C16:1n7, and C18:1n9 make up > 90% of the fatty acids, in general, in other oleaginous yeasts, e.g., Rhodotorula , Rhodosporidium , Yarrowia, Trichosporon , and Lipomyces species, the fatty acids C16:0 and C18:1n9 make up the bulk of the fatty acids with minor contributions from C16:1n7, C18:0, and C18:2n6 [ 5 , 6 , 8 , 11 , 39 ]. In general, the change in fatty acid composition of these two strains differed as the culture cells matured.…”

“…As current lipid productivities are not sufficient for producing lipid-based biofuels economically, a significant research to increase lipid accumulation or include the production of co-products to enable lipid-based biofuel production is ongoing [ 2 , 3 , 7 ]. Lipid accumulation in yeast can be through de novo biosynthesis, the fermentation of hydrophilic substrates such as sugars or other carbohydrates to lipids, or through ex novo biosynthesis, the conversion of hydrophobic substrates such as oil and alkanes [ 6 , 8 ]. Studies of oleaginous microorganisms, such as microalgae, yeasts, filamentous fungi, and bacteria, have revealed that de novo lipid metabolism is dependent on environmental conditions, particularly nutrient shortages with an excess of carbohydrates [ 1 , 9 – 11 ], while ex novo biosynthesis is not [ 8 ].…”

“…Lipid accumulation in yeast can be through de novo biosynthesis, the fermentation of hydrophilic substrates such as sugars or other carbohydrates to lipids, or through ex novo biosynthesis, the conversion of hydrophobic substrates such as oil and alkanes [ 6 , 8 ]. Studies of oleaginous microorganisms, such as microalgae, yeasts, filamentous fungi, and bacteria, have revealed that de novo lipid metabolism is dependent on environmental conditions, particularly nutrient shortages with an excess of carbohydrates [ 1 , 9 – 11 ], while ex novo biosynthesis is not [ 8 ]. Among the potential limiting nutrients, nitrogen limitation has emerged as a reliable and efficient strategy to promote lipid production.…”