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In this study, it was found that the type of phenolic acids derived from rice straw was the major factor affecting ethanol fermentation by Pichia stipitis . The aim of this study was to investigate the inhibitory effect of phenolic acids on ethanol fermentation with rice straw. Different cellulases produced different ratios of free phenolic acids to soluble conjugated phenolic acids, resulting in different fermentation efficiencies. Free phenolic acids exhibited much higher inhibitory effect than conjugated phenolic acids. The flow cytometry results indicated that the damage to cell membranes was the primary mechanism of inhibition of ethanol fermentation by phenolic acids. The removal of free phenolic acids from the hydrolysates increased ethanol productivity by 2.0-fold, indicating that the free phenolic acids would be the major inhibitors formed during saccharification. The integrated process for ethanol and phenolic acids may constitute a new strategy for the production of low-cost ethanol. [ABSTRACT FROM AUTHOR]

Miscanthus × giganteus is a perennial rhizomatous grass which is used as a biofuel crop. Due to its high yields, low production costs, resistance to low temperatures, low soil requirements and, above all, high cellulose content, miscanthus can be a useful resource for ethanol production. The aim of this study was to determine the effect of two fertilization regimes (sewage sludge/mineral NPK) during miscanthus cultivation on the chemical composition of biomass, the content of major lignocellulosic factions and the effectiveness of miscanthus conversion to bioethanol. The results indicate that fertilization treatments influenced biomass yield and the content of major lignocellulosic fractions. Bioethanol production was higher when hydrolysis and fermentation processes were conducted separately than when saccharification and fermentation were conducted simultaneously. Ethanol production increased by 30% and 40% in response to sewage sludge and NPK (equivalent nitrogen content = 160 kg N/ha) fertilization, respectively, in comparison with unfertilized crops. [ABSTRACT FROM AUTHOR]

In this study, dilute alkali salts (0.6% NaClO, 0.067% Na 2 S) pretreatment at 10% sulfidity under the autoclave system at 120 °C for 40 min was used for pretreating bamboo shoot shell (BSS). Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated BSS solid residue. After 72 h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50 g/L pretreated BSS in dilute NaClO/Na 2 S media could be obtained at 31.11 and 20.32 g/L, respectively. Finally, the obtained BSS-hydrolysates containing alkalic salt NaClO/Na 2 S resulted in slightly negative effects on the ethanol production. Glucose in BSS-hydrolysates was fermented from 20.0 to 0.17 g/L within 48 h, and an ethanol yield of 0.41 g/g glucose, which represents 80.1% of the theoretical yield, was obtained. This study provided an effective strategy for potential utilization of BSS. [ABSTRACT FROM AUTHOR]

Two different plants namely Phoenix canariensis and Opuntia ficus-indica were used as substrate for reducing sugar generation and ethanol production. Dilute acid, alkaline and steam explosion were used as pretreatment methods in order to depolymerize lignin and/or hemicellulose and recover cellulose. By using alkaline pretreatment with 2.5% NaOH 71.08% for P. canariensis and 74.61% for O. ficus-indica lignin removal and 81.84% for P. canariensis and 72.66% for O. ficus-indica cellulose recovery yields were obtained. Pretreated materials were hydrolyzed by cellulase with high efficiency (87.0% and 84.5% cellulose conversion yields for P. canariensis and O. ficus-indica ) and used as substrate for fermentation. Maximum ethanol production of 15.75 g/L and 14.71 g/L were achieved from P. canariensis and O. ficus-indica respectively. Structural differences were observed by XRD, FTIR and SEM for untreated, pretreated, hydrolyzed and fermented samples and were highly correlated with compositional analysis results. [ABSTRACT FROM AUTHOR]

An oxidative production process of xylonic acid using xylose in distillation stillage of cellulosic ethanol fermentation broth was designed, experimentally investigated, and evaluated. Dry dilute acid pretreated and biodetoxified corn stover was simultaneously saccharified and fermented into 59.80 g/L of ethanol (no xylose utilization). 65.39 g/L of xylose was obtained in the distillation stillage without any concentrating step after ethanol was distillated. Then the xylose was completely converted into 66.42 g/L of xylonic acid by Gluconobacter oxydans . The rigorous Aspen Plus modeling shows that the wastewater generation and energy consumption was significantly reduced comparing to the previous xylonic acid production process using xylose in pretreatment liquid. This study provided a practical process option for xylonic acid production from lignocellulose feedstock with significant reduction of wastewater and energy consumption. [ABSTRACT FROM AUTHOR]

Jerusalem artichoke (JA) is a potential energy crop for biorefinery due to its unique agronomic traits such as resistance to environmental stresses and high biomass yield in marginal lands. Although JA tubers have been explored for inulin extraction and biofuels production, there is little concern on its stalk (JAS). In this article, the pretreatment of JAS by alkaline hydrogen peroxide was optimized using the response surface methodology to improve sugars yield and reduce chemicals usage. Scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis were applied to characterize the structures of the pretreated JAS to evaluate the effectiveness of the pretreatment. Furthermore, the feeding of the pretreated JAS and cellulase was performed for high solid uploading (up to 30%) to increase ethanol titer, and simultaneous saccharification and fermentation with 55.6 g/L ethanol produced, 36.5% more than that produced through separate hydrolysis and fermentation, was validated to be more efficient. [ABSTRACT FROM AUTHOR]

In this study, a Saccharomyces cerevisiae recombinant strain 14 was constructed through genome shuffling method by transferring the whole genomic DNA of Candida intermedia strain 23 into a thermo-tolerant S. cerevisiae strain. The recombinant strain 14 combined the good natures of both parent strains that efficiently produced ethanol from glucose and single cell protein from xylose with 54.6% crude protein and all essential amino acids except cysteine at 35 °C. Importantly, the recombinant strain 14 produced 64.07 g/L ethanol from 25% (w/v) NaOH-pretreated and washed corn stover with the ethanol yield of 0.26 g/g total stover by fed-batch simultaneous saccharification and fermentation and produced 66.50 g/L dry cell mass subsequently from the residual hydrolysate and ethanol. Therefore, this study represents a feasible method to comprehensively utilize hexose and pentose in lignocellulosic materials. [ABSTRACT FROM AUTHOR]

Stillage reflux fermentation in food waste ethanol fermentation could reduce sewage discharge but exert a harmful effect because of side-product accumulation. In this study, regulation methods based on metabolic regulation and side-product alleviation were conducted. Result demonstrated that controlling the proper oxidation–reduction potential value (−150 mV to −250 mV) could reduce the harmful effect, improve ethanol yield by 21%, and reduce fermentation time by 20%. The methods of adding calcium carbonate to adjust the accumulated lactic acid showed that ethanol yield increased by 17.3%, and fermentation time decreased by 20%. The accumulated glyceal also shows that these two methods can reduce the harmful effect. Fermentation time lasted for seven times without effect, and metabolic regulation had a better effect than side-product regulation. [ABSTRACT FROM AUTHOR]

The use of field beans, a non-food leguminous crop, was studied for ethanol, feed components and fungal biomass production. The seeds were hydrolyzed using enzymes or with combination of acid (H 3 PO 4 ) and alkaline (Ca(OH) 2 ) pretreatment and enzymatic hydrolysis. Fermentation by Saccharomyces cerevisiae , with or without removal of suspended solids, yielded 38.3–42.5 g L −1 ethanol (71.3–79.2% efficiency). The filtration residues contained ca. 247–326 g kg −1 crude protein, 10.6–15.5% acid detergent fiber and 19.9–29.1% neutral detergent fiber. They were enriched in phenolics (by up to 93.4%) and depleted in condensed tannin (by up to 59.3%) in comparison to the raw material. The thin stillages were used for cultivation of edible fungus Neurospora intermedia which produced 8.5–15.9 g L −1 ethanol and 4.8–16.2 g L −1 biomass containing over 62% protein. The mass balances showed that fermentation of unfiltered mashes was more efficient yielding up to 195.9 g kg −1 ethanol and 84.4% of protein recovery. [ABSTRACT FROM AUTHOR]

In this paper, genetic algorithm was used to investigate mathematical modeling of ethanol fermentation in a continuous conventional bioreactor (CCBR) and a continuous membrane bioreactor (CMBR) by ethanol permselective polydimethylsiloxane (PDMS) membrane. A lab scale CMBR with medium glucose concentration of 100 g L −1 and Saccharomyces cerevisiae microorganism was designed and fabricated. At dilution rate of 0.14 h −1 , maximum specific cell growth rate and productivity of 0.27 h −1 and 6.49 g L −1 h −1 were respectively found in CMBR. However, at very high dilution rate, the performance of CMBR was quite similar to conventional fermentation on account of insufficient incubation time. In both systems, genetic algorithm modeling of cell growth, ethanol production and glucose concentration were conducted based on Monod and Moser kinetic models during each retention time at unsteady condition. The results showed that Moser kinetic model was more satisfactory and desirable than Monod model. [ABSTRACT FROM AUTHOR]

Raw materials and pollution control are key issues for the ethanol fermentation industry. To address these concerns, food waste was selected as fermentation substrate, and stillage reflux was carried out in this study. Reflux was used seven times during fermentation. Corresponding ethanol and reducing sugar were detected. Accumulation of by-products, such as organic acid, sodium chloride, and glycerol, was investigated. Lactic acid was observed to accumulate up to 120 g/L, and sodium chloride reached 0.14 mol/L. Other by-products did not accumulate. The first five cycles of reflux increased ethanol concentration, which prolonged fermentation time. Further increases in reflux time negatively influenced ethanol fermentation. Single-factor analysis with lactic acid and sodium chloride demonstrated that both factors affected ethanol fermentation, but lactic acid induced more effects. [ABSTRACT FROM AUTHOR]

The effect of time and pressure on the selective extraction of sugar beet pectin using steam pre-treatment on unprocessed Sugar Beet Pulp was evaluated using a design of experiments approach. This process gave the highest solubilisation of pectin oligomers at a relatively low pressure and longer time (5 Bar, 24 min), whilst leaving the majority of the cellulose fraction intact. This method of steam pre-treatment fits into the concept of a sugar beet biorefinery as it valorises an existing waste stream without requiring any further physical processing such as milling or dilution with water. The residual cellulose fraction was enriched in cellulose and could be effectively fermented into ethanol by yeast after enzymatic digestion, producing 0.48 g ethanol per gram of glucose. [ABSTRACT FROM AUTHOR]

Hyper thermal (HT) acid hydrolysis of Kappaphycus alvarezii , a red seaweed, was optimized to 12% (w/v) seaweed slurry content, 180 mM H 2 SO 4 at 140 °C for 5 min. The maximum monosaccharide concentration of 38.3 g/L and 66.7% conversion from total fermentable monosaccharides of 57.6 g/L with 120 g dw/L K. alvarezii slurry were obtained from HT acid hydrolysis and enzymatic saccharification. HT acid hydrolysis at a severity factor of 0.78 efficiently converted the carbohydrates of seaweed to monosaccharides and produced a low concentration of inhibitory compounds. The levels of ethanol production by separate hydrolysis and fermentation with non-adapted and adapted Kluyveromyces marxianus to high concentration of galactose were 6.1 g/L with ethanol yield ( Y EtOH ) of 0.19 at 84 h and 16.0 g/L with Y EtOH of 0.42 at 72 h, respectively. Development of the HT acid hydrolysis process and adapted yeast could enhance the overall ethanol fermentation yields of K. alvarezii seaweed. [ABSTRACT FROM AUTHOR]

Pretreatment with ozone combined with aqueous ammonia was used to recover residual organic carbon from recalcitrant solid digestate for ethanol production after anaerobic digestion (AD) of rice straw. Methane yield of AD at mesophilic and thermophilic conditions, and ethanol production of solid digestate were investigated. The results showed that the methane yield at thermophilic temperature was 72.2% higher than that at mesophilic temperature under the same conditions of 24 days and 17% solid concentration. And also the ethanol production efficiency of solid digestate after thermophilic process was 24.3% higher than that of solid digestate after mesophilic process. In this study, the optimal conditions for integrated methane and ethanol processes were determined as 55 °C, 17% solid concentration and 24 days. 58.6% of glucose conversion, 142.8 g/kg of methane yield and 65.2 g/kg of ethanol yield were achieved, and the highest net energy balance was calculated as 6416 kJ/kg. [ABSTRACT FROM AUTHOR]

In this study, the effects of different parts of corn stalk, including stem, leaf, flower, cob and husk on second generation ethanol production were evaluated. FTIR, XRD and SEM were performed to investigate the effect of dilute acid pretreatment. The bagasse obtained after pretreatment were further hydrolyzed by cellulase and used as the substrate for ethanol fermentation. As results, hemicelluloses fractions in different parts of corn stalk were dramatically removed and the solid fractions showed vivid compositions and crystallinities. Compared with other parts of corn stalk, the cob had higher sugar content and better enzymatic digestibility. The highest glucose yield of 94.2% and ethanol production of 24.0 g L −1 were achieved when the cob was used as feedstock, while the glucose yield and the ethanol production were only 86.0% and 17.1 g L −1 in the case of flower. [ABSTRACT FROM AUTHOR]

This study reported a new solution of lignocellulose feedstock storage based on the distributed pretreatment concept. The dry dilute sulfuric acid pretreatment (DDAP) was conducted on corn stover feedstock, instead of ammonia fiber explosion pretreatment. Then the dry dilute acid pretreated corn stover was stored for three months during summer season with high temperature and humidity. No negative aspects were found on the physical property, composition, hydrolysis yield and ethanol fermentability of the long term stored pretreated corn stover, plus the additional merits including no chemicals recovery operation, anti-microbial contaminant environment from stronger acid and inhibitor contents, as well as the mild and slow hydrolysis in the storage. The new pretreatment method expanded the distributed pretreatment concept of feedstock storage with potential for practical application. [ABSTRACT FROM AUTHOR]

The polydimethylsiloxane (PDMS) membrane, prepared in water phase, was investigated in separation ethanol from model ethanol/water mixture and fermentation–pervaporation integrated process. Results showed that the PDMS membrane could effectively separate ethanol from model solution. When integrated with batch ethanol fermentation, the ethanol productivity was enhanced compared with conventional process. Fed-batch and continuous ethanol fermentation with pervaporation were also performed and studied. 396.2–663.7 g/m 2 h and 332.4–548.1 g/m 2 h of total flux with separation factor of 8.6–11.7 and 8–11.6, were generated in the fed-batch and continuous fermentation with pervaporation scenario, respectively. At the same time, high titre ethanol production of ∼417.2 g/L and ∼446.3 g/L were also achieved on the permeate side of membrane in the two scenarios, respectively. The integrated process was environmental friendly and energy saving, and has a promising perspective in long-terms operation. [ABSTRACT FROM AUTHOR]

Commercialization of lignocellulosic ethanol fermentation requires its high titer, but the reactive oxygen species (ROS) accumulation during the bioprocess damaged the cells and compromised this goal. To improve the cellular anti-oxidative activity during non-detoxified corncob residue hydrolysate fermentation, seed cells were prepared to possess a higher level of intracellular biotin pool (IBP), which facilitated the biosyntheses of catalase and porphyrin. As a result, the catalase activity increased by 1.3-folds compared to control while the ROS level reduced by 50%. Cell viability in high-IBP cells was 1.7-folds of control and the final ethanol titer increased from 31.2 to 41.8 g L −1 in batch fermentation. The high-IBP cells were further used for repeated-batch fermentation in the non-detoxified lignocellulosic hydrolysate, and the highest titer and average productivity of ethanol reached 63.7 g L −1 and 1.2 g L −1 h −1 . The results were favorable to future industrial application of this lignocellulosic bioethanol process. [ABSTRACT FROM AUTHOR]

Ethanol fermentation was investigated at the high solids content of the dry dilute sulfuric acid pretreated corn stover feedstock using an evolutionary adapted Saccharomyces cerevisiae DQ1 strain. The evolutionary adaptation was conducted by successively transferring the S. cerevisiae DQ1 cells into the inhibitors containing corn stover hydrolysate every 12 h and finally a stable yeast strain was obtained after 65 days’ continuous adaptation. The ethanol fermentation performance using the adapted strain was significantly improved with the high ethanol titer of 71.40 g/L and the high yield of 80.34% in the simultaneous saccharification and fermentation (SSF) at 30% solids content. No wastewater was generated from pretreatment to fermentation steps. The results were compared with the published cellulosic ethanol fermentation cases, and the obvious advantages of the present work were demonstrated not only at the high ethanol titer and yield, but also the significant reduction of wastewater generation and potential cost reduction. [ABSTRACT FROM AUTHOR]

This paper reports on processing options for the conversion of feedlot cattle manures into composite sugars for ethanol fermentation. Small-scale anaerobic digestion trials revealed that the process significantly reduces the content of glucan and xylan (ca. 70%) without effecting lignin. Moreover, anaerobic digestate (AD) fibres were poor substrates for cellulase (Cellic® CTec 2) saccharification, generating a maximum combined sugar yield of ca. 12% per original dry weight. Dilute acid pretreatment and enzyme saccharification of raw manures significantly improved total sugar recoveries, totalling 264 mg/g (79% theoretical). This was attained when manures were pretreated with 2.5% H 2 SO 4 for 90 min at 121 °C and saccharified with 50 FPU CTec 2/g glucan. Saccharomyces cerevisiae efficiently fermented crude hydrolysates within 6 h, yielding 7.3 g/L ethanol, representing glucose to ethanol conversion rate of 70%. With further developments (i.e., fermentation of xylose), this process could deliver greater yields, reinforcing its potential as a biofuel feedstock. [ABSTRACT FROM AUTHOR]

While softwoods represent a potential feedstock for second generation ethanol production, compounds present in their hydrolysates can inhibit fermentation. In this study, a novel Design of Experiments (DoE) approach was used to identify significant inhibitory effects on Saccharomyces cerevisiae D 5 A for the purpose of guiding kinetic model development. Although acetic acid, furfural and 5-hydroxymethyl furfural (HMF) were present at potentially inhibitory levels, initial factorial experiments only identified ethanol as a significant rate inhibitor. It was hypothesized that high ethanol levels masked the effects of other inhibitors, and a subsequent factorial design without ethanol found significant effects for all other compounds. When these non-ethanol effects were accounted for in the kinetic model, R ¯ 2 was significantly improved over an ethanol-inhibition only model ( R ¯ 2 = 0.80 vs. 0.76). In conclusion, when ethanol masking effects are removed, DoE is a valuable tool to identify significant non-ethanol inhibitors and guide kinetic model development. [ABSTRACT FROM AUTHOR]

Unstructured kinetic models were proposed to describe the principal kinetics involved in ethanol fermentation in a continuous and closed-circulating fermentation (CCCF) process with a pervaporation membrane bioreactor. After ethanol was removed in situ from the broth by the membrane pervaporation, the secondary metabolites accumulated in the broth became the inhibitors to cell growth. The cell death rate related to the deterioration of the culture environment was described as a function of the cell concentration and fermentation time. In CCCF process, 609.8 g L −1 and 750.1 g L −1 of ethanol production were obtained in the first run and second run, respectively. The modified Gompertz model, correlating the ethanol production with the fermentation period, could be used to describe the ethanol production during CCCF process. The fitting results by the models showed good agreement with the experimental data. These models could be employed for the CCCF process technology development for ethanol fermentation. [ABSTRACT FROM AUTHOR]

Process control automation in the emerging biorefinery industry may be achieved by applying effective methods for monitoring compound concentrations during the production processes. This study examines the application of Raman spectroscopy with an excitation wavelength of 785 nm and an immersion probe for in situ monitoring the progression of pretreatment, hydrolysis and fermentation processes in the production of lignocellulosic ethanol. Raman signals were attenuated by light scattering cells and lignocellulosic particulates, which the quantification method to some degree could correct for by using an internal standard in the spectra. Allowing particulates to settle by using a slow stirring speed further improved results, suggesting that Raman spectroscopy should be used in combination with continuous separation when used to monitor process mixtures with large amounts of particulates. The root mean square error of prediction (RMSE) of ethanol and glucose measured in real-time was determined to be 0.98 g/L and 1.91 g/L respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] A more quantitative basis for understanding the inhibition. [•] Accumulative secondary metabolites in the pervaporation membrane bioreactor. [•] Improvement of ethanol fermentation at higher broth pH. [Copyright &y& Elsevier]

Highlights: [•] Continuous and complete coupling of ethanol fermentation and pervaporation. [•] Second cell growth feature. [•] Enhanced ethanol fermentation performance. [•] Convenient permeate vapor recovery and refining without refrigeration unit. [ABSTRACT FROM AUTHOR]

Highlights: [•] An integrated corn ethanol-methane fermentation system was established and assessed. [•] Ethanol fermentation and anaerobic digestion performed well in the recycling system. [•] The novel process had tech-economic advantage over the conventional process. [Copyright &y& Elsevier]

Highlights: [•] Three membranes concentrated sugars in rice straw liquid hydrolysate. [•] Sugars were selectively concentrated at pH 5.0. [•] Ethanol was produced by xylose-assimilating yeast from concentrated sugars. [Copyright &y& Elsevier]

Highlights: [•] We isolated Candida boidiniiUFMG14 from macaúba fruits. [•] We obtained for the first time a hemicellulosic hydrolysate of macaúba presscake. [•] C. boidinii UFMG14 was able to growth and ferment on acid hemicellulosic hydrolysate. [•] C. boidinii UFMG14 reached 0.4g/g ethanol yield and 0.3g/Lh volumetric productivity. [•] The hydrolysate supplementation affects ethanol yield but not ethanol productivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Treating bagasse (SCB) by 2-stage ultrasonic assisted dilute H 2 SO 4 (TUDA). • Lignin and hemicellulose can be efficiently removed by TUDA pretreatment at 90℃. • Optimal ethanol fermentation efficiency at cellulase 10 FPU/g SCB and 30% SCB. • Recovering xylose effectively from pretreated liquid by bagasse-derived biochar. • Full utilization was achieved for SCB from solid residue to pretreatment liquid. Pretreatment can improve biomass biodegradability. Here, a novel sugarcane bagasse (SCB) pretreatment process based on two-stage ultrasonic assisted dilute H 2 SO 4 (TUDA) under mild conditions was reported. After optimization, the pretreatment was shown to significantly degrade hemicellulose (92.40%) and remove lignin (57.41%) of SCB, leading to reduction of inhibitors and an ethanol fermentation efficiency of 93.37% by SSCF under cellulase 10 FPU/g SCB and 30% pretreated SCB loading. Physical characterization revealed that two-stage ultrasonic could better disrupt SCB than traditional ultrasonic by amplifying the collapse effect and synergistically promoting lignin removal through dilute H 2 SO 4. Furthermore, xylose was also effectively recovered from pretreatment supernatant by biochar derived from bagasse. This study established a simple and efficient pretreatment process for high value-added recycling of SCB from solid residue to pretreatment liquid. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dilute acid pretreatment of corn stover was optimized to yield maximum sugars and minimum furfural. [•] Temperature, H2SO4 dose and time were independent variables for pretreatment. [•] Sugar yield from pretreated corn stover was 90% of theoretical after enzymatic hydrolysis. [•] Recombinant E. coli FBR5 efficiently ferments non-detoxified hydrolyzate to ethanol. [ABSTRACT FROM AUTHOR]

Highlights: [•] Thermal acid hydrolysis and enzymatic saccharification resulted in 43.5g/L sugars. [•] Ethanol concentration of 20.5g/L was obtained using S. stipitis KCTC 7228. [•] Glucose uptake increased at HMF concentrations <5g/L in the fermentation medium. [•] HMF was converted to 2,5-bis-hydroxymethylfuran by S. stipitis KCTC 7228. [Copyright &y& Elsevier]

Abstract: In this study, the thermotolerant yeast Kluyveromyces marxianus CECT 10875 was compared to the industrial strain Saccharomyces cerevisiae Ethanol Red for lignocellulosic ethanol production. For it, whole slurry from steam-exploded wheat straw was used as raw material, and two process configurations, simultaneous saccharification and fermentation (SSF) and presaccharification and simultaneous saccharification and fermentation (PSSF), were evaluated. Compared to S. cerevisiae, which was able to produce ethanol in both process configurations, K. marxianus was inhibited, and neither growth nor ethanol production occurred during the processes. However, laccase treatment of the whole slurry removed specifically lignin phenols from the overall inhibitory compounds present in the slurry and triggered the fermentation by K. marxianus, attaining final ethanol concentrations and yields comparable to those obtained by S. cerevisiae. [Copyright &y& Elsevier]

Abstract: The subject of this study was to investigate the feasibility of the concentrate obtained after membrane ultrafiltration of sugar beet thin juice for ethanol production and selection of fermentation conditions (yeast strain and media supplementation). Resulting concentrate was subjected to batch ethanol fermentation using two strains of Saccharomyces cerevisiae (Ethanol Red and Safdistill C-70). The effect of different forms of media supplementation (mineral salts: (NH4)2SO4, K2HPO4, MgCl2; urea+Mg3(PO4)2 and yeast extract) on the fermentation course was also studied. It was stated that sugar beet juice concentrate is suitable for ethanol production yielding, depending on the yeast strain, ca. 85–87gL−1 ethanol with ca. 82% practical yield and more than 95% of sugars consumption after 72h of fermentation. Nutrients enrichment further increased ethanol yield. The best results were obtained for media supplemented with urea+Mg3(PO4)2 yielding 91.16–92.06gL−1 ethanol with practical yield ranging 84.78–85.62% and full sugars consumption. [Copyright &y& Elsevier]

Abstract: A gene coding for thermotolerant β-xylosidase from Aspergillus sp. BCC125 was characterized. The recombinant enzyme was expressed in methylotrophic yeast Pichia pastoris KM71 and especially high yield of secreted enzyme was obtained. β-xylosidase possessed high enzyme efficiency (K cat/K m =198.8mM−1 s−1) toward pNP-β-D-xylopyranoside (pNPβX) with optimal temperature and pH for activity of 60°C and pH 4.0–5.0, respectively. The identified β-xylosidase showed clear synergism with previously identified xylanase for hydrolysis of xylan in vitro as well as simultaneous saccharification and fermentation process (SSF) in vivo with Pichia stipitis. [Copyright &y& Elsevier]

Abstract: Tween 80, Tween 20, PEG 4000 or PEG 6000 was used in combination with ammonium hydroxide for the pretreatment of sugarcane bagasse. Pretreatment was carried out by mixing sugarcane bagasse, ammonium hydroxide (28% v/v solution), and water at a ratio of 1:0.5:20, adding 3% (w/w) surfactant based on the weight of dry biomass, and heating the mixture to 160°C for 1h. Fibers were hydrolyzed using two concentrations of commercially available enzymes, Spezyme CP and Novozyme 188. The results indicated that PEG 4000 and Tween 80 gave the highest cellulose digestibilities (62%, 66%) and ethanol yields (73%, 69%) as compared to the use of only dilute ammonia (38%, 42%) or water (27%, 26%) as catalysts, respectively. The enhanced digestibilities of non-ionic surfactant–dilute ammonia treated biomass can be attributed to delignification and reduction of cellulose crystallinity as confirmed by FTIR, TGA and XRD analysis. [Copyright &y& Elsevier]

Abstract: Dilute H3PO4 (0.0–2.0%, v/v) was used to pretreat corn stover (10%, w/w) for conversion to ethanol. Pretreatment conditions were optimized for temperature, acid loading, and time using central composite design. Optimal pretreatment conditions were chosen to promote sugar yields following enzymatic digestion while minimizing formation of furans, which are potent inhibitors of fermentation. The maximum glucose yield (85%) was obtained after enzymatic hydrolysis of corn stover pretreated with 0.5% (v/v) acid at 180°C for 15min while highest yield for xylose (91.4%) was observed from corn stover pretreated with 1% (v/v) acid at 160°C for 10min. About 26.4±0.1g ethanol was produced per L by recombinant Escherichia coli strain FBR5 from 55.1±1.0g sugars generated from enzymatically hydrolyzed corn stover (10%, w/w) pretreated under a balanced optimized condition (161.81°C, 0.78% acid, 9.78min) where only 0.4±0.0g furfural and 0.1±0.0 hydroxylmethyl furfural were produced. [Copyright &y& Elsevier]

Abstract: This study presents results regarding the successful cloning of the bacterial xylose isomerase gene (xylA) of Burkholderia cenocepacia and its functional expression in Saccharomyces cerevisiae. The recombinant yeast showed to be competent to efficiently produce ethanol from both glucose and xylose, which are the main sugars in lignocellulosic hydrolysates. The heterologous expression of the gene xylA enabled a laboratorial yeast strain to ferment xylose anaerobically, improving ethanol production from a fermentation medium containing a glucose–xylose blend similar to that found in sugar cane bagasse hydrolysates. The insertion of xylA caused a 5-fold increase in xylose consumption, and over a 1.5-fold increase in ethanol production and yield, in comparison to that showed by the WT strain, in 24h fermentations, where it was not detected accumulation of xylitol. These findings are encouraging for further studies concerning the expression of B. cenocepacia xylA in an industrial yeast strain. [Copyright &y& Elsevier]

Abstract: A small solar energy collector was run to heat lignocellulosic hydrolyzates through an exchanger, and the heated hydrolyzate was concentrated by vacuum membrane distillation (VMD). Under optimal conditions of velocity of 1.0m/s and 65°C, glucose rejection was 99.5% and the flux was 8.46Lm−2 h−1. Fermentation of the concentrated hydrolyzate produced 2.64 times the amount of ethanol as fermentation using the original hydrolyzate. The results of this work indicated the possibility to decrease the thermal energy consumption of lignocellulosic ethanol through using VMD. [Copyright &y& Elsevier]

Conditions for optimal pretreatment of eucalypt ( Eucalyptus dunnii ) and spotted gum ( Corymbia citriodora ) forestry thinning residues for bioethanol production were empirically determined using a 3 3 factorial design. Up to 161 mg/g xylose (93% theoretical) was achieved at moderate combined severity factors (CSF) of 1.0–1.6. At CSF > 2.0, xylose levels declined, owing to degradation. Moreover at high CSF, depolymerisation of cellulose was evident and corresponded to glucose (155 mg/g, ∼33% cellulose) recovery in prehydrolysate. Likewise, efficient saccharification with Cellic® CTec 2 cellulase correlated well with increasing process severity. The best condition yielded 74% of the theoretical conversion and was attained at the height of severity (CSF of 2.48). Saccharomyces cerevisiae efficiently fermented crude E. dunnii hydrolysate within 30 h, yielding 18 g/L ethanol, representing a glucose to ethanol conversion rate of 0.475 g/g (92%). Based on our findings, eucalyptus forest thinnings represent a potential feedstock option for the emerging Australian biofuel industry. [ABSTRACT FROM AUTHOR]

Abstract: An alternative route for bio-ethanol production from sugarcane stalks (juice and bagasse) featuring a previously reported low temperature alkali pretreatment method was evaluated. Test-tube scale pretreatment-saccharification experiments were carried out to determine optimal LTA pretreatment conditions for sugarcane bagasse with regard to the efficiency of enzymatic hydrolysis of the cellulose. Free fermentable sugars and bagasse recovered from 2kg of sugarcane stalks were jointly converted into ethanol via separate enzymatic hydrolysis and fermentation (SHF). Results showed that 98% of the cellulose present in the optimally pretreated bagasse was hydrolyzed into glucose after 72-h enzymatic saccharification using commercially available cellulase and β-glucosidase preparations at relatively low enzyme loading. The fermentable sugars in the mixture of the sugar juice and the bagasse hydrolysate were readily converted into 193.5mL of ethanol by Saccharomyces cerevisiae within 12h, achieving 88% of the theoretical yield from the sugars and cellulose. [Copyright &y& Elsevier]

Abstract: Yeast immobilized on alginate beads produced a higher ethanol yield more rapidly than did free yeast cells under the same batch-fermentation conditions. The optimal fermentation conditions were 30°C, pH 5.0, and 10% initial glucose concentration with 2% sodium alginate beads. The fermentation time using reused alginate beads was 10–14h, whereas fresh beads took 24h, and free cells took 36h. All bead samples resulted in nearly a 100% ethanol yield, whereas the free cells resulted in an 88% yield. Transmission electron microscopy (TEM) showed that the shortened time and higher yield with the reused beads was due to a higher yeast population per bead as well as a higher porosity. The ultrastructure of calcium alginate beads and the alginate matrix structure known as the “egg-box” model were observed using TEM. [Copyright &y& Elsevier]

Abstract: Using standard laboratory equipment, thermochemically pretreated oat straw was enzymatically saccharified and fermented to ethanol, and after removal of ethanol the remaining material was subjected to biogas digestion. A detailed mass balance calculation shows that, for steam explosion pretreatment, this combined ethanol fermentation and biogas digestion converts 85–87% of the higher heating value (HHV) of holocellulose (cellulose and hemicellulose) in the oat straw into biofuel energy. The energy (HHV) yield of the produced ethanol and methane was 9.5–9.8MJ/(kg dry oat straw), which is 28–34% higher than direct biogas digestion that yielded 7.3–7.4MJ/(kg dry oat straw). The rate of biogas formation from the fermentation residues was also higher than from the corresponding pretreated but unfermented oat straw, indicating that the biogas digestion could be terminated after only 24days. This suggests that the ethanol process acts as an additional pretreatment for the biogas process. [Copyright &y& Elsevier]

Abstract: In this study, a systemic analysis was initially performed to investigate the relationship between fermentation-related stress tolerances and ethanol yield. Based on the results obtained, two elite Saccharomyces cerevisiae strains, Z8 and Z15, with variant phenotypes were chosen to construct strains with improved multi-stress tolerance by genome shuffling in combination with optimized initial selection. After three rounds of genome shuffling, a shuffled strain, YZ1, which surpasses its parent strains in osmotic, heat, and acid tolerances, was obtained. Ethanol yields of YZ1 were 3.11%, 10.31%, and 10.55% higher than those of its parent strains under regular, increased heat, and high gravity fermentation conditions, respectively. YZ1 was applied to bioethanol production at an industrial scale. Results demonstrated that the variant phenotypes from available yeast strains could be used as parent stock for yeast breeding and that the genome shuffling approach is sufficiently powerful in combining suitable phenotypes in a single strain. [ABSTRACT FROM AUTHOR]

Abstract: The mild acid pretreatment and the combination of biological pretreatment by a white rot fungus Echinodontium taxodii or a brown rot fungus Antrodia sp. 5898 with mild acid pretreatment were evaluated under different pretreatment conditions for enzymatic hydrolysis and ethanol production from water hyacinth. The combined pretreatment with E. taxodii (10days) and 0.25% H2SO4 was proved to be more effective than the sole acid pretreatment. The reducing sugar yield from enzymatic hydrolysis of co-treated water hyacinth increased 1.13–2.11 fold than that of acid-treated water hyacinth at the same conditions. The following study on separate hydrolysis and fermentation with Saccharomyces cerevisiae indicated that the ethanol yield from co-treated water hyacinth achieved 0.192g/g of dry matter, which increased 1.34-fold than that from acid-treated water hyacinth (0.146g/g of dry matter). This suggested that the combination of biological and mild acid pretreatment is a promising method to improve enzymatic hydrolysis and ethanol production from water hyacinth with low lignin content. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that simultaneous saccharification and co-fermentation (SSCF) reduces cellulosic ethanol production cost compared to separate hydrolysis and fermentation (SHF). However, the traditional SSCF process of converting Ammonia Fiber Expansion (AFEX) pretreated switchgrass to ethanol using both commercial enzymes and Saccharomyces cerevisiae 424A(LNH-ST) gave reduced ethanol yield due to lower xylose consumption. To overcome this problem we have developed a two-step SSCF process, in which xylan was hydrolyzed and fermented first followed by the hydrolysis and fermentation of glucan. Important parameters, such as temperature, cellulases loading during xylan hydrolysis and fermentation, initial OD600 for inoculation of S. cerevisiae 424A(LNH-ST), and pH, were studied for best performance. Compared with traditional SSCF, the two-step SSCF showed higher xylose consumption and higher ethanol yield. The sugar conversion was also enhanced from 70% by enzymatic hydrolysis to 82% by two-step SSCF. One important finding is that the residue from enzymatic hydrolysis plays a significant role in reducing xylose consumption and ethanol metabolic yield during SSCF. [Copyright &y& Elsevier]

Abstract: The effects of ultrasound and heat pretreatments on ethanol yields from cassava chips were investigated. Cassava slurries were sonicated for 10 and 30s at the amplitudes of 80, 160, and 320μmpp (peak to peak amplitude in μm) corresponding to low, medium, and high power levels, respectively. The sonicated and non-sonicated (control) samples were then subjected to simultaneous liquefaction-saccharification and ethanol fermentation. Cassava starch-to-ethanol conversion efficiencies showed that higher ethanol yields were directly related to sonication times, but not to power levels. Significantly higher ethanol yields were observed only for sonicated samples at the high power level. The ethanol yield from the sonicated sample was 2.7-fold higher than yield from the control sample. Starch-to-ethanol conversion rates from sonicated cassava chips were also significantly higher; the fermentation time could be reduced by nearly 24h for sonicated samples to achieve the same ethanol yield as control samples. Thus, ultrasound pretreatment enhanced both the overall ethanol yield and fermentation rate. When compared to heat-treated samples, the sonicated samples produced nearly 29% more ethanol yield. Combined heat and ultrasound treatment had no significant effect on overall ethanol yields from cassava chips. Ultrasound is also preferable to heat pretreatment because of lower energy requirements, as indicated by energy balances. Integration of ultrasound application in cassava-based ethanol plants can significantly improve ethanol yields and reduce the overall production costs. [Copyright &y& Elsevier]

The design of an optimum and cost-efficient medium for high-level production of hydrogen by Ethanoligenens harbinense B49 was attempted by using response surface methodology (RSM). Based on the Plackett–Burman design, Fe2+ and Mg2+ were selected as the most critical nutrient salts. Subsequently, the optimum combination of the selected factors and the sole carbon source glucose were investigated by the Box–Behnken design. Results showed that the maximum hydrogen yield of 2.21mol/molglucose was predicted when the concentrations of glucose, Fe2+ and Mg2+ were 14.57g/L, 177.28mg/L and 691.98mg/L, respectively. The results were further verified by triplicate experiments. The batch reactors were operated under an optimized condition of the respective glucose, Fe2+ and Mg2+ concentration of 14.5g/L, 180mg/L and 690mg/L, the initial pH of 6.0 and experimental temperature of 35±1 oC. Without further pH adjustment, the maximum hydrogen yield of 2.20mol/molglucose was obtained based on the optimized medium with further verified the practicability of this optimum strategy. [Copyright &y& Elsevier]

Abstract: Ethanol fermentation by immobilized Saccharomyces cerevisiae cells in magnetic particles was successfully carried out in a magnetically stabilized fluidized bed reactor (MSFBR). These immobilized magnetic particles solidified in a 2 % CaCl2 solution were stable and had high ethanol fermentation activity. The performance of ethanol fermentation of glucose in the MSFBR was affected by initial particle loading rate, feed sugar concentration and dilution rate. The ethanol theoretical yield, productivity and concentration reached 95.3%, 26.7g/Lh and 66g/L, respectively, at a particle loading rate of 41% and a feed dilution rate of 0.4h−1 with a glucose concentration of 150g/L when the magnetic field intensity was kept in the range of 85–120Oe. In order to use this developed MSFBR system for ethanol production from cheap raw materials, cane molasses was used as the main fermentation substrate for continuous ethanol fermentation with the immobilized S. cerevisiae cells in the reactor system. Molasses gave comparative ethanol productivity in comparison with glucose in the MSFBR, and the higher ethanol production was observed in the MSFBR than in a fluidized bed reactor (FBR) without a magnetic field. [Copyright &y& Elsevier]

[Display omitted] • The types of HBA significantly affected ChCl-based DES pretreatment efficacy. • Combination with dilute NaOH and ChCl:LAC was successfully used for treating SS. • Combination pretreatment resulted in a much higher enzymatic digestibility. • SS-hydrolysate was fermented to ethanol with a yield of 0.45 g ethanol/g glucose. Hydrogen bond donor (HBD) in ChCl-based deep eutectic solvent (DESs) had significant influence on the Sorghum straw (SS) pretreatment. Lactic acid (LAC) was chosen as the appropriate HBD for preparing ChCl-based DES to pretreat Sorghum straw (SS). Furthermore, sequential pretreatment with dilute sodium hydroxide (0.75 wt%) for 1 h at 121 °C and ChCl:LAC soaking at 140 °C for 40 min was applied to pretreat SS for removing lignin (78.4%) and xylan (67.6%). Hydrolysis for 72 h, the reducing sugar yield reached 94.9%. Moreover, relationships of delignification and xylan removal with saccharification were explored after pretreatment. Finally, the fermentability of SS-hydrolysates was verified by bioethanol fermentation by S. cerevissiae with the yield of 0.45 g ethanol/g glucose. No significant inhibition was observed on ethanol fermentation. Obviously, establishment of high-efficient combination pretreatment with alkali extraction and ChCl:LAC soaking was successfully demonstrated for enhancing enzymatic saccharification of SS. [ABSTRACT FROM AUTHOR]

Abstract: A lactose utilizing yeast strain, Kluyveromyces marxianus DSMZ-7239 was used for ethanol formation from cheese-whey powder (CWP) solution in batch experiments. Effects of initial substrate (CWP) and yeast concentrations on the rate and extent of ethanol formation were investigated. The initial pH and oxidation–reduction potential (ORP) was kept at 5 and −250mV, respectively. The rate and extent of ethanol formation increased with increasing CWP concentration up to 156gl−1 (75gl−1 sugar) and then decreased for larger CWP concentrations due to substrate inhibition at high sugar concentrations. The ethanol yield coefficient was also maximum (0.54g EtOH/g sugar) and equal to the theoretical yield at CWP concentration of 156gl−1. The growth yield coefficient was found to be Y x/s =1.2±0.1g biomassgsugar−1. The rate of sugar utilization and ethanol formation also increased linearly with increasing initial biomass concentrations. A kinetic model describing the rate of sugar utilization and substrate inhibition as function of the initial substrate and the biomass concentrations was developed. The kinetic constants were determined using the experimental data. Model predictions of sugar utilization rates were in good agreement with the experimental data. The results indicated that the initial sugar concentration should be below 75gl−1 (CWP<156gl−1) and the initial biomass should be above 850mgl−1 to obtain high rates and yields of ethanol formation and to avoid substrate inhibition. [Copyright &y& Elsevier]