Next-generation biomass feedstocks for biofuel production

Simmons, Blake A.; Loqué, Dominique; Blanch, Harvey W.

doi:10.1186/gb-2008-9-12-242

Cited by 160 publications

(129 citation statements)

References 41 publications

(34 reference statements)

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“…Lignocellulosic feedstocks are primarily composed of complex matrices of polysaccharides (cellulose and hemicellulose) and lignin which form plant cell walls (Buchanan et al 2015). These durable cell walls are recalcitrant to biomass pretreatment processes due to the crystallinity of the cellulose (protecting cellulose from chemical and biological degradation), and the presence of covalent cross-linkages between lignin and hemicellulose (Blanch and Wilke 1982;Chandra et al 2007;Li et al 2010), resulting in a high cost for pretreatment (Chandra et al 2007;Merino and Cherry 2007;Simmons et al 2008;Yang and Wyman 2008).…”

Section: Introductionmentioning

confidence: 99%

Ionic liquid-tolerant microorganisms and microbial communities for lignocellulose conversion to bioproducts

Simmons

Singer

et al. 2016

Appl Microbiol Biotechnol

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Chemical and physical pretreatment of biomass is a critical step in the conversion of lignocellulose to biofuels and bioproducts. Ionic liquid (IL) pretreatment has attracted significant attention due to the unique ability of certain ILs to solubilize some or all components of the plant cell wall. However, these ILs not only inhibit enzyme activities, but also the growth and productivity of microorganisms used in downstream hydrolysis and fermentation processes.While pretreated biomass can be washed to remove residual IL and reduce inhibition, extensive washing is costly and not feasible in large-scale processes. IL tolerant microorganisms and microbial communities have been discovered from environmental samples and studies begun to elucidate mechanisms of IL tolerance. The discovery of IL tolerance in environmental microbial communities and individual microbes has lead to the proposal of molecular mechanisms of resistance. In this article, we review recent progress on discovering IL tolerant microorganisms, identifying metabolic pathways and mechanisms of tolerance, and engineering microorganisms for IL tolerance. Research in these areas will yield new approaches to overcome inhibition in lignocellulosic biomass bioconversion processes and increase opportunities for the use of ILs in biomass pretreatment.

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Section: Introductionmentioning

confidence: 99%

Ionic liquid-tolerant microorganisms and microbial communities for lignocellulose conversion to bioproducts

Simmons

Singer

et al. 2016

Appl Microbiol Biotechnol

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“…Unlike the crops currently used for commercial biofuel production, biofuel crops have been chosen on the basis of high yield in low input agricultural settings [8]. This approach is crucial because it will reduce the amount of land needed to produce the biofuel crops and at the same time avoid the need to add fertilizers and pesticides to maximize production as is common for food crops [6].…”

Section: Biofuel Cropsmentioning

confidence: 99%

Genetic and biotechnological approaches for biofuel crop improvement

Vega‐Sánchez

Ronald

2010

Current Opinion in Biotechnology

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Research and development efforts for biofuel production are targeted at converting plant biomass into renewable liquid fuels. Major obstacles for biofuel production include lack of biofuel crop domestication, low oil yields from crop plants as well as recalcitrance of lignocellulose to chemical and enzymatic breakdown. Researchers are expanding the genetic and genomic resources available for crop improvement, elucidating lipid metabolism to facilitate manipulation of fatty acid biosynthetic pathways and studying how plant cell walls are synthesized and assembled. This knowledge will be used to produce the next generation of biofuel crops by increasing fatty acid content and by optimizing the hydrolysis of plant cell walls to release fermentable sugars. Introduction Biofuels are commonly defined as fuels derived from renewable biological products and are often regarded as an attractive, 'green' alternative to fossil sources of energy due to their potential contribution to lowering carbon dioxide emissions [1]. Globally, plants produce an estimated 200 billion tones of biomass per year [2] in the form of sugars, polysaccharides, oils and other biopolymers, representing an unprecedented resource for biofuel production. However, despite its abundance and potential environmental benefits, the efficient and sustainable use of plant biomass for energy purposes remains a challenging endeavor, requiring major investments in science and technology [3,4].With the exception of sugar cane ethanol, biofuels are a nascent industry in many parts of the world. A few of the commercialized products include bioethanol derived from corn starch and biodiesel obtained from plants with a high content in fatty acids such as soybean, canola and sunflower ( Figure 1). However, the status of corn and soybean as major food crops, coupled to the fact that yields of starch and plant oil are too modest to cover the huge demand of transportation fuels has prompted the development of alternative biofuel production based on lignocellulosic biomass [4][5][6]. Lignocellulose, composed of the polysaccharides cellulose and hemicellulose, and lignin, a phenolic polymer, is the most abundant biomaterial on earth [2,7]. Most lignocellulosic feedstocks in consideration are perennial, non-food grasses such as switchgrass and Miscanthus, as well as woody plants such as poplar (Table 1).None of the current and potential crops has been domesticated or bred for improved polysaccharide or oil extraction for biofuel production. For this reason, biofuel research is focused towards understanding the plant biomass characteristics and traits that need to be modified to optimize crops for biofuel production. The wealth of genetic and genomic resources in model plants such as rice, Arabidopsis and Brachypodium are being used to answer fundamental scientific questions that cannot be addressed directly using potential biofuel crops. This review will discuss the recent advances in understanding lignocellulosic biomass recalcitrance and lipid metabolism for increasing oi...

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“…Although lignocellulose stored within the cell wall of plants is one of the largest reserves of convertible energy on the planet, extraction of this resource remains a challenge because of the recalcitrance of the plant cell wall to degradation (2,3). Cellulose and hemicellulose polysaccharides, the sources of fermentable sugars, are semicrystalline in nature and deeply embedded within a complex network of highly stable lignin polymers (4,5).…”

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confidence: 99%

Global transcriptome response to ionic liquid by a tropical rain forest soil bacterium,Enterobacter lignolyticus

Khudyakov

D’haeseleer

Borglin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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To process plant-based renewable biofuels, pretreatment of plant feedstock with ionic liquids has significant advantages over current methods for deconstruction of lignocellulosic feedstocks. However, ionic liquids are often toxic to the microorganisms used subsequently for biomass saccharification and fermentation. We previously isolated Enterobacter lignolyticus strain SCF1, a lignocellulolytic bacterium from tropical rain forest soil, and report here that it can grow in the presence of 0.5 M 1-ethyl-3-methylimidazolium chloride, a commonly used ionic liquid. We investigated molecular mechanisms of SCF1 ionic liquid tolerance using a combination of phenotypic growth assays, phospholipid fatty acid analysis, and RNA sequencing technologies. Potential modes of resistance to 1-ethyl-3-methylimidazolium chloride include an increase in cyclopropane fatty acids in the cell membrane, scavenging of compatible solutes, up-regulation of osmoprotectant transporters and drug efflux pumps, and down-regulation of membrane porins. These findings represent an important first step in understanding mechanisms of ionic liquid resistance in bacteria and provide a basis for engineering microbial tolerance.osmotic stress | osmolytes | membrane lipids | differential gene expression | whole genome metabolic reconstruction

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Next-generation biomass feedstocks for biofuel production

Abstract: A review of the potential for biofuel production in the United States from timber and non-grain crops.

Cited by 160 publications

References 41 publications

Ionic liquid-tolerant microorganisms and microbial communities for lignocellulose conversion to bioproducts

Ionic liquid-tolerant microorganisms and microbial communities for lignocellulose conversion to bioproducts

Genetic and biotechnological approaches for biofuel crop improvement

Global transcriptome response to ionic liquid by a tropical rain forest soil bacterium,Enterobacter lignolyticus

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