Second-generation Bioethanol Production Research Articles

Identification of the major fermentation inhibitors of recombinant 2G yeasts in diverse lignocellulose hydrolysates

BackgroundPresence of inhibitory chemicals in lignocellulose hydrolysates is a major hurdle for production of second-generation bioethanol. Especially cheaper pre-treatment methods that ensure an economical viable production process generate high levels of these inhibitory chemicals. The effect of several of these inhibitors has been extensively studied with non-xylose-fermenting laboratory strains, in synthetic media, and usually as single inhibitors, or with inhibitor concentrations much higher than those found in lignocellulose hydrolysates. However, the relevance of individual inhibitors in inhibitor-rich lignocellulose hydrolysates has remained unclear.ResultsThe relative importance for inhibition of ethanol fermentation by two industrial second-generation yeast strains in five lignocellulose hydrolysates, from bagasse, corn cobs and spruce, has now been investigated by spiking higher concentrations of each compound in a concentration range relevant for industrial hydrolysates. The strongest inhibition was observed with industrially relevant concentrations of furfural causing partial inhibition of both D-glucose and D-xylose consumption. Addition of 3 or 6 g/L furfural strongly reduced the ethanol titer obtained with strain MD4 in all hydrolysates evaluated, in a range of 34 to 51% and of 77 to 86%, respectively. This was followed by 5-hydroxymethylfurfural, acetic acid and formic acid, for which in general, industrially relevant concentrations caused partial inhibition of D-xylose fermentation. On the other hand, spiking with levulinic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid or vanillin caused little inhibition compared to unspiked hydrolysate. The further evolved MD4 strain generally showed superior performance compared to the previously developed strain GSE16-T18.ConclusionThe results highlight the importance of individual inhibitor evaluation in a medium containing a genuine mix of inhibitors as well as the ethanol that is produced by the fermentation. They also highlight the potential of increasing yeast inhibitor tolerance for improving industrial process economics.

The Availability and Assessment of Potential Agricultural Residues for the Regional Development of Second-Generation Bioethanol in Thailand

The agricultural sector is a major source of biomass feedstocks for biofuels. Even though biomass potential in Thailand has been analyzed on a national level, its distribution and potential have yet to be assessed on a regional and provincial scale. Therefore, the study aims to verify the possibility of decentralized second-generation bioethanol production from regionally available agricultural residues. Most of the generated residues stem from the country’s major crops (sugarcane, cassava, rice and palm), totaling 174.1 million tons per year. The volume of bioethanol from these residues is projected to be 20,213.5 million liters per year, meeting 31.2% of the overall fuel demand of the transport sector. At the regional level, the northeast produces the highest amount of bioethanol at 9099.7 million liters per year, followed by the central, northern and southern regions. In terms of provincial distribution, the highest amount of bioethanol is converted in Nakhon Ratchasima, amounting to 1328 million liters per year. Data from the top ten potential provinces suggest that decentralizing production facilities is possible. One of the hotspots is Surat Thani in the south which can potentially utilize palm residues as feedstocks. This regionalized assessment also found that conventional feedstocks could be substituted with regionally available residues in the 26 production plants currently in operation. The results confirm that there would be enough alternative regional feedstocks to meet existing production capacities and they indicate that there would be enough regional residues left over for future value-added utilization.Graphic

Toward waste valorization by converting bioethanol production residues into nanoparticles and nanocomposite films

A “waste-valorization” approach was developed to transform recalcitrant hydrolysis lignin (HL) from second-generation bioethanol production into multifunctional bio-based products. The hydrolysis lignin (HL) was extracted with aqueous acetone, yielding two fractions enriched in lignin and cellulose, respectively. The soluble hydrolysis lignin (SHL) was converted into anionic and cationic colloidal lignin particles (CLPs and c-CLPs). The insoluble cellulose-rich fraction was transformed into lignocellulosic nanofibrils that were further combined with CLPs or c-CLPs to obtain nanocomposite films with tailored mechanical properties, oxygen permeability and antioxidant properties. To enable prospective applications of lignin in nanocomposite films and beyond, CLPs and c-CLPs were also produced from a soda lignin (SL) and the influence of the lignin type on the particle size and ecotoxicity was evaluated. Finally, the carbon footprint of the entire process from hydrolysis lignin to films was assessed and an integration to industrial scale was considered to reduce the energy consumption. While most previous work utilizes purified lignin and pristine and often purified cellulose fibers to produce nanomaterials, this work provides a proof of concept for utilizing the recalcitrant lignin-rich side stream of the bioethanol process as raw material for functional nanomaterials and renewable composites.

Integration of First- and Second-generation Bioethanol Production from Beet molasses and Distillery Stillage After Dilute Sulfuric Acid Pretreatment

The possibility of using waste distillery stillage (first-generation technology) after dilute acid pretreatment, as a medium for the preparation of beet molasses mash, for ethanol production according to the simultaneous saccharification and fermentation (SSF) technology, was assessed. The combination of lignocellulosic hydrolysates made from acid-pretreated stillage with sugar-rich beet molasses is an effective way of utilizing the first-generation ethanol production by-products in the second-generation ethanol production technology. It was demonstrated that the final ethanol concentration could be as high as 90 g/L. The process yield was over 94% of the theoretical yield when the molasses was diluted using acid-pretreated maize distillery stillage. An attempt to increase the pool of fermentable sugars by using cellulases to hydrolyze cellulose failed due to product inhibition in the fermentation medium with a high glucose concentration. A more than threefold increase in the concentration of ethyl acetate (even up to 924.4±11.8 mg/L) was observed in the distillates obtained from the media incubated with cellulases. The use of beet molasses combined with the hydrolysate of pretreated distillery stillage also changed the concentration of other volatile by-products. An increase in the concentration of aldehydes (mainly acetaldehyde to a concentration of above 1500 mg/L), methanol, 1-propanol, and 1-butanol was observed, while the concentration of higher alcohols (isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol) decreased. Interestingly, the use of cellulases in fermentation media from molasses and stillage hydrolysates resulted in an average fourfold increase in the concentration of this ester to a maximum level of 924.4±11.8 mg/L. Hydrolysates made from acid-pretreated distillery stillage, combined with sugar-rich beet molasses to boost the efficiency of the conversion process, can be successfully used in the production of second-generation fuel ethanol. However, further optimization of the cellulose enzymatic hydrolysis process is required for efficient use of the raw material.

Comparative analysis of fresh and dry free-floating aquatic plant Pistia stratiotes via chemical pretreatment for second-generation (2G) bioethanol production

In the effort to manage global warming and fossil carbon emissions, many countries are suggesting brand-new policies to make their energy matrix much more renewable. The boost share of bioethanol as a transportation fuel becomes a short-term option since its production technology is fully grown and combined with gasoline. The 2nd generation ethanol still has involvement on the planet biofuels circumstance. In this study, water lettuce (Pistia stratiotes) fresh and dry biomass applied with alkalis (NaOH) and acid (H2SO4) were combined to pretreat the abundant free-floating aquatic plant water lettuce biomass. Naturally, the water lettuce accumulates food in the form of starch, suitable for bioethanol production. The results showed that the highest total sugar (11.350 ± 0.09%), reducing sugar (4.773 ± 0.15%), and ethanol (15. 385 g/L) were obtained after pretreatment of dried water lettuce with cellulase. Consequently, water lettuce was high feasible for sustainable bioethanol production.

Alternative Lime Pretreatment of Corn Stover for Second-Generation Bioethanol Production

In this work, a delignification process, using lime (Ca(OH)2) as an alternative alkali, was evaluated to improve enzymatic saccharification of corn stover cellulose, with the final goal of obtaining second-generation bioethanol. For that, an experimental design was conducted in order to assay the effect of temperature, lime loading, and time on the corn stover fractionation and enzymatic susceptibility of cellulose. Under conditions evaluated, lime pretreatment was selective for the recovery of cellulose (average of 91%) and xylan (average of 75.3%) in the solid phase. In addition, operating in mild conditions, a delignification up to 40% was also attained. On the other hand, a maximal cellulose-to-glucose conversion (CGCMAX) of 89.5% was achieved using the solid, resulting from the treatment carried out at 90 °C for 5 h and lime loading of 0.4 g of Ca(OH)2/g of corn stover. Finally, under selected conditions of pretreatment, 28.7 g/L (or 3.6% v/v) of bioethanol was produced (corresponding to 72.4% of ethanol conversion) by simultaneous saccharification and fermentation. Hence, the process, based on an alternative alkali proposed in this work, allowed the successful production of biofuel from the important and abundant agro-industrial residue of corn stover.

Effect of the Sugarcane Bagasse Deacetylation in the Pentoses Fermentation Process

Biomass alkaline deacetylation prior to acid pretreatment can be a promising alternative to reduce the toxicity of hemicellulosic hydrolysates and improve second-generation bioethanol production. In this paper, the effect of alkaline deacetylation of sugarcane bagasse on bioethanol production by Spathaspora passalidarum was evaluated. Sugarcane bagasse deacetylated hemicellulosic hydrolysate (DHH) was processed using the following sequence: (1) deacetylation (0.4%, w/v NaOH, 70 °C, 3 h) and (2) acid pretreatment (0.5% (v/v) of H2SO4, 140 °C, 15 min). Non-deacetylated, hemicellulosic hydrolysate (HH), was obtained applying only acid pretreatment (0.5% (v/v) of H2SO4, 140 °C, 15 min). Biomass deacetylation reduced the content of acetic acid and some phenolic compounds in the hydrolysate (DHH) compared to acid pretreatment (HH), which resulted in its low toxicity. Thus, the bioethanol production with DHH was of 16.92 g L−1, whereas only 1.3 g L−1 of bioethanol was obtained with HH fermentation. Deacetylation process provided a 13-fold increase in bioethanol production by S. passalidarum, showing that alkaline deacetylation followed by sulfuric acid pretreatment is a promising strategy to increase bioethanol production. This procedure provided a simple and practical alternative to the classic methods of detoxification of hemicellulosic hydrolysate from sugarcane bagasse.

Lignocellulosic Analysis of Corncob Biomass by Using Non-Thermal Pulsed Electric Field-NaOH Pretreatment

In recent years, the second-generation bioethanol and advanced bio-based material production from biomass are focused on the pretreatment process by separating cellulose components from other components such as lignin and hemicellulose. Therefore, a physicochemical pretreatment method is needed by applying a non-thermal pulsed electric field (PEF) and alkali methods to increase the cellulose availabilities with a short process and low energy input. The aim of this study was to analyze the lignocellulose content of corncob biomass by using non-thermal pulsed electric fields (PEF) and NaOH pretreatment. The pretreatment factors used were the electric field strength of PEF and the pretreatment time. Analysis of the structure and elements of the lignocellulose based on the characteristics of the gravimetric method and SEM-EDX for untreated and treated samples. The results showed that pretreatment of corncobs biomass by using PEF optimally at an electric field strength of 9 kV/cm and pretreatment time of 60 seconds that was increasing cellulose of 40.59% when compared with the control and also decreasing the hemicellulose and lignin content of 12.9% and 2.02%, respectively. Under these conditions, the energy per pulse and specific input energy of PEF required 0.0205 J and 8.72 kJ/L, respectively. The microstructure analysis by using SEM-EDX showed significantly visual differences and was an increase in the percentage of C and O atoms between untreated and treated corncob biomass. Furthermore, the corncob biomass treated by using non-thermal PEF and alkali can become effective and efficient for the next process into cellulose-derived products.Keywords: corncob biomass; pulsed electric field; NaOH; pretreatment; cellulose

Sustainable Second-Generation Bioethanol Production from Enzymatically Hydrolyzed Domestic Food Waste Using Pichia anomala as Biocatalyst

In the current study, a domestic food waste containing more than 50% of carbohydrates was assessed as feedstock to produce second-generation bioethanol. Aiming to the maximum exploitation of the carbohydrate fraction of the waste, its hydrolysis via cellulolytic and amylolytic enzymatic blends was investigated and the saccharification efficiency was assessed in each case. Fermentation experiments were performed using the non-conventional yeast Pichia anomala (Wickerhamomyces anomalus) under both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) modes to evaluate the conversion efficiencies and ethanol yields for different enzymatic loadings. It was shown that the fermentation efficiency of the yeast was not affected by the fermentation mode and was high for all handlings, reaching 83%, whereas the enzymatic blend containing the highest amount of both cellulolytic and amylolytic enzymes led to almost complete liquefaction of the waste, resulting also in ethanol yields reaching 141.06 ± 6.81 g ethanol/kg waste (0.40 ± 0.03 g ethanol/g consumed carbohydrates). In the sequel, a scale-up fermentation experiment was performed with the highest loading of enzymes in SHF mode, from which the maximum specific growth rate, μmax, and the biomass yield, Yx/s, of the yeast from the hydrolyzed waste were estimated. The ethanol yields that were achieved were similar to those of the respective small scale experiments reaching 138.67 ± 5.69 g ethanol/kg waste (0.40 ± 0.01 g ethanol/g consumed carbohydrates).

EFFECTS OF THE INCREASE IN SUBSTRATE LOAD AND HYDROLYSIS TIME IN THE SACCHARIFICATION OF SUGARCANE BAGASSE AND ETHANOL PRODUCTION

In this study, the enzymatic saccharification of alkaline pretreated sugarcane bagasse (PSB) and the production of second generation bioethanol were investigated under different conditions. The effects of percentage of dry substrate (3 and 10% w/v) and time of hydrolysis (24 and 72 h) were evaluated in order to obtain maximum contents of total reducing sugar (TRS), glucose and xylose. The monosaccharide concentrations were quantified by High Performance Liquid Chromatography (HPLC) and TRS by the 3.5-dinitrosalicylic acid (DNS) method. The saccharification of PSB with the Cellic Ctec3, promoted an efficient release of sugars. Among the four evaluated conditions, the hydrolysis HD (10% PSB and 72h) was selected as the most efficient with the highest concentrations of released sugars: TRS (73.96 g/L), glucose (31.78 g/L) and xylose (10.85 g/L). The alcoholic fermentation of hydrolysate HD with the yeast Saccharomyces cerevisiae produced the maximum concentration of 16.15 g/L of ethanol, with a volumetric productivity (QP) of 0.69 g/Lh and yield of ethanol as a function of the substrate (YP/S) of 0.48 gethanol/gsugar. S. cerevisiae was capable of fermenting 99.96% of glucose from hydrolysate HD. These results suggest that the increase of the substrate load and time in the enzymatic hydrolysis can be favourable alternatives to improve the sugar yields in hydrolysates and, consequently, the bioethanol production.

Comparing first- and second-generation bioethanol by-products from sugarcane: Impact on soil carbon and nitrogen dynamics

The first- and second-generation bioethanol by-products (bagasse and fermentation by-product, respectively) have different biochemical characteristics relating to carbon (C) and nitrogen (N) due to their production processes. To examine the impacts of fermentation by-product and bagasse on soil C and N dynamics, a 120 day laboratory incubation experiment was conducted by applying these amendments in soil at an equal carbon application rate (2.2 g C kg−1 soil). There was a significant increase in overall cumulative CO2-C production from amended soil compared to the control soil, though the loss was greatest in bagasse amended soil. However, δ13C-CO2 measurements suggested that fermentation by-product addition suppressed native soil C mineralization and prompted strong negative C priming (−57%). In contrast, bagasse amendment maintained similar native soil C mineralization to control soil. Decreased microbial biomass turnover time appears to be the major driving force for increased CO2-C production and soil C loss following bioethanol by-product amendments. Increased mineral N production indicated net N mineralization after fermentation by-product addition, while addition of bagasse resulted in lower N availability and N immobilization. Overall, results suggested that fermentation by-product application is advantageous in maintaining native soil C stock and N mineralization compared to bagasse. Thus, in a sustainable second-generation bioethanol production system, bagasse may be used for second-generation bioethanol production and the cogenerated by-product could be used as an amendment to improve soil C stock and N availability.

Imidazole green solvent pre-treatment as a strategy for second-generation bioethanol production from sugarcane bagasse

Sugarcane bagasse (SCB) is a potential source for second-generation bioethanol production. However, its recalcitrant structure (carbohydrates and phenolics) hinders the efficient release of sugars. Imidazole is a cheap green solvent that has demonstrated high efficiency in lignocellulosic biomass delignification. The main objective of this work was to study the SCB pre-treatment with imidazole for further enzymatic hydrolysis and bioethanol production. Significant modifications of imidazole-treated biomass were observed in the morphology and composition, such as cellulose enrichment, a great decrease of amorphous compounds (lignin and hemicellulose), and structural disorganization of lignocellulosic fibres. On the other hand, this pre-treatment also shows a substantial improvement of enzymatic conversion performance using Cellic CTec2®/Cellic HTec2® (15 FPU per gram of solid biomass) in all evaluated conditions compared to untreated material. After pre-treatment at 160 °C for 1 h, enzymatic conversion efficiency reached 100% for glucose and xylose, significantly decreasing the hydrolysis time to only 8 h. The hydrolysates obtained were used for bioconversion to bioethanol by S. cerevisiae LPB 2705, giving a high production yield (83.7%), which represents a production of 218 L of ethanol per ton of SCB. This means an increase of up to 4 times the ethanol production compared to untreated material. The results obtained showed the great potential of imidazole in SCB pre-treatment, because it increased the release of fermentable sugars, which leads to an efficient and economic use of agro-industrial waste to generate value-added products and reduce the environmental impact under a biorefinery concept.

Preliminary plant design of thermochemical conversion for rice straw-based second-generation bioethanol production in West Java

Thermochemical conversion is selected in the design of a rice straw-based bioethanol production plant. This study examines the gasification and catalytic synthetic process technologies of rice straw into ethanol. The size of rice straw was reduced and dried before entering the gasification reactor to convert into syngas. The clean gas goes to the mixed alcohol synthesis process in a plug flow reactor with CuO/ZnO as a catalyst. The product is then purified through several separation methods, i.e., column distillation, stripping, and absorption. The controlled parameters for this plant are temperature, flow rate, pressure, level, and concentration. The paper describes the piping instrumentation diagram with a graphical representation of the equipment, piping, and instrumentation. A Heat Exchanger Network analysis achieves an efficiency of 34.4%. The electricity required is fulfilled by turbine expander for about 1,493 kW, and the rest of it is provided by PLN, besides an emergency generator sets. The capacity of this plant is 100,000 kL/year.

Plant layout and health and safety analysis of thermochemical conversion for rice straw-based second-generation bioethanol production in West Java

Rice straw is one of the abundant lignocellulosic waste materials that potentially produce 205 billion liters bioethanol per year in Indonesia. This study examines the health, safety, and environmental aspects of a Bioethanol Production Plant. The main processes involved in the plant are pretreatment, gasification, water-gas shift reaction, carbon dioxide removal, alcohol synthesis, and purification. The plant will be located in Indramayu, West Java, Indonesia, with a total area of 3 hectares. The plant layout covers inside and outside the battery limit area, including but not limited to waste treatment area, office, QC Lab, and other supporting facilities. The HSE Assessment includes Hazard Identification, Hazard and Operability Study, Operational Details, Emergency Action Plant, and Waste Management. The paper discusses the 3D plant layout concerning HSE aspects. The most dangerous material in this plant is ethanol due to flammable risk. Hence, the most dangerous area is around the reactor to explosion risk. There are several types of equipment that need more attention due to its severe hazard effects, such as crusher, gasification reactor, char combustor, condenser, reboiler, distillation column, reflux drum, storage ethanol, also laboratory area. The plant layout is divided into several areas: production area, utility area, waste treatment area, and supporting area. The stable, liquid, and gas wastes will be treated in a waste treatment area. Measurements for reducing noise level includes performing regular maintenance and replacing parts causing the noise.

Economic evaluation of thermochemical conversion for rice straw-based second-generation bioethanol production in West Java

Production of bioethanol through several routes from cheap materials such as agricultural solid waste is getting more interesting nowadays. Rice straw is one of the potential agricultural solid wastes that can be used as feedstock for bioethanol production due to a huge amount of availability, especially in South East Asia countries. In this study, the economics of rice straw-based bioethanol plant by thermochemical conversion was evaluated. The main processes involved in the plant are pretreatment, gasification, water-gas shift reaction, carbon dioxide removal, alcohol synthesis, and purification. The plant was planned to be located in Indramayu, West Java, Indonesia. The price of bioethanol set on this evaluation is US$ 0.61 per liter. The total capital expenditure (CAPEX) and operational expenditure (OPEX) of this plant were found to be US$ 122,614,000 and US$ 20,175,910, respectively. The return on investment (ROI) is 66.96%. The internal rate of return (IRR) is 24.08%. The net present value (NPV) is US$ 689,074,000. Finally, the payback period is 4.5 years. The result of this study shows that this bioethanol plant is feasible and very profitable to be implemented.

Technology selection for rice straw-based second-generation bioethanol production in West Java

Production of bioethanol from the abundant sources of agroindustrial cellulose has the potential to reduce world dependency on fossil fuel and, at the same time, represent a potentially negative environmental impact. Cellulose makes up nearly half of all plant biomass. Therefore, cellulosic ethanol may be the most potent source of biofuel in the near future. Rice straw is one of the most abundant lignocellulose materials in Indonesia. This study examines technology selection for rice straw-based second-generation bioethanol production. Selected possible process alternatives for bioethanol production are discussed in this work. Physical, chemical, and biological pretreatments, as well as a combination of those pretreatment processes, are elaborated in this study. The process chosen is process D, biomass–gasification – synthetic catalytic process – ethanol. In this alternative, the main processes are gasification and synthetic catalytic. Overall, fluidized bed reactors have more significant potential for use with biomass conversion than fixed bed reactors or other types of gasifiers. The gasification of carbonaceous biomass occurs via three main reactions, partial oxidation, complete oxidation, and the water-gas reaction.

Oxygen reduction catalyst element, method of its production, and uses thereof

Non-isothermal autohydrolysis, an environmentally friendly pretreatment, was employed for the production of second generation bioethanol from fast-growing Paulownia wood, comparing two biorefinery strategies: (i) one-stage autohydrolysis pretreatment, and (ii) sequential two-stage autohydrolysis pretreatment. The first strategy allowed to either recover high amounts of hemicellulosic-derived compounds in the liquid phase (at lower severities) or to achieve high enzymatic susceptibility of the cellulose in the solid phase (at higher severities). Solid phase from lower severities pretreatments (optimal for the recovery of hemicellulosic compounds) achieved glucan to glucose conversions of 38.6–72.2% in the enzymatic hydrolysis assays. In this context, conditions for the obtainment of a liquor enriched in hemicelluloses and a highly enzymatically susceptible solid are not compatible. Therefore, the employment of the second strategy (sequential pretreatments in two stages) allowed to recover up to 85% of initial xylan as xylooligosaccharides and xylose in autohydrolysis liquor from first stage of autohydrolysis (at severity, S01 = 4.08) and enhance the enzymatic susceptibility of the solid phase to a glucan to glucose conversion close to 100% with the second stage of autohydrolysis (S01 = 4.08, S02 = 3.76, with a global severity of S0G = 4.25). Fermentation experiments confirmed the advantages of the sequential two-stage autohydrolysis (with a glucan to ethanol conversion close to 100% and high volumetric productivity). Finally, an overall mass balance and energy analysis were carried out, reflecting a suitable fractionation of Paulownia wood that would accomplish an energy recovery of 97.5%.

Sequential two-stage autohydrolysis biorefinery for the production of bioethanol from fast-growing Paulownia biomass

Non-isothermal autohydrolysis, an environmentally friendly pretreatment, was employed for the production of second generation bioethanol from fast-growing Paulownia wood, comparing two biorefinery strategies: (i) one-stage autohydrolysis pretreatment, and (ii) sequential two-stage autohydrolysis pretreatment. The first strategy allowed to either recover high amounts of hemicellulosic-derived compounds in the liquid phase (at lower severities) or to achieve high enzymatic susceptibility of the cellulose in the solid phase (at higher severities). Solid phase from lower severities pretreatments (optimal for the recovery of hemicellulosic compounds) achieved glucan to glucose conversions of 38.6–72.2% in the enzymatic hydrolysis assays. In this context, conditions for the obtainment of a liquor enriched in hemicelluloses and a highly enzymatically susceptible solid are not compatible. Therefore, the employment of the second strategy (sequential pretreatments in two stages) allowed to recover up to 85% of initial xylan as xylooligosaccharides and xylose in autohydrolysis liquor from first stage of autohydrolysis (at severity, S01 = 4.08) and enhance the enzymatic susceptibility of the solid phase to a glucan to glucose conversion close to 100% with the second stage of autohydrolysis (S01 = 4.08, S02 = 3.76, with a global severity of S0G = 4.25). Fermentation experiments confirmed the advantages of the sequential two-stage autohydrolysis (with a glucan to ethanol conversion close to 100% and high volumetric productivity). Finally, an overall mass balance and energy analysis were carried out, reflecting a suitable fractionation of Paulownia wood that would accomplish an energy recovery of 97.5%.

Expression of serpins by Clostridium thermocellum and simultaneous saccharification of lignocellulosic biomass to enhance ethanol production

Utilization of biomass for production of second generation bioethanol was considered as a way to reduce burdens of fossil fuel in Pakistan. The materials wheat straw, rice straw, cotton stalk, corn stover, and peel wastes were used in this experiment. Various parameters, such as acidic and alkali pretreatment, enzymatic hydrolysis by cellulases, and effect of proteases inhibitors on ethanol production, were examined. Fermentation was completed by the yeasts Saccharomyces cerevisiae and Clostridium thermocellum separately, and their ethanol production were compared and maximum ethanol yield was obtained with wheat straw i.e.,11.3 g/L by S. cerevisiae and 8.5 g/L by C. thermocellum. Results indicated that a higher quantity of sugar was obtained from wheat straw (19.6 ± 1.6 g/L) followed by rice straw (17.6 ± 0.6 g/L) and corn stover (16.1 ± 0.9 g/L) compared to the other evaluated biomass samples. A higher yield of ethanol (11.3 g/L) was observed when a glucose concentration of 21.7 g/L was used, for which yeast fermentation efficiency was 92%. Results also revealed the increased in ethanol production (93%) by using celluases in combination with recombinant Serine protease inhibitors from C. thermocellum. It is expected that the use of recombinant serpins with cellulases will play a major role in the biofuel production by using agricultural biomass. This will also help in the economics of the biofuel.

Lignocellulosic biomass and industrial bioprocesses for the production of second generation bio-ethanol, does it have a future in Algeria?

Algeria is facing two serious constraints, energy shortage and environment pollution. To overcome these two problems, renewable energies are the best sustainable alternatives. In this context, Algeria Government has established in 2011 a program for the development of renewable energies. The prospective results show a substantial contribution to supplying national energy demand as well as some significant environmental benefits, namely through major greenhouse gas savings. In fact, lignocellulosic sources as Algerian Alfa, olive pomace and cereal straw could provide up to 0.67 Mtoe which represents 4.37% of the energy consumption of transport sector in Algeria. In the same vein, introducing energy crops and dedicated cereal crop technologies allows Algeria to progressively increase its renewable energy supply. Up to 73.5 Mtoe and 57.9 Mtoe can be produced from the two cited resources respectively. That is more than the national energy consumption which reached 60.96 MToe in 2018.