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The feasibility of high-solids simultaneous saccharification and ethanol production was investigated using unwashed corncob residues (CRs) with tea-seed cake (TSC). Tea saponin of TSC could serve as an accelerant to enhance ethanol production and reduce the dosage of enzymes. The proteins of TSC could be the nitrogen resource for yeast. The effects of substrate concentration (10%, 15%, and 20% (w/w)), enzyme dosage (2.5–15 FPU/g-cellulose), and types of media on ethanol production were evaluated. An ethanol yield of 86.56% of the theoretical maximum could be obtained at a substrate concentration of 15% (w/w) with 10 FPU/g-cellulose. Furthermore, fermentations in different media showed that the surface tension (49.21 mN/m) and contact angle (42.6°) of the fermentation system with TSC were lower than those from the other systems. This study found that adding TSC to the fermentation system was an attractive strategy to achieve high ethanol yield without any pretreatment. Comprehensive utilization of CRs and TSC as feedstocks for ethanol production can reduce the cost of biorefineries with environmental benefits.

Co-production of glucose, furfural and other green materials based on a lignocellulosic biorefinery is a promising way to realize the commercial application of corncob residues. An effective process was developed for glucose production using low temperature bisulfite pretreatment and high-solids enzymatic hydrolysis. Corncob residues from furfural production (FRs) were pretreated with 0.1g NaHSO3/g dry substrate at 100°C for 3h. Lignin was sulfonated and sulfonic groups were produced during pretreatment, which resulted in decreasing the zeta potential of the samples. Compared with raw material, bisulfite pretreatment of FRs increased the glucose yield from 18.6 to 99.45% after 72h hydrolysis at a solids loading of 12.5%. The hydrolysis residues showed a relatively high thermal stability and concentrated high derivatives. Direct pretreatment followed by enzymatic hydrolysis is an environmentally-friendly and economically-feasible method for the production of glucose and high-purity lignin, which could be further converted into high-value products.

Although great progress has been made in the research on conversion of cellulosic ethanol, the high conversion cost still exists as an obstacle. Thus, various measures such as reducing the chemical usage, minimizing the enzyme loading, and decreasing the energy consumption are required to lower the cost. Adding surfactants in bioethanol production process is recognized as a simple, effective, and economical strategy to enhance the fermentable sugars production. Therefore, making full use of surfactants (e.g., natural saponin from agricultural and forestry wastes and lignosulfonate) and other industrial wastes in the production of cellulosic ethanol would bring significant economic and environmental benefits. In this review, the recent progress on the application of different types of surfactants (synthetic, natural, and biosurfactant) in cellulosic ethanol production was summarized. The possible mechanism by surfactants was explored. The challenges of current research and outlook of surfactants used in the bioconversion of lignocellulosic biomass were also discussed.

The price of raw material, energy demand in the pretreatment step, and enzyme usage rate are the major cost factors in the process of converting biomass to bioethanol. Unwashed furfural residues (FRs) possess great potential for application in bioethanol production. Surfactant addition is an effective method to enhance the fermentation rate. In this study, unwashed FRs were used directly as raw materials to produce bioethanol. Tea-seed cake (TSC), tea seed residues that contained protein and saponin, was added in the simultaneous saccharification and fermentation (SSF) process. The effect of TSC dosage on SSF was compared. TSC was added at the dosage of 10 g/L, which resulted in a final ethanol yield of 87.2%. However, a high concentration of TSC could induce cytotoxicity in yeast. The surface tension (approximately 33.92 mM/m) at SSF using TSC-medium was much lower than that of other fermentation systems (about 64.67 mN/m). Further contact angle testing showed that TSC-medium (21.7°) had better wetting capacity than FRs (45.6°). This study provided a proposed process strategy that SSF with the addition of TSC could be a minimum consumption of chemicals and enzymes for future cellulosic ethanol production process.

Background As the most abundant renewable resources, lignocellulosic materials are ideal candidates as alternative feedstock for bioethanol production. Cassava residues (CR) are byproducts of the cassava starch industry which can be mixed with lignocellulosic materials for ethanol production. The presence of lignin in lignocellulosic substrates can inhibit saccharification by reducing the cellulase activity. Simultaneous saccharification and fermentation (SSF) of furfural residues (FR) pretreated with green liquor and hydrogen peroxide (GL-H2O2) with CR saccharification liquid was investigated. The final ethanol concentration, yield, initial rate, number of live yeast cells, and the dead yeast ratio were compared to evaluate the effectiveness of combining delignificated lignocellulosic substrates and starchy substrates for ethanol production. Results Our results indicate that 42.0 % of FR lignin removal was achieved on FR using of 0.06 g H2O2/g-substrate and 9 mL GL/g-substrate at 80 °C. The highest overall ethanol yield was 93.6 % of the theoretical. When the ratio of 0.06 g/g-H2O2-GL-pretreated FR to CR was 5:1, the ethanol concentration was the same with that ratio of untreated FR to CR of 1:1. Using 0.06 g/g-H2O2-GL-pretreated FR with CR at a ratio of 2:1 resulted in 51.9 g/L ethanol concentration. Moreover, FR pretreated with GL-H2O2 decreased the concentration of byproducts in SSF compared with that obtained in the previous study. Conclusions The lignin in FR would inhibit enzyme activity and GL-H2O2 is an advantageous pretreatment method to treat FR and high intensity of FR pretreatment increased the final ethanol concentration. The efficiency of ethanol fermentation of was improved when delignification increased. GL-H2O2 is an advantageous pretreatment method to treat FR. As the pretreatment dosage of GL-H2O2 on FR increased, the proportion of lignocellulosic substrates was enhanced in the SSF of the substrate mixture of CR and FR as compared with untreated FR. Moreover, the final ethanol concentration was increased with a high ethanol yield and lower byproduct concentrations.