Biorefinery Framework Research Articles

Optimisation of microalgal cultivation via nutrient-enhanced strategies: the biorefinery paradigm

BackgroundThe production of microalgal biofuels, despite their sustainable and renowned potential, is not yet cost-effective compared to current conventional fuel technologies. However, the biorefinery concept increases the prospects of microalgal biomass as an economically viable feedstock suitable for the co-production of multiple biofuels along with value-added chemicals. To integrate biofuels production within the framework of a microalgae biorefinery, it is not only necessary to exploit multi-product platforms, but also to identify optimal microalgal cultivation strategies maximising the microalgal metabolites from which biofuels are obtained: starch and lipids. Whilst nutrient limitation is widely known for increasing starch and lipid formation, this cultivation strategy can greatly reduce microalgal growth. This work presents an optimisation framework combining predictive modelling and experimental methodologies to effectively simulate and predict microalgal growth dynamics and identify optimal cultivation strategies.ResultsMicroalgal cultivation strategies for maximised starch and lipid formation were successfully established by developing a multi-parametric kinetic model suitable for the prediction of mixotrophic microalgal growth dynamics co-limited by nitrogen and phosphorus. The model’s high predictive capacity was experimentally validated against various datasets obtained from laboratory-scale cultures of Chlamydomonas reinhardtii CCAP 11/32C subject to different initial nutrient regimes. The identified model-based optimal cultivation strategies were further validated experimentally and yielded significant increases in starch (+ 270%) and lipid (+ 74%) production against a non-optimised strategy.ConclusionsThe optimised microalgal cultivation scenarios for maximised starch and lipids, as identified by the kinetic model presented here, highlight the benefits of exploiting modelling frameworks as optimisation tools that facilitate the development and commercialisation of microalgae-to-fuel technologies.

A novel sequential ultrasound-rhamnolipid assisted [EMIM]OAc pretreatment for enhanced valorization of invasive Cogongrass to bioethanol

Cogongrass, one of the most invasive pest species worldwide, was considered as a promising bioresource for second-generation ethanol production. For the first time, it was successfully valorized to bioethanol using a novel sequential ionic liquid pretreatment assisted by synergistic effects of ultrasound irradiation and biosurfactant impregnation. The biomass was sonicated (50 and 100 W, 20 kHz) for 15 and 30 min, suspended in rhamnolipid solution (1, 2, and 3% w/w), and finally pretreated with 1-ethyl-3-methylimidazole acetate at 120 °C. Enzymatic digestibility of the regenerated biomass substantially enhanced by ~ 1.2-fold, upon a fast and low-intensity sonication (15 min, 50 W) followed by impregnation with the diluted rhamnolipid solution (2% w/w). Accordingly, non-isothermal simultaneous saccharification and fermentation of the pretreated Cogongrass by fungus M. hiemalis led to a maximum ethanol yield of ~ 195 (g/kg dry substrate), which was almost 1.6-fold higher than that obtained from the conventionally ionic liquid pretreated biomass. Comprehensive semi-quantitative analyses of the biomass together with FTIR and FESEM measurements revealed major improvements in surface area, surface hydrophilicity, pore sizes and volumes, cellulose crystallinity, and morphological features following the pretreatment. The findings may also provide a promising approach for enhanced recycling of the expensive ionic liquid and lignin in a biorefinery framework; however, more investigation should be dedicated to this subject.

Early-stage sustainability assessment of enzyme production in the framework of lignocellulosic biorefinery

The use and integration of enzymatic processes for the biotransformation of biomass within the biorefinery framework creates the need to confirm whether these novel production systems are in the route to environmental sustainability. In this study, the environmental profiles of the production of two oxidative enzymes, hydroxymethylfurfural oxidase (HMFO) from Methylovorus and unspecific peroxygenase (UPO) from Chaetomium globosum (CglUPO) for the enzymatic production of FDCA as precursor of bioplastics were analyzed. Laboratory-scale experiments allowed the identification of the consumption of energy, with over 80% share in every impact category for HMFO and chemicals and energy in CglUPO as primary hotspots of the systems. The results are transposed for HMFO when laboratory inventories were extrapolated to full scale processing, showing that impacts are attributed not only to energy demand but also to the use of chemicals required for the formulation of the culture medium. In terms of process units, the fermenter, where enzyme production takes place, corresponds to the stage that contributes the most to the environmental impacts, with a 57% share, followed by the downstream separation scheme (37%). Extrapolation of laboratory data to full-scale also represented a change in the relative difference of the impact per functional unit of 45% for CgIUPO. The endpoint damage categories showed a significant reduction in their full-scale impacts to about half the burden. The analysis of the outcomes of the uncertainty analysis showed that the resource depletion category had the least dispersion of data, while the level of uncertainty is more relevant for human health, as it takes into account the combined effect of a larger number of impact categories and the processes involved. This study shows that, although being bio-based catalysts, the production of enzymes involves several steps which may incur in environmental impact. Thus, it is recommended that enzymes are carefully included within the system boundaries for their evaluation, since they could be the major hotspot in the biorefinery value chain. De-fossilization of the plastic industry will be possible with thoroughly optimized bio-transformations, with carbon-based media from residual resources, minimized use of chemicals and the implementation of energy integration measures.

Optimization of Chlamydomonas reinhardtii cultivation with simultaneous CO2 sequestration and biofuels production in a biorefinery framework

Algal biomass is regarded as a sustainable energy feedstock for the future. Enhancement of the biomass and metabolite production of microalgae increases the economic feasibility of the biofuel production process. The present study encompasses on bioethanol production from Chlamydomonas reinhardtii through a biorefinery approach. The biomass and carbohydrate productivity of C. reinhardtii UTEX 90 and CC 2656 were enhanced by optimizing the physico-chemical parameters. The following conditions were found suitable for the improvement of biomass and metabolite content of C. reinhardtii: pH 6.5–7.0, incubation temperature 30 °C, initial acetate and ammonium chloride concentration of 1.56 g L−1 and 100–200 mg L−1, respectively. Under the optimized operational condition biomass and carbohydrate productivity of C. reinhardtii UTEX 90 and CC 2656 were 512 mg L−1 d−1 & 266.24 mg L−1 d−1 and 364 mg L−1 d −1 & 163.80 mg L−1 d−1, respectively. The amount of CO2 sequestered during the cultivation process by UTEX 90 and CC 2656 were 113 mg L−1 d−1 and 74.95 mg L−1 d−1, respectively. The depigmented and defatted carbohydrate rich biomass was considered as raw material for bioethanol production. The bioethanol yield range was 90–94% of the theoretical yield using Saccharomyces cerevisiae INVSC-1 in a double jacket reactor. To improve the viability of the process, the spent media after ethanol fermentation was subsequently used for methane production using mixed microbial consortium. The energy recovery from the process was 40.39% and 39.7% for UTEX 90 and CC 2656, respectively when C. reinhardtii biomass was used as substrate for biofuel production. The present investigation concedes with the potentiality of algae as a favourable 3rd generation feedstock to address the existing challenges of clean energy production with concomitant CO2 sequestration.

Yeast fermentation towards biodiesel: Maximizing resource recovery by integrating with biohydrogen production in biorefinery framework

This study presents an effective and sustainable approach for biodiesel production through oleaginous yeast fermentation by utilizing volatile fatty acids (VFAs) rich acidogenic effluents as an alternative feedstock. Experiments were designed in two stages to obtain high cell density and lipid productivity. Primarily, oleaginous yeast (Cryptococcus curvatus; MTCC 2698) was grown on glucose with varied initial concentrations at 25 °C. Maximum biomass concentration of 4.2 ± 0.05 g/L was achieved with 40 g/L glucose, which was subjected to the second stage along with the supplementation of 5 g/L of selected VFAs viz., acetic acid, propionic acid, butyric acid and mixed VFAs. Highest lipid concentration of 33.5% (w/w) was obtained with acetic acid supplementation followed by mixed VFAs (23% w/w). Further, to validate results from initial studies, yeast strain was cultivated on real field VFAs rich acidogenic effluent derived from renewable biohydrogen production process. Maximum of 4.85 ± 0.05 g/L biomass and 29.3% (w/w) of lipid was observed during real field application fatty acid profiling of produced lipids showed predominance of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1) and linoleic acid (C18:2) which has potential utility for biodiesel production. Integration of bioprocesses in a biorefinery format helps to maximize resource recovery apart from minimizing waste generation. The study confirms feasible utilization of acidogenic effluent as an alternative feedstock for the production of microbial lipids through yeast fermentation.

Vacuum-assisted production of hydrogen and volatile fatty acids from lignocellulosic biomass derived from energy-crops pruning

Energy crops are promising sources of liquid biofuels, but large amounts of lignocellulosic biomass must be harvested from these cultivations, which have remained unexplored to produce additional chemicals and energy. In the present study, pruning derived from energy crops (Jatropha curcas and Ricinus communis) was evaluated, for the first time, as feedstock for the production of hydrogen (H2) and volatile fatty acids (VFA) by anaerobic sludge. The highest H2 production rate and yield were obtained with hydrolysate derived from J. curcas, producing up to 44.6 mL H2/L-h and 66.6 mL H2/g residue. Application of intermittent vacuum increased the production of H2 (up to 5-fold) and VFA (up to 3-fold) as compared to fermentations performed without vacuum. This study proposes an integrative exploitation of these energy crops, by harnessing their pruning to produce extra fuels and chemicals within a bio-refinery framework.

Furfural production from rice husks within a biorefinery framework

Furfural production at the industrial level began 100 years ago, but its reaction conditions continue to be studied. Data on furfural production from rice husks, a by-product of the rice-peeling process, are particularly limited. This raw material must be disposed of and is usually combusted for combined heat and power generation. However, in a biorefinery framework, this material can be used to generate value-added chemicals as well as power. This study evaluated furfural production from rice husks through acid hydrolysis the potential of the remaining solid to generate power and the formation of by-products. The variables were temperature (180–230 °C), sulphuric acid concentration (0.05–3% (w/w) sulphuric acid in the solution) and time (1–105 min). The results obtained for furfural yield, solid yield and particle size distribution indicated that the best conditions are 200 °C, 0.10% (w/w) acid and 40 min, which generated a furfural production amounting to 6.0% (w/w) of the oven-dried rice husk weight (55% of the theoretical yield) and a 60% solid yield. The gross heating value of the solid fraction remained considerably constant after the treatment, and the characteristics of the ash fraction were improved. This study gives furfural yields higher than those typically achieved at the industrial level (35–50% of the theoretical yield), with hydroxymethylfurfural and acetic, formic and levulinic acids as additional products, as well as the novelty of a remaining solid in good condition for power generation, making it a successful valorisation-prior-to-combustion approach.

Bioconversion of Glycyrrhiza glabra residue to ethanol by sodium carbonate pretreatment and separate hydrolysis and fermentation using Mucor hiemalis

The non-valuable non-edible Glycyrrhiza glabra residue (GGR) was efficiently subjected to inexpensive sodium carbonate pretreatment for enhanced enzymatic hydrolysis and ethanol production. The process included sodium carbonate pretreatment at different concentrations (0.5 and 1 M), temperatures (60, 100 and 120 °C), and retention times (3, 5 and 8 h), followed by separate hydrolysis and fermentation using a rarely-reported fungus Mucor hiemalis. The GGR pretreated with 0.5 M sodium carbonate solution at 120 °C for 3 h exhibited the maximum digestibility yield of 94.6% which was 6.2-fold higher than that observed for the untreated GGR. Consequently, fermentation of GGR hydrolyzates by M. hiemalis led to a maximum ethanol production yield of over 94%. Composition analysis of the biomass indicated that the process could substantially remove the majority of lignin part but left the cellulose relatively intact. Moreover, in-depth analyses of the materials by rapid semi-quantitative methods (e.g., Simons’ stain) as well as FTIR, XRD, and FE-SEM investigations revealed that sodium carbonate pretreatment could not only modify biomass composition, but also expanded cellulosic surface area, increased surface hydrophilicity, enlarged the pores, and improved morphological quality of GGR; thereby, rendered it more accessible to the cellulase. The implication of the study may potentially provide the first insight into commercial utilization of GGR for large-scale bioethanol production in a biorefinery framework.

Mild sodium hydroxide pretreatment of tobacco product waste to enable efficient bioethanol production by separate hydrolysis and fermentation

Tobacco product waste (TPW) was considered as a novel and sustainable feedstock for second-generation ethanol production. TPW with over ~ 44% cellulose content was efficiently pretreated using concentrated (10% W/V) sodium hydroxide (SH) solution at different temperatures (0, 25, and 80 °C) and retention times (3 and 6 h). Subsequently, the pretreated biomass was subjected to separate enzymatic hydrolysis and fermentation by the filamentous fungus Mucor hiemalis. Promising results were achieved following 3 h pretreatment of TPW at 80 °C, whereas the hydrolysis yield was substantially increased up to 91.3%. Besides, comprehensive tacking of key features of biomass (e.g., composition, crystalline structure, surface hydrophilicity and morphology, and accessible surface area) by semi-quantitative methods together with FTIR and SEM observations revealed major improvements occurred after mild SH pretreatment. Consequently, the maximum ethanol production as high as ~ 97% of theoretical ethanol yield was obtained, while it was only 44.4% from the untreated TPW. The implication of the work could possibly support TPW utilization for large-scale ethanol production in a tobacco-based biorefinery framework.

Process simulation of renewable electricity from sugarcane straw: Techno-economic assessment of retrofit scenarios in Brazil

Approximately 7% of Brazilian electricity is generated from sugarcane biomass. Although this scenario is relatively optimistic when compared to the fossil-based energy matrix of other nations, there is a clear opportunity of expanding bioelectricity production in the country even more. Recent changes in the environmental legislation are progressively prohibiting burning before sugarcane harvesting in Brazilian Center-South region. Consequently, straw (i.e., sugarcane tops, dry and green leaves) has become available in most of the sugarcane fields. When considering the low availability of capital to invest in large-scale greenfield projects currently in Brazil, this paper focuses on retrofit investments, i.e., those related to existing sugarcane mills aiming to increase electricity production with incremental investments. This study is based on the Virtual Sugarcane Biorefinery framework that is developed in the Brazilian Biorenewables National Laboratory (LNBR/CNPEM). This simulation framework integrates both agricultural and industrial models to anticipate the impacts of biorefineries on different sustainability aspects. In this paper, process-based models are used to represent incremental changes caused by sugarcane straw recovery adopting the integral harvesting system. The techno-economic analysis shows that the internal rates of return (IRRs) of different alternatives depend on the conditions assumed in the sensitivity analysis. The main parameters assessed in the sensitivity are related to industrial plant scale, straw transport distance, industrial operating period, dry-cleaning system (DCS) efficiency and electricity prices. In the best incremental scenarios (operation during the offseason), IRRs ranged from 35 to 69%, 44–83%, and 54–99% per year when recovering straw in mills with original crushing capacities of 2, 4 and 8 million tons of sugarcane per year, respectively. This analysis ratifies that the economic feasibility increases as much as industrial scale increases; also, the system benefits from shorter straw transport distances. In general, higher DCS efficiencies can improve the economic viability, although some non-linear effects can be observed under specific conditions of the industrial operation. From all variables tested in the simulation, electricity price is one of the most sensitive parameters affecting the economic viability of straw recovery projects.

Formic acid pretreatment for enhanced production of bioenergy and biochemicals from organic solid waste

Organic solid waste is one of the most promising feedstocks for the implementation of the circular economy principles in waste management. Its anaerobic treatment can indeed promote organic matter conversion into a number of value-added products as well as energy carriers. However, the identification of sustainable strategies to handle organic solid waste in a biorefinery framework still poses technological as well as economic challenges. The aim of this study was in enhancing the potential of the organic fraction of municipal solid waste (OFMSW) to produce bioenergy and biochemicals by combining dark fermentation with a formic acid pretreatment. Hydrogen yields up to 31.6 ml/gVS were obtained pre-treating the OFMSW with 5% formic acid, at 80 °C for 70 min. Concomitantly, a wide range of metabolites of market significance, including acetic acid, butyric acid and ethanol, accumulated. The concentration of these metabolites further enhanced after the dark fermentation of the pretreated substrates. Experimental tests highlighted the influence of the different pretreatment operating conditions on the relative production of hydrogen and main metabolites as well as the related pathways. It was found that the acid concentration plays a key role in promoting the biological conversion of OFMSW and that the adjustment of the operating temperature and treatment time can be targeted towards the production of either building blocks or energy carriers, so as to ensure the viability of the process for its scale up.

Sustainability prioritization framework of biorefinery: A novel multi-criteria decision-making model under uncertainty based on an improved interval goal programming method

Abstract As a sustainable substitute of traditional petroleum refining technology, the biorefinery, which has advantages of higher resource utilization efficiency, better sustainability and lower negative environmental impacts, have developed and applied. However, the variety of developed biorefinery system makes it difficult for decision-makers to determine the most sustainable biorefinery system. How to deal with the uncertainties in the decision-making process is another issue existing in biorefinery prioritization. In order to solve the decision-making problem under uncertainties in the selection process of biorefineries, a novel decision-making framework based on an improved interval goal programming was developed. In this study, a case study, which is to select the most sustainable biorefinery technology from grain ethanol (GE), cellulosic ethanol (CE), and Fischer-Tropsch diesel (FTD), was adopted to practice the proposed method. Three other methods were also employed to validate the results determined by the proposed method in this study. The results revealed that FTD was recognized as the most sustainable scenario by the proposed method and the proposed method was validated and recognized as the most robust method in uncertain decision-making problem.

Deoiled algal biomass derived renewable sugars for bioethanol and biopolymer production in biorefinery framework

The present study is designed to evaluate the potential of deoiled algal biomass (DAB) residue as an alternative resource for the production of bioethanol and biopolymers in a biorefinery approach. Hybrid pretreatment method resulted in higher sugar solubilization (0.590 g/g DAB) than the corresponding individual physicochemical (0.481 g/g DAB) and enzymatic methods (0.484 g/g DAB). Subsequent utilization of sugars from hybrid pretreatment for bioethanol using Saccharomyces cerevisiaeresulted in maximum bioethanol production at pH 5.5 (0.145 ± 0.008 g/g DAB) followed by pH 5.0 (0.122 ± 0.004 g/g DAB) and pH 6.0 (0.102 ± 0.002 g/g DAB). The experiments for biopolymer (PHB: polyhydroxybutyrate) production resulted in 0.43 ± 0.20 g PHB/g DCW. Extracted polymer on NMR and FT-IR analysis showed the presence of PHB. Exploration of DAB as an alternative renewable resource for multiple biobased products supports sustainability and also enables entirety use of DAB by addressing the DAB-residue allied disposal issues.

Production of carbohydrate enrich microalgal biomass as a bioenergy feedstock

Microalgal biomass is considered as a propitious feedstock for bioenergy generation. The present research work aimed to maximize the biomass and carbohydrate productivity of Scenedesmus obliquus UTEX 393 by optimizing physico-chemical parameters using single and multi-parameter optimization strategies. Individual and interactive effects of different parameters (temperature, pH, carbon source concentration and nitrogen source concentration) were investigated. Multi-response optimization study resulted in maximum biomass and carbohydrate productivity of 491 mg L−1 d−1and 270 mg L−1 d−1, respectively at the initial pH 6.69, temperature 27.65 °C, glucose concentration 3.33 g L−1 and urea concentration 126.77 mg L−1. Effect of photobioreactor configuration on biomass and carbohydrate production was also investigated. The biomass and carbohydrate productivity were enhanced to 560 mg L−1d−1 and 309 mg L−1 d−1, respectively using airlift photobioreactor. In a biorefinery framework, before subjecting the biomass for fermentative biohydrogen production, the lipid present (22.6% w/w) in the microalgae was extracted and transesterified for biodiesel production. The potentiality of defatted microalgal biomass (rich in carbohydrate) as a substrate for the dark fermentation process was evaluated using acidogenic mixed consortia. Cumulative hydrogen production of 68.9 mL g−1 DCW was achieved, which suggested the suitability of deoiled algal biomass as a biohydrogen feedstock.

An integrated approach to explore UASB reactors for energy recycling in pulp and paper industry: a case study in Brazil

Brazil is currently focused on its energy matrix transition in favor of increasing of the share of renewable energy carriers for both enhanced energy security and mitigation of greenhouse gas emissions. In this context, the country`s pulp and paper industry whose different wastes teams are not generally exploited, could play a critical role. Accordingly, the main objective of this work is to develop a conceptual ‘systemic’ biorefinery framework integrating the treatment of pulp and paper mill wastewater using upflow anaerobic sludge blanket (UASB) reactor with energy recovery through biogas production and its conversion into heat and power in stationary engines and boilers, respectively. Based on the results obtained through the present case study, it was revealed that the adoption of UASB reactors by the paper mill industry could properly addresses the environmental concerns faced while could contribute to the national agenda favoring an increasing share of renewable energies in the country`s energy matrix. The financial analysis showed that the investment required for the implementation of UASB reactors within a biorefinery platform would be minor vs. the investment in the whole mill and would be returned in 6.4 yr with a high return on investment even when operated at half of operational capacity. Moreover, through the developed UASB reactor-based biorefinery, the Brazilian pulp and paper industry as a whole could avoid 1.06 ×105 CO2eq tons, effectively contributing to the decarbonization of the country`s economy.

Polyhydroxy butyrate production by Acinetobacter junii BP25, Aeromonas hydrophila ATCC 7966, and their co-culture using a feast and famine strategy

The study aimed to evaluate biopolymer production using two bacterial strains, Acinetobacter junii BP25 and Aeromonas hydrophila ATCC 7966, and their co-culture. Batch experiments were evaluated using acetate and butyrate as carbon sources in feast and famine strategy. Feast phase was studied using carbon, nitrates and phosphate in the ratio of 100:8:1 and famine phase was limited with the phosphate and nitrates. Co-culture resulted in highest specific growth rate (0.30 h−1) in the feast phase and the famine phase accounted the maximum polyhydroxybutyrate (PHB) accumulation (2.46 g PHB/L), followed by Acinetobacter junii BP25 (0.25 h−1 and 1.82 g PHB/L) and Aeromonas hydrophila ATCC 7966 (0.17 h−1 and 1.12 g PHB/L). Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR) structural analysis confirmed as PHB. PHB production using the co-culture could be integrated with biohydrogen process using volatile fatty acids (VFA) as a carbon source in the biorefinery framework.

Can circular bioeconomy be fueled by waste biorefineries — A closer look

With the depleting resources and climate change tipping us over the edge, what we urgently require is a rapid and revolutionary transformation-a circular economy (CE). The CE is represented as one of the most promising endeavors to integrate environmental benefits and economic activities in a sustainable way in this communication. Within the CE, bioeconomy is being established as a cornerstone for accomplishing a sustainable economy through dedicated use of waste resources. The intersection of CE and bioeconomy in the framework of waste biorefinery is also discussed with an additional emphasis on various elements that need to be considered for realizing sustainable transformations. It positions the concept of waste biorefinery as a tangible driver for combating the battles centered around resource scarcity, increasing demands, climate change and price volatility. It also traces the concepts of metabolism studies and policies to be putforth, which emphasize circularity as a substantial tool for industrial/urban innovations and revenue generation, while achieving environmental sustainability.

Utilisation/upgrading of orange peel waste from a biological biorefinery perspective.

Orange peel waste (OPW) (peels, pulp and seeds) is an underutilised residue coming from the orange juice industry. Its classical applications are cattle feeding and composting, while they cannot ensure a total use of OPW, so landfilling is also common practice. On the other side, OPW is very rich in sugars, polysaccharides, essential oils and polyphenols, so there is a vast literature focused on the development and optimization of technologies and processes to several products from OPW. In this review, papers on OPW-based bioprocesses are visited, discovering a wide landscape that goes from the composting and biogas processes on detoxified OPW (deoiled) to bioprocesses to bioethanol, chemicals, flavours and polymers. All these processes are prone to integration within the 2nd-generation biorefinery framework.

Autohydrolysis, pulping, and bleaching of Eucalyptus urograndis in a biorefinery framework

Autohydrolysis and kraft pulping were sequentially applied to Eucalyptus urograndis wood to obtain added-value products from hydrolysis liquor. A biorefinery approach was used to bleach the resulting solid phase containing the cellulose pulp with an optimized O–D–(EP)–D bleaching sequence, where O denotes delignification with the sequence D bleaching with chlorine dioxide and EP alkaline extraction with soda and hydrogen peroxide. The pulp was then beaten to obtain paper sheets. The two-stage process yielded pulp with a small Kappa number relative to conventional delignification (4.9 to 13.7 vs 17.1). Using autohydrolysis temperatures of 160 °C to 170 °C during 0 min to 15 min made the process selective towards the extraction of hemicelluloses (xylan up to 43.9%). Additionally, the Kappa number and brightness obtained after bleaching with an O-D-EP-D sequence were suitable for preparing dissolving grade pulp. The brightness of the pulp obtained was identical with that of the reference pulp (91.0%) and the Kappa number was smaller (0.2 to 0.6). Beating the pulp for 4500 PFI revolutions produced paper sheets with slightly better tensile strength and tear index than those for sheets from the reference pulp (viz., 90.3 N·m·g-1 and 9.9 mN·m²·g-1, respectively, versus 89.8 N·m·g-1 and 9.7 mN·m²·g-1, respectively).

Optimization of Laccase/Mediator System (LMS) Stage Applied in Fractionation of Eucalyptus globulus.

In a biorefinery framework, a laccase/mediator system treatment following autohydrolysis was carried out for eucalyptus wood prior to soda-anthraquinone pulping. The enzymatic and autohydrolysis conditions, with a view to maximizing the extraction of hemicelluloses while preserving the integrity of glucan, were optimized. Secondly, pulping of solid phase from Eucalyptus globulus wood autohydrolysis and the enzymatic process was carried out and compared with a conventional soda-anthraquinone (AQ) pulping process. The prehydrolysis and enzymatic delignification of the raw material prior to the delignification with soda- Anthraquinone (AQ) results in paper sheets with a lower kappa number and brightness and strength properties close to conventional soda-AQ paper and a liquid fraction rich in hemicellulose compounds that can be used in additional ways. The advantage of this biorefinery scheme is that it requires a lower concentration of chemical reagents, and lower operating times and temperature in the alkaline delignification stage, which represents an economic and environmental improvement over the conventional process.