Table 3.
Summary of relevant reports on the variation in conversion efficiency in C4 grass species.
| Crop | Genetic nature | Conversion technology | Summary of results | References |
|---|---|---|---|---|
| Maize | Experimental Mapping Population—Hybrid testcrosses of 223 recombinant inbred lines from the IBM collection. | Mild dilute-acid pretreatment followed by hydrolysis with commercial enzyme cocktails. | Variation within population for cell wall glucose release after mild pretreatment and enzymatic saccharification ranged from ~48–56%. Glucose conversion efficiency was strongly correlated to lignin content (r = −0.74). | Lorenzana et al., 2010 |
| Sugarcane | Transgenic lines with RNAi-induced down-regulation of caffeic acid O-methyltransferase (COMT). | Mild dilute-acid pretreatment followed by hydrolysis with commercial enzyme cocktails. | Maximum reduction in lignin content in transgenic lines compared to controls of 13.7% and a maximum increase in fermentable glucose yield of 35% (after pretreatment and enzymatic hydrolysis). | Jung et al., 2012 |
| Switchgrass | Two sets of genotypes obtained by divergent selection for ruminant digestibility. | Various intensities of dilute-acid pretreatments followed by simultaneous saccharification and fermentation (SSF). | A 40% difference in ethanol yield (after dilute-acid pretreatment followed by SSF) between the two genotypes with the largest contrast in lignin content. | Sarath et al., 2011 |
| Switchgrass | Transgenic lines with RNAi-induced down-regulation of caffeic acid O-methyltransferase (COMT). | Various intensities of dilute-acid pretreatments followed by SSF. | Maximum reduction in lignin content in transgenic lines compared to controls of ~15% and a maximum increase in ethanol yield of 38% [after severe pretreatment (0.5% H2SO4, 180°C) followed by SSF]. | Fu et al., 2011a,b |
| Sorghum | Collection of brown-midrib (bmr) mutant collection and their corresponding wild-types. | Mild dilute-acid pretreatment followed by hydrolysis with commercial enzyme cocktails. | Glucose conversion after thermo-chemical processing and enzymatic hydrolysis across a set of 5 bmr mutants and their corresponding counterparts ranged from 59–77%. The maximum increase in glucose fermentable yields (relative to wild-type) was of 21%. | Saballos et al., 2008 |