Experimental optimization and techno-economic analysis of bioethanol production by simultaneous saccharification and fermentation process using sugarcane straw

Decisional tool development and application for techno-economic analysis of fungal laccase production

Textile and medical effluents causing bioaccumulation and biomagnification have been successfully biodegraded by fungal laccases. Here, a decision-making tool was developed and applied to evaluate 45 different laccase production strategies which determined the best potential source from a techno-economical perspective. Laccase production cost was calculated with a fixed output of 109 enzymatic units per batch (USD$per109U) and a sensitivity analysis was performed. Results indicate that optimization of enzymatic kinetics for each organism is essential to avoid exceeding the fermentation time point at which production titer reaches its peak and, therefore, higher production costs. Overall, the most cost-effective laccase-producing strategy was obtained when using Pseudolagarobasidium acaciicola with base production cost of USD $42.46 per 109 U. This works serves as platform for decision-making to find the optimal laccase production strategy based on techno-economic parameters.

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 T_m 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 V_max 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.

A consolidated review of commercial-scale high-value products from lignocellulosic biomass

For decades, lignocellulosic biomass has been introduced to the public as the most important raw material for the environmentally and economically sustainable production of high-valued bioproducts by microorganisms. However, due to the strong recalcitrant structure, the lignocellulosic materials have major limitations to obtain fermentable sugars for transformation into value-added products, e.g., bioethanol, biobutanol, biohydrogen, etc. In this review, we analyzed the recent trends in bioenergy production from pretreated lignocellulose, with special attention to the new strategies for overcoming pretreatment barriers. In addition, persistent challenges in developing for low-cost advanced processing technologies are also pointed out, illustrating new approaches to addressing the global energy crisis and climate change caused by the use of fossil fuels. The insights given in this study will enable a better understanding of current processes and facilitate further development on lignocellulosic bioenergy production.

Evaluation of Saccharomyces cerevisiae modified via CRISPR/Cas9 as a cellulosic platform microorganism in simultaneously saccharification and fermentation processes

The nonrenewable character and deleterious effects of fossil fuels foster the need for cleaner and more inexhaustible energy sources, such as bioethanol. Especially from lignocellulosic biomasses. However, the economic viability of this product in the market depends on process optimization and cost reduction. This research applied a sequential experimental project to investigate the process of enzymatic saccharification and simultaneous fermentation to produce ethanol with sugarcane bagasse. The differential of the work was the application of the strain of Saccharomyces cerevisiae AGY001 which was improved by evolutionary engineering to become thermotolerant and by a heterologous expression based on genomic integration by CRISPR/Cas9 to produce endoglucanase and β-glucosidase (AsENDO-AsBGL). The maximum ethanol yield found was 89% of the maximum theoretical yield (released sugars), obtained at temperature concentrations, sugarcane bagasse and inoculum at 40 °C, 16.5%, and 4.0 g/L, respectively (12.5 FPU/g bagasse). The mathematical model obtained can predict approximately 83% of the data set with 95% confidence. Therefore, these findings demonstrated the potential of sugarcane bagasse and S. cerevisiae AGY001 strain (CRISPR/Cas9 modified) in bioethanol production without the need for impractical selection media on an industrial scale, in addition to providing useful insights for the development of SSF processes.

Recent advances in valorization of organic municipal waste into energy using biorefinery approach, environment and economic analysis

Researcher's all around works on a copious technique to lessen waste production and superintend the waste management for long-term socio-economic and environmental benefits. Value-added products can be produced from municipal waste by using holistic and integrated approaches. In this review, a detail about the superiority of the different methods like anaerobic digestion, biofuel production, incineration, pyrolysis and gasification were used for the conversion of municipal waste to feedstock for alternate energy and its economic- environmental impacts were consolidated. Most conversion techniques were environmentally friendly to manage municipal waste. The biological process was more economically feasible compare to the thermal process, for the reason thermal process required a large amount of capital investment and energy utilization. In the thermal process, gasification shows low emission, and pyrolysis shows low capital investment and economically feasible compare to other thermal processes. Waste to energy technology significantly reduced the emission and energy demand.

Emerging trends in high-solids enzymatic saccharification of lignocellulosic feedstocks for developing an efficient and industrially deployable sugar platform

For the techno-commercial success of any lignocellulosic biorefinery, the cost-effective production of fermentable sugars for the manufacturing of bio-based products is indispensable. High-solids enzymatic saccharification (HSES) is a straightforward approach to develop an industrially deployable sugar platform. Economic incentives such as reduced capital and operational expenditure along with environmental benefits in the form of reduced effluent discharge makes this strategy more lucrative for exploitation. However, HSES suffers from the drawback of non-linear and disproportionate sugar yields with increased substrate loadings. To overcome this bottleneck, researchers tend to perform HSES at high enzyme loadings. Nonetheless, the production costs of cellulases are one of the key contributors that impair the entire process economics. This review highlights the relentless efforts made globally to attain a high-titer of sugars and their fermentation products by performing efficient HSES at low cellulase loadings. In this context, technical innovations such as advancements in new pretreatment strategies, next-generation cellulase cocktails, additives, accessory enzymes, novel reactor concepts and enzyme recycling studies are especially showcased. This review further covers new insights, learnings and prospects in the area of lignocellulosic bioprocessing.

Hybridization of Selected Nigerian Lignocellulosic Biomass Feedstocks for Bioethanol Production: Modeling and Optimization of Pretreatment and Fermentation Process Parameters Using Response Surface Methodology

In this study, hybridized feedstocks (mixtures of biomass) of cassava peels plus yam peels, as well as corn cobs plus rice husks biomass, were optimized using the response surface methodology centered on the statistical design of experiments (DOE) of the Box-Behnken design (BBD), to produce bioethanol. The feedstocks were locally sourced, hybridized (mixed), pretreated, and fermented before being distilled in a UOP3CC continuous distillation column. The BBD was applied using a 3-level, 3-factor process variables using pH, time, and particle size, and indicated as X₁, X₂, and X₃, respectively. The bioethanol yield from the two hybridized biomass feedstocks was predicted by the developed quadratic polynomial models from BBD. For the hybridized biomass mixture of cassava peels plus yam peels, the optimal condition was statistically predicted as pH 5.00, fermentation time of 120.00 hours, and particle size of 362.5 microns, the predicted bioethanol yield under the optimal condition was 115.75 mL per 1500 g of hybridized biomass and the average volume of bioethanol obtained was 125.00 mL per 1500 g of biomass, which is within the projected range of the model equation, same applies to rice husks plus corn cobs hybridized biomass, but with a better prospect for bioethanol production.

Resource recovery and biorefinery potential of apple orchard waste in the circular bioeconomy

In this review investigate the apple orchard waste (AOW) is potential organic resources to produce multi-product and there sustainable interventions with biorefineries approaches to assesses the apple farm industrial bioeconomy. The thermochemical and biological processes like anaerobic digestion, composting and , etc., that generate distinctive products like bio-chemicals, biofuels, biofertilizers, animal feed and biomaterial, etc can be employed for AOW valorization. Integrating these processes can enhanced the yield and resource recovery sustainably. Thus, employing biorefinery approaches with allied different methods can link to the progression of circular bioeconomy. This review article mainly focused on the different biological processes and thermochemical that can be occupied for the production of waste to-energy and multi-bio-product in a series of reaction based on sustainability. Therefore, the biorefinery for AOW move towards identification of the serious of the reaction with each individual thermochemical and biological processes for the conversion of one-dimensional providences to circular bioeconomy.

Cellulosic Ethanol: Improving Cost Efficiency by Coupling Semi-Continuous Fermentation and Simultaneous Saccharification Strategies

A novel approach to improve ethanol production from sugarcane bagasse is proposed. Biomass was pretreated with sodium hydroxide, sulfuric, oxalic, and maleic acids (1% w/v) at different temperatures (130–170 °C) and times (10–30 min). The pretreatment with NaOH at 160 °C for 20 min was found to be the most efficient for further enzymatic saccharification. A semi-continuous fermentation system coupled with a simultaneous saccharification and fermentation strategy was used, attaining fermented liquor every 24 h. The amount of enzymes needed for saccharification was optimized, as well as the production time and ethanol concentration. The process occurred with near to complete depletion of glucose, obtaining ethanol concentrations ranging from 8.36 to 10.79% (v/v). The whole system, at bench scale, showed stability over 30 days, and ease of management and control. This strategy may improve cost efficiency in the production of cellulosic ethanol at industrial scale.

Saccharification of water hyacinth biomass by a combination of steam explosion with enzymatic technologies for bioethanol production

In the present work, bioethanol was produced by sugar fermentation obtained from water hyacinth using a novelty hybrid method composed of steam explosion and enzymatic hydrolysis, using hydrolytic enzymes produced by solid-state fermentation and water hyacinth as substrate. The highest activity, 42 U for xylanase and 2 U for cellulase per gram of dry matter, respectively, was obtained. Steam explosion pretreatment was performed at 190 ℃ for 1, 5, and 10 min, using water hyacinth sampled from the Maria Lizamba Lagoon, the Arroyo Hondo and the Amapa River. The highest amounts of reducing sugars of water hyacinth were obtained form the samples from the lagoon (5.4 g/50 g of dry matter) after 10 min of treatment. Steamed biomass was hydrolysed using the enzymes obtained by solid-state fermentation, obtained reducing sugars (maximum 15.5 g/L); the efficiency of enzymatic hydrolysis was 0.51 g of reducing sugars per gram of water hyacinth. Finally, reducing sugars were fermented using Saccharomyces cerevisiae for conversion to ethanol, with the highest ethanol concentration (7.13 g/L) and an ethanol yield of 0.23 g/g of dry matter.

Using low carbon footprint high-pressure carbon dioxide in bioconversion of aspen branch waste for sustainable bioethanol production

An innovative approach was developed by incorporating high-pressure CO₂ into the separate hydrolysis-fermentation of aspen leftover branches, aiming to enhance the bioethanol production efficiency. The high-pressure CO₂ significantly increased the 72-h enzymatic hydrolysis yield of converting aspen into glucose from 53.8% to 82.9%. The hydrolysis process was performed with low enzyme loading (10 FPU g^-1 glucan) with the aim of reducing the cost of fuel bioethanol production. The ethanol yield from fermentation of the hydrolyzed glucose using yeast (Saccharomyces cerevisiae) was 8.7 g L^-1, showing increment of 10% compared with the glucose control. Techno-economic analysis indicated that the energy consumption of fuel bioethanol production from aspen branch chips was reduced by 35% and the production cost was cut 44% to 0.615 USD L^-1, when 68 atm CO₂ was introduced into the process. These results furtherly emphasized the low carbon footprint of this sustainable energy production approach.

Techno-Economic Analysis of Producing Glacial Acetic Acid from Poplar Biomass via Bioconversion

Most of the current commercial production of glacial acetic acid (GAA) is by petrochemical routes, primarily methanol carbonylation. GAA is an intermediate in the production of plastics, textiles, dyes, and paints. GAA production from biomass might be an economically viable and sustainable alternative to petroleum-derived routes. Separation of acetic acid from water is a major expense and requires considerable energy. This study evaluates and compares the technical and economic feasibility of GAA production via bioconversion using either ethyl acetate or alamine in diisobutylkerosene (DIBK) as organic solvents for purification. Models of a GAA biorefinery with a production of 120,650 tons/year were simulated in Aspen software. This biorefinery follows the path of pretreatment, enzymatic hydrolysis, acetogen fermentation, and acid purification. Estimated capital costs for different scenarios ranged from USD 186 to 245 million. Recovery of GGA using alamine/DIBK was a more economical process and consumed 64% less energy, due to lower steam demand in the recovery distillation columns. The estimated average minimum selling prices of GGA were USD 756 and 877/ton for alamine/DIBK and ethyl acetate scenarios, respectively. This work establishes a feasible and sustainable approach to produce GGA from poplar biomass via fermentation.