Impact and prospective of fungal pre-treatment of lignocellulosic biomass for enzymatic hydrolysis
01 May 2012-Biofuels, Bioproducts and Biorefining (John Wiley & Sons, Ltd)-Vol. 6, Iss: 3, pp 335-350
TL;DR: White-rot fungi (WRF) are commonly used in the bio pre-treatment process for secreting ligninolytic enzymes, a variety of donor substrates and selective degradation of lignin this paper.
Abstract: The presence of lignin in lignocellulosic biomass leads to a protective barrier which prevents enzymes from being accessible to cellulose and hemicellulose for hydrolysis. As a result, pre-treatment is a 'must' step for subse- quent enzymatic hydrolysis. Bio pre-treatment is normally conducted at low temperatures and low pressures without using expensive equipment, chemical agents, reactors, and additional energy for lignin removal and biomass struc- ture destruction. Therefore, it is a green, safe, and inexpensive method. White-rot fungi (WRF), a group of fungi (more than 1500 different species) are successfully applied in bioconversion processes such as sewage treatment, biopulp- ing, conversion of forest and agricultural residues to animal feeds, and the production of edible or medicinal mush- rooms. In the bio pre-treatment process, WRF are mostly used for secreting ligninolytic enzymes, a variety of donor substrates and selective degradation of lignin. Current research related to WRF bio pre-treatment is mainly focusing on the following four aspects: (i) selection of candidate strains for certain biomass materials; (ii) optimization of cul- tivation methods; (iii) characterization of fungal treated materials; and (iv) evaluation of combining bio pre-treatment with chemical or physicochemical approaches. Future prospects and recommended research work on applying WRF in bio pre-treatment are also briefl y introduced and summarized in this review. These include (i) integrated methods (i.e. co-treatment with organic solvents, diluted acids, supercritical CO2 and ionic liquids) to resolve problems exist- ing in fungal pre-treatment applications; (ii) mutation breeding and crossbreeding of fungal mycelia to obtain engi- neering strains; and (iii) integration of fungal pre-treatment with simultaneous saccharifi cation and fermentation to produce biofuels and value-added products. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd
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Kunming Institute of Botany1, Chinese Academy of Sciences2, University of Montpellier3, University of Mauritius4, Chiang Mai University5, Iloilo Science and Technology University6, Mae Fah Luang University7, Thailand Ministry of Agriculture and Cooperatives8, World Agroforestry Centre9, Aix-Marseille University10, Ohio State University11, VIT University12, Shenzhen University13, University of Electronic Science and Technology of China14, University of Santo Tomas15, University of Science and Technology16, University of Agricultural Sciences, Dharwad17, University of the Philippines Visayas18, Ramakrishna Mission19
TL;DR: This manuscript reviews fifty ways in which fungi can potentially be utilized as biotechnology and provides a flow chart that can be used to convince funding bodies of the importance of fungi for biotechnological research and as potential products.
Abstract: Fungi are an understudied, biotechnologically valuable group of organisms. Due to
the immense range of habitats that fungi inhabit, and the consequent need to compete against a diverse array of other fungi, bacteria, and animals, fungi have developed numerous survival mechanisms. The unique attributes of fungi thus herald great promise for their application in biotechnology and industry. Moreover, fungi can be grown with relative ease, making production at scale viable. The search for fungal biodiversity, and the construction of a living fungi collection, both have incredible economic potential in locating organisms with novel industrial uses that will lead to novel products. This manuscript reviews fifty ways in which fungi can potentially be utilized as biotechnology. We provide notes and examples for each potential exploitation and give examples from our own work and the work of other notable researchers. We also provide a flow chart that can be used to convince funding bodies of the importance of fungi for biotechnological research and as potential products. Fungi have provided the world with penicillin, lovastatin, and other globally significant medicines, and they remain an untapped resource with enormous industrial potential.
404 citations
Cites background from "Impact and prospective of fungal pr..."
...While the ability of a few white-rot fungi (basidiomycetes) to delignify lignocellulosic biomass has been explored in pre-treatment strategies (Tian et al. 2012; López-Abelairas et al. 2013), and cellulases and hemicellulases of Trichoderma reesei and Aspergillus niger (filamentous ascomycetes)…...
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TL;DR: A comprehensive and in-depth review on BP for LCB and microalgae biomass by focusing on the relevant overviews and perspectives, technological approaches, mechanisms, influencing factors, and recent research progresses is presented.
Abstract: Biological pretreatment (BP) is a promising approach for treating microalgae and lignocellulosic biomass (LCB) during biofuels production that uses mostly fungal and bacterial strains or their enzymes. Pretreatment with fungi requires long incubation time (weeks to months), whereas, bacterial and enzymatic pretreatments can be completed by only a few hours to days. Nevertheless, fungal pretreatment especially with white-rot fungi (WRF) is predominantly used in BP of biomass for its high efficiency and downstream yields. According to the recent reports, delignification of LCB by WRF may vary between 3% and 72% with a maximum 120% increase in the biofuel yield. Compared to the untreated microalgae biomass, the downstream yields of the respective biofuels were found to be increased by 22–159% after bacterial pretreatment, while enzymatic pretreatment improved as much as 485% of the final yield. Despite the results are promising, exploitation of BP on large scale is still bottlenecked by some technoeconomic hurdles, which need to be overcome through further fundamental and applied researches. This paper presents a comprehensive and in-depth review on BP for LCB and microalgae biomass by focusing on the relevant overviews and perspectives, technological approaches, mechanisms, influencing factors, and recent research progresses. Finally, challenges and future outlooks are discussed in the concluding sections.
278 citations
TL;DR: This paper reviews the recent progress of the fundamental researches of various biomass pre‐treatment processes, especially on how these pre‐treatments alter chemical composition and physically change cell wall structure, and would aid in developing novel pre‐ treatment methods.
Abstract: A number of pre-treatment methods have been developed during the last few decades to overcome bio- mass recalcitrance. Although the mechanisms of these pre-treatments are different, the fi nal objective is the same - increasing cellulose accessibility to cellulase enzymes. Generally, pre-treatment is the process to disrupt the compact structure of lignocellulosic biomass and expose cellulose fi bers, which can be achieved by mechanical comminu- tion, chemical modifi cations of biomass compositions, biological degradation, or a combination of these methods. After pre-treatment, the accessible surface area is increased resulting in the enhancement of cellulose digestibility. In this paper, we review the recent progress of the fundamental researches of various biomass pre-treatment proc- esses, especially on how these pre-treatments alter chemical composition and physically change cell wall struc- ture. Understanding these changes would be helpful to further optimize existing pre-treatments, and would aid in developing novel pre-treatment methods.© 2012 Society of Chemical Industry and John Wiley & Sons, Ltd
251 citations
TL;DR: A comprehensive review of current fungal pretreatments and feasibility for biofuel production, with a focus on combining fungal Pretreatment with other methods.
Abstract: Biofuel production from lignocellulose has recently been gaining much more attention as a result. One major problem of using lignocellulosic materials for the production of biofuel is the low accessibility of cellulose to enzymes and microorganisms. Therefore, pretreatment of lignocellulose is a critical step in biofuel production from such materials. Of the pretreatments, fungal treatment has become an important process due to its low energy demands and selective degradation of lignin and hemicellulose. This capability comes from the unique enzymatic systems, cellulolytic and ligninolytic enzymes, especially in white rot fungi. The low energy demand of fungal pretreatment has generated interest in studying the applicability of fungal pretreatment for biofuel production from woody materials. The most significant drawback of fungal pretreatment is the lengthy time required for the process. Combining fungal pretreatment with other pretreatment methods might reduce the time necessary for the whole process to operate. It can also introduce cost-effectiveness. Thus combining fungal pretreatment with other physical and chemical methods has been recently contemplated. This paper provides a comprehensive review of current fungal pretreatments and feasibility for biofuel production, with a focus on combining fungal pretreatment with other methods. The advantages and disadvantages of all physical and chemical methods were also briefly reviewed. The applicability of the combination of fungal with other pretreatment methods has been considered in a number of recent publications. To be commercially attractive, both energy demand and processing time should be reduced. In terms of energy demand reduction, combined fungal physico-chemical pretreatment has been effective. However, the lengthy time taken for the whole process has not been significantly improved upon. A great deal of work is still required to be done regarding time reduction for the process (combined fungal-physico chemical pretreatment). Therefore, it seems to remain an open field for research and process development.
243 citations
TL;DR: In this article, the authors compared fungal pretreatment with other biological treatments for anaerobic digestion of lignocellulosic biomass, including enzymes, enzymes and white-rot fungi.
Abstract: Anaerobic digestion of lignocellulosic biomass appears to be an efficient process for the production of energy whilst answering present-day environmental challenges. However, lignin contained in lignocellulosic biomass is hardly biodegradable, thus representing a major obstacle for maximum methane production. Consequently, although pretreatments need to be considered, their cost is a limit for their full-scale use. Biological pretreatments are a cheaper alternative in this context. Several biological pretreatments have been studied for anaerobic digestion: ensiling, partial composting, specific microbial consortia, enzymes and fungi. Simple, inexpensive and efficient pretreatments can be obtained using fungi. White-rot fungi (WRF), have been considered as most capable of delignifying a substrate. However, their use in the pretreatment of substrates for anaerobic digestion is quite recent and still needs to be investigated. This review compares fungal pretreatment with other biological treatments for anaerobic digestion of lignocellulosic biomass. Enzymatic mechanisms for WRF pretreatments are then exposed. The literature data regarding the improvement of anaerobic digestibility with WRF pretreatment are summarized (anaerobic digestion and in vitro digestibility with rumen microorganisms). Finally, lignocellulosic biomass features allowing the improvement of anaerobic digestion are exposed (porosity, cellulose crystallinity, etc.). The possible effects of WRF on these characteristics are discussed and industrial perspectives for WRF pretreatments are presented.
219 citations
References
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TL;DR: A review of various pretreatment process methods and the recent literature that has been developed can be found in this paper, where the goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels.
Abstract: Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that...
3,450 citations
TL;DR: This paper presents a meta-analyses of IGNIN as a stimulus and its applications in medicine and physiology, and discusses the role that IGNIN plays in the development of disease and its role in medicine.
Abstract: INTRODUCTION ....................................................................................................................................... 465 LIGNIN AS A SUBSTRATE ............................................................................................................................... 466 MICROBIOLOGY OF LIGNIN BIODEGRADATI ON ........................................................................... 468 Anaerobic Conditions ............................................................................................................................... 469 Aerobic Conditions ................................................................................................................................... 469 LIGNIN DEGRADATION BY WHITEROT FUNGI ............................................................................. 471 Physiology .......................................................................................................................................................... 472 Biochemistry ............................................................................................................................................ 475 Genetics ..............................................................................................................................................................486 Molecular Biology .................................................................................................................................... 489 CONCLUSIONS AND RECOMMENDATIONS ..................................................................................... 491 ENZYMATIC “COMBUSTION” ........................................................................................................................ 493
2,556 citations
TL;DR: The different technologies for producing fuel ethanol from sucrose-containing feedstocks (mainly sugar cane, starchy materials and lignocellulosic biomass) are described along with the major research trends for improving them.
1,792 citations
Book•
14 Mar 2012
TL;DR: The oil crisis during the 1970s turned interest towards the utilization of renewable resources and towards lignocellulosics in particular, and the commercial utilization of this technology has not progressed as rapidly as one would have desired.
Abstract: The oil crisis during the 1970s turned interest towards the utilization of renewable resources and towards lignocellulosics in particular. The 1970s were also the cradle period of biotechnology, and the years when biotechnical utilization of lignocellulosic waste from agriculture and forestry gained priori ty. This was a logical conclusion since one of nature's most important biologi cal reactions is the conversion of wood and other lignocellulosic materials to carbon dioxide, water and humic substances. However, while biotechnology in other areas like medicine and pharmacology concerned production of expen sive products on a small scale, biotechnical utilization and conversion of ligno cellulosics meant production of inexpensive products on a large scale. Biotechnical utilization of lignocellulosic materials is therefore a very difficult task, and the commercial utilization of this technology has not progressed as rapidly as one would have desired. One reason for this was the lack of basic knowledge of enzyme mechanisms involved in the degradation and conversion of wood, other lignocellulosics and their individual components. There are also risks associated with initiating a technical development before a stable platform of knowledge is available. Several of the projects started with en thusiasm have therefore suffered some loss of interest. Also contributing to this failing interest is the fact that the oil crisis at the time was not a real one. At present, nobody predicts a rapid exhaustion of the oil resources and fuel production from lignocellulosics is no longer a high priority."
1,408 citations
TL;DR: In this article, the effect of culture parameters on lignin decomposition was studied in shallow batch cultures of the ligninolytic wood-destroying HymenomycetePhanerochaete chrysosporium Burds.
Abstract: Culture parameters influencing metabolism of synthetic14C-lignins to14CO2 in defined media have been studied in shallow batch cultures of the ligninolytic wood-destroying HymenomycetePhanerochaete chrysosporium Burds. Study of the effect of O2 concentration in the gas phase above non-agitated cultures indicated essentially complete absence of attack on the lignin polymer at 5% O2 in N2, and a 2- to 3-fold enhancement by 100% O2 as compared to air (21% O2). Agitation of the cultures resulting in the formation of mycelial pellets greatly suppressed lignin decomposition. The optimum culture pH for lignin decomposition was 4 to 4.5, with marked suppression above 5.5 and below 3.5. The source of nutrient nitrogen (NO
3
−
, NH
4
+
, amino acids) had little influence on lignin decomposition, but the concentration of nitrogen was critical; decomposition at 24 mM was only 25–35% of that at 2.4 mM N. Thiamine was the only vitamin required for growth and lignin decomposition. Under the optimum conditions developed, decomposition of 5 mg of synthetic lignin was accompanied by utilization of approximately 100 mg of glucose. The influence of the various culture parameters was analogous for metabolism of synthetic lignin labeled in the ring-,side chain-, and methoxyl carbon atoms.
1,032 citations