Physical fractionation of sweet sorghum and forage/energy sorghum for optimal processing in a biorefinery

Integration of Pretreatment With Simultaneous Counter-Current Extraction of Energy Sorghum for High-Titer Mixed Sugar Production

“…As can be observed, the hydrolysis yields for the more severe conditions for both the NaOH and LHW pretreatments were higher than the lower severity conditions, while the NaOH pretreatment at an alkali loading of 0.10 g/g resulted in the highest glucose hydrolysis yields ( Figure 3A). These hydrolysis yields are within the range identified in our prior work with TX08001 sorghum (Li et al, 2018), where mild NaOH pretreatment of sorghum fractionated by tissue type could result in glucose hydrolysis yields ranging from 53% to the theoretical maximum. It is well-understood that the general mechanisms of reducing recalcitrance in alkaline pretreatments is by delignification as well as minor xylan solubilization (Ong et al, 2014) and not surprisingly, the levels of delignification were highest for the NaOH pretreatment and increased with increasing severity (Figure 3B).…”

“…Potential reasons for this discrepancy may be a combination of both the system not yet reaching steady-state and differences in water sorption between untreated and alkali-pretreated biomass. It is known that alkali-pretreated graminaceous biomass is capable of sorbing substantially more water than unpretreated biomass as demonstrated in our prior work with maize (Li et al, 2015) and sorghum (Li et al, 2018). Another important finding from this study is that the high pH (i.e., >12) reached during the FIGURE 3 | Results for separate extraction and deconstruction for two conditions each for alkali (0.06 or 0.10 g NaOH/g biomass at 80 • C for 1 h) and liquid hot water (LHW) pretreatment (120 • C or 160 • C for 1 h) demonstrating differences in (A) glucose hydrolysis yields based on structural glucan in extractives-free biomass, (B) lignin removal based on quantified Klason lignin content and mass yields, and (C) mass yields from pretreatment based on extractives-free original mass.…”

“…The composition of the TX08001 sorghum on a total dry mass basis is presented in Table 1 and shows the content of both extractives as well as cell wall biopolymers. Prior research on sorghum stems showed that significant compositional and structural heterogeneity among cell and tissue types and stage of plant development (Li et al, 2018). The current analysis averages these diverse sub-cellular compositions and examines sugar content only during vegetative phase growth when stem sucrose levels are relatively low compared to levels that accumulate postanthesis (McKinley et al, 2016).…”

“…Alkaline pretreatments are another class of promising pretreatments for the liberation of cell wall polysaccharides. Soda pulping of graminaceous feedstocks such as de-pithed sugarcane is practiced commercially, NaOH pretreatments are known to be effective at delignifying graminaceous biomass at relatively mild (i.e., <130 • C) conditions, and these processes have been adapted to facilitate high sugar yields during enzymatic hydrolysis (Karp et al, 2014;Liu et al, 2014;Li et al, 2018). An additional advantage of mild alkaline pretreatments is that pretreatmentgenerated inhibitors are benign enough that a detoxification is not required to facilitate fermentation (Sato et al, 2014) as in other pretreatments such as dilute acid pretreatment (Jönsson et al, 2013).…”

Possibilities and Prospects Regarding Ethanol Production from Saccharin Sorghum [Sorghum bicolor (L.) Moench]

“…Several alternative raw materials have been studied and shown to be efficient in alcohol production, such as sugar-based materials (e.g., cane syrups, beet molasses), starch-based materials (e.g., cassava, corn, potatoes), and lignocellulosic materials (e.g., rice straw; sugarcane bagasse; corn stalks; grasses; pineapple stems, leaves and husks), in addition to sugar cane, cassava, and sorghum [25]. Sorghum offers tremendous potential as a raw material for the production of fuels and chemicals from cell wall sugars and biopolymers, whereas its structural and compositional heterogeneity within the plant may allow physical fractions to adapt the properties of the raw material to a biorefining process [26].…”