Cutaneotrichosporon curvatum and Yarrowia lipolytica as key players for green chemistry: efficient oil producers from food waste via the carboxylate platform.

Cutaneotrichosporon curvatum and Yarrowia lipolytica can accumulate microbial oils using short-chain fatty acids (SCFA) as carbon sources. SCFAs-rich media often contain significant amounts of nitrogen that prevent high carbon:nitrogen (C:N) ratios necessary to boost lipid production. This work assessed the intrinsic ability of C. curvatum and Y. lipolytica to produce high amounts of microbial oils from these unusual carbon sources. Results demonstrated that minor differences in SCFA concentration (only 2 g/L) had a significant effect on yeast growth and lipid production. A C:N of 80 promoted yeast growth at all SCFA concentrations and favored SCFA consumption at 19 g/L SCFAs. The different SCFA uptake preferences in C. curvatum and Y. lipolytica highlighted the importance of considering the SCFA profile to select a suitable yeast strain for microbial oils production. At the most challenging SCFA concentration (19 g/L), 57.2% ±1.6% (w/w) and 78.4 ± 0.6% (w/w) lipid content were obtained in C. curvatum and Y. lipolytica, respectively. These values are among the highest reported for wild-type strains. To circumvent the challenges associated with media with high nitrogen content, this report also proved struvite precipitation as an effective method for increasing lipid production (from 17.9 ± 3.9% (w/w) to 41.9 ± 2.6% (w/w)) after nitrogen removal in food waste-derived media.

Slight variations in SCFA concentrations have a relevant effect on yeast lipid productionHigh nitrogen availability is crucial to promote cell growth at very high SCFA concentrationsC:N effect on cell growth and lipid production is specie-specific and may depend on yeast robustnessYeast strains have diverse SCFA preferences and differently metabolize these acidsStruvite precipitation effectively removes nitrogen from real digestates increasing C:N.

Tuning microbial community in non-conventional two-stage anaerobic bioprocess for microalgae biomass valorization into targeted bioproducts.

Unspecific microorganisms consortia are normally used in anaerobic biodegradation of solid wastes. However, these consortia can be tuned to optimally obtain determined bioproducts. In this study, high value-added products and biogas were obtained via an innovative two-stage anaerobic bioprocess from microalgae biomass. The anaerobic fermentation (AF) entailed the production of short-chain fatty acids (SCFAs) and subsequently, only the solid spent of AF effluent was valorized for methane production via conventional anaerobic digestion (AD). Applied conditions in AF (25 °C, HRT 8 days) favored Firmicutes predominance (64%) enabling a conversion efficiency of 32.1% g SCFAs-COD/g CODin. Opposite, a wider microbial biodiversity was determined in the AD reactor (35 °C, HRT 20 days), being mainly composed by Firmicutes (28.6%), Euryarchaeota (17.7%) and Proteobacteria (15.3%). AD of the AF-solid spent reached 168.9 mL CH4 /g CODin. Strikingly, operational conditions imposed mediated a microbial specialization that maximized product output.

Volatile fatty acids as novel building blocks for oil-based chemistry via oleaginous yeast fermentation.

Microbial oils are proposed as a suitable alternative to petroleum-based chemistry in terms of environmental preservation. These oils have traditionally been studied using sugar-based feedstock, which implies high costs, substrate limitation, and high contamination risks. In this sense, low-cost carbon sources such as volatile fatty acids (VFAs) are envisaged as promising building blocks for lipid biosynthesis to produce oil-based bioproducts. VFAs can be generated from a wide variety of organic wastes through anaerobic digestion and further converted into lipids by oleaginous yeasts (OYs) in a fermentation process. These microorganisms can accumulate in the form of lipid bodies, lipids of up to 60% wt/wt of their biomass. In this context, OY is a promising biotechnological tool for biofuel and bioproduct generation using low-cost VFA media as substrates. This review covers recent advances in microbial oil production from VFAs. Production of VFAs via anaerobic digestion processes and the involved metabolic pathways are reviewed. The main challenges as well as recent approaches for lipid overproduction are also discussed.