Physico-Chemical Alternatives in Lignocellulosic Materials in Relation to the Kind of Component for Fermenting Purposes (original) (raw)
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The complete bioconversion of the carbohydrate fraction is of great importance for a lignocellulosic-based biorefinery. However, due to the structure of the lignocellulosic materials, and depending basically on the main parameters within the pretreatment steps, numerous byproducts are generated and they act as inhibitors in the fermentation operations. In this sense, the impact of inhibitory compounds derived from lignocellulosic materials is one of the major challenges for a sustainable biomass-to-biofuel and-bioproduct industry. In order to minimise the negative effects of these compounds, numerous methodologies have been tested including physical, chemical, and biological processes. The main physical and chemical treatments have been studied in this work in relation to the lignocellulosic material and the inhibitor in order to point out the best mechanisms for fermenting purposes. In addition, special attention has been made in the case of lignocellulosic hydrolysates obtained by chemical processes with SO 2 , due to the complex matrix of these materials and the increase in these methodologies in future biorefinery markets. Recommendations of different detoxification methods have been given.
The current review is an attempt to cover various pre-treatment strategies such as physical, chemical, organosolve and biological pre-treatment in order to change the crystallinity of lignocellulosic biomass along with methods and strategies for inhibitor detoxification for improving the cellulose hydrolysis and fermentation. The presence of lignin in lignocellulosic biomass is the biggest hurdle and therefore a judicial pre-treatment selection technique is important, based on lignocellulosic mass composition analysis for improving overall saccharification. The production of inhibitors during pre-treatment is another cause of low saccharification owing to deactivation of cellulase enzyme. In this review a comprehensive discussion has been made of the impact of various pre-treatment strategies on overall hydrolysis and saccharification in view of the varied composition of lignocellulosic biomass. Various detoxification approaches have also been discussed, along with the economical bioprocessing issue, and their advantages and disadvantages. Bio refinery approaches have been important in this regard to make bioethanol production more economical
Molecules, 2018
A pretreatment of lignocellulosic biomass to produce biofuels, polymers, and other chemicals plays a vital role in the biochemical conversion process toward disrupting the closely associated structures of the cellulose-hemicellulose-lignin molecules. Various pretreatment steps alter the chemical/physical structure of lignocellulosic materials by solubilizing hemicellulose and/or lignin, decreasing the particle sizes of substrate and the crystalline portions of cellulose, and increasing the surface area of biomass. These modifications enhance the hydrolysis of cellulose by increasing accessibilities of acids or enzymes onto the surface of cellulose. However, lignocellulose-derived byproducts, which can inhibit and/or deactivate enzyme and microbial biocatalysts, are formed, including furan derivatives, lignin-derived phenolics, and carboxylic acids. These generation of compounds during pretreatment with inhibitory effects can lead to negative effects on subsequent steps in sugar flat-form processes. A number of physico-chemical pretreatment methods such as steam explosion, ammonia fiber explosion (AFEX), and liquid hot water (LHW) have been suggested and developed for minimizing formation of inhibitory compounds and alleviating their effects on ethanol production processes. This work reviews the physico-chemical pretreatment methods used for various biomass sources, formation of lignocellulose-derived inhibitors, and their contributions to enzymatic hydrolysis and microbial activities. Furthermore, we provide an overview of the current strategies to alleviate inhibitory compounds present in the hydrolysates or slurries.
Origin, Impact and Control of Lignocellulosic Inhibitors in Bioethanol Production—A Review
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Bioethanol production from lignocellulosic biomass is still struggling with many obstacles. One of them is lignocellulosic inhibitors. The aim of this review is to discuss the most known inhibitors. Additionally, the review addresses different detoxification methods to degrade or to remove inhibitors from lignocellulosic hydrolysates. Inhibitors are formed during the pretreatment of biomass. They derive from the structural polymers-cellulose, hemicellulose and lignin. The formation of inhibitors depends on the pretreatment conditions. Inhibitors can have a negative influence on both the enzymatic hydrolysis and fermentation of lignocellulosic hydrolysates. The inhibition mechanisms can be, for example, deactivation of enzymes or impairment of vital cell structures. The toxicity of each inhibitor depends on its chemical and physical properties. To decrease the negative effects of inhibitors, different detoxification methods have been researched. Those methods focus on the chemical mo...
Pretreatment of Lignocellulosic Materials as Substrates for Fermentation Processes
Molecules, 2018
Lignocellulosic biomass is an abundant and renewable resource that potentially contains large amounts of energy. It is an interesting alternative for fossil fuels, allowing the production of biofuels and other organic compounds. In this paper, a review devoted to the processing of lignocellulosic materials as substrates for fermentation processes is presented. The review focuses on physical, chemical, physicochemical, enzymatic, and microbiologic methods of biomass pretreatment. In addition to the evaluation of the mentioned methods, the aim of the paper is to understand the possibilities of the biomass pretreatment and their influence on the efficiency of biofuels and organic compounds production. The effects of different pretreatment methods on the lignocellulosic biomass structure are described along with a discussion of the benefits and drawbacks of each method, including the potential generation of inhibitory compounds for enzymatic hydrolysis, the effect on cellulose digestibi...
Bioconversion of lignocellulose: inhibitors and detoxification
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Bioconversion of lignocellulose by microbial fermentation is typically preceded by an acidic thermochemical pretreatment step designed to facilitate enzymatic hydrolysis of cellulose. Substances formed during the pretreatment of the lignocellulosic feedstock inhibit enzymatic hydrolysis as well as microbial fermentation steps. This review focuses on inhibitors from lignocellulosic feedstocks and how conditioning of slurries and hydrolysates can be used to alleviate inhibition problems. Novel developments in the area include chemical in-situ detoxification by using reducing agents, and methods that improve the performance of both enzymatic and microbial biocatalysts.
Pretreatment and conversion of lignocellulose biomass into valuable chemicals
In the past three decades, many studies on the production of biofuels and other chemicals have been conducted using renewable sources such as lignocellulosic biomass. Lignocellulosic biomasses are abundantly available in most countries and furthermore they are carbon neutral. However, the main problem in utilizing lignocellulosic materials lies in the recalcitrance of its bonding. This review provides a comprehensive overview and a brief discussion on producing biofuel and valuable chemicals from lignocellulose biomass. Various aspects of the physical, chemical, thermophysical, thermochemical and biological pretreatment of lignocellulosic materials are discussed in this review. The success in biofuel and chemical production strongly depends on the pretreatment method used. Overall, pretreatment is the major step in the successful production of valuable products from lignocellulosic biomass. a In % dry wt. b In $/dry ton. Fig. 1 Schematic diagram showing utilization of lignocellulose biomass.
Bio-based Products from Lignocellulosic Waste Biomass
Chemical & biochemical engineering quarterly, 2021
This review presents data on the chemical composition of harvest residues and food industry by-products as widely abundant representatives of lignocellulosic waste biomass. Pretreatment methods, with special emphasis on biological methods, are presented as an important step in utilization of lignocellulosic waste biomass for the production of sustainable biofuels and high-value chemicals. Special attention was paid to the methods of lignin isolation and its possible utilization within lignocellulosic biorefinery. The objectives of circular bioeconomy and the main aspects of lignocellulosic biorefinery are highlighted. Finally, current data on industrial, pilot, and research and development plants used in Europe for the production of a variety of bio-based products from different feedstocks are presented.
Pretreatmentsemployed in lignocellulosic materials for bioethanol production: An overview
Lignocellulosic materials are raw materials with high cellulose content and they constitute the most abundant sources of biomass on planet. They are attractive for their low cost and high availability in diverse climates and places for the bioethanol production, however, the main impediment for its use is the appropriate selection from the technological and economic point of view of the stages of pretreatments and hydrolysis, that allow the breaking down of the lignocellulosic matrix to obtain the necessary substrates in the processes of fermentation. Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol, which have been divided in three groups for its study in: physical-chemical, hydrothermal and biological. The aim of this paper is to analyze the potential of several pretreatment methods for bioethanol production from lignocellulosic materials.