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Dilute inorganic acids hydrolysis is one of the most promising pretreatment strategies with high recovery of fermentable sugars and low cost for sustainable production of biofuels and chemicals from lignocellulosic biomass. The diverse phenolics derived from lignin degradation during pretreatment are the main inhibitors for enzymatic hydrolysis and fermentation. However, the content features of derived phenolics and produced glucose under different conditions are still unclear due to the highly non-linear characteristic of biomass pretreatment. Here, an artificial neural network (ANN) model was developed for simultaneous prediction of the derived phenolic contents (CPhe) and glucose yield (CGlc) in corn stover hydrolysate before microbial fermentation by integrating dilute acid pretreatment and enzymatic hydrolysis. Six processing parameters including inorganic acid concentration (CIA), pretreatment temperature (T), residence time (t), solid-to-liquid ratio (RSL), kinds of inorganic acids (kIA), and enzyme loading dosage (E) were used as input variables. The CPhe and CGlc were set as the two output variables. An optimized topology structure of 6–12-2 in the ANN model was determined by comparing root means square errors, which has a better prediction efficiency for CPhe (R2 = 0.904) and CGlc (R2 = 0.906). Additionally, the relative importance of six input variables on CPhe and CGlc was firstly calculated by the Garson equation with net weight matrixes. The results indicated that CIA had strong effects (22%-23%) on CPhe or CGlc, then followed by E and T. In conclusion, the findings provide new insights into the sustainable development and inverse optimization of biorefinery process from ANN modeling perspectives. [ABSTRACT FROM AUTHOR]

Efficient deconstruction of lignocellulosic biomass by pretreatment is important for the production of fermentable sugars and biofuels. This study used butyric acid as a novel catalyst for corn stover pretreatment. The effects of butyric acid pretreatments on chemical composition and enzymatic digestibility were systematically investigated. The results indicate that a high linear correlation between xylan removal and fermentable sugars yield (r 2 = 0.91) was found. Pretreatment of corn stover with 50 g/L butyric acid at 180 °C for 0.5 h removed 83.17% of xylan and recovered 86.99% of glucan, and fermentable sugars yield of pretreated corn stover reached 97.16%. The physiochemical characterization results show that crystalline index (CrI) of corn stover was increased from 30.13% to 45.04%−48.38% after pretreatments, and the chemical structure and morphological features also exhibited positive changes for enhancing enzymatic hydrolysis. Meanwhile, the liquid fraction of pretreated slurry can be used for recycled pretreatment with 73.81% of fermentable sugars yield after four cycles. Additionally, the residual butyric acid was re-utilized as the co-substrate for Clostridium acetobutylicum ATCC 824 to produce biobutanol via acetone-butanol-ethanol (ABE) fermentation. The final production of butanol and solvents reached 8.38 g/L and 12.63 g/L under an optimized intermittent feeding strategy with a higher butanol/acetone ratio of 2.40 g/g. Overall, this work presents a novel pretreatment strategy to co-produce fermentable sugars and advanced biofuel from abundant lignocellulosic biomass. [Display omitted] • A novel butyric acid pretreatment method was developed for corn stover utilization. • The xylan removal has a positive effect on glucose and fermentable sugars yields. • Butyric acid pretreatment improved the glucose yield by 2.59-fold with cellulase. • Liquid fraction of pretreated slurry can be used for recycled biomass pretreatment. • Butanol titer was enhanced by 22.51% under intermittent feeding butyrate strategy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Liquid fraction containing glycerol was used for recycled corn stover pretreatment. • Dry cell weight of P. pastoris reached ∼ 40 g/L with glycerol as sole carbon source. • The titer of human lysozyme reached 1.3 g/L by P. pastoris with methanol induction. • Mixing pretreated corn stover with cassava as co-substrate to produce biobutanol. • Final butanol titer of 13.9 g/L was produced from mixed substrates under SSF. Glycerol organosolv pretreatment (GOP) is considered an efficient method to deconstruct lignocellulose for producing fermentable sugars. Herein, the liquid fraction containing glycerol after GOP was utilized for recycled pretreatment of corn stover (CS) for four cycles. Enzymatic yield of glucose after recycled pretreatment was enhanced by 2.4–3.5 folds compared with untreated CS. Meanwhile, residual glycerol was used as carbon source for cultivation of Pichia pastoris to obtain high cell-density, and a final titer of 1.3 g/L human lysozyme was produced by P. pastoris under low temperature methanol induction strategy. Additionally, the pretreated CS was mixed with cassava as fermentable substrates for butanol production by wild-type Clostridium acetobutylicum ATCC 824. Final butanol production of 13.9 g/L was obtained from mixed substrates (25%:75% of CS/cassava) at 10% solids loading by simultaneous saccharification and fermentation. Overall, integration of residual glycerol utilization and butanol production by microbial fermentation provided an efficient strategy for biorefinery. [ABSTRACT FROM AUTHOR]

[Display omitted] • Glycerol organosolv pretreatment could efficiently deconstruct corn stover. • The yield of glucose/xylose reached ∼80 % with glycerol pretreatment by cellulase. • l -cysteine-assisted glycerol pretreatment was developed for enhanced enzymolysis. • Fermentable sugars production reached 26.08 g/100 g by the proposed pretreatment. • Effects of raw materials prices on economic feasibility of processes were studied. Deconstruction of lignocellulose via efficient pretreatment is crucial for producing fermentable sugars. In this study, effects of glycerol organosolv pretreatment (GOP) on main chemical composition of corn stover were investigated. Results indicate that the residual corn stover after 80 wt% glycerol pretreatment (at 220 °C for 0.5 h) yielded 75.97 % glucose and 78.21 % xylose after enzymatic hydrolysis, which were enhanced by 3.39- and 6.08-fold compared to the untreated corn stover. Subsequently, an l -cysteine-assisted GOP was proposed with higher yields of glucose (86.20 %) and xylose (91.13 %). When pretreating corn stover with 80 wt% glycerol containing 0.07 wt% l -cysteine at 220 °C for 0.5 h, higher fermentable sugars of 26.08 g were produced from 100 g feedstock after enzymolysis. Intrinsic mechanisms of the proposed pretreatment for enhancing enzymatic digestibility were elucidated by physiochemical characterization technologies and techno-economic analysis was also studied. This study provides guidance for fermentable sugars production from renewable lignocellulose. [ABSTRACT FROM AUTHOR]