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Bioenergy and Biobased Technologies to Support a Green Transition
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Bioenergy and Biobased Technologies to Support a Green Transition

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A4: Bio-Energy".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 15753

Special Issue Editors

Prof. Dr. Solange I. Mussatto

E-Mail Website
Guest Editor
Department of Biotechnology and Biomedicine, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
Interests: fermentation; biomass; biorefinery; biofuels; bio-based products; techno-economic analysis; life cycle assessment
Special Issues, Collections and Topics in MDPI journals
Dr. Giuliano Dragone

E-Mail Website
Guest Editor
Department of Biotechnology and Biomedicine, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
Interests: lignocellulosic biomass; fermentation; biorefinery; industrial biotechnology; bioethanol; biofuels; biobased products; sustainability

Special Issue Information

Dear Colleagues,

The need to reduce the environmental footprint and the desire to convert the fossil-based economy into a greener economy have led to a growing interest in the development of biobased technologies in all industrial sectors. Today, the development of new biomass-based processes is one of the main drivers of our current society to move toward a more sustainable future with reduced greenhouse gas emissions and a more appropriate use of natural resources.

Several studies on technoeconomic assessment and life cycle analysis have shown promising data on the use of biomass for the production of valuable compounds. However, some important points still have to be improved in order to create technologies with enough robustness for implementation on a large scale. Efforts are still required, for example, to develop efficient and cost-competitive strategies for biomass fractionation, fermentation, as well as for product separation from hydrolysate-based fermentation media. Lignin valorization and the development of biorefineries are also promising approaches to make the conversion of biomass into valuable products more economically feasible.

The aim of this Special Issue on “Bioenergy and Biobased Technologies to Support a Green Transition” is to collect high-quality scientific contributions regarding recent developments and ideas in areas related to the production of bioenergy, biofuels, and biobased products. Potential topics include but are not limited to: (a) biomass conversion by chemical, thermal or fermentation routes; (b) biomass pretreatment and hydrolysis; (c) fermentation of biomass hydrolysates (including strain selection and process optimization); (d) engineering of microbial strains for fermentation of biomass hydrolysates; (e) development and/or use of chemical catalysts for application on the conversion of biomass; (f) downstream process for separation and purification of biobased products; (g) lignin conversion/valorization; (h) process integration and development of biorefineries; (i) technoeconomic assessment and lifecycle analysis of biobased processes.

Prof. Dr. Solange I. Mussatto
Dr. Giuliano Dragone
Guest Editors

Manuscript Submission Information

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Keywords

  • Bioenergy production
  • Biofuel production
  • Biobased products
  • Chemical and thermal conversion of biomass
  • Biomass pretreatment and hydrolysis
  • Fermentation of biomass hydrolysates
  • Microorganisms of interest for use in the conversion of biomass hydrolysates
  • Strain improvement for conversion of biomass hydrolysates
  • Downstream process for separation of biobased products
  • Lignin conversion/valorization
  • Biorefinery
  • Technoeconomic assessment of biobased technologies
  • Life cycle analysis of biobased technologies

Published Papers (7 papers)

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Research

19 pages, 3778 KiB  
Article
Effective Mild Ethanol-Based Organosolv Pre-Treatment for the Selective Valorization of Polysaccharides and Lignin from Agricultural and Forestry Residues
by Florbela Carvalheiro, Luís C. Duarte, Filipa Pires, Vanmira Van-Dúnem, Luís Sanfins, Luísa B. Roseiro and Francisco Gírio
Energies 2022, 15(15), 5654; https://doi.org/10.3390/en15155654 - 4 Aug 2022
Cited by 7 | Viewed by 1652
Abstract
Organosolv pre-treatments aiming to selectively remove and depolymerise lignin and hemicellulose and yield an easily digestible cellulose fraction are one of the potential options for industrial implementation within the biorefinery concept. However, the use of high temperatures and/or high catalyst concentrations is still [...] Read more.
Organosolv pre-treatments aiming to selectively remove and depolymerise lignin and hemicellulose and yield an easily digestible cellulose fraction are one of the potential options for industrial implementation within the biorefinery concept. However, the use of high temperatures and/or high catalyst concentrations is still hindering its wide adoption. In this work, mild temperature organosolv processes (140 °C) that were either non-catalysed or catalysed with sulphuric or acetic acid were compared to standard similar conditions using ethanol-based organosolv for both wheat straw (WS) and eucalyptus wood residues (ERs) as agricultural and forestry-derived model raw materials, respectively. The experimental results demonstrated that high cellulose purities could be obtained for the catalysed ethanol-based processing of the WS, which resulted in high saccharification yields (>80%), conversely to the non-catalysed process, which only reached values close to 70%. For eucalyptus residues (ERs), the pulp yields obtained were lower than the values obtained for the WS, suggesting that the ERs were a more reactive material. Cellulose purity was higher than that obtained for the corresponding treatment for the WS, with the highest cellulose purity being obtained for the ethanol-based process catalysed with sulphuric acid. Both materials presented high lignin yield recovery in the liquid stream. Full article
(This article belongs to the Special Issue Bioenergy and Biobased Technologies to Support a Green Transition)
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Figure 1

Figure 1
<p>Particle size distribution (expressed in g/100 g of raw material) of the wheat straw (<bold>a</bold>) and eucalyptus residue (<bold>b</bold>) samples used in this work.</p> Full article ">Figure 2
<p>Product distribution obtained for wheat straw (WS) using ethanol-based organosolv fractionation (no catalyst added) for glucan (<bold>a</bold>), (arabino)xylan (<bold>b</bold>), and lignin (<bold>c</bold>). Gn, glucan; GlcOS, gluco-oligosaccharides; ArXn, (arabino)xylan; (A)XOS, xylo-oligosaccharides (arabinosyl-substituted); Glc, glucose; Xyl, xylose; Ara, arabinose; HMF, 5-hydroxymethylfurfural.</p> Full article ">Figure 3
<p>Product distribution obtained for eucalyptus residues (ERs) using ethanol-based organosolv fractionation (no catalyst added) for glucan (<bold>a</bold>), (arabino)xylan (<bold>b</bold>) and lignin (<bold>c</bold>). Abbreviations are as in caption of <xref ref-type="fig" rid="energies-15-05654-f002">Figure 2</xref>.</p> Full article ">Figure 4
<p>Product distribution obtained for eucalyptus residues (ER) using ethanol-based organosolv fractionation (acetic acid added as catalyst, 190 °C, 120 min) for glucan (<bold>a</bold>) and lignin (<bold>b</bold>). Abbreviations are as in caption of <xref ref-type="fig" rid="energies-15-05654-f002">Figure 2</xref>.</p> Full article ">Figure 5
<p>Electropherogram showing the phenolic profile for non-catalysed ethanol organosolv hydrolysates from wheat straw (190 °C, 120 min). Matching was obtained via comparison with authentic standards (*) run under the same conditions as the sample.</p> Full article ">Figure 6
<p>Electropherogram showing the phenolic profile for non-catalysed ethanol organosolv washing solution from wheat straw (190 °C, 120 min). Matching was obtained via comparison with authentic standards (*) run under the same conditions as the sample.</p> Full article ">Figure 7
<p>Enzymatic saccharification of ethanol–water organosolv pulp obtained at 190 °C (no catalyst added) for wheat straw (WS) and eucalyptus residues (ERs).</p> Full article ">Figure 8
<p>Comparison of enzymatic saccharification of ethanol–water organosolv pulp obtained at 140 °C and 190 °C without (0) or with 50 mM acetic acid (50) as catalyst for wheat straw (WS) and eucalyptus residues (ERs).</p> Full article ">Figure 9
<p>Comparison of enzymatic saccharification of ethanol–water organosolv pulp obtained at 140 °C without (0) or with 50 mM sulphuric acid (50) as catalyst for wheat straw (WS) and eucalyptus residues (ERs).</p> Full article ">Figure 10
<p>Effect of enzyme dosage and enzymatic reaction time on the enzymatic saccharification of wheat straw ethanol–water organosolv pulp obtained at 190 °C without (<bold>a</bold>) and with 50 mM acetic acid (<bold>b</bold>), or at 140 °C and with 50 mM sulphuric acid as catalyst (<bold>c</bold>).</p> Full article ">Figure 11
<p>Effect of enzyme dosage and reaction time on the enzymatic saccharification of eucalyptus residues ethanol–water organosolv pulp obtained at 190 °C without (<bold>a</bold>) and with 50 mM acetic acid (<bold>b</bold>) or 140 °C and with 50 mM sulphuric acid as catalyst (<bold>c</bold>).</p> Full article ">Figure 11 Cont.
<p>Effect of enzyme dosage and reaction time on the enzymatic saccharification of eucalyptus residues ethanol–water organosolv pulp obtained at 190 °C without (<bold>a</bold>) and with 50 mM acetic acid (<bold>b</bold>) or 140 °C and with 50 mM sulphuric acid as catalyst (<bold>c</bold>).</p> Full article ">Figure 12
<p>Mass balance of the main constituents for the ethanol organosolv processing of wheat straw at 190 °C (120 min) without catalyst, followed by enzymatic hydrolysis and lignin precipitation of the organosolv liquid stream. AI Lignin, acid-insoluble lignin; * Denotes sugars in oligomeric form.</p> Full article ">Figure 13
<p>Balance and flow of the main constituent processing of eucalyptus residues using ethanol-organosolv at 190 °C (120 min) without catalyst and enzymatic hydrolysis. * Denotes sugars in oligomeric form.</p> Full article ">Figure 14
<p>Balance and flow of the main constituent processing of eucalyptus residues using ethanol organosolv at 140 °C (120 min) catalysed with sulphuric acid and enzymatic hydrolysis.</p> Full article ">
28 pages, 1860 KiB  
Article
Switchgrass and Giant Reed Energy Potential when Cultivated in Heavy Metals Contaminated Soils
by Leandro Gomes, Jorge Costa, Joana Moreira, Berta Cumbane, Marcelo Abias, Fernando Santos, Federica Zanetti, Andrea Monti and Ana Luisa Fernando
Energies 2022, 15(15), 5538; https://doi.org/10.3390/en15155538 - 30 Jul 2022
Cited by 10 | Viewed by 2049
Abstract
The cultivation of energy crops on degraded soils contributes to reduce the risks associated with land use change, and the biomass may represent an additional revenue as a feedstock for bioenergy. Switchgrass and giant reed were tested under 300 and 600 mg Cr [...] Read more.
The cultivation of energy crops on degraded soils contributes to reduce the risks associated with land use change, and the biomass may represent an additional revenue as a feedstock for bioenergy. Switchgrass and giant reed were tested under 300 and 600 mg Cr kg−1, 110 and 220 mg Ni kg−1, and 4 and 8 mg Cd kg−1 contaminated soils, in a two year pot experiment. Switchgrass yields (average aerial 330 g.m−2 and below ground 430 g.m−2), after the second year harvest, were not affected by Cd contamination and 110 mg Ni kg−1, but 220 mg Ni kg−1 significantly affected the yields (55–60% reduction). A total plant loss was observed in Cr-contaminated pots. Giant reed aboveground yields (control: 410 g.m−2), in the second year harvest, were significantly affected by all metals and levels of contamination (30–70% reduction), except in 110 mg Ni kg−1 pots. The belowground biomass yields (average 1600 g.m−2) were not affected by the tested metals. Contamination did not affect the high heating value (HHV) of switchgrass (average 18.4 MJ.kg−1) and giant reed aerial fractions (average 18.9 MJ.kg−1, stems, and 18.1 MJ.kg−1, leaves), harvested in the second year, indicating that the biomass can be exploited for bioenergy. Full article
(This article belongs to the Special Issue Bioenergy and Biobased Technologies to Support a Green Transition)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Switchgrass dry biomass production on Cd- and Ni- contaminated soils. For each biomass fraction and year, different lower-case letters indicate statistical significance (<span class="html-italic">p</span> &lt; 0.05) between treatments. Cd<sub>4</sub> and Cd<sub>8</sub>, 4 and 8 mg Cd kg<sup>−1</sup> dry matter; Ni<sub>110</sub> and Ni<sub>220</sub>, 110 and 220 mg Ni kg<sup>−1</sup> dry matter.</p> Full article ">Figure 2
<p>Giant reed aboveground dry biomass production on Cd-, Ni-, and Cr-contaminated soils. For each total aerial biomass (leaves and stems) and year, different lower-case letters indicate statistical significance (<span class="html-italic">p</span> &lt; 0.05) between treatments. Cd<sub>4</sub> and Cd<sub>8</sub>, 4 and 8 mg Cd kg<sup>−1</sup> dry matter; Ni<sub>110</sub> and Ni<sub>220</sub>, 110 and 220 mg Ni kg<sup>−1</sup> dry matter; Cr<sub>300</sub> and Cr<sub>600</sub>, 300 and 600 mg Cr kg<sup>−1</sup> dry matter.</p> Full article ">Figure 3
<p>Giant reed belowground dry biomass production on Cd-, Ni-, and Cr-contaminated soils. For each belowground biomass, different lower-case letters indicate statistical significance (<span class="html-italic">p</span> &lt; 0.05) between treatments. Cd<sub>4</sub> and Cd<sub>8</sub>, 4 and 8 mg Cd kg<sup>−1</sup> dry matter; Ni<sub>110</sub> and Ni<sub>220</sub>, 110 and 220 mg Ni kg<sup>−1</sup> dry matter; Cr<sub>300</sub> and Cr<sub>600</sub>, 300 and 600 mg Cr kg<sup>−1</sup> dry matter.</p> Full article ">Figure 4
<p>Global evaluation of switchgrass energy potential when cultivated in Cd- and Ni-contaminated soils. Yields (g/m<sup>2</sup>) are related with ash content (% dry weight, dw) (<b>A</b>), HHV (MJ/kg) (<b>B</b>), % mBAF (modified bioaccumulation factor) (<b>C</b>), and nitrogen content (g.kg<sup>−1</sup> dry weight, dw) (<b>D</b>). Cd<sub>4</sub> and Cd<sub>8</sub>, 4 and 8 mg Cd kg<sup>−1</sup> dry matter; Ni<sub>110</sub> and Ni<sub>220</sub>, 110 and 220 mg Ni kg<sup>−1</sup> dry matter.</p> Full article ">Figure 5
<p>Global evaluation of giant reed stems energy potential when cultivated in Cd-, Cr-, and Ni-contaminated soils. Yields (g/m<sup>2</sup>) are related with ash content (% dry weight, dw) (<b>A</b>), HHV (MJ/kg) (<b>B</b>), % mBAF (modified bioaccumulation factor) (<b>C</b>), and nitrogen content (g.kg<sup>−1</sup> dry weight, dw) (<b>D</b>). Cd<sub>4</sub> and Cd<sub>8</sub>, 4 and 8 mg Cd kg<sup>−1</sup> dry matter; Cr<sub>300</sub> and Cr<sub>600</sub>, 300 and 600 mg Cr kg<sup>−1</sup> dry matter; Ni<sub>110</sub> and Ni<sub>220</sub>, 110 and 220 mg Ni kg<sup>−1</sup> dry matter.</p> Full article ">
13 pages, 2763 KiB  
Article
Towards the Physiological Understanding of Yarrowia lipolytica Growth and Lipase Production Using Waste Cooking Oils
by Mattia Colacicco, Cosetta Ciliberti, Gennaro Agrimi, Antonino Biundo and Isabella Pisano
Energies 2022, 15(14), 5217; https://doi.org/10.3390/en15145217 - 19 Jul 2022
Cited by 8 | Viewed by 2023
Abstract
The yeast Yarrowia lipolytica is an industrially relevant microorganism, which is able to convert low-value wastes into different high-value, bio-based products, such as enzymes, lipids, and other important metabolites. Waste cooking oil (WCO) represents one of the main streams generated in the food [...] Read more.
The yeast Yarrowia lipolytica is an industrially relevant microorganism, which is able to convert low-value wastes into different high-value, bio-based products, such as enzymes, lipids, and other important metabolites. Waste cooking oil (WCO) represents one of the main streams generated in the food supply chain, especially from the domestic sector. The need to avoid its incorrect disposal makes this waste a resource for developing bioprocesses in the perspective of a circular bioeconomy. To this end, the strain Y. lipolytica W29 was used as a platform for the simultaneous production of intracellular lipids and extracellular lipases. Three different minimal media conditions with different pH controls were utilized in a small-scale (50 mL final volume) screening strategy, and the best condition was tested for an up-scaling procedure in higher volumes (800 mL) by selecting the best-performing possibility. The tested media were constituted by YNB media with high nitrogen restriction (1 g L−1 (NH4)2SO4) and different carbon sources (3% w v−1 glucose and 10% v v−1 WCO) with different levels of pH controls. Lipase production and SCO content were analyzed. A direct correlation was found between decreasing FFA availability in the media and increasing SCO levels and lipase activity. The simultaneous production of extracellular lipase (1.164 ± 0.025 U mL−1) and intracellular single-cell oil accumulation by Y. lipolytica W29 growing on WCO demonstrates the potential and the industrial relevance of this biorefinery model. Full article
(This article belongs to the Special Issue Bioenergy and Biobased Technologies to Support a Green Transition)
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Figure 1

Figure 1
<p>Small-scale batch cultures: optical density (OD<sub>600</sub>) measurements. Conditions A, B, and C were tested in the presence of 3% <span class="html-italic">w v</span><sup>−1</sup> glucose (Panel (<b>A</b>)) or 10% <span class="html-italic">v v</span><sup>−1</sup> WCO (Panel (<b>B</b>)) for 216 h. Data are mean values of three different measurements, and bars represent standard deviations.</p> Full article ">Figure 2
<p>Lipase activity over time for small-scale cultures during 216 h containing either glucose or WCO as a carbon source. Data are mean values of three different measurements, and bars represent standard deviations.</p> Full article ">Figure 3
<p>Nile red fluorescence intensities (BL-2 and BL-3) of yeast cells over time for small-scale cultures ((<b>A</b>): YNB at initial pH 4.5, (<b>B</b>): YNB at initial pH 7, and C: YNB in 0.4 M Tris-HCl buffer at final pH 7.2). Glc: 3% <span class="html-italic">w v</span><sup>−1</sup> glucose; WCO: 10% <span class="html-italic">v v</span><sup>−1</sup> waste cooking oil with 1% <span class="html-italic">v v</span><sup>−1</sup> Tween<sup>®</sup> 80. All media are presented with addition of 1 g L<sup>−1</sup> (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> as nitrogen source and were grown in 100 mL flasks in a final volume of 50 mL of liquid media for 216 h at 29 °C and 180 rpm.</p> Full article ">Figure 3 Cont.
<p>Nile red fluorescence intensities (BL-2 and BL-3) of yeast cells over time for small-scale cultures ((<b>A</b>): YNB at initial pH 4.5, (<b>B</b>): YNB at initial pH 7, and C: YNB in 0.4 M Tris-HCl buffer at final pH 7.2). Glc: 3% <span class="html-italic">w v</span><sup>−1</sup> glucose; WCO: 10% <span class="html-italic">v v</span><sup>−1</sup> waste cooking oil with 1% <span class="html-italic">v v</span><sup>−1</sup> Tween<sup>®</sup> 80. All media are presented with addition of 1 g L<sup>−1</sup> (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> as nitrogen source and were grown in 100 mL flasks in a final volume of 50 mL of liquid media for 216 h at 29 °C and 180 rpm.</p> Full article ">Figure 4
<p>Lipase activity data and growth data for up-scale batch cultures of <span class="html-italic">Y. lipolytica</span> W29 cells grown in condition C media supplemented with 10% <span class="html-italic">v v</span><sup>−1</sup> waste cooking oil. Data are mean values of three different measurements, and bars represent standard deviations.</p> Full article ">Figure 5
<p>HPLC analysis of released FFAs from scale-up cultures. Relative absorbance of released FFAs using heptadecanoic acid as internal standard (final concentration 1 mM). LA: linoleic acid; OA: oleic acid; SA: stearic acid; PA: palmitic acid. Data represent a representative experiment (from three independent experiments) performed in a single run.</p> Full article ">Figure 6
<p>Combination chart of number of cells × 10<sup>6</sup>/mL (<b>line</b>) and Nile red fluorescence intensity (BL-2) (<b>bars</b>) of yeast cells for up-scale batch cultures. For the determination of the number of cells × 10<sup>6</sup>/mL, data are mean values of three different measurements, and bars represent standard deviations, while for Nile red fluorescence intensity, data represent a representative experiment (from three independent experiments) performed in a single run.</p> Full article ">
21 pages, 4038 KiB  
Article
The Consistency of Yields and Chemical Composition of HTL Bio-Oils from Lignins Produced by Different Preprocessing Technologies
by Hilde Vik Halleraker, Konstantinos Kalogiannis, Angelos Lappas, Rafael C. A. Castro, Ines C. Roberto, Solange I. Mussatto and Tanja Barth
Energies 2022, 15(13), 4707; https://doi.org/10.3390/en15134707 - 27 Jun 2022
Cited by 4 | Viewed by 1546
Abstract
This work evaluates the effect of feedstock type and composition on the conversion of lignin to liquid by solvolysis with formic acid as hydrogen donor (LtL), by analyzing the yields and molecular composition of the liquid products and interpreting them in terms of [...] Read more.
This work evaluates the effect of feedstock type and composition on the conversion of lignin to liquid by solvolysis with formic acid as hydrogen donor (LtL), by analyzing the yields and molecular composition of the liquid products and interpreting them in terms of both the type and the preprocessing of the lignocellulosic biomass using chemometric data analysis. Lignin samples of different types and purities from softwood, hardwood, and grasses (rice straw and corn stover) have been converted to bio-oil, and the molecular composition analyzed and quantified using GC-MS. LtL solvolysis was found to be a robust method for lignin conversion in terms of converting all samples into bio-oils rich in phenolic compounds regardless of the purity of the lignin sample. The bio-oil yields ranged from 24–94 wt.% relative to lignin input and could be modelled well as a function of the elemental composition of the feedstock. On a molecular basis, the softwood-derived bio-oil contained the most guaiacol-derivatives, and syringol was correlated to hardwood. However, the connection between compounds in the bio-oil and lignin origin was less pronounced than the effects of the methods for biomass fractionation, showing that the pretreatment of the biomass dominates both the yield and molecular composition of the bio-oil and must be addressed as a primary concern when utilization of lignin in a biorefinery is planned. Full article
(This article belongs to the Special Issue Bioenergy and Biobased Technologies to Support a Green Transition)
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Figure 1

Figure 1
<p>Chromatogram of the oil from experiment SW1-kraft-360. Peaks from impurities in the solvent are in grey. Internal standard (IS) is hexadecane.</p> Full article ">Figure 2
<p>Chromatogram of the oil from experiment HW1-wetox-360. Peaks from impurities in the solvent are in grey. Internal standard (IS) is hexadecane.</p> Full article ">Figure 3
<p>Chromatogram of the oil from experiment G3-deac-360. Internal standard (IS) is hexadecane.</p> Full article ">Figure 4
<p>Quantification of guaiacol and selected substituted guaiacols in the produced bio-oils, given as wt.% in the obtained bio-oil. Sample names are specified in the experimental section.</p> Full article ">Figure 5
<p>Quantification of catechol and selected substituted catechols in the produced bio-oils, given as wt.% in the obtained bio-oil.</p> Full article ">Figure 6
<p>Quantification of phenol, selected substituted phenols and 2-(4-hydroxyphenyl) ethanol in the produced bio-oils, given as wt.% in the obtained bio-oil.</p> Full article ">Figure 7
<p>Quantification of syringol, 3-methoxy catechol, and 2-naphthol, given as wt.% in the obtained bio-oil.</p> Full article ">Figure 8
<p>Van Krevelen plot displaying the oxygen to carbon ratio (<span class="html-italic">x</span>-axis) and hydrogen to carbon ratio (<span class="html-italic">y</span>-axis) of samples of lignin feedstock and LtL-oils. The ratios are based on mol% (all samples were analyzed in duplicates and presented in this plot as an average of the two analyses. Where replicate experiments were performed, the average of the experiments in question is presented in this plot).</p> Full article ">Figure 9
<p>Multivariate regression model of predicted vs. measured oil yield based on the elemental analysis of lignin as specified in Equation (4). The regression coefficient is 0.87.</p> Full article ">Figure 10
<p>LtL-oil yield and solid yield presented as the weight percent of lignin input. SW3 experiments are included for comparison. The gas yields are given as a continuous line. Gas yields larger than 100% imply a significant contribution of gas-phase products from lignin feedstock reactions. All results regarding SW3 have previously been published in Løhre et al. [<a href="#B36-energies-15-04707" class="html-bibr">36</a>].</p> Full article ">Figure 11
<p>Biplot containing all variables and all experiments from this work. Experiments done with kraft-lignin are marked in green, the blue experiments are done with lignin from oxidative preprocessing, and the red experiments are performed with lignin from a deacetylation preprocessing.</p> Full article ">
12 pages, 555 KiB  
Article
Development of Sustainable Biorefinery Processes Applying Deep Eutectic Solvents to Agrofood Wastes
by María Guadalupe Morán-Aguilar, Iván Costa-Trigo, Alexandra María Ramírez-Pérez, Esther de Blas, Montserrat Calderón-Santoyo, María Guadalupe Aguilar-Uscanga and José Manuel Domínguez
Energies 2022, 15(11), 4101; https://doi.org/10.3390/en15114101 - 2 Jun 2022
Cited by 9 | Viewed by 1777
Abstract
The growing demand for renewable energies and the application of sustainable and economically viable biorefinery processes have increased the study and application of lignocellulosic biomass. However, due to lignocellulosic biomass recalcitrance hindering its efficient utilization, the pretreatment in the biorefinery is an essential [...] Read more.
The growing demand for renewable energies and the application of sustainable and economically viable biorefinery processes have increased the study and application of lignocellulosic biomass. However, due to lignocellulosic biomass recalcitrance hindering its efficient utilization, the pretreatment in the biorefinery is an essential stage for success in the process. Therefore, Deep Eutectic Solvent (DES) has emerged as a promising green pretreatment. During this study, the effect of choline chloride [ChCl]:glycerol and [ChCl]:urea on sugarcane bagasse and brewery bagasse is evaluated. Results have demonstrated that using [ChCl]:glycerol in SCB reduced about 80% and 15% for acid-soluble lignin and Klason lignin, respectively, and improved efficiency on saccharification yields, achieving conversions of 60, 80, and 100% for glucan, xylan, and arabinan, correspondingly. In the case of BSG saccharification yields, about 65% and 98% are attained for glucan and xylan, respectively, when [ChCl]:glycerol was employed. These results confirm the effectiveness and facility of DES pretreatment as a suitable method that can improve the biorefinery processes. Full article
(This article belongs to the Special Issue Bioenergy and Biobased Technologies to Support a Green Transition)
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Figure 1

Figure 1
<p>Released sugars (<b>a</b>) and saccharification yield (<b>b</b>) obtained after enzymatic hydrolysis carried out in SCB untreated and pretreated with different eutectic mixtures.</p> Full article ">Figure 2
<p>Released sugars (<b>a</b>) and saccharification yield (<b>b</b>) obtained after enzymatic hydrolysis carried out in BSG untreated and pretreated with different eutectic mixtures.</p> Full article ">
23 pages, 2376 KiB  
Article
A Simplified Techno-Economic Analysis for Sophorolipid Production in a Solid-State Fermentation Process
by María Martínez, Alejandra Rodríguez, Teresa Gea and Xavier Font
Energies 2022, 15(11), 4077; https://doi.org/10.3390/en15114077 - 1 Jun 2022
Cited by 13 | Viewed by 3095
Abstract
Sophorolipids (SLs) are microbial biosurfactants with an important role in industry and a continuously growing market. This research addresses the use of sustainable resources as feedstock for bioproducts. Winterization oil cake (WOC) and molasses are suitable substrates for SLs via solid-state fermentation (SSF). [...] Read more.
Sophorolipids (SLs) are microbial biosurfactants with an important role in industry and a continuously growing market. This research addresses the use of sustainable resources as feedstock for bioproducts. Winterization oil cake (WOC) and molasses are suitable substrates for SLs via solid-state fermentation (SSF). The model proposed herein was established for annually processing 750 t of WOC and comparing three support materials: wheat straw (WS), rice husk (RH), and coconut fiber (CF). Production capacity ranged 325–414 t of SLs per year. Unit Production Cost was 5.1, 5.7, and 6.9 USD/kg SL for WS, RH, and CF production models, respectively, and was slightly lower with other substrates. Financial parameters were CAPEX 6.7 MM USD and OPEX 1.9 MM USD/y, with a NPV, IRR and payback time of 6.4 MM USD, 31% and 3.2 y, respectively. SLs recovery from the solid matrix was the major contributor to operating costs, while fermentation equipment shaped capital costs. Results show that the physical properties (bulk density, WHC) of substrates and supports define process costs beyond substrate purchase costs and process yields in SSF systems. To our knowledge, this is the first attempt to model SLs production via SSF at full scale for the economic valuation of the SSF process. Full article
(This article belongs to the Special Issue Bioenergy and Biobased Technologies to Support a Green Transition)
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<p>Flow diagram for SL production from WOC by solid-state fermentation and by organic solvent recovery. Nomenclature: WOC: winterization oil cake, MOL: molasses, WS: wheat straw, EA: Ethyl acetate, SL: sophorolipids.</p> Full article ">Figure 2
<p>Major flows of the mass balance for the production of sophorolipids through Solid-State Fermentation. <sup>1</sup> Inert materials, not used in the bioconversion; <sup>2</sup> Material not considered as soluble carbohydrates and fats from MOL or WOC (proteins, fiber, and ash). <sup>3</sup> Water added to the solid mixture to reach water content suitable for yeast growth; <sup>4</sup> SL includes sophorolipids and impurities; <sup>5</sup> Includes reactive and non-reactive materials apart from fats entering the fermentation stage and cell proliferation during fermentation.</p> Full article ">Figure 3
<p>Financial parameters for the three supports (wheat straw, rice husk and coconut fiber) for a process in an existing edible oil plant and in a new facility (base scenario).</p> Full article ">Figure 4
<p>Financial parameters for the SLs production scenarios using different substrates. Nomenclature: WOC: Winterization oil cake; MOL: sugar molasse. (1) Jiménez-Peñalver et al., [<a href="#B41-energies-15-04077" class="html-bibr">41</a>] (2); Parekh et al. [<a href="#B25-energies-15-04077" class="html-bibr">25</a>].</p> Full article ">Figure 5
<p>Financial parameters for the SLs production scenarios using sunflower oil cake (SOC) and soybean oil (SO) as substrates. SSF: Solid State Fermentation. SmF: Submerged fermentation.</p> Full article ">Figure 6
<p>Investment of the studied cases for SL production by different substrates, supports and technology. (1) Jiménez-Peñalver et al. [<a href="#B41-energies-15-04077" class="html-bibr">41</a>]; (2) Parekh et al. [<a href="#B25-energies-15-04077" class="html-bibr">25</a>]; (3) Rashad et al., [<a href="#B12-energies-15-04077" class="html-bibr">12</a>].</p> Full article ">Figure 7
<p>Sensitivity analysis on SL production from WOC by SSF on the net present value (NPV) for the WS scenario under the conditions assumed in the model. Nomenclature: WS: wheat straw; WOC: Winterization oil cake.</p> Full article ">Figure 8
<p>Sensitivity analysis on SL production from WOC by SSF on the unit production cost (UPC) for the WS scenario under the conditions assumed in the model. Nomenclature: WS: wheat straw; WOC: Winterization oil cake.</p> Full article ">
12 pages, 2387 KiB  
Article
Effects of Inhibitory Compounds Present in Lignocellulosic Biomass Hydrolysates on the Growth of Bacillus subtilis
by Lucas van der Maas, Jasper L. S. P. Driessen and Solange I. Mussatto
Energies 2021, 14(24), 8419; https://doi.org/10.3390/en14248419 - 14 Dec 2021
Cited by 12 | Viewed by 2529
Abstract
This study evaluated the individual and combined effects of inhibitory compounds formed during pretreatment of lignocellulosic biomass on the growth of Bacillus subtilis. Ten inhibitory compounds commonly present in lignocellulosic hydrolysates were evaluated, which included sugar degradation products (furfural and 5-hydroxymethylfurfural), acetic [...] Read more.
This study evaluated the individual and combined effects of inhibitory compounds formed during pretreatment of lignocellulosic biomass on the growth of Bacillus subtilis. Ten inhibitory compounds commonly present in lignocellulosic hydrolysates were evaluated, which included sugar degradation products (furfural and 5-hydroxymethylfurfural), acetic acid, and seven phenolic compounds derived from lignin (benzoic acid, vanillin, vanillic acid, ferulic acid, p-coumaric acid, 4-hydroxybenzoic acid, and syringaldehyde). For the individual inhibitors, syringaldehyde showed the most toxic effect, completely inhibiting the strain growth at 0.1 g/L. In the sequence, assays using mixtures of the inhibitory compounds at a concentration of 12.5% of their IC50 value were performed to evaluate the combined effect of the inhibitors on the strain growth. These experiments were planned according to a Plackett–Burman experimental design. Statistical analysis of the results revealed that in a mixture, benzoic acid and furfural were the most potent inhibitors affecting the growth of B. subtilis. These results contribute to a better understanding of the individual and combined effects of inhibitory compounds present in biomass hydrolysates on the microbial performance of B. subtilis. Such knowledge is important to advance the development of sustainable biomanufacturing processes using this strain cultivated in complex media produced from lignocellulosic biomass, supporting the development of efficient bio-based processes using B. subtilis. Full article
(This article belongs to the Special Issue Bioenergy and Biobased Technologies to Support a Green Transition)
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Figure 1

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<p>Experimental growth curves of <span class="html-italic">Bacillus subtilis</span> in M9 minimal media containing different concentrations of inhibitory compounds. (<b>A</b>) Furfural; (<b>B</b>) 5-Hydroxymethylfurfural (5-HMF); (<b>C</b>) Acetic acid; (<b>D</b>) Benzoic acid; (<b>E</b>) Ferulic acid; (<b>F</b>) Vanillic acid; (<b>G</b>) Vanillin; (<b>H</b>) <span class="html-italic">p</span>-Coumaric acid; (<b>I</b>) 4-Hydroxybenzoic acid; (<b>J</b>) Syringaldehyde. Average standard deviation of the data points was 17%. The lag phases shown in the bar graphs are average values of multiple experiments. The black line corresponds to the average lag phase of the controls without inhibitors present.</p> Full article ">Figure 1 Cont.
<p>Experimental growth curves of <span class="html-italic">Bacillus subtilis</span> in M9 minimal media containing different concentrations of inhibitory compounds. (<b>A</b>) Furfural; (<b>B</b>) 5-Hydroxymethylfurfural (5-HMF); (<b>C</b>) Acetic acid; (<b>D</b>) Benzoic acid; (<b>E</b>) Ferulic acid; (<b>F</b>) Vanillic acid; (<b>G</b>) Vanillin; (<b>H</b>) <span class="html-italic">p</span>-Coumaric acid; (<b>I</b>) 4-Hydroxybenzoic acid; (<b>J</b>) Syringaldehyde. Average standard deviation of the data points was 17%. The lag phases shown in the bar graphs are average values of multiple experiments. The black line corresponds to the average lag phase of the controls without inhibitors present.</p> Full article ">Figure 2
<p>Average growth rates of <span class="html-italic">Bacillus subtilis</span> cultivated in M9 minimal media containing different concentrations of inhibitory compounds. (<b>A</b>) Furan derivatives; (<b>B</b>) Weak acids; (<b>C</b>) Guaiacyl derivatives; (<b>D</b>) <span class="html-italic">p</span>-Hydroxyl derivatives; (<b>E</b>) Syringaldehyde. Data from 4 independent experiments were normalized to the corresponding control, and average values are shown.</p> Full article ">Figure 3
<p>(<b>A</b>): Pareto chart of standardized effects to estimate the effect of inhibitors on the reduction in the growth rate of <span class="html-italic">B. subtilis</span>. Bars exceeding the dashed red reference line have a significant main effect for <span class="html-italic">p</span> &lt; 0.05. A: 5-HMF; B: Furfural; C: Acetic acid; D: Vanillin; E: Vanillic acid; F: Benzoic acid; G: 4-Hydroxybenzoic acid (4HBA); H: Ferulic acid (TFA); J: Syringaldehyde; K: <span class="html-italic">p</span>-Coumaric acid (PCA). (<b>B</b>): IC50 values determined to each inhibitory compound.</p> Full article ">
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