Theoretical Ethanol Yield Research Articles

Impact of crop residue removal on crop production, feedstock quality, and theoretical ethanol production in the Mid‐Atlantic United States

AbstractCellulosic biomass‐to‐bioenergy systems provide fuel, reduce emissions, and offer economic benefits. Corn (Zea mays L.) and wheat (Triticum aestivum L.) residues could be used as feedstocks for biofuel production. However, the impact of residue removal on crop productivity in the Mid‐Atlantic region has not been thoroughly assessed. A trial was conducted to assess crop yield and quality response to different biomass retention rates in grain cropping systems during 2015–2017. Various combinations of corn stover (0–10 Mg ha−1) and wheat straw (0–3 Mg ha−1) were applied in a corn–wheat/soybean [Glycine max (L.) Merr.] rotation in New Kent, VA. In Blacksburg, VA, corn stover (0–20 Mg ha−1) was applied in the continuous corn system. Residues were applied after grain harvest over two production cycles for each system. Residue retention showed no significant impact on grain or crop residue yields or nutrient uptake in either system. Treatment minimally impacted feedstock quality, except wheat straw's sulfur (S) concentration, optimized at around 70% retention in New Kent. Theoretical ethanol potential (TEP) and yield remained unaffected by total residue rates in New Kent. In Blacksburg, over 2 years, a minimum TEP for corn stover corresponded to a retention rate of approximately 30%. A retention rate of more than 30% increased TEP, likely due to improved feedstock quality. Nutrient replacement costs for primary macronutrients and S uptake ranged from $18.3 to $36.9 ha−1 for corn stover and $6.1 to $11.8 ha−1 for wheat straw. Residue harvest or addition did not harm short‐term biomass yield in Virginia's grain‐based cropping systems.

Phenotypic Evaluation of Saccharum spp. Genotypes during the Plant-Cane Crop for Biomass Production in Northcentral Mississippi

Saccharum is relatively new to 33° N latitude. S. spontaneum readily hybridizes with commercial sugarcane (Saccharum spp.) and lends cold tolerance and greater yield to the hybrid progeny, called energycane. Since 2007, there have been numerous new hybrid and backcross energycane genotypes developed but there is a paucity of information about them. Twenty energycane genotypes were tested in the first season of growth from cane propagules (plant cane; PC) against Ho 02-113 (a control) for two site-years in northcentral Mississippi. Grand (exponential) growth continued into October. The prevailing paradigm is that tonnage is what matters. Except for percentage cellulose, all factors tested (dry matter yield, extractable juice volume, °Brix, theoretical ethanol from fermentation, theoretical ethanol from cellulose, and total theoretical ethanol) were greater from the second site-location compared to the first. Dry matter yield (DMY) and total theoretical ethanol yield (TTEY) were moderately correlated. Over the two years of this test only Ho 14-9213 exceeded in mean DMY of Ho 02-113. Sixteen of the 19 test genotypes in this test equaled or exceeded the mean TTEY of Ho 02-113.

Development of a Robust Saccharomyces cerevisiae Strain for Efficient Co-Fermentation of Mixed Sugars and Enhanced Inhibitor Tolerance through Protoplast Fusion.

The economical and efficient commercial production of second-generation bioethanol requires fermentation microorganisms capable of entirely and rapidly utilizing all sugars in lignocellulosic hydrolysates. In this study, we developed a recombinant Saccharomyces cerevisiae strain, BLH510, through protoplast fusion and metabolic engineering to enhance its ability to co-ferment glucose, xylose, cellobiose, and xylooligosaccharides while tolerating various inhibitors commonly found in lignocellulosic hydrolysates. The parental strains, LF1 and BLN26, were selected for their superior glucose/xylose co-fermentation capabilities and inhibitor tolerance, respectively. The fusion strain BLH510 demonstrated efficient utilization of mixed sugars and high ethanol yield under oxygen-limited conditions. Under low inoculum conditions, strain BLH510 could completely consume all four kinds of sugars in the medium within 84 h. The fermentation produced 33.96 g/L ethanol, achieving 84.3% of the theoretical ethanol yield. Despite the challenging presence of mixed inhibitors, BLH510 successfully metabolized all four sugars above after 120 h of fermentation, producing approximately 30 g/L ethanol and reaching 83% of the theoretical yield. Also, strain BLH510 exhibited increased intracellular trehalose content, particularly under conditions with mixed inhibitors, where the intracellular trehalose reached 239.3 mg/g yeast biomass. This elevated trehalose content contributes to the enhanced stress tolerance of BLH510. The study also optimized conditions for protoplast preparation and fusion, balancing high preparation efficiency and satisfactory regeneration efficiency. The results indicate that BLH510 is a promising candidate for industrial second-generation bioethanol production from lignocellulosic biomass, offering improved performance under challenging fermentation conditions. Our work demonstrates the potential of combining protoplast fusion and metabolic engineering to develop superior S. cerevisiae strains for lignocellulosic bioethanol production. This approach can also be extended to develop robust microbial platforms for producing a wide array of lignocellulosic biomass-based biochemicals.

Optimizing Bioethanol (C2H5OH) Yield of Sweet Sorghum Varieties in a Semi-Arid Environment: The Impact of Deheading and Deficit Irrigation

Bioethanol production offers promise in mitigating environmental impacts from ethanol consumption despite water scarcity. This study endeavors to evaluate the nuanced influence of different deheading times (45 days before harvest, 21 days before harvest, and no deheading) along with varying water regimes on select sweet sorghum cultivars (Honey, Willy, MN1500, and Atlas), focusing on yield traits, theoretical ethanol production, and water productivity. Findings underscore the substantial impact of cultivation practices on bioethanol yield. A water deficit ranging from 30% to 70% resulted in a discernible reduction in stalk yields of 17.86% to 18.54% and in sugar yields of 0.2 to 0.31 Mg ha−1, accompanied by a corresponding decline in theoretical ethanol yield of 120.9 to 180.9 L ha−1. Additionally, notable enhancements in Brix and sugar content of 16.32% to 18.42% and 16.81% to 19.03%, respectively, were observed across both seasons. Of particular significance, the Honey variety, subjected to a 30% water deficit and deheading at 21 days before harvest, demonstrated exceptional growth and yield characteristics. These empirical insights furnish valuable guidance for optimizing sweet sorghum cultivation practices, thereby augmenting sustainable bioethanol production and propelling forward the frontier of renewable energy technologies towards a more environmentally sustainable future.

Catalytic action of hydronium-ion in rice straw pretreatment and enhancement of enzymatic hydrolysis and ethanol production

The present investigation will focus on the catalytic effect of hydronium ion during liquid-water/ dilute sulfuric acid/ferric chloride pretreatment (LWP/ SAP/ FCP) on the hydrolysate and pretreated rice straw. The overall pretreatment process has been represented as a sequential catalytic reactions. The temperature range of pretreatment is varied in the range of 140–180 °C and the concentration of dilute sulfuric acid and ferric chloride is 0.1 M. The first order rate constants of xylan and glucan degradation have been determined for LWP/ SAP/ FCP. The maximum xylan and glucan conversion of 96.8% w/wand 31.4%w/w respectively are achieved for FCP at 180 °C. Xylose, glucose, furfural, 5-hydroxymethyl furfural, acetic acid and formic acid appear as the main products for all pretreatments. Only in case of FCP levulinic acid also appears as a hydrolysis product. The thermal characteristics, functional groups, crystallinity, surface morphology of untreated and pretreated rice straw have been evaluated. Among all pretreatment processes under study, the highest values of glucose yield of 78.96% (w/w) using enzymatic hydrolysis and 83.79% of theoretical yield of ethanol using Saccharomyces cerevisiae have been achieved for ferric chloride pretreatment.

Engineered Saccharomyces cerevisiae harbors xylose isomerase and xylose transporter improves co-fermentation of xylose and glucose for ethanol production

Saccharomyces cerevisiae cannot assimilate xylose, second to glucose derived from lignocellulosic biomass. Here, the engineered S. cerevisiae strains INVSc-XI and INVSc-XI/XT were constructed using xylA and Xltr1p to co-utilize xylose and glucose, achieving economic viability and sustainable production of fuels. The xylose utilization rate of INVSc-XI/XT was 2.3-fold higher than that of INVSc-XI, indicating that overexpressing Xltr1p could further enhance xylose utilization. In mixed sugar media, a small amount of glucose enhanced the consumption of xylose by INVSc-XI/XT. Transcriptome analysis showed that glucose increased the upregulation of acetate of coenzyme A synthetase (ACS), alcohol dehydrogenase (ADH), and transketolase (TKL) gene expression in INVSc-XI/XT, further promoting xylose utilization and ethanol yield. The highest ethanol titer of 2.91 g/L with a yield of 0.29 g/g at 96 h by INVSc-XI/XT was 56.9% and 63.0% of the theoretical ethanol yield from glucose and xylose, respectively. These results showed overexpression of xylA and Xltr1p is a promising strategy for improving xylose and glucose conversion to ethanol. Although the ability of strain INVSc-XI/XT to produce ethanol was not very satisfactory, glucose was discovered to influence xylose utilization in strain INVSc-XI/XT. Altering the glucose concentration is a promising strategy to improve the xylose and glucose co-utilization.

Segmentation and evaluation of pathway module efficiency: Quantitative approach to monitor and overcome evolving bottlenecks in xylose to ethanol pathway

Engineering microbes that can efficiently ferment xylose to ethanol is critical to the development of renewable fuels from lignocellulosic biomass. To accelerate the strain optimization process, a method termed Segmentation and Evaluation of Pathway Module Efficiency (SEPME) was developed to enable rapid and iterative identification and removal of metabolic bottlenecks. Using SEPME, the overall pathway was segmented into two modules: the upstream xylose assimilation pathway and the downstream pentose phosphate pathway, glycolysis, and fermentation. The efficiencies of both modules were then quantified to identify the rate controlling module, followed by analyses of control coefficients, reaction rates, and byproduct concentrations to narrow down targets within the module. SEPME analysis revealed that as the strain was engineered with increasing xylose-to-ethanol yields, the bottlenecks shifted within a module and across the two modules. Guided by SEPME, these bottlenecks were removed one by one, and a strain approaching the theoretical ethanol yield was obtained.

<i>Nocardiopsis synnemataformans</i> NBRM9, an extremophilic actinomycete producing extremozyme cellulase, using lignocellulosic agro-wastes and its biotechnological applications

<abstract> <p>Actinomycetes are an attractive source of lignocellulose-degrading enzymes. The search for actinomycetes producing extremozyme cellulase using cheap lignocellulosic waste remains a priority goal of enzyme research. In this context, the extremophilic actinomycete NBRM9 showed promising cellulolytic activity in solid and liquid assays. This actinomycete was identified as <italic>Nocardiopsis synnemataformans</italic> based on its phenotypic characteristics alongside phylogenetic analyses of 16S rRNA gene sequencing (OQ380604.1). Using bean straw as the best agro-waste, the production of cellulase from this strain was statistically optimized using a response surface methodology, with the maximum activity (13.20 U/mL) achieved at an incubation temperature of 40 °C, a pH of 9, an incubation time of 7 days, and a 2% substrate concentration. The partially purified cellulase (PPC) showed promising activity and stability over a wide range of temperatures (20–90 °C), pH values (3–11), and NaCl concentrations (1–19%), with optimal activity at 50 °C, pH 9.0, and 10% salinity. Under these conditions, the enzyme retained >95% of its activity, thus indicating its extremozyme nature. The kinetics of cellulase showed that it has a V<sub>max</sub> of 20.19 ± 1.88 U/mL and a Km of 0.25 ± 0.07 mM. The immobilized PPC had a relative activity of 69.58 ± 0.13%. In the in vitro microtiter assay, the PPC was found to have a concentration-dependent anti-biofilm activity (up to 85.15 ± 1.60%). Additionally, the fermentative conversion of the hydrolyzed bean straw by <italic>Saccharomyces cerevisiae</italic> (KM504287.1) amounted to 65.80 ± 0.52% of the theoretical ethanol yield. Overall, for the first time, the present work reports the production of extremozymatic (thermo, alkali-, and halo-stable) cellulase from <italic>N. synnemataformans</italic> NBRM9. Therefore, this strain is recommended for use as a biotool in many lignocellulosic-based applications operating under harsh conditions.</p> </abstract>

Ethanol production from Agave salmiana leaf juices by consolidated bioprocessing comparing two strains of Kluyveromyces marxianus

The present work addressed the conversion of Agave salmiana leaf juice to ethanol by consolidated bioprocessing (CBP). CBP was tested at 30, 35, and 40 ºC and compared with a conventional fermentation previously subjecting the juices to an acid-thermal pretreatment. An FTIR-DRIFTS analysis was applied on the functional groups of the juice. Fermentation was evaluated by comparing the strains K. marxianus OFF1 and K. marxianus TX4; the latter was isolated in this work from the sap of A. salmiana. In results, the optimal condition pretreatment (H2SO4 0.65% (v/v), 15.7 min, 88 °C) increased the reducing sugars concentration up to 45.15 g/L. FTIR-DRIFTS showed higher peaks of functional groups related to fructose and glucose in the pretreated juice vs the raw. Both strains reached enzymatic activities of up to 2.26 U/mL growing in raw A. salmiana juice. Conventional fermentation showed a similar behavior with both strains, with reducing sugar consumption efficiencies of 98%, 16 g ethanol/L, corresponding to yields of 77%. CBP at different temperatures, showed significant differences, registering the highest ethanol production (22 g/L) and yield (99%) at 40 ºC. The native strain showed a fermentation behavior similar to that of K. marxianus OFF1. Theoretical annual ethanol yields obtained from the results (3828 L/ha/year) were compared to those obtained from other biomass juices such as sweet sorghum and sugarcane bagasse. CBP showed high efficiency in the hydrolysis of polysaccharides from Agave salmiana juice and their conversion to ethanol.

Quantifying synergies and trade-offs in the food-energy-soil-environment nexus under organic fertilization

Recycling livestock manure in agroecosystems can maintain crop production, improve soil fertility, and reduce environmental losses. However, there has been no comprehensive assessment of synergies and trade-offs in the food-energy-soil-environment nexus under manure application. Here, we evaluate the sustainability of maize production under four fertilization regimes (mineral, mineral and manure mixed, manure, and no fertilization) from the aspect of food security, energy output, soil quality, and environmental impact based on a five-year field experiment. Manure and mineral mixed fertilization maintained grain and straw quantity and quality compared with mineral fertilization. Manure and mineral mixed fertilization increased stem/leaf ratio and field residue index by 9.1–28.9% and 4.5–17.9%, respectively. Manure also maintained the theoretical ethanol yield but reduced the straw biomass quality index by increasing ash. Further, manure application increased the soil quality index by 40.5% and reduced N2O emissions by 55.0% compared with mineral fertilization. Manure application showed the highest sustainability performance index of 19, followed by mineral (15), mixed (13), and without fertilization (8). In conclusion, manure application maintains food production and energy output, enhances soil quality, and reduces environmental impact, thereby improving the sustainability of maize production.

Adaptability comparison and application assessment of various bioenergy grasses on different marginal lands in China

To understand the effects of different marginal land and environments on the growth, biomass yield, quality, and theoretical ethanol yield of different bioenergy grasses, and to compare the adaptability of different bioenergy grasses. This study was conducted in four representative marginal lands located in Chongqing, Liuyang, Nanyang, and Beijing. The agronomic traits, cell wall compositions, and theoretical alcohol yield of nine energy grasses containing 22 accessions were compared. The effects of environmental factors on biomass yield, quality, and theoretical ethanol yield of different accessions were evaluated via parametric and non-parametric statistics and AMMI analysis, and the stability and adaptability of all accessions were also compared. The results revealed that there were significant differences in biomass yield, quality, and theoretical alcohol yield among different species at the same trial site, and the same species also showed large differences between trial sites. Grasses exhibited divergent adaptability across trial sites, such as Saccharum arundinaceum and Miscanthus floridulus were sensitive to low temperatures and could not overwinter normally in Beijing. The biomass yield of Miscanthus sacchariflorus declined as the latitude decreased. Miscanthus × giganteus, Miscanthus lutarioriparius × sinensis, and Panicum virgatum exhibited greater resistance to environmental changes, indicating superior stability and environmental adaptability.

Potential of thermophilic bacteria isolated from cow dung-grass compost for bioethanol production using floral waste

In recent years, various efforts have been invested in producing bioethanol from lignocellulosic biomass (LCB) using thermophilic bacteria. Twelve thermophilic ethanologenic bacteria were isolated from cow dung-grass compost using an enrichment technique, and the isolate, CSD6, which produced the highest bioethanol, was studied further. CSD6 utilized both pentose and hexose sugars producing ethanol, lactic acid and acetic acid as major soluble products and was identified through 16S rRNA gene sequencing as a strain of Geobacillus stearothermophilus. The highest ethanol production was found to be 25.05 mM from 5 g/L glucose, equivalent to 55% of the theoretical ethanol yield at 55 °C and initial pH 7.5. The isolate showed average tolerance to ethanol and acetic acid concentration and initial substrate loading. The bioethanol potential of CSD6 was also studied using autoclave-treated mixed floral waste (FW) as a no-cost substrate. CSD6 produced a maximum of 8.9 mM of bioethanol with a 75.47% decrease in reducing sugars using 20 g/L FW as substrate without any enzymatic pretreatment, indicating the ability of CSD6 to produce bioethanol from easily available substrates.

Novel thermotolerant yeast suitable for industrial bioethanol production

A thermotolerant yeast capable of converting 100 g/L glucose to 46 g/L ethanol was isolated. The isolate was identified as a strain of Pichia kudriavzevii based on sequences generated by amplifying the 18s ribosomal DNA and a blast search on the NCBI database. The strain could grow and produce ethanol from 30 °C to 45 °C with theoretical ethanol yield above 90% and an ethanol productivity of 2 g/L/h. The strain produced ethanol at acidic pH of 1.5 and 3 at 37 °C and 42 °C respectively. At 42 °C, the strain could tolerate up to 10% ethanol which further increased to 15% when the temperature was reduced to 37 °C. Pichia kudriavzevii LC671435 could utilize peanut and soybean meal as nitrogen sources for ethanol production in addition to its ability to produce ethanol from fructose with the same efficiency as glucose. P. kudriavzevii LC671435 produced 0.47, 0.45 and 0.40 g ethanol/g glucose from 100 g/L, 160 g/L and 200 g/L glucose respectively at 42 °C. When used for repeated batch ethanol production, P. kudriavzevii LC671435 produced above 46 g/L ethanol up to fifth batch at 37 °C and fourth batch at 42 °C. With its thermotolerant ability, this novel isolate has great prospects for industrial fermentation at high temperature without additional cooling costs.

An Efficient and Cost- Effective Pretreatment of Rice Straw Using Steam Explosion: A Pilot Scale Experience

Surplus availability of rice straw (RS) presents it as a potential feedstock for ethanol production. Steam explosion (SE) is considered as a green approach to extract fermentable sugars at lower cost. The present study deals with the reaction condition optimization for water and dilute acid assisted steam explosion of rice straw at different temperatures and explores the effect of structural properties of solid residue on enzymatic hydrolysis along with mass balance. SE conditions were optimized at pilot scale, raising the temperature from 170 to 200 °C in water assisted SE resulting in an increased glucan conversion from 21.4 to 42.5% at 15% solid loading using 1.5 FPU of cellulases g–1 biomass. Further, it was improved up to 58.7% by increasing the enzyme dosage to 5 FPU, although it might lead to enhanced enzyme cost by threefold. To reduce costs, small amount of dilute acid (DA) was added during SE and lowering of enzyme consumption i.e. 1.5 FPU/g cellulose has been used to achieve 65.5% glucan conversion. Varying temperature and incorporate dilute acid during pretreatment induced structural alterations in biomass evident by compositional analysis, FT-IR and mass balance. Mass balance study revealed that the overall sugar recovery i.e. 58.7 and 38.8% and theoretical yield of ethanol shall be 222 and 186 L ton–1 RS respectively, with and without DA addition.Graphical

Engineering natural isolates of Saccharomyces cerevisiae for consolidated bioprocessing of cellulosic feedstocks

Saccharomyces cerevisiae has gained much attention as a potential host for cellulosic bioethanol production using consolidated bioprocessing (CBP) methodologies, due to its high-ethanol-producing titres, heterologous protein production capabilities, and tolerance to various industry-relevant stresses. Since the secretion levels of heterologous proteins are generally low in domesticated strains of S. cerevisiae, natural isolates may offer a more diverse genetic background for improved heterologous protein secretion, while also displaying greater robustness to process stresses. In this study, the potential of natural and industrial S. cerevisiae strains to secrete a core set of cellulases (CBH1, CBH2, EG2, and BGL1), encoded by genes integrated using CRISPR/Cas9 tools, was evaluated. High levels of heterologous protein production were associated with a reduced maximal growth rate and with slight changes in overall strain robustness, compared to the parental strains. The natural isolate derivatives YI13_BECC and YI59_BECC displayed superior secretion capacity for the heterologous cellulases at high incubation temperature and in the presence of acetic acid, respectively, compared to the reference industrial strain MH1000_BECC. These strains also exhibited multi-tolerance to several fermentation-associated and secretion stresses. Cultivation of the strains on crystalline cellulose in oxygen-limited conditions yielded ethanol concentrations in the range of 4–4.5 g/L, representing 35–40% of the theoretical maximum ethanol yield after 120 h, without the addition of exogenous enzymes. This study therefore highlights the potential of these natural isolates to be used as chassis organisms in CBP bioethanol production.Key points• Process-related fermentation stresses influence heterologous protein production.• Transformants produced up to 4.5 g/L ethanol, ~ 40% of the theoretical yield in CBP.• CRISPR/Cas9 was feasible for integrating genes in natural S. cerevisiae isolates.

Bioethanol potential of switchgrass cultivars for rainfed and irrigated conditions in marginal lands

ABSTRACT Bioethanol is a climate-friendly alternative to conventional energy sources. This study was conducted to determine bioenergy potential of switchgrass cultivation in Central Anatolia where water scarcity limits the agricultural production. Field trials were conducted in a randomized blocks design with three replications under irrigated and rainfed conditions for three growing seasons (2019, 2020 and 2021). Biomass yield (BY), theoretical cellulosic ethanol yield (TEY), theoretical ethanol potential (TEP) with several quality parameters of 10 switchgrass cultivars were evaluated. Highest BY averages were obtained from Boomaster cultivar with 5.28 (rainfed) and 18.45 t ha−1 (irrigated) when Dacotah had the lowest BY averages of 1.55 (rainfed) and 5.29 t ha−1 (irrigated). ANOVA and Genotype Trait Biplot results revealed higher BY, TEY and TEP with lower ADF, NDF and ADL of lowland ecotype cultivars. Lowland ecotypes provided superior results in both rainfed and irrigated conditions with a higher response to irrigation. TEY of switchgrass were found as positively associated with BY, plant height and stem weight which could be used as indicators of TEY for genotype selection. In conclusion, lowland ecotype cultivars of switchgrass were recommended for bioethanol production in water limited environments.

Evaluation of Generic Fertiliser as an Alternative Inorganic Nitrogen Source for Ethanolic Glucose Fermentation by Saccharomyces cerevisiae

In the studies and production of bioethanol, the preferred fermenting yeast (Saccharomyces cerevisiae) is usually cultured in liquid broth that contains yeast extract and peptone. However, the use of these laboratory and scientific grade chemicals is costly, making them impractical for mass bioethanol production. Therefore, this study was conducted to evaluate the feasibility of glucose ethanolic fermentation by S. cerevisiae using generic fertiliser formulations to provide inorganic nitrogen, phosphorus, potassium and trace elements (NPK-TE). Fermentation media of different generic fertiliser strength at 0.5X, 1.0X and 2.0X Fertiliser Nitrogen Equivalents (FNE), as compared to the conventional Yeast Extract-Peptone (YEP) medium as control, was used as fermentation broth during the ethanolic fermentation of glucose. Based on the results, S. cerevisiae cultured in YEP broth produced the highest cell concentration for both wet (21.93 g/L) and dry cells (3.87 g/L), with rapid increment observed in the first 72 h of fermentation. By the end of the fermentation period, lactic acid (3.14 g/L) and acetic acid (0.96 g/L) levels were recorded to be the lowest in YEP medium while their concentration (lactic acid, 8.08 g/L) and (acetic acid, 2.67 g/L) were highest in 2.0X FNE fertiliser medium. Results indicated that the best theoretical ethanol yield (TEY) among the fertiliser media was achieved when fermentation was performed in the 0.5X FNE fertiliser medium, with a TEY of 86.18%. TEY yields were 78.68% and 51.54% in broth with 1.0X and 2.0X FNE, respectively. In general, all three fertiliser media supported ethanolic fermentation of glucose, with the 0.5X FNE fertiliser broth showing a yield that is significantly close to the conventional YEP medium, as seen in the statistical analysis. Similarities in other fermentation profiles such as acetic acid, lactic acid, and biomass production, as well as glucose utilisation, between the results from the YEP samples and samples from the fertiliser broths (at 0.5X and 1.0X FNE) have also shown that generic fertiliser has the potential to be used as an alternative medium to replace the conventional YEP to produce ethanol at a lower cost.

Combination of surfactants and enzyme cocktails for enhancing woody biomass saccharification and bioethanol production from lab-scale to pilot-scale

Converting woody biomass to bioethanol might be more affordable, environmentally friendly, and efficient for making biofuel commercially feasible, but it would still need a significant optimization process and expand pilot-scale research. A combination of commercial low enzymes loading at 10 FPU/g glucan and compound additives utilizing Tween 80, PEG8000 and sophorolipid applied from lab-scale to pilot-scale have been studied in this work at economically viable dosages for enhancing bioethanol production. In lab-scale saccharification and fermentation, pretreated poplar at a high solid loading of 20% yielded the highest ethanol titers of 30.96 g/L and theoretical ethanol yield of 92.79%. Additionally, pilot-scale operation was used to investigate the bioethanol amplification, a final volume of 33 m3 which yielded the greatest ethanol amount of 599.6 kg from poplar wood while gaining on-site value-added production of hemicellulosic and cellobiose liquor 1122 kg and lignin residues 2292 kg.

Evaluation of eastern gamagrass as dual‐purpose complementary bioenergy and forage feedstock to switchgrass

AbstractSwitchgrass (SG) is considered a model bioenergy crop and a warm‐season perennial grass (WSPG) that traditionally served as forage feedstock in the United States. To avoid the sole dependence on SG for bioenergy production, evaluation of other crops to diversify the pool of feedstock is needed. We conducted a 3‐year field experiment evaluating eastern gamagrass (GG), another WSPG, as complementary feedstock to SG in one‐ and two‐cut systems, with or without intercropping with crimson clover or hairy vetch, and under different nitrogen (N) application rates. Our results showed that GG generally produced lower biomass (by 29.5%), theoretical ethanol potential (TEP, by 2.8%), and theoretical ethanol yield (TEY, by 32.9%) than corresponding SG under the same conditions. However, forage quality measures, namely acid detergent fiber (ADF), crude protein (CP), and elements P, K, Ca, and Mg were significantly higher in GG than those in SG. Nitrogen fertilizer significantly enhanced biomass (by 1.54 Mg ha−1), lignin content (by 2.10 g kg−1), and TEY (787.12 L ha−1) in the WSPGs compared to unfertilized treatments. Intercropping with crimson clover or hairy vetch did not significantly increase biomass of the WSPGs, or TEP and TEY in unfertilized plots. This study demonstrated that GG can serve as a complementary crop to SG and could be used as a dual‐purpose crop for bioenergy and forage feedstock in farmers' rotations.

Ethanol production from non-detoxified hardwood spent sulfite liquor in submerged fed-batch culture using advanced yeasts

To improve process feasibility, it is essential to use hardwood spent sulfite liquor (HSSL) as the main feedstock for bioethanol production, without prior detoxification. In addition, operating at large-scale under cost-effective conditions such as a small inoculum size (< 1 g/L), pH 5, using industrially acceptable nutrients, and without sugar addition, will require the use of harsh, concentrated HSSL streams. The potential of non-detoxified HSSL as a feedstock for ethanol production using two recombinant Saccharomyces cerevisiae strains, CelluX™4 and TFA7, was assessed. The inhibitory effect of non-detoxified HSSL was mitigated, and the ethanol titer increased from 4.1 to 7.9 g/L when pulse fed-batch was used instead of batch production, with CelluX™4 performing best. Both strains made use of the xylose isomerase (XI) pathway, with strain TFA7 engineered for increased tolerance against inhibitors. By administering concentrated HSSL in pulses to shake-flask cultures, the ethanol titer could be increased by approximately 50–90% when compared to simple batch cultures supplemented with 20%, 40%, and 60% (v/v) dilutions of HSSL. CelluX™4 was used in non-aerated, non-sterile 5-L bioreactor fermentations with a low cell concentration (< 1 g/L), pH 5, and 5 g/L corn steep liquor (CSL) as the nitrogen source. In comparison, undiluted HSSL was fed continuously to obtain a final 65% (v/v) HSSL supplementation, which corresponded to a total sugar concentration of 70.8–80.8 g/L. Despite the use of harsher, concentrated feedstock and inexpensive process conditions, the reactor fed-batch fermentations obtained ethanol yields of 0.35–0.43 g/g, which, based on a maximum theoretical ethanol yield of 0.51 g/g of hexoses or pentoses, corresponds to yield efficiencies of 68.6 and 84.3%. This illustrates an improvement on the highest titers reported in the literature for non-detoxified HSSL. The use of the advanced industrial S. cerevisiae strain, CelluX™4, combined with a fed-batch strategy, offers an inexpensive and straightforward process with real upscaling potential for industrial HSSL fermentations.