# Lignocellulosic Biomass as a Substrate for Oleaginous Microorganisms: A Review
## 7 SCO Production from Hydrolyzed Lignocellulosic Biomass
Genetically modified strains of _Saccharomyces cerevisiae_, yeast widely used in the conversion of lignocellulosic substrates to ethanol, showing increased tolerance to inhibitors, such as furfural and HMF, have been constructed, and this knowledge could be used for constructing new oleaginous strains. For example, _S. cerevisiae_ strains ADH6p and ADH7 overexpressing alcohol dehydrogenase exhibit strong furfural and HMF reducing activities, and in some cases improve growth performance in the presence of aldehyde [232]. On the other hand, the experience of genetic manipulations in the oleaginous yeast _Y. lipolytica_ can be used in this context [274]. Both streams of research pave the way for the genetic transformation of oleaginous yeasts, such as the yeast _Candida phanggenesis_, the modified strain JQCP04 of which, overexpressed the alcohol dehydrogenase gene of _S. cerevisiae_ (ADH6p) under strong control of the TEF constitutive promoter of _Y. lipolytica_[275]. This overexpression allows the reduction of the aldehyde group of the furfural inhibitor to an alcohol, greatly decreasing toxicity, reducing the lag time by 58% and increasing the growth rate compared to wild-type _C. phangensis._ In a similar study, ADH6 was overexpressed in _Y. lipolytica_ YB-392 [276]. The modified strain, although it presented a furfural reduction capacity, did not present significant difference in terms of lag time, specific growth rate or biomass yield in the presence of 10 mM furfural, when compared to the wild type. Some oleaginous red yeasts of the Division Basidiomycota, such as _Rhodotorula mucilaginous_ BIS11 and _Rhodotorula (Rhodosporidium) toruloides_ BIS18, are known to convert hexoses, pentoses, organic acids and aromatic monomers into cell mass rich in lipids, carotenoids, terpen and precursors of various bioproducts, such as bisabolene [277; 278]. The aforementioned yeasts have been genetically modified, and the derived strains present an enhanced ability to synthesize bioactive compounds, such as bisabolene, when grown on different ULH [109]. Finally, alternatively or in addition to genetic engineering, directed evolution strategies can be developed in order to enhance lipid accumulation inoleaginous microorganisms. An adaptive evolution strategy of _Yarrougia lipolytica_ growing in alternative environments that promote growth and encourage the synthesis of storage lipids, followed by conditions that reward the high-energy containing cells, has been developed. The oleaginous lineages obtained give rise to populations capable of accumulating 30% _w/w_ more lipids than the initial strain. Similar strategies could be used as a robust tool to generate tolerant strains able to grow on ULH and accumulate high amounts of lipids [20]. Regardless of the approach used for improving productivity of oleaginous microorganisms, the environmental and economic viability of SCOs can be improved by adopting biorefinery approaches, as the exploitation and commercialization of the various by-products of the SCO production process, such as proteins, amino acids, carbohydrates, carotenoids, glycerol, organic acids, and alcohols [50; 135; 232; 279; 280; 281] may be critical in determining the minimum selling price of microbial oil.