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Catalysts
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Biomass Valorization
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Biomass Valorization

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Biomass Catalysis".

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 27358

Special Issue Editors

Dr. Jinguang Hu

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Guest Editor
Biorefining and Photo-Bioprocessing Research Lab, Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB T2L 1Y1, Canada
Interests: biomass valorization; sustainable energy; bioinspired materials/systems; protein engineering
Prof. Dr. Fei Shen

E-Mail Website
Guest Editor
Institute of Ecological and Environmental Sciences, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
Interests: waste biomass valorization; bioenergy resources; biobased materials
Prof. Dr. Brett I. Pletschke

E-Mail Website
Guest Editor
Enzyme Science Programme (ESP), Department of Biochemistry and Microbiology, Rhodes University, Makhanda (Grahamstown) 6140, Eastern Cape, South Africa
Interests: enzyme synergism; lignocellulose degradation; cellulase-hemicellulase synergism; biomass conversion; bio-economy

Special Issue Information

Dear Colleagues,

Concerns about increasing levels of energy security and environmental issues have motivated governments around the world to gradually transit from the traditional hydrocarbon-based “oil-refinery” to the sustainable carbohydrate-based “bio-refinery”. This biorefinery concept has been proposed as a means to maximally produce value-added bioproducts such as fuels, chemicals, and biomaterials from various biomass resources (namely, biomass valorization). Currently, there are two major conversion platforms for biomass-based biorefinery, employing either thermochemical processes such as combustion, pyrolysis, and gasification or biological processes such as enzymatic hydrolysis and aerobic/anaerobic fermentation. In addition, the novel biomass photo/photoelectric reforming platform has also started to receive increased attention. Realization of these biomass valorization technologies heavily depends on the development of tailored catalysts to overcome the thermodynamic barriers of recalcitrant biomass deconstruction and/or to modify/functionalize/activate the bio-products derived from biomass degradation.

This Special Issue is mainly devoted to the development and application of various conversion technologies for biomass valorization, with special focuses on heterogeneous catalytic, biocatalytic, and photo-electrocatalytic biomass deconstruction and modification/functionalization in a sustainable manner. Reviews and original research papers are invited from fundamental to applied research, and the potential topics include but are not limited to:

-   Biomass catalytic processing and pretreatment;

-   Biomass thermocatalytic conversion;

-   Biomass enzymatic deconstruction;

-   Biomass active enzyme discovery and application;

-   Biomaterial production, modification, and application;

-   Biomass photo-electrocatalytic reforming;

-   Catalysts development and characterization;

-   Biomass catalytic conversion modeling;

-   Biomass resources development;

-   New concepts or processes for biomass valorization;

-   Clean production of bio-refinery;

-   Biomass valorization LCA and tech-economic analysis.

Assist. Prof. Dr. Jinguang Hu
Prof. Dr. Fei Shen
Prof. Dr. Brett I. Pletschke
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (7 papers)

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Research

Jump to: Review

10 pages, 3424 KiB  
Article
Biomass Photoreforming for Hydrogen Production over Hierarchical 3DOM TiO2-Au-CdS
by Na Zhong, Xinti Yu, Heng Zhao, Jinguang Hu and Ian D. Gates
Catalysts 2022, 12(8), 819; https://doi.org/10.3390/catal12080819 - 26 Jul 2022
Cited by 5 | Viewed by 1570
Abstract
Photocatalytic hydrogen production is a promising route to the provision of sustainable and green energy. However, the excess addition of traditional electron donors as the sacrificial agents to consume photogenerated holes greatly reduces the feasibility of this approach for commercialization. Herein, considering the [...] Read more.
Photocatalytic hydrogen production is a promising route to the provision of sustainable and green energy. However, the excess addition of traditional electron donors as the sacrificial agents to consume photogenerated holes greatly reduces the feasibility of this approach for commercialization. Herein, considering the abundant hydroxyl groups in cellulose, the major component of biomass, we adopted glucose (a component unit of cellulose), cellobiose (a structure unit of cellulose) and dissolving pulp (a pretreated cellulose) as electron donors for photocatalytic hydrogen production over a TiO2-Au-CdS material. The well-designed ternary TiO2-Au-CdS possesses a hierarchical three-dimensional ordered macroporous (3DOM) structure, which not only benefits light harvesting but can also facilitate mass diffusion to boost the reaction kinetics. As expected, the fabricated photocatalyst exhibits considerable hydrogen production from glucose (645.1 μmol·h−1·g−1), while the hydrogen production rates gradually decrease with the increased complexity in structure from cellobiose (273.9 μmol·h−1·g−1) to dissolving pulp (79.7 μmol·h−1·g−1). Other gaseous components such as CO and CH4 are also produced, indicating the partial conversion of biomass during the photoreforming process. This work demonstrates the feasibility of sustainable hydrogen production from biomass by photoreforming with a rational photocatalyst design. Full article
(This article belongs to the Special Issue Biomass Valorization)
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17 pages, 3431 KiB  
Article
Catalyst and Elemental Analysis Involving Biodiesel from Various Feedstocks
by Ines Simbi, Uyiosa Osagie Aigbe, Oluwaseun Oyekola and Otolorin Adelaja Osibote
Catalysts 2021, 11(8), 971; https://doi.org/10.3390/catal11080971 - 14 Aug 2021
Cited by 5 | Viewed by 2693
Abstract
The world is currently faced with the depletion of fossil fuel energy sources and their use is associated with environmental pollution. This has triggered the need to seek alternative energy sources that are renewable, sustainable and environmentally benign. Biodiesel, an alternative fuel of [...] Read more.
The world is currently faced with the depletion of fossil fuel energy sources and their use is associated with environmental pollution. This has triggered the need to seek alternative energy sources that are renewable, sustainable and environmentally benign. Biodiesel, an alternative fuel of interest, is obtainable from biomass feedstocks. In existing biodiesel fuel, there are concerns that it is a contaminant due to its elemental contents, which over time also affect its quality. This study aimed to investigate the influence of a bifunctional catalyst on the conversion of free fatty acids and the elemental composition of biodiesel obtained from waste oils of sunflower and palm feedstocks. The synthesised catalyst was characterised using BET, XRD, FTIR and SEM while ICP-OES and Rancimat were used for elemental contents and oxidation in feedstocks and biodiesels. The effect of Cu, Zn and Fe metals on the stability of synthesised biodiesel was further studied. The catalyst showed characteristics of bifunctionality with improved textural properties necessary for the conversion of high free fatty acids feedstocks to biodiesel, despite increasing Ca content within the produced biodiesel. Sunflower biodiesel showed superior fuel quality, although palm biodiesel had more oxidation stability. An increase in the concentration of metals decreased the induction period, with Cu and Fe being more effective than Zn metal. Full article
(This article belongs to the Special Issue Biomass Valorization)
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13 pages, 497 KiB  
Article
Revisiting the Phenomenon of Cellulase Action: Not All Endo- and Exo-Cellulase Interactions Are Synergistic
by Mariska Thoresen, Samkelo Malgas, Mpho Stephen Mafa and Brett Ivan Pletschke
Catalysts 2021, 11(2), 170; https://doi.org/10.3390/catal11020170 - 27 Jan 2021
Cited by 7 | Viewed by 2921
Abstract
The conventional endo–exo synergism model has extensively been supported in literature, which is based on the perception that endoglucanases (EGs) expose or create accessible sites on the cellulose chain to facilitate the action of processive cellobiohydrolases (CBHs). However, there is a lack of [...] Read more.
The conventional endo–exo synergism model has extensively been supported in literature, which is based on the perception that endoglucanases (EGs) expose or create accessible sites on the cellulose chain to facilitate the action of processive cellobiohydrolases (CBHs). However, there is a lack of information on why some bacterial and fungal CBHs and EGs do not exhibit synergism. Therefore, the present study evaluated and compared the synergistic relationships between cellulases from different microbial sources and provided insights into how different GH families govern synergism. The results showed that CmixA2 (a mixture of TlCel7A and CtCel5A) displayed the highest effect with BaCel5A (degree of synergy for reducing sugars and glucose of 1.47 and 1.41, respectively) in a protein mass ratio of 75–25%. No synergism was detected between CmixB1/B2 (as well as CmixC1/C2) and any of the EGs, and the combinations did not improve the overall cellulose hydrolysis. These findings further support the hypothesis that “not all endo-to exo-cellulase interactions are synergistic”, and that the extent of synergism is dependent on the composition of cellulase systems from various sources and their compatibility in the cellulase cocktail. This method of screening for maximal compatibility between exo- and endo-cellulases constitutes a critical step towards the design of improved synergistic cellulose-degrading cocktails for industrial-scale biomass degradation. Full article
(This article belongs to the Special Issue Biomass Valorization)
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Review

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19 pages, 1552 KiB  
Review
Defining the Frontiers of Synergism between Cellulolytic Enzymes for Improved Hydrolysis of Lignocellulosic Feedstocks
by Mpho S. Mafa, Brett I. Pletschke and Samkelo Malgas
Catalysts 2021, 11(11), 1343; https://doi.org/10.3390/catal11111343 - 8 Nov 2021
Cited by 17 | Viewed by 2377
Abstract
Lignocellulose has economic potential as a bio-resource for the production of value-added products (VAPs) and biofuels. The commercialization of biofuels and VAPs requires efficient enzyme cocktail activities that can lower their costs. However, the basis of the synergism between enzymes that compose cellulolytic [...] Read more.
Lignocellulose has economic potential as a bio-resource for the production of value-added products (VAPs) and biofuels. The commercialization of biofuels and VAPs requires efficient enzyme cocktail activities that can lower their costs. However, the basis of the synergism between enzymes that compose cellulolytic enzyme cocktails for depolymerizing lignocellulose is not understood. This review aims to address the degree of synergism (DS) thresholds between the cellulolytic enzymes and how this can be used in the formulation of effective cellulolytic enzyme cocktails. DS is a powerful tool that distinguishes between enzymes’ synergism and anti-synergism during the hydrolysis of biomass. It has been established that cellulases, or cellulases and lytic polysaccharide monooxygenases (LPMOs), always synergize during cellulose hydrolysis. However, recent evidence suggests that this is not always the case, as synergism depends on the specific mechanism of action of each enzyme in the combination. Additionally, expansins, nonenzymatic proteins responsible for loosening cell wall fibers, seem to also synergize with cellulases during biomass depolymerization. This review highlighted the following four key factors linked to DS: (1) a DS threshold at which the enzymes synergize and produce a higher product yield than their theoretical sum, (2) a DS threshold at which the enzymes display synergism, but not a higher product yield, (3) a DS threshold at which enzymes do not synergize, and (4) a DS threshold that displays anti-synergy. This review deconvolutes the DS concept for cellulolytic enzymes, to postulate an experimental design approach for achieving higher synergism and cellulose conversion yields. Full article
(This article belongs to the Special Issue Biomass Valorization)
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30 pages, 1090 KiB  
Review
Potential Valorization of Organic Waste Streams to Valuable Organic Acids through Microbial Conversion: A South African Case Study
by Sesethu Gift Njokweni, Annica Steyn, Marelize Botes, Marinda Viljoen-Bloom and Willem Heber van Zyl
Catalysts 2021, 11(8), 964; https://doi.org/10.3390/catal11080964 - 12 Aug 2021
Cited by 12 | Viewed by 4201
Abstract
The notion of a “biobased economy” in the context of a developing country such as South Africa (SA) necessitates the development of technologies that utilize sustainable feedstocks, have simple and robust operations, are feasible at small scale and produce a variety of valuable [...] Read more.
The notion of a “biobased economy” in the context of a developing country such as South Africa (SA) necessitates the development of technologies that utilize sustainable feedstocks, have simple and robust operations, are feasible at small scale and produce a variety of valuable bioproducts, thus fitting the biorefinery concept. This case study focuses on the microbial production of higher-value products from selected organic waste streams abundant in the South African agricultural sector using microbes adapted to utilize different parts of biomass waste streams. A ruminant-based carboxylate platform based on mixed or undefined anaerobic co-cultures of rumen microorganisms can convert the carbohydrate polymers in the lignocellulosic part of organic waste streams to carboxylic acids that can be upgraded to biofuels or green chemicals. Furthermore, yeast and fungi can convert the simpler carbohydrates (such as the sugars and malic acid in grape and apple pomace) to ethanol and high-value carboxylic acids, such as lactic, fumaric, succinic and citric acid. This review will discuss the combinational use of the ruminal carboxylate platform and native or recombinant yeasts to valorize biomass waste streams through the production of higher-value organic acids with various applications. Full article
(This article belongs to the Special Issue Biomass Valorization)
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41 pages, 5048 KiB  
Review
Heterogeneous Ru Catalysts as the Emerging Potential Superior Catalysts in the Selective Hydrogenation of Bio-Derived Levulinic Acid to γ-Valerolactone: Effect of Particle Size, Solvent, and Support on Activity, Stability, and Selectivity
by Mulisa Maumela, Sanette Marx and Reinout Meijboom
Catalysts 2021, 11(2), 292; https://doi.org/10.3390/catal11020292 - 23 Feb 2021
Cited by 20 | Viewed by 3860
Abstract
Catalytic hydrogenation of a biomass-derived molecule, levulinic acid (LA), to γ-valerolactone (GVL) has been getting much attention from researchers across the globe recently. This is because GVL has been identified as one of the potential molecules for replacing fossil fuels. For instance, GVL [...] Read more.
Catalytic hydrogenation of a biomass-derived molecule, levulinic acid (LA), to γ-valerolactone (GVL) has been getting much attention from researchers across the globe recently. This is because GVL has been identified as one of the potential molecules for replacing fossil fuels. For instance, GVL can be catalytically converted into liquid alkenes in the molecular weight range close to that found in transportation fuels via a process that does not require an external hydrogen source. Noble and non-noble metals have been used as catalysts for the selective hydrogenation of LA to GVL. Of these, Ru has been reported to be the most active metal for this reaction. The type of metal supports and solvents has been proved to affect the activity, selectivity, and yields of GVL. Water has been identified as a potential, effective “green” solvent for the hydrogenation of LA to GVL. The use of different sources of H2 other than molecular hydrogen (such as formic acid) has also been explored. In a few instances, the product, GVL, is hydrogenated further to other useful products such as 1,4-pentanediol (PD) and methyl tetrahydrofuran (MTHF). This review selectively focuses on the potential of immobilized Ru catalysts as a potential superior catalyst for selective hydrogenation of LA to GVL. Full article
(This article belongs to the Special Issue Biomass Valorization)
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22 pages, 1887 KiB  
Review
Production of Levulinic Acid from Cellulose and Cellulosic Biomass in Different Catalytic Systems
by Chen Liu, Xuebin Lu, Zhihao Yu, Jian Xiong, Hui Bai and Rui Zhang
Catalysts 2020, 10(9), 1006; https://doi.org/10.3390/catal10091006 - 3 Sep 2020
Cited by 34 | Viewed by 8237
Abstract
The reasonable and effective use of lignocellulosic biomass is an important way to solve the current energy crisis. Cellulose is abundant in nature and can be hydrolyzed to a variety of important energy substances and platform compounds—for instance, glucose, 5-hydroxymethylfurfural (HMF), levulinic acid [...] Read more.
The reasonable and effective use of lignocellulosic biomass is an important way to solve the current energy crisis. Cellulose is abundant in nature and can be hydrolyzed to a variety of important energy substances and platform compounds—for instance, glucose, 5-hydroxymethylfurfural (HMF), levulinic acid (LA), etc. As a chemical linker between biomass and petroleum processing, LA has become an ideal feedstock for the formation of liquid fuels. At present, some problems such as low yield, high equipment requirements, difficult separation, and serious environmental pollution in the production of LA from cellulose have still not been solved. Thus, a more efficient and green catalytic system of this process for industrial production is highly desired. Herein, we focus on the reaction mechanism, pretreatment, and catalytic systems of LA from cellulose and cellulosic biomass, and a series of existing technologies for producing LA are reviewed. On the other hand, the industrial production of LA is discussed in depth to improve the yield of LA and make the process economical and energy efficient. Additionally, practical suggestions for the enhancement of the stability and efficiency of the catalysts are also proposed. The use of cellulose to produce LA is consistent with the concept of sustainable development, and the dependence on fossil resources will be greatly reduced through the realization of this process route. Full article
(This article belongs to the Special Issue Biomass Valorization)
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