Generation Ethanol Research Articles

Study of acid hydrolysis and submerged fermentation parameters in second generation ethanol production using cassava waste

Biofuels are an alternative to reduce the environmental impacts caused by the use of petroleum-based fuels. Second generation ethanol comes from lignocellulosic materials that are little used or discarded in the environment, including agro-industrial waste. These residues are rich in sugars that can be converted by ethanol-producing microorganisms. In this context, the present work uses cassava waste (Manihot esculenta Crantz) obtained during the processing of starch as a raw material for the production of cellulosic ethanol, as well as evaluating different parameters in acid hydrolysis and during submerged fermentation using the strain Saccharomyces cerevisiae ATCC 26602. Experiments of acid hydrolysis of these residues with sulfuric acid in concentrations of 0.5% to 5.0% (v/v) were carried out. The results demonstrated that 2.0% H2SO4 for 10 min. reaction at 121 ºC/1.1 atm in an autoclave reached the highest release of reducing sugars present in the residue (131.09 g.L-1). The ideal conditions for alcoholic fermentation using yeast were pH 6.5, temperature of 35 ºC, without rotation and initial reducing sugar concentration of 50 g.L-1, resulting in 21.23 g.L-1 of ethanol with productivity of 1.86 g.L-¹.h-¹ and theoretical yield of 96.5% after 12 hours of fermentation. The results indicated that the cassava waste serve as a potential substrate for the production of second generation ethanol. Thus, this study provides data on the most suitable conditions for the use of these industrial wastes aiming at the generation of a renewable fuel, an increasingly attractive feature for the world, where the economic and environmental concern is growing.

Paper-Mill Wastes for Bioethanol Production in Relation to Circular Economy Concepts: A Review

This review explores circular economy principles in regard to ethanol production from paper-mill sludge. Environmental sustainability and renewability over fossil fuels make second generation ethanol an attractive energy source in a rapidly growing population and consumption world. Paper sludge (PS), a by-product of the pulp and paper (P&P) industry, can no longer be recycled for paper production and is mainly disposed of in landfills. Therefore, it poses a major environmental challenge. However, it has shown potential as a valuable raw material for ethanol production, along with other pulp and paper products, due to its abundant availability and high cellulosic content. This waste-to-energy (WtE) technology for ethanol production is proposed as an alternative, aligning with circular economy concepts to maximize resource efficiency and minimize waste. This review underlines the circular economy aspects of bioethanol production within paper mill sludge management systems. Circular economy principles applied to ethanol production from PS offer a promising avenue for sustainable biofuel development that not only addresses waste management challenges but also enhances the overall environmental performance of biofuel production. Furthermore, economic benefits are described, highlighting the potential for job creation and community development.

Selection and improvement of Saccharomyces cerevisiae by direct and mass mating for integrated first and second generation (1G + 2G) ethanol production

The integrated 1G + 2G ethanol production process seems to be a feasible strategy considering the Brazilian scenario, in which sugarcane molasses and bagasse are available substrates in biorefineries. However, such process imposes harsh conditions to yeasts, which must be able to simultaneously deal with several stresses from molasses and hydrolysate. In this work, improved hybrid strains of Saccharomyces cerevisiae with higher resistance for an integrated 1G + 2G ethanol production were obtained by hybridization technique. Initially, 663 wild S. cerevisiae strains were screened in microculture growth assays. Seven strains were pre-selected out of 40 based on their stress multi-tolerance traits. Subsequently, these pre-selected strains underwent evaluation in cell-recycling fed-batch fermentation conditions utilizing a medium containing molasses-bagasse hydrolysate. The two most successful strains from this evaluation were subjected to sporulation, yielding haploid cells. These haploid cells were then subjected to crossbreeding, employing direct and mass mating techniques. From the initial pool of 7 pre-selected strains, 3 hybrid strains were selected due to their enhanced resistance under the demanding conditions of cell recycling fed-batch fermentation, particularly when utilizing a higher osmotic molasses-hydrolysate medium. These hybrid strains consistently exhibited high cell viability rates and effectively accumulated elevated levels of trehalose and glycogen over the course of five fermentation cycles. Remarkably, they maintained ethanol productivity at levels comparable to their respective parental strains. The genotyping molecular identification attested the difference between the hybrids and the parental strains. The 3 hybrids selected seem to present valuable backgrounds for metabolic engineering for lignocellulosic-derived xylose fermentation.

Integrated techno-economic, investment risk and life cycle analysis of Indian lignocellulosic biomass valorisation via co-gasification and syngas fermentation

The current work presents techno-economic and life cycle assessment of a co-gasification- fermentation hybrid model of bio-ethanol production with recycle and recovery of different resources. The model is also equipped with waste heat recovery from the hot syngas and power generation from unconverted syngas. The co-gasification process is based on Gibbs’ free energy minimization and syngas fermentation follows chemical equilibrium. With the objective of studying the economic feasibility and environmental sustainability of the proposed model, techno-economic assessment followed by financial risk analysis and life cycle analysis has been conducted. On the basis of 1 kg product bio-ethanol the results of the life cycle analysis, the present bio-ethanol production process have been compared to those of 1st generation ethanol production and biomass to bio-ethanol conversion via sugar platform. The present process is found to be economically viable with a net present value, internal rate of return and payback period of 18.7 M$, 13.33% and 6.7 years respectively. Monte Carlo simulation of financial risk has been modelled to predict the uncertainty over net present value and 81.8% is the probability of getting a non-negative net present value. Life cycle analysis suggest that the presented process emits 1.23 kg less CO2 per kg of bio-ethanol compared to the conventional bio-ethanol production process from biomass.

Obtaining oil, fermentable sugars, and platform chemicals from Butia odorata seed using supercritical fluid extraction and subcritical water hydrolysis

Butia odorata seeds (BOS) present high economical potential because they contain oil and lignocellulosic compounds. Oil extracted by supercritical technology may have potential use in the food industry and the remaining solid from the process can be used to produce second- generation ethanol from the hydrolysis of its carbohydrates to obtain fermentable sugars. This work evaluates the processing of BOS using supercritical fluid extraction (SFE), to obtain oil, and subsequent subcritical water hydrolysis (SWH) of SFE residue (BOSR), to obtain fermentable sugars and platform chemicals. Kinetic curves at temperatures of 40 °C and 60 °C, and pressures of 18, 20, and 22 MPa were obtained for SFE using CO2 as solvent, with the best oil yield of 29.05 ± 1.42 wt% at 60 °C and 22 MPa. In the SWH, the explored conditions were 230 °C and 260 °C for temperature, 50 and 100 for solvent to feed ratio (S/F) with a constant pressure of 15 MPa. The best results for the yields of fermentable sugars and platform chemicals were 5.78 ± 1.15 g/100 g and 2.90 ± 0.24 g/100 g, respectively, at 260 °C and S/F 50.

Chemical and histological characterization of internodes of sugarcane and energy-cane hybrids throughout plant development

Sugarcane and energy-cane are important Saccharum spp. hybrids that encompass desirable features for energy production. Their stem lignocellulose can be used as the raw material for the second-generation ethanol industry, contributing to accelerated fossil-fuel replacement. However, knowledge on the internode composition and saccharification of these hybrids is still needed to optimize their uses, especially in energy-cane. In this work, the agronomical, chemical, and histological internode features and saccharification potential were analyzed in sugarcane and energy-cane hybrids across four critical developmental stages (tillering, grand growth, early ripening and late ripening) and several internode positions along the stem. Except for galactose content that was higher in the sugarcane hybrid compared to the energy-cane, cell-wall composition was fairly similar in both types of cane across the growing cycle. Among main cell-wall components, maximum crystalline cellulose and matrix polysaccharides contents were observed at tillering and late ripening, respectively. Lignin concentrated towards upper internode positions and advanced developmental stages. Saccharification potential augmented towards apical internodes and early developmental stages, and negatively correlated to lignin and xylose contents. The energy-cane hybrid showed lower number of vascular bundles and metaxylem diameter and its lignin deposition was more extended towards the parenchymal tissue, when compared to the commercial sugarcane throughout the growth cycle. Taken together, these findings demonstrate that developmental stage and internode position largely affect cell-wall composition and its recalcitrance to enzymatic degradation. The use of sugarcane/energy-cane lignocellulose from early developmental stages could be beneficial for the second generation ethanol production. Novel management practices for that usage should consider economic, social and environmental sustainability standards under a sugar/ethanol production scheme.

Qualitative Analysis of Polyphenols in Glycerol Plant Extracts Using Untargeted Metabolomics.

Glycerol is a reliable solvent for extracting polyphenols from food and waste products. There has been an increase in the application of glycerol over benchmark alcoholic solvents such as ethanol and methanol for natural product generation because of its non-toxic nature and high extraction efficiency. However, plant extracts containing a high glycerol concentration are unsuitable for mass spectrometry-based investigation utilising electrospray ionization, inhibiting the ability to analyse compounds of interest. In this investigation, a solid phase extraction protocol is outlined for removing glycerol from plant extracts containing a high concentration of glycerol and their subsequent analysis of polyphenols using ultra-performance liquid chromatography coupled with quadrupole time of flight tandem mass spectrometry. Using this method, glycerol-based extracts of Queen Garnet Plum (Prunus salicina) were investigated and compared to ethanolic extracts. Anthocyanins and flavonoids in high abundance were found in both glycerol and ethanol extracts. The polyphenol metabolome of Queen Garnet Plum was 53% polyphenol glycoside derivatives and 47% polyphenols in their aglycone forms. Furthermore, 56% of the flavonoid derivates were found to be flavonoid glycosides, and 44% were flavonoid aglycones. In addition, two flavonoid glycosides not previously found in Queen Garnet Plum were putatively identified: Quercetin-3-O-xyloside and Quercetin-3-O-rhamnoside.

Characterization of a New Glucose-Tolerant GH1 β-Glycosidase from Aspergillus fumigatus with Transglycosylation Activity.

Concern over environmental impacts has spurred many efforts to replace fossil fuels with biofuels such as ethanol. However, for this to be possible, it is necessary to invest in other production technologies, such as second generation (2G) ethanol, in order to raise the levels of this product and meet the growing demand. Currently, this type of production is not yet economically feasible, due to the high costs of the enzyme cocktails used in saccharification stage of lignocellulosic biomass. In order to optimize these cocktails, the search for enzymes with superior activities has been the goal of several research groups. For this end, we have characterized the new β-glycosidase AfBgl1.3 from A. fumigatus after expression and purification in Pichia pastoris X-33. Structural analysis by circular dichroism revealed that increasing temperature destructured the enzyme; the apparent Tm value was 48.5 °C. The percentages of α-helix (36.3%) and β-sheet (12.4%) secondary structures at 25 °C were predicted. Biochemical characterization suggested that the optimal conditions for AfBgl1.3 were pH 6.0 and temperature of 40 °C. At 30 and 40 °C, the enzyme was stable and retained about 90% and 50% of its activity, respectively, after pre-incubation for 24 h. In addition, the enzyme was highly stable at pH between 5 and 8, retaining over 65% of its activity after pre-incubation for 48 h. AfBgl1.3 co-stimulation with 50-250 mM glucose enhanced its specific activity by 1.4-fold and revealed its high tolerance to glucose (IC50 = 2042 mM). The enzyme was active toward the substrates salicin (495.0 ± 49.0 U mg-1), pNPG (340.5 ± 18.6 U mg-1), cellobiose (89.3 ± 5.1 U mg-1), and lactose (45.1 ± 0.5 U mg-1), so it had broad specificity. The Vmax values were 656.0 ± 17.5, 706.5 ± 23.8, and 132.6 ± 7.1 U mg-1 toward p-nitrophenyl-β-D-glucopyranoside (pNPG), D-(-)-salicin, and cellobiose, respectively. AfBgl1.3 displayed transglycosylation activity, forming cellotriose from cellobiose. The addition of AfBgl1.3 as a supplement at 0.9 FPU/g of cocktail Celluclast® 1.5L increased carboxymethyl cellulose (CMC) conversion to reducing sugars (g L-1) by about 26% after 12 h. Moreover, AfBgl1.3 acted synergistically with other Aspergillus fumigatus cellulases already characterized by our research group-CMC and sugarcane delignified bagasse were degraded, releasing more reducing sugars compared to the control. These results are important in the search for new cellulases and in the optimization of enzyme cocktails for saccharification.

Sweet Sorghum And Sweet Pearl Millet Carbohydrate Extraction and Preservation for Bioethanol Production and Bagasse Valorization: A Review

Highlights Sweet sorghum and sweet pearl millet are interesting feedstocks for ethanol production. Biomass and juice storage are key steps for carbohydrate preservation. Produced bagasse can be valorized in many ways, including as silage or for cellulosic ethanol production. Abstract. Sweet sorghum and sweet pearl millet have been considered as potential energy crops. They have many advantages in terms of ethanol production compared to corn and sugarcane, such as lower requirements for water and fertilizers, higher tolerance to drought, and lower competition with the food sector. Sweet sorghum and sweet pearl millet stems are rich in water-soluble carbohydrates (WSC) (sucrose, fructose, and glucose), and their biomass has to be crushed for juice extraction. However, the extraction efficiency of WSC varied widely depending on the press type used and the parameters considered during the pressing process (stripping stems from leaves or not, compressive force magnitude, smooth or grooved press rollers, number of times of biomass pressing, etc.). WSCs are easily degradable, causing technical challenges related to crop handling before pressing and juice storage thereafter. Some studies focused on stem preserving methods, whereas others dealt with extending the shelf life of the juice. To make the use of sweet sorghum and sweet pearl millet as energy crops more profitable, the bagasse (residue) generated from biomass pressing can be valorized in different ways, mainly as silage or for second generation ethanol production. The objective of this review was to assess the efficiency of different presses used for juice extraction and discuss various methods tested for WSC conservation from deterioration as well as possible bagasse valorization. Keywords: Bagasse, Carbohydrates, Ethanol, Press, Sweet pearl millet, Sweet sorghum.

Metaproteomic Analysis of the Anaerobic Community Involved in the Co-Digestion of Residues from Sugarcane Ethanol Production for Biogas Generation

The proteomics analysis could contribute to better understand about metabolic pathways in anaerobic digestion community because it still as a “black-box” process. This study aimed to analyze the proteins of the anaerobic co-digestion performed in reactors containing residues from the first and second generation ethanol production. Metaproteomics analysis was carried out for three types of samples: anaerobic sludge without substrate (SI), semi-continuous stirred reactor (s-CSTR) with co-digestion of filter cake, vinasse, and deacetylation liquor (R-CoAD) and s-CSTR with co-digestion of these aforementioned residues adding Fe3O4 nanoparticles (R-NP). The R-CoAD reactor achieved 234 NmLCH4 gVS−1 and 65% of CH4 in the biogas, while the R-NP reactor reached 2800 NmLCH4 gVS−1 and 80% of CH4. The main proteins found were enolase, xylose isomerase, pyruvate phosphate dikinase, with different proportion in each sample, indicating some change in pathways. However, according to those identified proteins, the main metabolic routes involved in the co-digestion was the syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis, with the CH4 production occurring preferentially via CO2 reduction. These findings contributed to unravel the anaerobic co-digestion at a micromolecular level, and may select a more appropriate inoculum for biogas production according to that residue, reducing reaction time and increasing productivity.

Homo- and heterofermentative lactobacilli are distinctly affected by furanic compounds.

Second generation (2G) ethanol is produced using lignocellulosic biomass. However, the pre-treatment processes generate a variety of molecules (furanic compounds, phenolic compounds, and organic acids) that act as inhibitors of microbial metabolism, and thus, reduce the efficiency of the fermentation step in this process. In this context, the present study aimed to investigate the effect of furanic compounds on the physiology of lactic acid bacteria (LAB) strains that are potential contaminants in ethanol production. Homofermentative and heterofermentative strains of laboratory LAB, and isolated from first generation ethanol fermentation, were used. LAB strains were challenged to grow in the presence of furfural and 5-hydroxymethylfurfural (HMF). We determined that the effect of HMF and furfural on the growth rate of LAB is dependent on the metabolic type, and the growth kinetics in the presence of these compounds is enhanced for heterofermentative LAB, whereas they are inhibitory to homofermentative LAB. Sugar consumption and product formation were also enhanced in the presence of furanic compounds for heterofermentative LAB, who displayed effective depletion kinetics when compared to the homofermentative LAB. Homo- and heterofermentative LAB are affected differently by furanic compounds, in a way that the latter type is more resistant to the toxic effects of these inhibitors. This knowledge is important to understand the potential effects of bacterial contamination in 2G bioprocesses.

Transforming second-generation ethanol production waste into sustainable enzymatic cosmetic inputs

Agro-industrial residues were used as a successful, cheap and renewable substrate, capable of increasing activity of ligninolytic enzymes for further use in melanin degradation assays to develop inputs for the treatment of skin hyperpigmentation. The analysis of melanin degradation was performed in a quantitative and qualitative way. The enzymatic crude broth extract, rich in laccases , produced by Marasmiellus palmivorus VE111 in medium formulated with lignocellulosic residues of Araucaria angustifolia subjected to hydrolysis and alcoholic fermentation , degraded almost 33% of the melanin content and enzymatic crude broth extract produced by Pycnoporus sanguineus PR_32 degraded 13%, in just 8 h, using vanillin as a mediator. Proton 2D NMR spectra show melanin changes after laccase treatment. This work has provided an insight for the development of ecofriendly, sustainable and innovative cosmetics to deal with skin hyperpigmentation. • By-products from 2nd generation ethanol production act as inducer to laccases activity. • Vanillin can be used as a safe redox mediator for laccase activity in cosmetics. • Laccase from Marasmiellus palmivorus VE111 can degrade melanin. • HSQC 2D NMR data shows changes in melanin after enzymatic treatment.

Evaluation of the production of second generation Ethanol by co-culture of saccharomyces cerevisiae and pachysolen tannophilus immobilized in Sodium alginate

The production of an alternative form of fuel that replaces fossil fuels has been increasingly studied due to the environmental impacts generated by its excessive use, as well as the depletion of these fossil energy sources. Ethanol obtained from the crushing of sugar cane has been used as a substitute for these fuels, mainly in the automotive area. However, alternative sources are being studied to produce the so called second generation bioethanol. This would avoid competition for food producing agricultural areas and agroindustrial waste is a great source for obtaining it. In general, these residues are not always completely reused and are disposed of inappropriately in the environment, becoming contaminants. Therefore, the use of agroindustrial waste can become a renewable source of energy, in addition to reducing environmental impacts. The objective of this work is to produce second generation bioethanol as an alternative to the one currently used, using the rice husk hydrolyzate by the consortium formed by Saccharomyces cerevisiae and Pachysolen tannophilus. For this, an acid hydrolysis was performed with 2% sulfuric acid during 10 minutes of heating in an autoclave, after which the hydrolyzate was detoxified with the use of activated carbon. The crude and detoxified hydrolysates were used as a substrate for the fermentation medium with an initial concentration of 50 mg/mL of reducing sugars. The fermentation process with the use of both yeasts in the crude hydrolyzate medium, in the detoxified medium and in a synthetic medium composed of glucose, was carried out for 24 h, 30º C, 0 rpm and pH 6.5. The best results for the ethanol production of Saccharomyces cerevisiae was the synthetic medium with 20.6 mg/mL. For the yeast Pachysolen tannophilus, its highest production was in a synthetic medium with 11.67 mg/mL. The intercropping of the two yeasts proved to be efficient with a greater ethanol production reaching 21.5 mg/mL, the hydrolyzed and detoxified media showed great potential for ethanol production both in intercropping and in monoculture.

A sustainable process for co-production of xylooligosaccharides and ethanol from alkali treated sugarcane bagasse: A strategy towards waste management

Present study aims at sustainable utilization of sugarcane bagasse (SCB) for production of valuable prebiotic xylooligosaccharides (XOS) along with second generation ethanol. Fractionation of SCB into hemicellulose rich liquid fraction and cellulose rich solid residue was achieved using alkaline treatment. Carbohydrate rich precipitate obtained from liquid fraction was utilized for XOS production using inhouse produced endoxylanase. XOS production from SCB xylan was optimized by employing response surface methodology. Under optimized conditions, maximum XOS yield was 227.72 mg/g of carbohydrate rich precipitates. The solid residue obtained after alkaline pretreatment was used for ethanol fermentation by prehydrolysis and simultaneous saccharification and fermentation (P-SSF) process using cellulolytic enzyme cocktail and Saccharomyces cerevisiae SM1. Maximum ethanol concentration, productivity and yield were 79.76 ± 0.16 g/L, 0.83 g/L/h and 69.38%, respectively by employing P-SSF process. Based on the experimental data it can be predicted that bioconversion of 100 g raw SCB can yield 6.26 g of XOS (DP 2-DP 5), 15.95 g ethanol and 1.44 g of xylitol. Present investigation reports an integrated process for effective bioconversion of SCB into value added products by maximum utilization of cellulosic and hemicellulosic fractions simultaneously using indigenously produced fungal enzymes.

Price volatility spillovers between Canadian and US, agricultural and fuel markets

A good understanding of risk transmission between agricultural and energy industries can be important to the sustainability of agriculture and the development of renewable energy industries. Literature has shown that the volatility of international agricultural and energy markets has mutual influences, and that these influences may change over time and space. This analysis adds value to the literature by identifying whether, and to what extent, price and volatility spillovers exist between the Canadian wheat market and US corn and energy markets (i.e. gasoline and ethanol). Though many studies have investigated pass-through between corn and energy markets, the addition of wheat markets in Canada is of interest because of the increasing use of wheat in producing first generation ethanol, and the potential for second generation ethanol that could use Canadian wheat straw as a feedstock. Our investigation adopts a modified vector error-correction model with a multivariate generalized autoregressive conditional heteroskedasticity framework. Key results include: (1) wheat and ethanol prices adjust to a deviation in the equilibrium relationship with corn and gasoline prices; (2) price volatility in the wheat market is only affected by its own shocks, not by the spillovers from US corn, ethanol or gasoline markets; (3) corn price volatility is not affected by shocks to wheat, ethanol, or gasoline markets. However, corn price volatility is largely affected by the covariance between wheat and corn. This information is useful for developing business strategies, as well as for policy makers interested in the development of a second-generation wheat straw-based ethanol industry in Canada. Our results also improve the understanding of impacts of US energy policies on Canada.

Supply chain of biorefineries based on Coffee Cut-Stems: Colombian case

The viability of bio-based processes is linked to key factors, such as technical, economic, environmental, social, experimental and logistic performance. The suitable synergy between these factors allows achieving a sustainable process. In this sense, two biorefineries based on Coffee Cut-Stems (CCS), which have already been assessed from the five perspectives, are analyzed in the context of a supply chain (SC) that considers the feedstock availability and main products demand. The SC is located in Colombia according to different targets, such as production of second-generation ethanol and biomass for electricity generation. The results obtained are organized in five cases of study. As a result, the subregions, such as “Antioquia_Suroeste”, “Huila_Sur”, “Santander”, “Tolima_Sur” and “Quindio” are more suitable to install a biorefinery. The larger the amount of available feedstock in a subregion, the lower the transportation costs. However, regions with limited availability must be close to others with resources for a biorefinery to be installed. In remote zones and those with zero feedstock availability, the possibility that a biorefinery exists is low. It is possible to substitute 40% of the ethanol demand using CSS remaining with an investment of 77.88 M-USD. However, only 0.43% of the electricity demand can be achieved using residues.

Integration of first- and second-generation ethanol production: Evaluation of a mathematical model to describe sucrose and xylose co-fermentation by recombinant Saccharomyces cerevisiae

The use of hydrolysates of lignocellulosic materials and microbial platforms present themselves as viable alternatives to the current system energy. The metabolization of the different carbohydrates present in the hydrolysates by yeasts is a process bottleneck. Genetically modified yeasts can ferment different carbohydrates. Furthermore, mathematical modelling helps to understand the dynamics and interactions during the process and predicts other conditions. The performance of the recombinant yeast Saccharomyces cerevisiae was evaluated for co-fermentation in different carbohydrates proportions (C12 – C5, 30.67 ± 0.71–70.17 ± 2.64%) and initial cell densities (0.28 ± 0.07, 10.95 ± 0.250 and 30.25 ± 0.25 g·L−1) using an unstructured – unsegregated kinetic model aiming the integration of first-and-second generation ethanol production. The method to obtain confidence region, the parameter's correlation, and the convergence of the parameters followed a pipeline previously developed by our researcher group. The mathematical models described the fermentations, and μGlu,max, μFru,max, πGlu,max, πXyl,max, ρXyl,max and ψXyl,max were the parameters with the slightest variation during the convergence process. Also, it was identified that the yeast consumed glucose and fructose simultaneously to form cell, however μGlu,max was higher relative to μFru,max in all cases (0.1909, 0.0341, 0.1815 h−1 for μGlu,max, and 1.00E-5, 2.86E-05, 2.44E-05 h−1 for μFru,max). On the other hand, πGlu,max and πFru,max were higher relative to πXyl,max.

Extraction of furfural inhibitor from biomass hydrolysate of rice husk

The production of second generation ethanol (E2G) has proven to be an alternative to non-renewable fuels, through transforming lignocellulosic waste into renewable fuel. In turn, rice husk has great potential due to its availability and composition. The conversion of lignocellulosic biomass to biofuel comprises a fundamental pre-treatment step, however, at this stage, the formation of degradation products (inhibitory compounds) occurs, among them, furfural, which cause negative effects on the viability of fermentative cells, making the production of E2G unfeasible. Given the above, the objective of this work was to remove the furfural inhibitor present in the lignocellulosic broth after the pre-treatment process, using oleic acid, through liquid-liquid extraction. The quantification of total reducing sugars in the hydrolyzate did not show significant variation between the pre and post extraction stages. Regarding the furfural inhibitor, in tests performed with a solution made in the laboratory, removal of up to 62.30% was obtained when the initial concentration was 5.00 g.L-1. With respect to the tests with the hydrolyzate from the rice husk pre-treatment, the maximum removal observed was 10.40%, but the initial concentration of furfural was 1.64 g.L-1. The results obtained indicate the possibility of using oleic acid as an extracting agent of the furfural inhibitor from lignocellulosic hydrolysates.

Investigation of sugar extraction capability from rice paddy straw for potential use of bioethanol production towards energy security

ABSTRACT Over the past decades, bioethanol has emerged as an important alternative to fossil fuels. Moreover, bioethanol reduces the overall CO2 emission (greenhouse gas emission) compared to petroleum fuels as these are plant derived. Bioethanol will also provide energy security in the regions/countries where fossil fuels are in scarcity. Bioethanol is produced widely using edible resources like sugarcane, rice, and corn grains, etc. It has been a concern that the edible sources may create problem in food security. With these concerns, non-edible feedstock such as rice paddy straw and corn straw-based lignocellulose biomass has drawn tremendous attention toward the second generation (2G) ethanol production as a sustainable bioenergy source for internal combustion (IC) engine. Cellulose and hemicellulose contents are higher in biomass, which can be used as a source of reducing sugar to produce ethanol. Higher concentration of lignin fibers in the non-edible raw materials makes the sugar extraction challenging. The use of acidic medium such as hydrochloric acid (HCl) and sulfuric acid (H2SO4) makes it easier to break down the lignin fibers and enhances the sugar extraction. In this work, varying concentrations of HCl and H2SO4 were used to examine and maximize the sugar extraction from rice paddy straw. HCl was observed to provide higher yielding of sugar compared to H2SO4. Furthermore, a temperature-variation study (during the hydrolysis process) was also performed to evaluate the variation in sugar yielding with 2.0% HCl (v/v).

Visible light active black TiO2 nanostructures and its RGO based nanocomposite for enhanced hydrogen generation and electrochemical potency

Hydrogen is considered to be a sustainable, clean form of energy and a fundamental pillar to combat global warming. Hence, it is necessary to develop an eco – friendly, efficient energy storage device for future generations. Herein, we have developed an effective, vacuum annealing synthetic protocol to prepare black TiO2 (BT), black-nitrogen doped TiO2 (BNT) and RGO composited black TiO2 (BTG) in the presence of ethanol for an efficient photocatalytic hydrogen generation. Change in the optical and electronic properties of black nanocomposites are examined by UV-vis and PL studies. Investigation of FTIR and XPS confirms the reduction of functional groups on the nanocomposites. Meanwhile, low photocatalytic efficiency and capacitance of BNT than expected has been associated with the formation of N-O moiety during the annealing process. Plausible mechanism has been proposed for the low efficiency of BNT to understand the electronic structures of black nanocomposite.