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Xylose is abundant in lignocellulosic biomass. The fermentation of xylose is still a key problem in cellulose ethanol fermentation. In this research, the xylose fermentation strains were isolated from the soil sample. Strain N6 was chosen for further xylose fermentation experiments. Comparison of its 16S rDNA gene sequence with available sequences in GenBank showed that it was 100 % identical to that of Bacillus cereus strain SWFU2816 (Accession No. JN935015.1). Strain N6, which ferments xylose and hexose to ethanol, can produce fuel ethanol. The ability of strain N6 to transform xylose was better than its ability to transform glucose. As a result, the optimal condition for xylose fermentation was determined. The optimum fermentation conditions at 150 rpm for 48 h in a shake flask were as follows: pH 7.0, reducing sugar 70 g L-1, inoculation amount 5 %, and temperature 38 °C. The xylose to ethanol yield coefficient could reach a maximum of 0.26 g g-1. At the same time, the influence of the acid hydrolysis by-products on the isolated strain was studied. Compared to the commonly used saccharomycetes, the tolerance of strain N6 on furaldehyde had greatly improved, which could help ethanol fermentation from lignocellulose materials. [ABSTRACT FROM AUTHOR]

• The SPAP removed part of lignin and disrupted the crystalline regions of bamboo. • Glucose yield of SPAP-DS was 89.06 %, which was 4.5 times higher than PAP-DS. • Sulfomethylation contributed to the decrystallize of bamboo cellulose in the subsequent H 3 PO 4 -pretreatment. The sulfomethylation-aided phosphoric acid pretreatment (SPAP) was investigated for bamboo biorefinery. The yield of glucose and xylose were increased from 19.8 % and 13.88 % for H 3 PO 4 -pretreated D. sinicus alone (PAP-DS) to 89.06 % and 72.92 % for SPAP-DS. Ethanol concentration for SPAP-DS was 13.26 g/L, which improved by about 3-folds than PAP-DS. The SPAP-DS exhibited the lower lignin content and cellulose crystallinity, thus resulting in the enzyme accessibility to cellulose increased remarkably. The pre-step of sulfomethylation loosened compact structure of bamboo, which significantly contributed to the decrystallization of cellulose in the following H 3 PO 4 -pretreatment. The study has potential implications in biomass pretreatments, which should target synergistically and simultaneously toward cellulose, hemicellulose, or lignin fraction for obtaining higher bio-based chemical compounds and biofuels. [ABSTRACT FROM AUTHOR]

Abstract: Ethanol production by Flammulina velutipes from high substrate concentrations was evaluated. F. velutipes produces approximately 40–60 g l−1 ethanol from 15 % (w/v) d-glucose, d-fructose, d-mannose, sucrose, maltose, and cellobiose, with the highest conversion rate of 83 % observed using cellobiose as a carbon source. We also attempted to assess direct ethanol fermentation from sugarcane bagasse cellulose (SCBC) by F. velutipes. The hydrolysis rate of 15 % (w/v) SCBC with commercial cellulase was approximately 20 %. In contrast, F. velutipes was able to produce a significant amount of ethanol from 15 % SCBC with the production of β-glucosidase, cellobohydrolase, and cellulase, although the addition of a small amount of commercial cellulase to the culture was required for the conversion. When 9 mg g−1 biomass of commercial cellulase was added to cultures, 0.36 g of ethanol was produced from 1 g of cellulose, corresponding to an ethanol conversion rate of 69.6 %. These results indicate that F. velutipes would be useful for consolidated bioprocessing of lignocellulosic biomass to bioethanol. [Copyright &y& Elsevier]

Abstract: The aim of the work was to study the properties of the bacterial cellulose membrane (BCM) and the feasibility of using it as a new, environmentally friendly support carrier for yeast cell immobilization. It was observed that the morphology of BCM varied with different cultivation methods and the scanning electron microscopy (SEM) images confirmed that the yeast cells were entrapped in the porous network of BCM obtained from the static culture and stabilized by the cross-linked fibrils. Particularly, the research confirmed the effectiveness of yeast immobilization in BCM reflected by the high yield of alcohol (9.7% v/v, a 21.25% increase of those using free cells) and the high stability. The specific rate of ethanol production by the immobilized cells in BCM was 2.1gg−1 h−1, 31.3% greater than that of the suspended cells. Results implied that applying BCM as the support carrier had little adverse effects on cell viability and proliferation. Instead, it facilitated the product leakage and nutrients transportation through the porous network. [Copyright &y& Elsevier]

Saccharomyces cerevisiae was engineered for assembly of minicellulosomes by heterologous expression of a recombinant scaffolding protein from Clostridium cellulovorans and a chimeric endoglucanase E from Clostridium thermocellum. The chimeric endoglucanase E fused with the dockerin domain of endoglucanase B from C. cellulovorans was assembled with the recombinant scaffolding protein. The resulting strain was able to ferment amorphous cellulose [carboxymethyl-cellulose (CMC)] into ethanol with the aid of β-glucosidase 1 produced from Saccharomycopsis fibuligera. The minicellulosomes assembled in vivo retained the synergistic effect for cellulose hydrolysis. The minicellulosomes containing the cellulose-binding domain were purified by crystalline cellulose affinity in a single step. In the fermentation test at 10 g L−1 initial CMC, approximately 3.45 g L−1 ethanol was produced after 16 h. The yield (in grams of ethanol produced per substrate) was 0.34 g g−1 from CMC. This result indicates that a one-step processing of cellulosic biomass in a consolidated bioprocessing configuration is technically feasible by recombinant yeast cells expressing functional minicellulosomes. [ABSTRACT FROM AUTHOR]

• A packed-bed bioreactor for SSSF with N 2 stripping was fabricated. • Ethanol mass transfer was reasonably simulated by the established kinetic model. • Sparging N 2 effectively stripped ethanol out of the packed bed and improved SSSF. • Initial yeast concentration caused obvious influence on biofilm formation and SSSF. In this work, a solid simultaneous saccharification and fermentation (SSSF) system with N 2 stripping was constructed for ethanol production, and the glucose inhibition to enzymatic saccharification of cellulose and the ethanol inhibition to anaerobic fermentation of yeast cells could be relieved. First, effects of flow rate of carrier gas and initial yeast concentration on mass transfer of ethanol and performance of SSSF were experimentally investigated. It is found that the peaks of total ethanol amount (6.32 g), cellulose consumption amount (13.29 g), ethanol yield (0.48 g/g substrate) and change rate of porosity of the packed bed (57.45 %) were obtained at an initial yeast concentration of 2% and a N 2 flow rate of 30 mL/min. The results reveal that mass transfer efficiency during SSSF could be improved at an appropriate N 2 flow rate and an optimal initial yeast concentration. Then, a novel kinetic model was established to simulate mass transfer of ethanol during SSSF. The data predicted by the model were in good accordance with the experimental results, which shows that the established model could reasonably reflect the characteristics of ethanol mass transfer in the packed bed. This work demonstrates that the produced ethanol could be effectively stripped out of the packed bed by convection of the sparged N 2 , leading to improving performances of enzymatic hydrolysis and ethanol fermentation. [ABSTRACT FROM AUTHOR]