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Pretreatment and Bioconversion of Crop Residues II

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A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Agricultural Biosystem and Biological Engineering".

Deadline for manuscript submissions: closed (20 December 2023) | Viewed by 13305

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Special Issue Editors

Prof. Dr. Carlos Martín

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Guest Editor

1. Department of Biotechnology, Inland Norway University of Applied Sciences, 2317 Hamar, Norway
2. Department of Chemistry, Umeå University, 901 87 Umeå, Sweden
Interests: lignocellulosic materials; pretreatment; enzymatic hydrolysis of cellulose; biorefineries; biochemical conversion of lignocellulose; cellulosic ethanol; biofuels
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Prof. Dr. Eulogio Castro

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Department of Chemical, Environmental and Materials Engineering, University of Jaén, 23071 Jaén, Spain
Interests: agricultural residues; lignocellulosic materials; sugars; biorefineries; bioproducts
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Decreasing the dependence on fossil resources is crucial for alleviating climate change threats. Biorefineries are an alternative for producing fuels and chemicals that are, today, produced by fossil-based industries. Crop residues, generated in large amounts due to the expansion of agricultural production, are renewable and cost-effective feedstocks for biorefineries.

Pretreatment is fundamental for lignocellulose biorefining, since it activates cellulose for enzymatic saccharification and facilitates the selective separation of biomass components for their further processing. The effectiveness of pretreatment is feedstock-dependent, and efficient methods need to be developed, so that the biorefining of different crop residues can be implemented at the commercial scale.

As a response to the readers’ acceptance of the recently published Special Issue “Pretreatment and Bioconversion of Crop Residues”, we are pleased to invite contributions to the second edition of the series. This call is aimed at presenting the latest advances in pretreatment and novel bioconversion approaches applicable to agricultural, agro-industrial, and food industry residues.

Prof. Dr. Carlos Martín
Prof. Dr. Eulogio Castro
Guest Editors

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Keywords

pretreatment
bioconversion
crop residues
biomass
enzymatic hydrolysis
lignocellulosic materials
biorefineries

Published Papers (9 papers)

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Research

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12 pages, 616 KiB

Open AccessArticle

Comparative Study of the Convertibility of Pretreated Miscanthus Straw Using Enzyme Preparations Produced by Different Recombinant Strains of Penicillium verruculosum

by Dmitrii O. Osipov, Anna S. Dotsenko, Margarita V. Semenova, Alexandra M. Rozhkova and Arkady P. Sinitsyn

Agronomy 2024, 14(3), 499; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy14030499 - 28 Feb 2024

Viewed by 546

Abstract

Non-edible cellulosic biomass from perennial herbaceous plants is a promising and abundant feedstock for replacing slow-growing woody plants used in biotechnological applications. Herbaceous plant biomass, as other types of plant biomass, requires pretreatment before biochemical conversion. In this study, miscanthus straw was pretreated using different methods and subjected to enzymatic hydrolysis with Penicillium verruculosum enzyme complexes under laboratory conditions. The convertibility after enzymatic hydrolysis varied from 15% to 66%, depending on the pretreatment method. Dilute alkaline pretreatment showed the highest convertibility compared to other methods, reaching up to 66%. The efficiency of dilute acid pretreatment was relatively low compared to other methods. The maximum convertibility was 37% for sulfuric acid pretreatment (the least efficient) and 51% for nitric acid. Convertibility was almost equal with 43% for white liquor and 46% for hot water. The glucose-to-xylose ratio was 4.7:1 for dilute alkaline pretreatment and 11–13:1 for white liquor. Both sulfuric and nitric acid resulted in a low xylose content in the enzymatic hydrolysates. Low-xylose hydrolysates with less than 2% of the glucose amount can be produced by hot water pretreatment. Preparation C, enriched with endoglucanase I from T. reesei and endoglucanase II from P. verruculosum, was found to be the most effective of the different enzyme preparations (EPs) tested. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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18 pages, 2731 KiB

Open AccessArticle

Sodium Carbonate Pulping of Wheat Straw—An Alternative Fiber Source for Various Paper Applications

by Friedrich Steffen, Tamas Kordsachia, Tobias Heizmann, Maximilian Paul Eckardt, Yue Chen and Bodo Saake

Agronomy 2024, 14(1), 162; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy14010162 - 11 Jan 2024

Cited by 2 | Viewed by 1225

Abstract

European paper mills are currently facing the question of whether recovered paper, their main raw material, will be available in sufficient quantities and an acceptable quality in the future. An alternative to recovered paper or wood fiber is the use of agricultural residues such as wheat straw. Sodium carbonate-based straw pulping processes have the advantage of not requiring recausticizing for chemical recovery, which reduces investment and operating costs. With the addition of oxygen, delignification can be significantly improved to provide pulps suitable for bleaching. This study compares the pulping of wheat straw using sodium carbonate, sodium carbonate + oxygen, and sodium carbonate + sodium hydroxide + oxygen. Pulping parameters such as temperature, retention time, and chemical charge were varied, and their influence on pulp properties was studied. The use of sodium carbonate alone produced pulps with high yields of up to 72% and comparably high burst and compressive strength. The addition of oxygen and small amounts of sodium hydroxide produced pulps with a high initial brightness of 42 %ISO and a low kappa number (18), still at high pulp yields of 62%. These pulps were two-stage bleached to achieve brightness levels of up to 73 %ISO. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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23 pages, 1943 KiB

Open AccessArticle

Sequential Acid/Alkali Pretreatment for an Olive Tree Pruning Biorefinery

by Manuel J. Díaz, Pedro M. Ferrero and Manuel Moya

Agronomy 2023, 13(11), 2682; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13112682 - 25 Oct 2023

Viewed by 784

Abstract

Olive tree pruning is an abundant and renewable lignocellulosic residue, which is generally burned in the fields, causing economic costs and environmental problems. This lignocellulosic residue can be considered a suitable raw material for the production of a wide range of byproducts in a biorefinery context due to its high content of potentially fermentable carbohydrates. To take advantage of its sugar content, pretreatment is necessary to enhance the accessibility of the enzymes to the cellulosic fraction. The aim of this work is to obtain sugars contained in olive tree pruning as a substrate for the production of bioethanol by fermentation. Specifically, the production of fermentable sugars by sequential pretreatment with sulfuric acid and sodium hydroxide is studied. A two-factor rotatable composite central design temperature and catalyst concentration (H₂SO₄ and NaOH) has been generated, and response surface methodology has been used to discuss and optimize the responses. This work shows that under optimal pretreatment conditions (130 °C, 1.90% w/v H₂SO₄ and 130 °C, 1.49% w/v NaOH) of 1 kg of olive tree pruning, a solution rich in sugars (102 g of glucose and 61 g of xylose) and a solid residue generating 99 g of glucose by enzymatic hydrolysis is obtained. Moreover, applying the combined severity to the acid pretreatment, it has been determined that 20% of the olive tree pruning is fast solubilization, and it was also found that the apparent activation energy of the acid hydrolysis reaction is 85.07 kJ/mol. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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21 pages, 2336 KiB

Open AccessArticle

Techno-Economic Evaluation of Downdraft Fixed Bed Gasification of Almond Shell and Husk as a Process Step in Energy Production for Decentralized Solutions Applied in Biorefinery Systems

by Luís Carmo-Calado, Manuel Jesús Hermoso-Orzáez, José La Cal-Herrera, Paulo Brito and Julio Terrados-Cepeda

Agronomy 2023, 13(9), 2278; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13092278 - 29 Aug 2023

Viewed by 850

Abstract

The objective of the present study was to carry out a technical study of the gasification of almond shells and husks at different temperatures and, subsequently, an economic analysis for the in situ installation of a decentralized unit to produce electricity, through a syngas generator, that would overcome the use of fossil fuels used in this agroindustry. The gasification tests were carried out at three different temperatures (700, 750 and 800 °C) and the results for the tests carried out were as follows: a 50:50 mixture of almond husks and shells was found to have a lower heating value of value of 6.4 MJ/Nm³, a flow rate of 187.3 Nm³/h, a syngas yield of 1.9 Nm³/kg, cold gas efficiency of 68.9% and carbon conversion efficiency of 70.2%. Based on all the assumptions, a 100 kg/h (100 kWh) installation was proposed, located near the raw material processing industries studied, for an economic analysis. The technical–economic analysis indicated that the project was economically viable, under current market conditions, with a calculated net present value of k€204.3, an internal rate of return of 20.84% and a payback period of 5.7 years. It was concluded that thermal gasification is a perfectly suitable technology for the recovery of raw materials of lignocellulosic origin, presenting very interesting data in terms of economic viability for the fixed bed gasification system. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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24 pages, 3453 KiB

Open AccessArticle

Alternatives for the Valorization of Avocado Waste Generated in the Different Links of the Value Chain Based on a Life-Cycle Analysis Approach

by Maria Camila Garcia-Vallejo, Tatiana Agudelo Patiño, Jhonny Alejandro Poveda-Giraldo, Sara Piedrahita-Rodríguez and Carlos Ariel Cardona Alzate

Agronomy 2023, 13(9), 2229; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13092229 - 25 Aug 2023

Cited by 3 | Viewed by 1371

Abstract

This work evaluates the sustainability of small-scale biorefineries as a potential enterprise alternative to be introduced in rural areas based on experimental and simulation data. Four scenarios were evaluated: the first scenario involves the production of guacamole, the second involves the production of animal feed, and the third and fourth scenarios involve the extraction of bioactive compounds and the production of avocado oil or animal feed, respectively. In addition, all scenarios produce biogas and fertilizer. Each of the scenarios were evaluated considering the technical, economic, environmental, and social aspects. As a main result, the first scenario showed the lowest operating and investment costs, as well as the lowest economic profitability (profit margin 35%). On the other hand, the third and fourth scenarios present the highest investment and operating expenses (OpEx USD 6.2 million per year and CapEx USD 1.0 million), but their profit margins are in the 60–70% range. Furthermore, a life-cycle assessment (LCA) was carried out and allows inferring that the transformer link presents the highest environmental impact of the entire value chain and that the carbon footprint for all scenarios ranges between 1.01–2.41 kg

C O_{2}

eq per kg avocado. Similarly, the social impact methodology shows that the proposed scenarios do not present any social risk. Thus, the biorefinery for animal feed, bioactive compounds, biogas, and fertilizer was selected as the best option to be implemented in Caldas. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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20 pages, 11091 KiB

Open AccessArticle

Energy Assessment of Second-Generation (2G) Bioethanol Production from Sweet Sorghum (Sorghum bicolor (L.) Moench) Bagasse

by Iosvany López-Sandin, Rosa M. Rodríguez-Jasso, Guadalupe Gutiérrez-Soto, Gilver Rosero-Chasoy, Shiva, K. D. González-Gloria and Héctor A. Ruiz

Agronomy 2022, 12(12), 3106; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12123106 - 07 Dec 2022

Cited by 3 | Viewed by 1401

Abstract

Sweet sorghum bagasse (SSB) provides a raw material rich in polysaccharides that can be converted into biofuel and other high-value-added bioproducts under the biorefinery concept. The aim of this study was to evaluate the effect of hydrothermal pretreatment on the availability of SSB fermentable sugars for bioethanol production, considering the energy balance of the process. For this, the biomass was subjected to one process, pre-saccharification simultaneous and fermentation (PSSF). Previously, the temperature, time, and particle size effect were determined, as well as the enzymatic load for the more significant release of monomeric sugars. It was observed that the increase in the pretreatment severity, defined by the severity factor [log(R_o)], resulted in a more significant release of sugar and energy consumption. In the PSSF, bioethanol production was 22.17 g/L, with a total energy consumption of 2.46 MJ/g of processed biomass, of which 79.14% was by concept of electricity. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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16 pages, 3298 KiB

Open AccessArticle

Covalent Immobilisation of an Aspergillus niger Derived Endo-1,4-β-Mannanase, Man26A, on Glutaraldehyde-Activated Chitosan Nanoparticles for the Effective Production of Prebiotic MOS from Soybean Meal

by Amy S. Anderson, Lithalethu Mkabayi, Samkelo Malgas, Naveen Kango and Brett I. Pletschke

Agronomy 2022, 12(12), 2993; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12122993 - 28 Nov 2022

Viewed by 1303

Abstract

An Aspergillus niger endo-1,4-β-mannanase, Man26A, was confirmed by FTIR and XRD to be immobilised on glutaraldehyde-activated chitosan nanoparticles via covalent bonding. The immobilisation (%) and activity yields (%) were 82.25% and 20.75%, respectively. The biochemical properties (pH, temperature optima, and stability) were then comparatively evaluated for both the free and immobilised Man26A. The optimal activity of Man26A shifted to a lower pH after immobilisation (pH 2.0–3.0, from pH 5 for the free enzyme), with the optimum temperature remaining unchanged (60 °C). The two enzymes exhibited identical thermal stability, maintaining 100% activity for the first 6 h at 55 °C. Substrate-specific kinetic analysis showed that the two enzymes had similar affinities towards locust bean gum (LBG) with varied V_max values. In contrast, they showed various affinities towards soybean meal (SBM) and similar V_max values. The immobilised enzyme was then employed in the enhancement of the functional feed/prebiotic properties of SBM from poultry feed, increasing mannooligosaccharides (MOS) quantities. The SBM main hydrolysis products were mannobiose (M2) and mannose (M1). The SBM-produced sugars could be utilised as a carbon source by probiotic bacteria; Streptococcus thermophilus, Bacillus subtilis, and Lactobacillus bulgaricus. The results indicate that the immobilised enzyme has the potential for use in the sustainable and cost-effective production of prebiotic MOS from agricultural biomass. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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19 pages, 4044 KiB

Open AccessArticle

Bioethanol Production from Steam-Exploded Barley Straw by Co-Fermentation with Escherichia coli SL100

by Manuel J. Díaz, Manuel Moya and Eulogio Castro

Agronomy 2022, 12(4), 874; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy12040874 - 02 Apr 2022

Cited by 18 | Viewed by 2576

Abstract

Second-generation bioethanol is considered a suitable option for replacing fossil fuels. Agricultural residues are being studied as feedstocks for sugar generation, which are in turn converted into ethanol. Among them, barley straw (BS) is a promising raw material, due to its high abundance, lignocellulosic composition and lack of other practical applications. Under these assumptions, the central aim of this study is to suggest an efficient bioethanol production scheme from BS at different levels of integration in co-fermentation with Escherichia coli SL100, including separate hydrolysis and co-fermentation (SHCF), simultaneous saccharification and co-fermentation (SSCF), and presaccharification and simultaneous saccharification and co-fermentation (PSSCF), using the water-insoluble solid (WIS) and slurry fractions obtained after steam explosion (SE) pretreatment. The best results in terms of ethanol yield were achieved following the SHCF process, using the WIS and the slurry as substrates, with yields of 89.1% and 78.8% of the theoretical maximum, respectively. Considering all of the above points, the following scheme is proposed for the conversion of BS into ethanol: SE pretreatment (160 °C, 30 min) of BS previously soaked overnight in 2.88% w/v phosphoric acid solution, filtration of the slurry, followed by enzymatic hydrolysis and co-fermentation of the two fractions obtained separately, with previous detoxification of the prehydrolysate with ammonium hydroxide (5 N). Under these conditions, 19.43 g of bioethanol was produced from 100 g of BS. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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Review

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28 pages, 1788 KiB

Open AccessReview

Pretreatment and Bioconversion for Valorization of Residues of Non-Edible Oilseeds

by Eulogio Castro, Knut Olav Strætkvern, Juan Miguel Romero-García and Carlos Martín

Agronomy 2023, 13(9), 2196; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13092196 - 22 Aug 2023

Cited by 1 | Viewed by 1332

Abstract

Biodiesel production currently follows a first-generation model using edible oils as raw materials. Such a production model is unsustainable, considering that it is limited by the high cost of edible oils, competes with the food sector, and is linked to deforestation and other environmental threats. Changing the raw material base to non-edible oils provides an opportunity to increase the sustainability of the biodiesel industry and to avoid conflicts with food production. Processing non-edible oilseeds for extracting the oil to be used for producing biodiesel generates large amounts of residues, such as de-oiled cakes, seed husks, and fruit shells and pods as well as plant stems and leaves resulting from pruning and other agronomy practices. Most of those residues are currently disposed of by burning or used in a suboptimal way. Bioconversion following the sugar platform route, anaerobic digestion, or enzyme production provides means for upgrading them to advanced biofuels and high-added value products. Bioconversion of plant biomass, including oilseed residues, requires pretreatment to enhance their susceptibility to enzymes and microorganisms. This review provides an outlook on bioconversion approaches applicable to different residues of oilseed-bearing plant species. Recent reports on the pretreatment of non-edible oilseed residues for enhancing their bioconversion through either the sugar platform route or anaerobic digestion are critically discussed. This review is based on an exhaustive Web of Science search performed in January–May 2023. Full article

(This article belongs to the Special Issue Pretreatment and Bioconversion of Crop Residues II)

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