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Toxin-tolerant yeast strains that produce high ethanol yield are inevitably requited for cost-effective ethanol production from undetoxified steam-exploded corn stover. To verify the ethanol-producing capability of the strain Saccharomyces cerevisiae Y5 developed in our laboratory, simultaneous saccharification and fermentation of undetoxified steam-exploded corn stover with solids loading of 30 % ( w/ v) was carried out in different-sized flasks and an automatic fermenter. After 96 h, the ethanol concentrations had reached 50, 47.8, and 47.5 g/L in the 100-mL flask, 3,000-mL flask, and 5-L automatic fermenter, respectively. The experiment demonstrates that ethanol production from undetoxified steam-exploded corn stover using S. cerevisiae Y5 simplifies the production process, reduces equipment investment and water consumption, and generates highly concentrated ethanol. S. cerevisiae Y5 is a promising strain that could reduce the cost of producing ethanol from steam-exploded corn stover. [ABSTRACT FROM AUTHOR]

The unwashed alkali-treated lignocellulose can be directly enzymatically hydrolyzed and fermented via pH adjustment with acids. The use of acids would give a burden on production cost. Furfural residue (FR) which is the acidic solid waste from lignocellulose-derived furfural production process was employed in this study as a pH regulator. The corn cob-derived FR was used to adjust the pH value of alkali-treated corn stover (PCS) to 4.8 for enzymatic hydrolysis and ethanol fermentation. The unwashed PCS adjusted by FR got higher enzymatic hydrolysis efficiency (EHE) than the washed PCS samples. Meanwhile, the mixing of PCS and FR had a synergistic effect on the EHE of PCS. The fermentation of enzymatic hydrolysate from unwashed PCS-FR mixture at 20% solid concentration could attain ethanol production of 26.54 ± 0.02 mg/mL with a yield of 89.53 ± 0.08%. This work created a novel recycling way of FR as a pH regulator for improving the bioconversion of alkali-treated lignocellulose. It also provided a novel clue for the valuable valorization of wastes from corn production. [ABSTRACT FROM AUTHOR]

Integration of first- and second-generation ethanol production is a strategy to strengthen the economic viability of individual processes and the overall viability of biorefineries. The sharing of storage, fermentation, distillation, and energy infrastructure is an important advantage of process integration. Furthermore, integration contributes to the utilization and valorization of all products and by-products, which is key to the success of a biorefinery. Selenium-enriched yeasts have aroused great interest as mineral sources for their high bioavailability and low toxicity. This study aimed to evaluate the effect of selenium on yeast cell growth and production of ethanol and xylitol from hydrolyzed hemicellulosic biomass and sugarcane molasses. For this, cultures were enriched with sodium selenite at concentrations ranging from 1 to 20 mg/L. A miniaturization protocol was used to simulate biorefinery production of first-generation ethanol. The yeasts Spathaspora passalidarum and Kluyveromyces marxianus were able to grow under all tested conditions. The maximum specific growth rate, lag time, and biomass production were influenced by selenium concentration. S. passalidarum provided the best fermentation results, with 77.9% ethanol fermentation efficiency, 24.7% xylitol fermentation efficiency, 0.25 g/g glycerol yield, and 3.3 g cell biomass production. K. marxianus accumulated 122.92 mg selenium/kg biomass, whereas S. passalidarum had a maximum accumulation of 37.40 mg selenium/kg biomass. Yeasts also accumulated other minerals. Therefore, S. passalidarum has great potential as a biological platform and the results of this work could be useful for supporting the development of integrated processes to produce ethanol-, xylitol-, glycerol-, and selenium-enriched yeast products. [ABSTRACT FROM AUTHOR]

Marine algae are promising third-generation feedstocks for bioethanol production as they are fast growing, require minimal inputs, and do not compete for land. However, marine algae have complex cell walls which necessitate pretreatment prior to fermentation, and this represents a major component of the cost of bioethanol production. Standard pretreatment processes using acids are costly and generate hazardous waste streams. This study aims to develop an economic and environmentally friendly pretreatment process using ozonolysis for the marine algae Kappaphycus alvarezii and Gelidium amansii. Acid and ozone pretreatments were compared across the pretreatment, enzyme hydrolysis, and fermentation stages of bioethanol production. Acid pretreatment outperformed ozonolysis over the pretreatment and enzyme hydrolysis stages. However, it also generated as by-products the compounds 5-hydroxymethyl furfural (5-HMF) and levulinic acid (LA), which inhibited ethanol fermentation and reduced the efficiency of the process overall. Ozone pretreatment did not produce these inhibitory compounds, and as such outperformed acid pretreatment across the process as a whole. These results indicate the potential of ozonolysis as an economic and environmentally friendly pretreatment for the production of bioethanol from marine algae. [ABSTRACT FROM AUTHOR]

Cassava (Manihot esculenta) is a woody bush extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates. The main residue from its cultivation is the cassava stalk, which is normally used as soil fertilizer or in culture propagation. The main goal of this paper is to evaluate two routes (biochemical and thermochemical) for bioenergy production (ethanol and synthesis gas—electricity) using cassava stalk as raw material. A detailed techno-economic and energy assessment is carried out based on the simulation approach of both conversion routes to determine the production costs of main products and the overall energy efficiency of the processes. The electricity production costs vary from 0.008 to 0.037 USD/MJ, whereas the ethanol production costs range from 1.11 to 2.02 USD/L (including subsidies). The change in the production costs was observed due to the assumptions of the model, e.g., cassava stalk, transportation, and enzyme costs. The overall energy efficiency of the gasification and ethanol fermentation was 68.7 and 25.1%, respectively. [ABSTRACT FROM AUTHOR]

Spathaspora passalidarum is a naturally pentose-fermenting yeast with the potential to be applied for biotransformation of sugars from lignocellulosic biomasses. Despite being mostly investigated for ethanol production from sugarcane bagasse sugars (mainly xylose and glucose), this microorganism is also capable of producing high xylitol concentrations as a by-product of the ethanol fermentation. The integration of ethanol and xylitol production can improve the economic viability of the process due to the lower sale price of ethanol and the higher added-value of xylitol, a sucrose-substitute sugar with healthier properties. Considering the metabolic pathways interaction from glucose and xylose, it is essential to understand the effect of different glucose and xylose concentrations in the production of ethanol and xylitol by S. passalidarum. In this way, a simultaneous production of both products for the development of an integrated platform for food and chemical and biofuel industries can be accessed. Yeast biomass can also be recovered and applied as a protein source. Therefore, in this study, the fermentative performance of S. passalidarum was investigated in batch fermentations with different xylose and glucose concentrations, using synthetic substrate. The ATP levels and the enzymatic activities of xylose reductase (XR), xylitol dehydrogenase (XDH), and alcohol dehydrogenase (ADH) were also determined for each condition. The results indicated that low amounts of glucose (35%) were necessary to promote a higher xylitol production (10.58 ± 0.29 g/L) without losses on ethanol yield (78.99 ± 4.41%), being the most interesting condition for simultaneous formation of both products. [ABSTRACT FROM AUTHOR]

High quantity of potato wastage from the process and cold storage facilities in India poses serious disposal issues and loss of carbonaceous starches. Waste potato biomass has the potential estimated to be 6.3–7.2 MMT of fermentable sugar equivalent per annum. This study evaluates ethanol and yeast lipid production feasibility using the non-marketable waste potato. For obtaining optimum sugar, the dilute acid hydrolysis was first optimized by one variable at a time (OVAT) approach, and an artificial neural network was formulated to model the hydrolysis process. The optimized variables considered were reaction time, temperature, and acid concentration. The optimum glucose concentration of 55.82 g/L was utilized as a carbon source for ethanol and yeast lipid production by Saccharomyces cerevisiae and Rhodotorula mucilaginosa IIPL32. Ethanol and lipid concentrations of 33.74 and 2.6 g/L were obtained, respectively. The carbon balance of the two processes showed that the flow of net carbon concerning the feedstock was more towards the waste streams. The finding, therefore, proposes that with proper supply chain management, this fermentable carbon can be destined as a co-feed in any existing distillery, or even a separate decentralized system can be envisaged. This study thus investigates the stepwise carbon mapping from the feedstock to the product leading to a cradle to gate carbon flow assessment to understand the net carbon sustainability. [ABSTRACT FROM AUTHOR]

Effective pretreatment is essential for successfully utilizing renewable resources such as lignocellulosic biomass in the production of bioethanol. In this study, ternary deep eutectic solvents (DESs), namely choline chloride/lactic acid/glycerol (ChCl/LA/Gly), choline chloride/oxalic acid/glycerol (ChCl/OA/Gly), choline chloride/lactic acid/ethylene glycol (ChCl/LA/EG), and choline chloride/oxalic acid/ethylene glycol (ChCl/OA/EG) were prepared and employed for the pretreatment of cellulose-rich Napier grass (NG). Post treatment, the NG hydrolysate was subjected to enzymatic saccharification followed by ethanol fermentation. The results showed effective delignification of NG after treatment with the prepared ternary DESs, with ChCl/LA/EG removing a maximum of 92.89% lignin. The efficiency of the prepared DESs is attributed to their low densities, pH, and viscosity. Enzymatic saccharification of ChCl/LA/EG-treated NG resulted in a 1.68 fold increase in reducing sugar yield compared to that of untreated NG. All pretreated NG produced more bioethanol via a separate hydrolysis and fermentation (SHF) process than untreated NG after Saccharomyces cerevisiae fermentation. A maximum of 0.37 g bioethanol/g of biomass was obtained from the one-pot process using ChCl/LA/Gly pretreatment. FTIR and XRD analyses of untreated and pretreated NG corroborated the efficacy of the ternary DESs on cellulose recovery and delignification. Also, enzymatic and microbial inhibition studies on the prepared DESs show their potential to be employed in a one-pot process for biorefinery. The results of the present investigation show the potential of utilizing eco-friendly DESs and renewable resources for the production of bioethanol, a viable option to fossil fuels. [ABSTRACT FROM AUTHOR]

Biofuels, especially ethanol, have gained immense popularity in the global energy sector, driven by a significant increase in demand. Ethanol production using agroindustrial residues reduces costs and can provide a destination for these residues that are generally wasted. In this context, the cashew apple emerges as an attractive and unconventional feedstock for bioethanol production. Although the technology to obtain ethanol from cashew apple juice is present in several studies, the key elements that determine its economic feasibility have never been defined. Then, this study aimed to present the first techno-economic assessment of ethanol production from cashew apple juice. Two industrial full-detailed scenarios were proposed based on the application of the obtained ethanol, where in scenario I, 2.1 × 106 liters of ethanol are produced for combustion purposes (94% w/w), while in scenario II, 2.8 × 106 liters of ethanol are produced for antiseptic purposes (70% w/w). The yields calculated in the proposed scenarios I and II were 66.5 L/ton and 88.9 L/ton, respectively, values comparable with those found in the literature using sugar cane and sweet sorghum as feedstocks. Then, the production of ethanol from cashew apple juice proved technically feasible. Economic sensibility analysis showed that both proposed scenarios are economically viable, as long as the cashew apple acquisition cost is at most 17.2 US$/ton for the scenario I and 28.1 US$/ton for scenario II. The raw material cost was the most crucial parameter to impact the economic analysis. In conclusion, the proposed biorefinery returned promising results, and it can consolidate a new raw material for ethanol production, provided that idle capacity is reduced and heat generation from cashew apple bagasse is optimized. [ABSTRACT FROM AUTHOR]

The present study analyses the impact of biological pretreatment of rice straw on the degradation of recalcitrant lignin vis-à-vis chemical pretreatment. A fungal consortium was set up with Phanerochaete chrysosporium and Pleurotus ostreatus and the ligninolytic enzyme produced by it was used for biological pretreatment. The chemical pretreatment was achieved using a sequential treatment with H2SO4 followed by NaOH. The biological pretreatment showed promising results on par with the robust chemical pretreatment method. The biological and chemical pretreatment of rice straw resulted in 80.9% and 82.6% delignification, respectively. The saccharification of pretreated straw with 30 FPU/g of commercial cellulase yielded 49.2 g/100 g dry substrate and 56.6 g/100 g dry substrate reducing sugars from biological and chemical pretreated rice straw, respectively. The sequential fermentation under separate hydrolysis and fermentation (SHF) conditions with 10% (v/v) Saccharomyces cerevisiae and Pachysolen tannophilus achieved a maximum ethanol concentration of 9.25 g/L (fermentation efficiency; 73.8%) and 12.0 g/L (fermentation efficiency; 74.2%) from biological and chemical pretreated straw, respectively. The cost for the bioethanol production from 1.0 kg rice straw was calculated to be 31.92 Rs while it is 36.45 Rs for chemical pretreatment. [ABSTRACT FROM AUTHOR]

In the present study, the OFMSW was utilized for ethanol and methane production in a two-stage process. First, the OFMSW was fermented by adjusting different levels of total solids (10%, 20%, and 29%) and a yeast dose (6, 12, and 24 g/kgOFMSW) for bioaugmentation with Saccharomyces cerevisiae. A control treatment without bioaugmentation was used for benchmarking. In the self-fermentation of the OFMSW with its indigenous microbiota, lactic acid was mainly produced, followed by ethanol and acetic acid, where a maximum ethanol production of 113 ± 2 gCOD/kgTS, corresponding to 10.8 ± 0.4 g/L, at 20% of total solids was observed. The results showed that in all treatments with bioaugmentation, regardless of the content of total solids, the main metabolites were ethanol, lactic acid, and acetic acid, which represented more than 95% of the total metabolites. The ethanol concentration was increased by increasing the total solids and the yeast dose. The highest ethanol production was 407 ± 3 gCOD/kgTS with the bioaugmentation of 24 g/kgOFMSW and 20% of total solids, whereas the maximum ethanol concentration of 43.4 ± 0.1 g/L was obtained with bioaugmentation of 12 g/kgOFMSW and 29%. The methane potential of the raw OFMSW was 329 ± 5 NL-CH4/kgVS, whereas the solid digestates resulting from the fermentation exhibited similar or even higher methane yields than raw OFMSW. A maximum methane potential of 464 ± 2 NL-CH4/kgVS from the solid digestate obtained after fermentation of the OFMSW with bioaugmentation of 6 g/kgOFMSW of yeast and 10% of total solids was achieved. Thus, large amounts of ethanol and methane were achieved without the application of pretreatment and/or enzymatic hydrolysis, which implies a low-cost alternative for the production of biofuels. [ABSTRACT FROM AUTHOR]

Sweet sorghum and sweet pearl millet are considered promising alternative feedstocks for bioethanol production. Water soluble carbohydrate (WSC) extraction from the stems for first generation ethanol production is practically well mastered. However, structural carbohydrate (SC) release from the bagasse for cellulosic ethanol production still needs to be more understood and improved, especially for sweet pearl millet. In this study, the effects of two bagasse particle sizes (4.5–9 mm and 1 mm) and two pretreatment solutions (NaOH and H2SO4) at two concentrations (1% and 3%) on the release of SC from sweet sorghum and sweet pearl millet bagasse were investigated. After the extraction of juice, the bagasse pretreatment was carried out at 121 °C for 60 min followed by an enzymatic saccharification. Results indicated that hemicellulose and lignin were better solubilized when the bagasse from both crops was pretreated with NaOH than with H2SO4. The highest glucose concentration (320 and 249 g/kg DM of bagasse for sweet sorghum and sweet pearl millet, respectively) was reached after enzymatic saccharification of the bagasse chopped to 4.5–9 mm particle size and pretreated with 3% NaOH. Under these conditions, cellulose saccharification efficiency reached 88% and 73% for sweet sorghum and sweet pearl millet, respectively, while that of hemicellulose saccharification approached 100% for sweet sorghum and reached 90% for sweet pearl millet. Potential first generation ethanol of 80.3 and 60.7 L/kg DM of biomass and cellulosic ethanol of 138.8 and 115 L/kg DM of biomass were estimated for sweet sorghum and sweet pearl millet, respectively. [ABSTRACT FROM AUTHOR]

Eucalyptus sawdust is a forest residue that, through a biorefinery approach, can be used to manufacture value-added products in the pulp and paper industries as well as to produce a biofuel. This study examines the suitability of a sequential thermochemical pretreatment that uses processes and reagents commonly utilized in the pulp and paper industry to separate valuable biomass components from eucalyptus sawdust and increase its enzymatic digestibility for ethanol production. The research strategy was based on a forest biorefinery that can be integrated into an existing industrial plant for the production of cellulose pulp. A combination of alkaline solutions was evaluated to obtain an extract rich in tannins and intended to be used in the formulation of wood adhesives. A second alkaline treatment was used to recover lignin and hemicellulose components and improve cellulose digestibility. The cellulose fraction was fermented using three commercial Saccharomyces cerevisiae yeasts (Thermosacc®, PE-2, and CAT). Different process configurations (separate hydrolysis and fermentation (SHF), pre-saccharification followed by simultaneous saccharification and fermentation (PSSF), and simultaneous saccharification and fermentation (SSF)) at 16% (w/v) solid loading by Thermosacc® yeast were also studied. Thermosacc® yeast enabled higher ethanol production than the other strains but resulted in similar productivity. The two-stage alkaline pretreatment of eucalyptus sawdust was successful in recovering 34 g of tannins, 56 g of xylo-saccharides, 16 g of acetic acid, and 90 g of lignin and produced 152 g of ethanol from 1 kg of dry eucalyptus sawdust. [ABSTRACT FROM AUTHOR]

Overcoming key bottlenecks for 2G ethanol production, such as the most suitable biomass pretreatment, process layout, and appropriate microorganism, is crucial to achieve a technically and economically feasible technology. The consolidated bioprocessing (CBP) is an approach that embodies one single step of enzyme production, biomass hydrolysis, and sugars fermentation. In this work, the CBP using S. cerevisiae AC14, a recombinant strain capable of secreting 7 different lignocellulosic enzymes and ferment xylose and glucose, was investigated in synthetic medium (cellobiose, corncob xylan, glucose, and xylose) and in industrial medium consisting of the solid fraction of hydrothermally pretreated sugarcane bagasse and its liquor. Results obtained were promising, with ethanol productivity of 4.46 g/L/h and complete hydrolysis of cellobiose and corncob xylan. In real industrial medium, 1.86 g/L/h of ethanol was reached, with partial conversion of both solid and liquid fractions. Further strategies to enhance enzymes access to complex substrates can improve process feasibility. [ABSTRACT FROM AUTHOR]

The effects of ultrasonic factors (acoustic power and sonication time) and substrate mixture (tomato waste and cow manure) on the lignocellulosic structure degradability, elimination of feedstock pollutants and solids, and bio-H2 fermentation improvement were studied using the integration of multiple regression modeling and structural equation modeling. Analyses indicated that (i) a mixture of substrates is needed for improving the feedstock quality and bio-H2 fermentation, (ii) highest feedstock solid removal was attained in 0.42 W/mL acoustic power at 15-min sonication time with mixture 75%:25% cow manure/tomato waste, (iii) highest feedstock pollutant removal was obtained in ultrasonic power of 0.34 W/mL at 15 min with higher amounts of tomato waste in the mixtures, (iv) highest lignin removal was achieved for ultrasonic power of 0.42 W/mL at 15 min with higher amounts of cow manure in the mixtures, and (v) highest amount of bio-H2 was produced in ultrasonic power of 0.1 W/mL at 25 min with mixtures 0–25%:75–100% or 75–100%:0–25% cow manure/tomato waste. In proper conditions of pretreatment and substrate mixture, the removal of solid, volatile solid, lignin, cellulose, and hemicellulose contents increased respectively by 3.58%, 17.95%, 57.67%, 24.38%, and 38.7% compared to the control system, leading to a 6% increase in bio-H2 production. [ABSTRACT FROM AUTHOR]

The pre-treatment of lignocellulose material towards cellulosic bioethanol production releases microbial inhibitors that severely limit the fermentation ability of Saccharomyces cerevisiae. This study evaluated to what degree robust xylose-capable strains may improve the fermentability of non-detoxified sugarcane bagasse (SCB) slurries derived from steam explosion (StEX) and further compared this to slurries derived from ammonia fibre expansion (AFEX) pre-treatment. Initial screening in separate hydrolyses and co-fermentation processes using StEx-SCB hydrolysates identified S. cerevisiae TP-1 and CelluXTM4 with higher xylose consumption (≥ 88%) and ethanol concentrations (≥ 50 g/L), and ethanol metabolic yields (≥89% relative to theoretical maximum), even in the presence of approximately 8 g/L of acetic acid. Under industrially relevant pre-hydrolysis simultaneous saccharification and co-fermentation (PSSCF) conditions of high solids loading (15%, w/w) and low enzyme dosage (8 mg protein per gram untreated biomass), the fermentation of StEx-treated SCB whole slurry achieved ethanol yields of 208 and 224 L per Mg raw dry SCB using S. cerevisiae TP-1 and CelluXTM4, respectively. Under the same solids loading and enzyme dosages, the PSSCF of ammonia fibre expansion (AFEXTM) pre-treated SCB achieved ethanol yields of 234 and 251 L per Mg raw dry SCB using TP-1 and CelluXTM4, respectively. The study achieved non-detoxified whole-slurry co-fermentation using StEx pre-treated SCB, with higher ethanol yields than previously reported, by utilising robust xylose-capable strains. The results of this work provide insights into the potential use of inhibitor-tolerant S. cerevisiae strains TP-1 and CelluXTM4 as ethanologens for the fermentation of steam-exploded and undetoxified SCB whole slurries. [ABSTRACT FROM AUTHOR]

In the present work, a new alternative of hydrodynamic cavitation–assisted pretreatment associated with an advanced oxidative process was proposed, together with a new approach to obtain bioproducts in sequential fermentations. Enzymatic hydrolysate of sugarcane bagasse (SCB) was fermented to ethanol by Saccharomyces cerevisiae. After distillation of this alcohol, the obtained vinasse was used to produce xylitol by Candida tropicalis. Influent variables in pretreatment were evaluated by performing experiments according to a statistical design, and, at optimum conditions (ozone flowrate of 10 mg/min, and H2O2 concentration of 0.61%), about 84% and 78% of glucan and xylan hydrolysis yields were obtained in enzymatic hydrolysis, respectively. In the sequential fermentations for ethanol and xylitol production, yield values of 0.41 g/g and 0.55 g/g, respectively, were obtained, with corresponding volumetric productivities of 8.33 g/Lh and 0.64 g/Lh, respectively. The proposed strategy was shown as a promising approach for biorefineries, considering the mild conditions of pretreatment and the possibility of high ethanol production using S. cerevisiae in a fermentation process similar to that one already available in sucro-alcoholic sector, followed by xylitol production in vinasse-based medium. [ABSTRACT FROM AUTHOR]

Reducing the cost of cellulosic ethanol production, especially the use of expensive exogenous cellulose hydrolytic enzymes such as cellulase and β-glucosidase, is a critical challenge and vital for a sustainable advanced biofuel industry. Here, we report a novel ethanologenic yeast strain Clavispora NRRL Y-50464 that produces sufficient innate β-glucosidase enzyme activity for cellulosic ethanol production by simultaneous saccharification and fermentation (SSF). In a bottled SSF, strain Y-50464 produced 40.44 g/L ethanol from pure cellulose within 72 h at a conversion rate of 0.04 g/L/h, applying conventional cellulase without supplementary β-glucosidase. Ethanol conversion from delignified corn stover by Y-50464 showed significantly higher titers and rates at various solids loading levels than that from conventional pretreated corn stover with over 40 to 60 % improved efficiency in a bottled SSF. However, the bottled SSF was inefficient for mixing higher levels of cellulose feedstock and should be replaced by a more suitable experimental apparatus. In a 2-L bioreactor SSF using conventional dilute acid pretreated corn stover, strain Y-50464 produced 32 g/L ethanol from 20 % solids loading at 48 h applying cellulase alone without addition of β-glucosidase. This represented a conversion rate of 0.088 g/L/h, the highest rate so far for cellulosic ethanol production from lignocellulosic materials. Elimination of β-glucosidase in cellulose-to-ethanol fermentation would be expected to reduce cost of cellulose conversion. The robustness, fast growth rate, and the capability of producing both ethanol and β-glucosidase illustrated the potential of strain Y-50464 as a potential candidate biocatalyst for advanced biofuel production from lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Methods to increase the energy density of biofuel feedstock for shipment are important towards improving supply chain efficiency in upstream processes. Towards this end, densified pretreated lignocellulosic biomass was produced using hot-pressing. The effects of fiber hornification induced by hot-pressing on enzymatic digestibilities of lodgepole pine and poplar NE222 wood chips pretreated by sulfite pretreatment to overcome recalcitrance of lignocelluloses (SPORL) were examined. Pretreated wood chips were pressed at 25, 70, 90, 110, and 177 °C. The cellulose accessibilities of the pressed and unpressed substrates were evaluated using water retention value and direct cellulase adsorption measurements. Hot-pressing below 110 °C produced a degree of hornification (DH) below 0.26 and had limited effect on cellulose accessibility and enzymatic digestibility. Hot-pressing at 177 °C produced a DH of 0.86 that substantially hornified the fibers and resulted near zero saccharification. The saccharification results were consistent with cellulose accessibility data. Ethanol fermentation studies at 18 % solids suggest that a pressing below 110 °C is preferred to reduce its effect on biofuel yield. [ABSTRACT FROM AUTHOR]

Tomato pomace, a solid by-product of tomato processing industries, was assessed for the first time as a feedstock for acetone-butanol-ethanol-isopropanol (ABEI) fermentation. After the pretreatment with hydrothermal process and enzymatic hydrolysis of tomato pomace with a 20% solid-to-solvent ratio, a broth containing 44.1 g/L total sugars was obtained (61.0% saccharification yield). Twelve Clostridium strains were compared to find an appropriate microorganism for the transformation of tomato pomace hydrolysate. Four of these strains produced 0.22–5.95 g/L acetone, 5.82–7.00 g/L butanol, 0.17–0.39 g/L ethanol, 0.05–8.28 g/L isopropanol and 11.03–15.07 g/L ABEI. The strain C. beijerinckii DSM 6423 obtained 2.67 g butanol, 2.99 g isopropanol and 5.92 g ABEI from 100 g dry tomato pomace (containing 30.6 g carbohydrates). In addition, another pretreatment was performed with a 30% solid-to-solvent ratio in order to obtain higher sugar concentrations, obtaining a hydrolysate with 85.1 g/L total sugars (66.8% saccharification efficiency), which was employed for bioethanol production by comparing twelve different yeast and bacterial strains. Kluyveromyces marxianus DSM 5422, Saccharomyces cerevisiae Ethanol Red®, S. cerevisiae Hércules and Lachancea thermotolerans DSM 3434 produced 20.1–21.7 g/L ethanol (about 5.21 g ethanol per 100 g dry tomato pomace). According to these results, tomato pomace could be an interesting feedstock for ABEI biorefineries. [ABSTRACT FROM AUTHOR]

Several non-conventional yeasts are emerging as potential candidate with an ability to produce lignocellulosic ethanol along with other biofuels. Capability to effectively ferment a variety of sugars especially, which are released during lignocellulosic biomass degradation, makes Pichia an organism of choice. By utilizing five carbon sugars along with the six carbon sugars, and generating biofuels with high yields, Pichia is a possible complement with conventional yeasts. Recent research has indicated that these yeasts may have the ability to function as an exoelectrogen, generating electrical energy by extracellular electron transfer. The metabolic pathways and the important products and by-products produced in electrochemical bioreactors by using lignocellulosic hydrolysate and the formation of ethanol and other biofuels are reviewed in the present study. Additionally, it emphasizes Pichia's potential to be used as a flexible biocatalyst for the synthesis of value-added compounds and bioremediation in microbial fuel cells. The article further highlights some gaps and possibilities for future engineering and optimization of Pichia strains for large-scale production. [ABSTRACT FROM AUTHOR]

Co-cultivation and effective downstream processing of microalgae and oleaginous yeast are potential strategies to enhance lipid yield. The findings of this work suggest that each cultivable partner should be screened and optimized for the best mutualistic co-cultures. In this case, T. pullulans was found to be the most effective yeast culture with microalgae S. obliquus, C. sorokiniana, and C. protothecoides along with additional cell disruption techniques. Co-cultures of C.protothecoides and T.pullulans had the highest relative lipid yield (RLY) of 68.71%, 59.32%, 55.33%, 53.19%, and 47.3% with sonication, microwave, osmotic shock, freeze-drying, and autoclave, respectively. Sonication was concluded as the best disruption technique with five out of nine co-cultures showing significant lipid enhancement. Even though T. pullulans was the best yeast partner with disruption techniques, co-culture of Y. lipolytica and S.obliquus (RLY 37.11%) produced lipids which was significantly higher than that of their respective monocultures (S. obliquus RLY 23.96%, Y. lipolytica RLY 4.96%) without any disruption process. R. glutinis and Y. lipolytica produced significantly enhanced lipid yield with C.sorokiniana and S. obliquus with sonication (RLY 51.44%) and osmotic shock (RLY 57.70%), respectively. FAME analysis reported that the co-cultures produced higher percentage of total FAME nearly 100% in the case of C. sorokiniana and R. glutinis with high content of saturated fatty acids (SFAs). The presence of biofuel precursors like palmitic acid, linoleic acid, oleic acid, and heptadecanoic acid, confirms their suitability for biofuel production. [ABSTRACT FROM AUTHOR]

The transport sector is responsible for 25% of greenhouse gas emissions, mainly carbon dioxide (CO2). Its emissions are the main driver of the worsening global climate change scenario. Finding feasible options to sequester this greenhouse gas is a great challenge for scientists, governments, and industry. Carbon capture, utilization, and storage (CCUS) are technologies that capture CO2 directly or indirectly by transforming it into other products of interest. In this context, biological CO2 conversion can be performed by photosynthetic microorganisms, such as microalgae and cyanobacteria, producing a wide variety of bio-based added-value products, such as third-generation (3G) bioethanol. However, the main obstacle to the spread of 3G bioethanol is economical, as it is still a recent and little-explored technology, lacking technical and scientific development for its production to become economically viable. Within this perspective, this work presents a patent-based mapping of current technological trends in 3G bioethanol production, which revealed that it is an emerging field with 171 patent deposits since 1979, with a tendency of at least 10 patents published per year in the last 15 years. The main drawbacks industries are focused on remain those from 2G bioethanol production, such as biomass hydrolysis. Therefore, with extensive cooperation between governments, scientists, and industries, it may be a matter of time before 3G bioethanol production becomes a reality. The presented data are expected to contribute to technical knowledge of 3G ethanol production, including the knowledge transfer from the academy to the industrial sector. [ABSTRACT FROM AUTHOR]

Pretreatment is a necessary step to converting lignocellulosic biomass from its native form into a more accessible form for the value-added utilization of its main components. Herein, we developed a one-step acid bleachable pretreatment method using a recyclable acid hydrotrope (p-toluenesulfonic acid, p-TsOH) and chlorate to achieve the fibers bleaching and lignin extraction simultaneously. Under a pretreatment condition of a p-TsOH concentration of 80 wt.%, a pretreatment temperature of 80 °C, and a pretreatment time of 45 min, 84.33% of hemicelluloses and 76.79% of lignin were dissolved out from poplar wood. The obtained dispersed solids with a whiteness of 60.13% can be used for papermaking or ethanol production. The results from quasi-simultaneous enzymatic saccharification and combined fermentation (Q-SSF) of the pretreated substrate indicated that the ethanol concentration and yield reached to 39.30 ± 0.57 g/L and 82.36 ± 1.15%, respectively. According to the results of lignin characterization, the aromatic rings in extracted lignin were opened forming dicarboxylic acids as well as derivatives due to the oxidation effect of chlorate, which is beneficial for its catalytic upgrading and composites preparation. Therefore, this study is important to valorization of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Water hyacinth is a non-edible plant having a severe impact on aquatic ecosystems through native vegetation displacement and lower dissolved oxygen concentration. High cellulose and low lignin content make water hyacinth a potential source for biofuel production. Water hyacinth was subjected to acid pretreatment using organic acids (citric acid (CA) and oxalic acid (OA)) and mineral acid (hydrochloric acid (HA)) to enhance enzymatic saccharification, and ethanol and biogas production. Under optimized pretreatment condition, the reducing sugars released from enzymatic saccharifications of CA-, OA-, and HA-pretreated samples increased by 2.56-, 1.71-, and 1.62-fold, respectively, than untreated sample. Maximum ethanol yield (8.97 g/L) was observed for OA-pretreated (1.68-fold increase) than untreated water hyacinth, whereas CA-pretreated sample produced the highest biogas yield (3421.5 mL) after anaerobic digestion for 45 days. The increase in the yield of ethanol and biogas for OA and CA is attributed to the changes in the hemicellulose and lignin structure. The change in the structural morphology was observed through FTIR characterization of untreated and treated water hyacinth. In addition, the effect of post-washing after pretreatment on fermentation efficiency was evaluated and the result suggested that CA residues had no negative effect on ethanol production. Pretreatment of water hyacinth using organic acids could benefit the biorefineries through the biofuel production and reduction of wastewater generated from this process. [ABSTRACT FROM AUTHOR]

Mixed vegetable and food wastes left from consumption and processing were important uncontrolled sources of greenhouse gas emissions. Biofuel production from mixed vegetable waste is ineffective due to the recalcitrant structure of lignocellulose. In this work, an artificial neural network (ANN) and response surface methodology (RSM) have been used to optimize the process parameters for the pretreatment of mixed vegetable waste by using organic acid (acetic, citric, oxalic acid) and inorganic acid (hydrochloric acid). The study revealed that the maximum reducing sugars yield of 314.1 mg g−1 biomass was obtained from acetic acid-pretreated biomass at a time of 68.32 min, a temperature of 140 °C, and an acid concentration of 10% w/v, which was 1.66 fold higher than the HCl-pretreated sample. The analysis of biomass composition and FTIR suggested that both inorganic acid and organic acid pretreatment removed hemicellulose and lignin from biomass, and subsequently enhanced the cellulase accessibility to biomass during enzymatic saccharification. It was observed that organic acid pretreatment is more effective to remove lignin compared to inorganic acid. The pretreated samples were converted to ethanol, and the maximum yield of 7.60 g L−1 was obtained for the oxalic acid-pretreated sample, which was 2.82 fold higher than the HCl-pretreated biomass. Also, the maximum biogas yield of 110.72 mL g-VS−1 was obtained for citric acid-pretreated biomass, which was fivefold higher than the untreated biomass. Hence, organic acid pretreatment is highly recommended for bioethanol and biogas production from mixed vegetable wastes. [ABSTRACT FROM AUTHOR]