Figure 1.
A flow diagram of two potential biomass-to-biofuel bioprocessing configurations that utilize IL-pretreatment.
A) Diagrams a configuration based on methods currently established in the literature and lists some potential barriers to commercialization (Problems). B) This configuration combines IL-pretreatment and saccharification into a single pot and may overcome barriers outlined in A (as listed in the solutions section), but requires an IL-tolerant cellulase cocktail, such as JTherm.
Figure 2.
A pie chart showing the percent relative abundance of each taxon in the McCel-adapted thermophilic bacterial consortia.
SSU pyrosequencing was conducted to identify community members. Only members with a relative abundance greater than 1% are reported. Relative abundance is calculated as a percentage of the total number of SSU reads for the community. The closest taxon to each organism in the community is reported in the legend. The percent identity between the consortial and closest taxon SSU sequence is in parentheses.
Table 1.
Glycoside hydrolase activities produced by the thermophilic community.
Table 2.
Cellulase and xylanase from the thermophilic community identified by proteomics.
Figure 3.
Enzymatic saccharification of IL-pretreated switchgrass by JTherm at 70°C pH 5.5.
The supernatant from the thermophilic community at fixed concentration of 0.6× was augmented with various amounts of CBH and BG, and liberated glucose (♦) and cellobiose (▪) from IL-pretreated switchgrass were measured after 72 h incubation. Enzyme combinations were as follows: (A) supernatant, CBH, and BG; (B) CBH and BG without supernatant. The reaction was in a 1 ml volume with 25 mg of IL-pretreated switchgrass.
Figure 4.
Activity of the JTherm and CTec2 cellulase cocktails on ionic-liquid pretreated switchgrass at various temperatures and in the presence of the ionic liquid [C2mim][OAc].
Samples were run at 2.5% w/v biomass loadings in 1 ml and incubated at pH 5.5 for 72 h with shaking.
Figure 5.
Biodiesel produced by an engineered E. coli strain fed hydrolysates derived from JTherm or CTec2 hydrolysis of IL-pretreated switchgrass.
(A), and percentage of glucose remaining after fermentation (B). Glucose levels were adjusted to 2% for all hydrolysates and controls. The JTherm and CTec2 controls contained purified glucose and xylose at the same levels as their corresponding hydrolysate. No xylose was consumed during the fermentation (data not shown). Error bars indicate the standard deviation of triplicate experiments.
Figure 6.
Effects of ionic liquids on biodiesel production by an engineered E. coli strain.
The strain was fed either 2% glucose or a CTec2 hydrolysate of IL- pretreated switchgrass containing 0–1% (w/v) [C2mim][OAc] [(A). The percentage of glucose remaining after fermentation was measured (B). Glucose levels were adjusted to 2% for all hydrolysates and controls. The CTec2 control contained equivalent amounts of purified glucose and xylose as the hydrolysate. No xylose was consumed during the fermentation (data not shown). Error bars indicate the standard deviation of triplicate experiments.
Figure 7.
Growth of an E. coli strain engineered to produce biodiesel on CTec2 hydrolysate
(A) and control sample containing 2% glucose and 1% xylose (B). Oxygen transfer rate (OTR), and cell density (OD600) were monitored during the fermentation to determine the impacts of the hydrolysate on growth and respiration.