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Despite the significant progress in the research, the problem of finding an efficient method for producing bioethanol from renewable lignocellulosic waste materials remains unresolved. Our investigation aimed to assess the efficacy of ethanol production from sugar beet pulp (SBP) utilising various approaches, including pretreatment variations, enzymatic processes, and microbial hydrolysis. Our research involved using the post-cultivation concentrate of T. viride LOCK 0588 grown in the SBP-based medium as a source of enzymes. The SBP hydrolysis process was carried out for 48 h at 50 °C. The quantity of sugar released, up to 61 g dm−3, through the utilisation of this extract proved to be on par with the outcomes achieved by the application of the commercial Cellic Ctec2 preparation. The final yields of the ethanol production with the use of the coculture of S. cerevisiae (Ethanol Red) and Scheffersomyces stipitis LOCK 0047 strain were in the range 5.1 ± 0.11 kg 100 kg−1 ÷ 5.38 ± 0.11 kg 100 kg−1. These results provide a solid basis for improving larger-scale industrial procedures that involve converting SBP into bioethanol using a cost-efficient approach of microbial hydrolysis with T. viride and a blend of pentose and hexose fermenting yeast. [ABSTRACT FROM AUTHOR]

Abstract Methods for obtaining high-concentration (ca. 40 g/L) ethanol from cassava stem (CS) were explored by investigating the effects of acid hydrolysis conditions, hydrolysate concentration, and intermittent inoculation of yeast on ethanol fermentation. Two-step acid hydrolysis demonstrated that a reduction in autoclaving temperature from 121 °C to 111 °C remarkably lowered the furfural concentration in the hydrolysate, with only ±10% differences in the glucose and xylose concentrations. For the concentration of sugars in the CS hydrolysate, the acid hydrolysate prepared with CS concentration of 200 g/L was used instead of distilled water for the second step of acid hydrolysis using new CS biomass (i.e., two-times acid hydrolysis). This produced a concentrated hydrolysate containing 95 g/L of glucose and 0.95 g/L furfural. Saccharomyces cerevisiae strain IAM 4178 was inoculated into the concentrated CS hydrolysate after verifying its furfural tolerance. Furfural was rapidly degraded and glucose was converted to ethanol during the startup period, whereas cell density decreased to approximately 10% of the initial value and ethanol production ceased by 72 h. IAM 4178 was then re-inoculated intermittently to maintain the cell density at 108 cells/mL, which eventually resulted in the complete uptake of glucose and the production of high concentrations of ethanol, up to 37.5 g/L. Highlights • Two-time acid hydrolysis of cassava stem to produce high-concentration bioethanol. • Reduction of furfural in the hydrolysate by lowering the autoclaving temperature. • Concentration of glucose in the hydrolysate by two-time acid hydrolysis. • Maintenance of yeast cell density by intermittent yeast inoculation. • Complete uptake of glucose and production of 37.5 g/L of 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]

[Display omitted] • Whole-cell biomass utilization was completed with newly integrated biorefinery. • Hydrolysis yielded 89 % of total carbohydrate within 4 min using optimized process. • Volume reduction decreased solvent usage by 75 % and recovered all oil within 20 min. • Bioethanol yield of sole hydrolysate was comparable with conventional YPD medium. • Newly developed process decreased OPEX and CAPEX by 82.7 % and 70.1 %, respectively. Microalgae are a promising source of biomass for the production of biofuels, but their use is currently infeasible because of changes in the biofuel market and the lack of an optimized refinery process. The biomass of oleaginous microalgae consists of up to 50% lipids and 50% carbohydrates and proteins, so the biorefinery process must be able to use whole cell biomass. In this work, an alternative process to the standard biorefinery approach of lipid extraction and treatment of lipid-extracted residue was developed and tested using oleaginous Chlorella sp. ABC-001. First, a hydrolysis process was optimized to achieve cell lysis. At 170 °C and 0.1 N H 2 SO 4 , 89.0% of total carbohydrates were hydrolyzed to monosaccharides within 4 min. Then, a volume reduction process (brief and mild centrifugation) was applied to reduce the extraction time and the use of organic solvent. By reducing the aqueous phase from the hydrolysate, all lipids were extracted by vortexing with just a quarter of the original volume (10 mL) within 20 min. Finally, after extraction the aqueous phase was utilized as the sole growth medium for ethanol production by Saccharomyces cerevisiae KL17. The resulting ethanol yield was 0.39 g ethanol/g sugar, comparable to that achieved using conventional yeast-peptone-dextrose (YPD) medium (0.41 g ethanol/g sugar). Furthermore, relative to the conventional process, techno-economic analysis confirmed that the newly developed process decreased operational expenditures by 82.7% and decreased capital expenditures by 70.1%. [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]

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]

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]

Background: Due to the depletion of fossil resources and their environmental impact, woody biomass has received much attention as an alternative resource. Lignin, as the third most abundant biopolymer from biomass, is now considered as an excellent alternative feedstock for chemicals and materials. The conversion of lignin to the value-added products is a key process to achieve an integrated biorefinery of woody biomass. Among these value-added products, lignin-based derivatives with good surface activity can be applied to enhance the conversion of cellulose into fermentable sugars, which not only decrease the cost of bioethanol production, but also reduce the environmental pollution and green house effect resulting from the burning of fossil resources. Results: Water-soluble alkaline lignin was synthesized by the reaction between polyethylene glycols (PEG600 and PEG1000) and epoxy lignin. FT-IR and NMR analyses indicated that PEGs were successively introduced into epoxy alkaline lignin using potassium persulfate as a catalyst. Emulsification and surface activity tests indicated that the surface tension of the prepared lignin derivative solution was 43.30 mN/m at the critical micelle concentration (1.03 %). A stable emulsions layer was formed with hexanes and the emulsion particle diameter in the emulsion phase for all products was observed at 10-50 μm. The results of enzymatic hydrolysis indicated that the products derived from PEG1000-grafted lignin resulted in the highest increasing rate of 18.6 % of glucose yield during the enzymatic hydrolysis of hardwood bleached pulp. The results of fermentation experiments suggested that the product had no toxicity for fermentation micro-organisms. Conclusion: Water-soluble alkaline lignin derivatives were prepared through epoxidation and etherification, which are promising feedstocks for detergents, emulsifier, and additive to enhance enzymatic hydrolysis efficiency and ethanol fermentation. [ABSTRACT FROM AUTHOR]

This study proposes a novel alternative for utilization of whey permeate, a by-product stream from the dairy industry, in wheat fermentation for ethanol production using Saccharomyces cerevisiae. Whey permeates were hydrolyzed using enzymes to release fermentable sugars. Hydrolyzed whey permeates were integrated into wheat fermentation as a co-substrate or to partially replace process water. Cold starch hydrolysis-based simultaneous saccharification and fermentation was done as per the current industrial protocol for commercial wheat-to-ethanol production. Ethanol production was not affected; ethanol yield efficiency did not change when up to 10% of process water was replaced. Lactic acid bacteria in whey permeate did not negatively affect the co-fermentation or reduce ethanol yield. Whey permeate could be effectively stored for up to 4 wk at 4°C with little change in lactose and lactic acid content. Considering the global abundance and nutrient value of whey permeate, the proposed strategy could improve economics of the dairy and biofuel sectors, and reduce environmental pollution. Furthermore, our research may be applied tofermentation strategies designed to produce value-added products other than ethanol. [ABSTRACT FROM AUTHOR]

The necessity of amylolytic enzymes to convert starch into glucose during ethanol production is considered one of the cost increasing factors for corn ethanol. Enzyme consumption could be decreased partially by increasing free sugar contents in corn kernels that will be released and fermented simultaneously with the product of starch hydrolysis, producing an additional amount of ethanol without consuming any enzyme. The present work was conducted to evaluate the effects of grain sugar on the fermentable sugar and ethanol yields as well as enzyme requirement using four high sugary corn genotypes (HSGs) and their parent field corn lines (PFCs). The reducing sugar yield in HSGs did not vary significantly above the enzyme load of 1.5 kg/MT of dry corn, while PFCs showed a range between 2.0 and 2.5 kg/MT. The average final ethanol concentrations in HSGs and PFCs ranged from 15.25% to 17.5% (v/v) and 11.66% to 13.65%, respectively with the enzyme load at 1.5 kg/MT, which reached to 16.49–17.94% in HSGs and 14.32–16.85% in PFCs as the enzyme load increased to 2.0 kg/MT. These results suggest that high sugar content in corn kernels has the potential for decreasing enzyme consumption during dry-grind ethanol production with higher yields. [ABSTRACT FROM AUTHOR]

Phytic acid is one of the compounds that can limit the availability of biogenic substances responsible for the environmental stress response of the yeast. The aim of the study was determining the influence of hydrolysis of the phytic acid complexes in the HG maize mashes on the availability of free amino nitrogen (FAN) released from hydrolyzed proteins and the resulting change in the fermentation activity of the yeast. Prospects for the optimization of the alcoholic fermentation process by combined application of phytase, protease and augmented set of amylolytic enzymes were also assessed. The application of protease phytase resulted in an increase of FAN concentration during subsequent hours of the alcoholic fermentation process which indicated an increased availability of proteins susceptible to hydrolysis. A positive effect of combined application of phytase, protease and amylolytic enzymes (with pullulanase) on technological indicators of the fermentation process was observed. The final ethanol concentration increased by 1% v v −1 and the yield increased by 6 L EtOH 100 kg −1 of starch. The optimization of the mashing process, involving the application of additional enzymes (phytase, pullulanase, protease), improved the yield of fermentation in relation to the theoretical yield to the level of 93%. A combined application of α-amylase, pullulanase, glucoamylase, protease and phytase during HG mashes preparation lowered the concentration of higher alcohols by 450 mg L −1 EtOH, on average, as compared to the control variant. At the same time, the concentration of acetaldehyde in the spirits increased above 480 mg L −1 EtOH. [ABSTRACT FROM AUTHOR]

The production of raw starch-degrading amylases by recombinant Saccharomyces cerevisiae provides opportunities for the direct hydrolysis and fermentation of raw starch to ethanol without cooking or exogenous enzyme addition. Such a consolidated bioprocess (CBP) for raw starch fermentation will substantially reduce costs associated with energy usage and commercial granular starch hydrolyzing (GSH) enzymes. The core purpose of this review is to provide comprehensive insight into the physiological impact of recombinant amylase production on the ethanol-producing yeast. Key production parameters, based on outcomes from modifications to the yeast genome and levels of amylase production, were compared to key benchmark data. In turn, these outcomes are of significance from a process point of view to highlight shortcomings in the current state of the art of raw starch fermentation yeast compared to a set of industrial standards. Therefore, this study provides an integrated critical assessment of physiology, genetics and process aspects of recombinant raw starch fermenting yeast in relation to presently used technology. Various approaches to strain development were compared on a common basis of quantitative performance measures, including the extent of hydrolysis, fermentation-hydrolysis yield and productivity. Key findings showed that levels of α-amylase required for raw starch hydrolysis far exceeded enzyme levels for soluble starch hydrolysis, pointing to a pre-requisite for excess α-amylase compared to glucoamylase for efficient raw starch hydrolysis. However, the physiological limitations of amylase production by yeast, requiring high biomass concentrations and long cultivation periods for sufficient enzyme accumulation under anaerobic conditions, remained a substantial challenge. Accordingly, the fermentation performance of the recombinant S. cerevisiae strains reviewed in this study could not match the performance of conventional starch fermentation processes, based either on starch cooking and/or exogenous amylase enzyme addition. As an alternative strategy, the addition of exogenous GSH enzymes during early stages of raw starch fermentation may prove to be a viable approach for industrial application of recombinant S. cerevisiae, with the process still benefitting from amylase production by CBP yeast during later stages of cultivation. [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]

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]

The subject of this research project was assessment of direct starch to ethanol conversion process course of waste wheat-rye bread using granular starch hydrolyzing enzyme (GSHE). Several pretreatment methods (enzymatic prehydrolysis, microwave irradiation, sonification) were used to improve the course of fermentation and were compared with separate hydrolysis and fermentation (SHF). Due to high water binding capacity of raw material fermentations were conducted at a substrate loading of 150 g kg-1. Only during enzymatic pretreatment and the SHF process the raw material was preliminary liquefied so its higher concentrations could be applied. The dynamics of fermentation was similar in all studied variants. The fermentation of unpretreated waste bread ended with 80.00% ethanol yield (354.36 g kg-1 of raw material). Pretreatment of raw material improved ethanol yield by ca. 3-8%. [ABSTRACT FROM AUTHOR]

Background The Rapid Bioconversion with Integrated recycle Technology (RaBIT) process reduces capital costs, processing times, and biocatalyst cost for biochemical conversion of cellulosic biomass to biofuels by reducing total bioprocessing time (enzymatic hydrolysis plus fermentation) to 48 h, increasing biofuel productivity (g/L/h) twofold, and recycling biocatalysts (enzymes and microbes) to the next cycle. To achieve these results, RaBIT utilizes 24-h high cell density fermentations along with cell recycling to solve the slow/incomplete xylose fermentation issue, which is critical for lignocellulosic biofuel fermentations. Previous studies utilizing similar fermentation conditions showed a decrease in xylose consumption when recycling cells into the next fermentation cycle. Eliminating this decrease is critical for RaBIT process effectiveness for high cycle counts. Results Nine different engineered microbial strains (including Saccharomyces cerevisiae strains, Scheffersomyces (Pichia) stipitis strains, Zymomonas mobilis 8b, and Escherichia coli KO11) were tested under RaBIT platform fermentations to determine their suitability for this platform. Fermentation conditions were then optimized for S. cerevisiae GLBRCY128. Three different nutrient sources (corn steep liquor, yeast extract, and wheat germ) were evaluated to improve xylose consumption by recycled cells. Capacitance readings were used to accurately measure viable cell mass profiles over five cycles. Conclusion The results showed that not all strains are capable of effectively performing the RaBIT process. Acceptable performance is largely correlated to the specific xylose consumption rate. Corn steep liquor was found to reduce the deleterious impacts of cell recycle and improve specific xylose consumption rates. The viable cell mass profiles indicated that reduction in specific xylose consumption rate, not a drop in viable cell mass, was the main cause for decreasing xylose consumption. [ABSTRACT FROM AUTHOR]

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]

Highlights: [•] Furfural was produced from corn stover by one stage dilute H3PO4 pretreatment process. [•] Maximum furfural yield was obtained at 200°C and 0.75% (v/v) acid dose. [•] Glucose yield was high from solid residues after enzymatic hydrolysis. [•] Ethanol was produced efficiently from glucose by Saccharomyces cerevisiae. [ABSTRACT FROM AUTHOR]

Highlights: [•] Biomass pelleting is an effective biomass densification method required for biofuels production. [•] Biomass pelleting leads to partial deconstruction of the complex biomass structure and facilitates bioethanol production. [•] Pelleting process led to better enzymatic hydrolysis of pretreated biomasses without affecting the quality of sugars for fermentation. [•] Ethanol yield on the basis of released sugars did not differ significantly between pelleted and unpelleted samples. [•] Schematic diagram for complete utilization of lignocellulosic biomass is proposed. [Copyright &y& Elsevier]

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: 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: Corncob containing ∼70% mass fraction of holocellulose has been used as a low-cost feedstock for ethanol production. Among various inorganic and organic acids tested, the acid hydrolysis of corncob using HCl (1.5% mass divided by volume) at 120 °C for 30 min resulted in optimal recovery of 360.0 g kg−1 sugars along with fermentation inhibitors like phenolics and furans. In order to make the acid hydrolysate fermentable, various detoxification strategies were applied, of these activated charcoal method was found comparatively more effective in removing 95% mass fraction of phenolics and 80% mass fraction of furans. The acid hydrolysed biomass was treated with sodium chlorite (4.0%) to remove ∼80% mass fraction of lignin. The delignified substrate containing mostly cellulose was enzymatically hydrolysed to ∼78% saccharification. The acid and enzymatic hydrolysates containing 38.43 g L−1 and 36.47 g L−1 sugars, when fermented with Pichia stipitis NCIM 3499 and Saccharomyces cerevisiae HAU produced 11.84 and 16.08 g L−1 of ethanol with corresponding yield of 0.31 g g−1 and 0.43 g g−1, respectively. Moreover, the mass balance of the complete process showed 62% mass fraction of ethanol conversion from the carbohydrate fraction of corncob. [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]

The aim of the present study was to examine ethanol production from concentrated food waste hydrolysates using whole cells of S. cerevisiae immobilized on corn stalks. In order to improve cell immobilization efficiency, biological modification of the carrier was carried out by cellulase hydrolysis. The results show that proper modification of the carrier with cellulase hydrolysis was suitable for cell immobilization. The mechanism proposed, cellulase hydrolysis, not only increased the immobilized cell concentration, but also disrupted the sleek surface to become rough and porous, which enhanced ethanol production. In batch fermentation with an initial reducing sugar concentration of 202.64 ± 1.86 g/l, an optimal ethanol concentration of 87.91 ± 1.98 g/l was obtained using a modified corn stalk-immobilized cell system. The ethanol concentration produced by the immobilized cells was 6.9% higher than that produced by the free cells. Ethanol production in the 14th cycle repeated batch fermentation demonstrated the enhanced stability of the immobilized yeast cells. Under continuous fermentation in an immobilized cell reactor, the maximum ethanol concentration of 84.85 g/l, and the highest ethanol yield of 0.43 g/g (of reducing sugar) were achieved at hydraulic retention time (HRT) of 3.10 h, whereas the maximum volumetric ethanol productivity of 43.54 g/l/h was observed at a HRT of 1.55 h. [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: 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: Hemicellulose is a potential by-product currently under-utilized in the papermaking industry. It is a hetero-carbohydrate polymer. For hardwood hemicelluloses, D-xylose is the major component upon depolymerization. At SUNY-ESF, wood extracts were obtained by extracting sugar maple wood chips with hot water at an elevated temperature. The wood extracts were then concentrated and acid hydrolyzed. Ethanologenic bacteria, E. coli FBR5, had a good performance in pure xylose medium for ethanol production. However, FBR5 was strongly inhibited in dilute sulfuric acid hydrolyzate of hot-water wood extract. FBR5 was challenged by hot-water wood extract hydrolyzate in this study. After repeated strain adaptation, an improved strain: E. coli FBHW was obtained. Fermentation experiments indicated that FBHW was resistant to the toxicity of hydrolyzate in the fermentation media of concentrated hydrolyzate, and xylose was completely utilized by the strain to produce ethanol. FBHW was grown in the concentrated hydrolyzate without any detoxification treatment and has yielded 36.8g/L ethanol. [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]

Abundant plant biomass has the potential to become a sustainable source of fuels and chemicals. Realizing this potential requires the economical conversion of recalcitrant lignocellulose into useful intermediates, such as sugars. We report a high-yielding chemical process for the hydrolysis of biomass into monosaccharides. Adding water gradually to a chloride ionic liquid-containing catalytic acid leads to a nearly 90% yield of glucose from cellulose and 70-80% yield of sugars from untreated corn stover. Ion-exclusion chromatography allows recovery of the ionic liquid and delivers sugar feedstocks that support the vigorous growth of ethanologenic microbes. This simple chemical process, which requires neither an edible plant nor a cellulase, could enable crude biomass to be the sole source of carbon for a scalable biorefinery. [ABSTRACT FROM AUTHOR]

Abstract: A two-stage fermentation process, consisting of a simultaneous saccharification and fermentation (SSF) stage and a dry methane fermentation stage, was developed to utilize garbage for the production of fuel ethanol and methane. Garbage from families, canteens and concessionaires was used for the study. Saccharification method was studied and the results indicated that the liquefaction pretreatment and the combination of cellulase and glucoamylase was effective for polysaccharide hydrolysis of family garbage with a high content of holocellulose and that SSF was suitable for ethanol fermentation of garbage. Ethanol productivity could be markedly increased from 1.7 to 7.0 g/l/h by repeated-batch SSF of family garbage. A high ethanol productivity of 17.7 g/l/h was achieved when canteen garbage was used. The stillage after distillation was treated by dry methane fermentation and the results indicated that the stillage was almost fully digested and that about 850 ml of biogas was recovered from 1 g of volatile total solid (VTS). Approximately 85% of the energy of the garbage was converted to fuels, ethanol and methane by this process. [Copyright &y& Elsevier]

Abstract: Renewable energy sources have received increased interest from the international community with biomass being one of the oldest and the most promising ones. In the concept of exploitation of agro-industrial residues, the present study investigates the pre-treatment and ethanol fermentation potential of the olive pulp, which is the semi solid residue generated from the two-phase processing of the olives for olive oil production. Wet oxidation and enzymatic hydrolysis have been applied aiming at the enhancement of carbohydrates'' bioavailability. Different concentrations of enzymes and enzymatic durations have been tested. Both wet oxidation and enzymic treatment were evaluated based on the ethanol obtained in a subsequent fermentation step by Saccharomyces cerevisiae and Thermoanaerobacter mathranii. It was found that a four-day hydrolysis time was adequate for a satisfactory release of glucose and xylose. The combination of wet oxidation and enzymatic hydrolysis resulted in the glucose and xylose concentration increase of 138 and 444%, respectively, compared to 33 and 15% with only enzymes added. However, the highest ethanol production was obtained when only enzymic pre-treatment was applied, implying that wet oxidation is not a recommended pre-treatment process for olive pulp at the conditions tested. It was also showed that increased dry matter concentration did not have a negative effect on the release of sugars, indicating that the cellulose and xylan content of the olive pulp is relatively easily available. The results of the experiments in batch processes clearly emphasize that the simultaneous saccharification and fermentation (SSF) mode is advantageous in comparison with the separate hydrolysis and fermentation (SHF) mode concerning process contamination. [Copyright &y& Elsevier]

Abstract: Four commonly used chemical pretreatment processes based on dilute acid, lime, aqueous ammonia steeping followed by dilute acid hydrolysis, and sodium hydroxide, were evaluated to provide comparative performance data. An obverse correlation between lignin removal and enzymatic digestibility of pretreated corn stover was observed. Compared with other three pretreatments, pretreatment of corn stover with 2% NaOH substantially increased the lignin removal and enhanced the accessibility and digestibility of cellulose. The hydrolysis yield of NaOH-pretreated corn stover reached 81.2% by 48 h at 8.0% substrate concentration and cellulase dosage of 20 FPU g−1 substrate. Chemical analysis showed that the enzymatic hydrolysate from NaOH-pretreated corn stover contained higher content of fermentable sugars and less inhibitors, which is suitable for subsequent fermentation process to produce ethanol. The research results are meaningful in bioconversion and utilization of renewable lignocellulosic biomass. [Copyright &y& Elsevier]

Although food waste (FW) can serve as a valuable substrate containing large amounts of organic materials such as soluble sugar, starch, and cellulose, it is recognized as an environmental pollutant, and the hydrolysis of solids in FW still serves as a rate-limiting step in its biological processes. To evaluate a new potential application of FW as an alternative substrate for ethanol production through laboratory experiments, we investigated FW hydrolysis by using individual commercial enzymes and their mixtures; batch ethanol fermentation by Saccharomyces cerevisiae; and the effect of salt, which is inherently included in FW, on ethanol fermentation. A comparison of the glucose yields of the FW broth pretreated with amyloglucosidase, carbohydrase, and a mixture of both enzymes revealed that a higher glucose yield was obtained when the enzyme mixture was used (0.46 g g-1 of dry FW) than when amyloglucosidase (0.41) or carbohydrases (0.35) were used at 3 h from the initiation of the reaction. A high ethanol yield (0.23 g g-1 of dry FW) was obtained after 15 h of fermentation by S. cerevisiae by using the FW broth hydrolyzed by the enzyme mixture and was estimated to be nearly equivalent to the ethanol yields of lignocellulose biomasses. With regard to the effect of salt on ethanol fermentation, no alteration in the fermentation parameters was observed up to a salt content of 3% w/v. At a salt content of over 4%, however, substrate uptake and cell growth dramatically decreased, and a slight reduction in ethanol yield was observed. FW utilization for ethanol production by enzymatic hydrolysis and ethanol fermentation by S. cerevisiae suggests a promising practical approach to prevent environmental pollution and obtain a product of high value, ethanol. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Aims: To study fuel ethanol fermentation with Kluyveromyces marxianus ATCC8554 from Jerusalem artichoke ( Helianthus tuberosus) grown in salina and irrigated with a mixture of seawater and freshwater. Methods and Results: The growth and ethanol fermentation of K. marxianus ATCC8554 were studied using inulin as substrate. The activity of inulinase, which attributes to the hydrolysis of inulin, the main carbohydrate in Jerusalem artichoke, was monitored. The optimum temperatures were 38°C for growth and inulinase production, and 35°C for ethanol fermentation. Aeration was not necessary for ethanol fermentation with the K. marxianus from inulin. Then, the fresh Jerusalem artichoke tubers grown in salina and irrigated with 25% and 50% seawater were further examined for ethanol fermentation with the K. marxianus, and a higher ethanol yield was achieved for the Jerusalem artichoke tuber irrigated with 25% seawater. Furthermore, the dry meal of the Jerusalem artichoke tubers irrigated with 25% seawater was examined for ethanol fermentation at three solid concentrations of 200, 225 and 250 g l−1, and the highest ethanol yield of 0·467, or 91·5% of the theoretical value of 0·511, was achieved for the slurry with a solid concentration of 200 g l−1. Conclusions: Halophilic Jerusalem artichoke can be used for fuel ethanol production. Significance and Impact of the Study: Halophilic Jerusalem artichoke, not competing with grain crops for arable land, is a sustainable feedstock for fuel ethanol production. [ABSTRACT FROM AUTHOR]

Abstract: Enzymatic hydrolysis of corncob and ethanol fermentation from cellulosic hydrolysate were investigated. After corncob was pretreated by 1% H2SO4 at 108°C for 3h, the cellulosic residue was hydrolyzed by cellulase from Trichoderma reesei ZU-02 and the hydrolysis yield was 67. 5%. Poor cellobiase activity in T. Reesei cellulase restricted the conversion of cellobiose to glucose, and the accumulation of cellobiose caused severe feedback inhibition to the activities of β-1,4-endoglucanase and β-1,4-exoglucanase in cellulase system. Supplementing cellobiase from Aspergillus niger ZU-07 greatly reduced the inhibitory effect caused by cellobiose, and the hydrolysis yield was improved to 83. 9% with enhanced cellobiase activity of 6. 5CBUg−1 substrate. Fed-batch hydrolysis process was started with a batch hydrolysis containing 100gl−1 substrate, with cellulosic residue added at 6 and 12h twice to get a final substrate concentration of 200gl−1. After 60h of reaction, the reducing sugar concentration reached 116. 3gl−1 with a hydrolysis yield of 79. 5%. Further fermentation of cellulosic hydrolysate containing 95. 3gl−1 glucose was performed using Saccharomyces cerevisiae 316, and 45. 7gl−1 ethanol was obtained within 18h. The research results are meaningful in fuel ethanol production from agricultural residue instead of grain starch. [Copyright &y& Elsevier]

Fermentation of lactose in whey permeate directly into ethanol has had only limited commercial success, as the yields and alcohol tolerances of the organisms capable of directly fermenting lactose are low. This study proposes an alternative strategy: treat the permeate with acid to liberate monomeric sugars that are readily fermented into ethanol. We identified optimum hydrolysis conditions that yield mostly monomeric sugars and limit formation of fermentation inhibitors such as hydroxymethyl furfural by caramelization reactions. Both lactose solutions and commercial whey permeates were hydrolyzed using inorganic acids and carbonic acid. In all cases, more glucose was consumed by secondary reactions than galactose. Galactose was recovered in approximately stoichiometric proportions. Whey permeate has substantial buffering capacity--even at high partial pressures (>5500 kPa[g]), carbon dioxide had little effect on the pH in whey permeate solutions. The elevated temperatures required for hydrolysis with CO2-generated inhibitory compounds through caramelization reactions. For these reasons, carbon dioxide was not a feasible acidulant. With mineral acids reversion reactions dominated, resulting in a stable amount of glucose released. However, the Maillard browning reactions also appeared to be involved. By applying Hammet's acidity function, kinetic data from all experiments were described by a single line. With concentrated inorganic acids, low reaction temperatures allowed lactose hydrolysis with minimal by-product formation and generated a hexose-rich solution amenable to fermentation. [ABSTRACT FROM AUTHOR]

• Feasibility of using waste pizza for ethanol fermentation was examined. • Enzymatic hydrolysis of WP by α-amylase could be completed within 50 min. • The total power consumed for the whole bio-process was 1.1 kW⋅h. • The highest ethanol yield of 0.292 g/g WP was obtained. • This is the first study to report bio-ethanol production from WP. In this work, the feasibility of ethanol production from waste pizza (WP) by enzymatic hydrolysis and fermentation was investigated. The effects of enzyme volumes (0.02-0.08 mL/L) and WP mass ratios (50−160 g/L) on the performance of enzymatic hydrolysis and ethanol fermentation were also examined. It was observed that the lowest enzyme volume (0.02 mL/L) could completely hydrolyze WP with mass ratio of 50 g/L. The reducing sugar (RS) increased obviously with increasing of WP mass ratio from 50 g/L to 160 g/L when the enzyme volume of 0.02 mL/L was applied. The WP hydrolysate was utilized as substrate for bio-ethanol production with the highest cumulative ethanol production of 27.58 g/L and ethanol yield of 0.292 g/g WP, respectively. To our knowledge, this is the first study to report ethanol production from WP by enzymatic hydrolysis and fermentation. [ABSTRACT FROM AUTHOR]

This paper evaluated the effectiveness of nitric acid pretreatment on the hydrolysis and subsequent fermentation of Jerusalem artichoke stalks (JAS). Jerusalem artichoke is considered a potential candidate for producing bioethanol due to its low soil and climate requirements, and high biomass yield. However, its stalks have a complexed lignocellulosic structure, so appropriate pretreatment is necessary prior to enzymatic hydrolysis, to enhance the amount of sugar that can be obtained. Nitric acid is a promising catalyst for the pretreatment of lignocellulosic biomass due to the high efficiency with which it removes hemicelluloses. Nitric acid was found to be the most effective catalyst of JAS biomass. A higher concentration of glucose and ethanol was achieved after hydrolysis and fermentation of 5% (w/v) HNO3-pretreated JAS, leading to 38.5 g/L of glucose after saccharification, which corresponds to 89% of theoretical enzymatic hydrolysis yield, and 9.5 g/L of ethanol. However, after fermentation there was still a significant amount of glucose in the medium. In comparison to more commonly used acids (H2SO4 and HCl) and alkalis (NaOH and KOH), glucose yield (% of theoretical yield) was approximately 47–74% higher with HNO3. The fermentation of 5% nitric-acid pretreated hydrolysates with the absence of solid residues, led to an increase in ethanol yield by almost 30%, reaching 77–82% of theoretical yield. [ABSTRACT FROM AUTHOR]