Abstract
Microbial lipids have similar fatty acid composition to plant oils, and therefore, are considered as an alternative feedstock for biodiesel production. Oleaginous yeasts accumulate considerable amounts of lipids intracellularly during growth on low-cost renewable feedstocks such as lignocellulosic biomass. In this study, we cultivated yeast Trichosporon oleaginosus on hydrolysate of alkaline pretreated corn cobs. Different process configurations were evaluated and compared, including separate hydrolysis and fermentation (SHF) with cellulase recycle and simultaneous saccharification and fermentation (SSF) in batch and fed-batch mode. At low enzyme loading, the highest lipid concentration of 26.74 g L−1 was reached in fed-batch SSF fed with 2.5% (g g−1) substrate. Batch SHF was conducted for four rounds with recycling the cellulase adsorbed on unhydrolyzed lignocellulosic biomass. Thirty percent of cellulase saving was achieved for rounds 2–4 without compromising productivity and lipid yield. The addition of Tween 80 to lignocellulosic slurry improved the hydrolysis rate of structural carbohydrates in pretreated lignocellulosic biomass. Furthermore, supplementing the growth medium with Tween 80 improved lipid yield and productivity without affecting yeast growth. Oleaginous yeast T. oleaginosus is a promising strain for the sustainable and efficient production of lipids from renewable lignocellulosic feedstock.
Highlights
The latest biofuel production trends call for green and renewable raw materials at low prices and green technologies that can effectively replace today’s fossil fuel production.The European Union has set an ambitious target of 10% for the share of renewable energy used in transport by 2020 and14% in 2030, with advanced biofuels counting double to the target
This study showed that glucose cost accounts for more than 35% of the total cost for biodiesel production [7]
Plant-derived lignocellulosic biomass has been used as a source of energy-rich carbohydrates, which could be further efficiently converted to biofuels or feedstocks for their production as well as bio-based chemicals [22]
Summary
The latest biofuel production trends call for green and renewable raw materials at low prices and green technologies that can effectively replace today’s fossil fuel production. Plant-derived lignocellulosic biomass has been used as a source of energy-rich carbohydrates, which could be further efficiently converted to biofuels (ethanol, butanol) or feedstocks for their production (lipids for production of biodiesel) as well as bio-based chemicals [22]. Productivities and lipid titres in yeast cultures grown on lignocellulosic hydrolysates are lower than those obtained in synthetic media with glucose as carbon sources, especially at high substrate loadings due to increased inhibitors concentration. T. oleaginosus grown on lignocellulosic biomass, including cultivation method (batch and fed-batch), the process configuration (SHF and SSF), the addition of surfactant, and enzyme recycling. The hydrolysis of lignocellulosic biomass in SSF was conducted at low cellulase loading for prolonged reaction times to obtain higher yields and product concentrations. A decrease of freshly added enzyme in SHF was obtained by recycling the cellulases bound to the unhydrolyzed biomass in subsequent hydrolysis steps
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