Ethanol fermentation from biomass resources: current state and prospects.
TL;DR: The prospects included are fermentation technology converting xylose to ethanol, cellulase enzyme utilized in the hydrolysis of lignocellulosic materials, immobilization of the microorganism in large systems, simultaneous saccharification and fermentation, and sugar conversion into ethanol.
Abstract: In recent years, growing attention has been devoted to the conversion of biomass into fuel ethanol, considered the cleanest liquid fuel alternative to fossil fuels. Significant advances have been made towards the technology of ethanol fermentation. This review provides practical examples and gives a broad overview of the current status of ethanol fermentation including biomass resources, microorganisms, and technology. Also, the promising prospects of ethanol fermentation are especially introduced. The prospects included are fermentation technology converting xylose to ethanol, cellulase enzyme utilized in the hydrolysis of lignocellulosic materials, immobilization of the microorganism in large systems, simultaneous saccharification and fermentation, and sugar conversion into ethanol.
Citations
More filters
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
Cites background from "Ethanol fermentation from biomass r..."
...Several reviews have been published on the theme of fuel ethanol production especially from lignocellulosic biomass (Chandrakant and Bisaria, 1998; Lee, 1997; Lin and Tanaka, 2006; Lynd, 1996)....
[...]
TL;DR: In this paper, the authors present a review of the current status of the hydrothermal liquefaction of biomass with the aim of describing the current state of the technology, which is a medium-temperature, high-pressure thermochemical process which produces a liquid product, often called bio-oil or bi-crude.
1,451 citations
TL;DR: A review of the biological and thermochemical methods that could be used to produce bioethanol is made and an analysis of its global production trends is carried out in this paper, where the authors evaluate the utilization of different feedstocks (i.e., sucrose containing, starchy materials, lignocellulosic biomass) is required considering the big share of raw materials in bio-ethanol costs.
1,379 citations
Cites background from "Ethanol fermentation from biomass r..."
...This is possible because, during the last two decades, technology for bioethanol production from nonfood-plant sources has been developed to the point at which largescale production will be a reality in the next few years [22]....
[...]
TL;DR: The main problem with bioethanol production is the availability of raw materials for the production as mentioned in this paper, which can highly affect the production costs of the bio-ethanol, as the price of the raw materials is highly volatile.
1,265 citations
TL;DR: This review focuses on inhibitors from lignocellulosic feedstocks and how conditioning of slurries and hydrolysates can be used to alleviate inhibition problems.
Abstract: 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.
1,180 citations
Cites background from "Ethanol fermentation from biomass r..."
...cerevisiae and Zymomonas mobilis can tolerate ethanol concentrations up to 18 and 12%, respectively [68]....
[...]
...Ethanol production from diluted hydrolysates with low sugar content is associated with a high operating cost due to a more expensive distillation process [68]....
[...]
References
More filters
TL;DR: Simultaneous saccharification and fermentation effectively removes glucose, which is an inhibitor to cellulase activity, thus increasing the yield and rate of cellulose hydrolysis, thereby increasing the cost of ethanol production from lignocellulosic materials.
5,860 citations
"Ethanol fermentation from biomass r..." refers background in this paper
...These diverse feedstocks have caused researchers to test numerous pretreatment processes ranging from hot water and steam explosion treatments, to alkaline and solvent pretreatments, to many useful versions of acid pretreatment (Kaar and Holtzapple 2000; Maiorella 1985; Sun and Cheng 2002)....
[...]
...The recombinant efficiently fermented both glucose and xylose, which is essential for economical conversion of lignocellulosic biomass to ethanol (Ingram and Doran 1995; Lynd et al. 2002; McMillan et al. 1999; Sun and Cheng 2002; Zhang et al. 1995)....
[...]
TL;DR: A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.
Abstract: Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.
4,769 citations
"Ethanol fermentation from biomass r..." refers background in this paper
...The recombinant efficiently fermented both glucose and xylose, which is essential for economical conversion of lignocellulosic biomass to ethanol (Ingram and Doran 1995; Lynd et al. 2002; McMillan et al. 1999; Sun and Cheng 2002; Zhang et al. 1995)....
[...]
...The recombinant efficiently fermented both glucose and xylose, which is essential for economical conversion of lignocellulosic biomass to ethanol (Ingram and Doran 1995; Lynd et al. 2002; McMillan et al. 1999; Sun and Cheng 2002; Zhang et al. 1995)....
[...]
TL;DR: Bacterial growth is considered as a method for the study of bacterial physiology and biochemistry, with the interpretation of quantitative data referring to bacterial growth limited to populations considered genetically homogeneous.
Abstract: The study of the growth of bacterial cultures does not constitute a specialized subject or branch of research: it is the basic method of Microbiology. It would be a foolish enterprise, and doomed to failure, to attempt reviewing briefly a \"subject\" which covers actually our whole discipline. Unless, of course, we considered the formal laws of growth for their own sake, an approach which has repeatedly proved sterile. In the present review we shall consider bacterial growth as a method for the study of bacterial physiology and biochemistry. More precisely, we shall concern ourselves with the quantitative aspects of the method, with the interpretation of quantitative data referring to bacterial growth. Furthermore, we shall considerz exclusively the positive phases of growth, since the study of bacterial \"death,\" i.e., of the negative phases of growth, involves distinct problems and methods. The discussion will be limited to populations considered genetically homogeneous. The problems of mutation and selection in growing cultures have been excellently dealt with in recent review articles by Delbriick (1) and Luria (2). No attempt is made at reviewing the literature on a subject which, as we have just seen, is not really a subject at all. The papers and results quoted have been selected as illustrations of the points discussed.
4,104 citations
TL;DR: In this article, the effect of various detoxification methods on the fermentability and chemical composition of lignocellulosic hydrolysates is discussed. But, the main focus of this paper is on the effects of different batch, fed-batch, and continuous fermentation strategies in relation to inhibition of fermentation.
1,320 citations
"Ethanol fermentation from biomass r..." refers background in this paper
...Ethanol inhibition of yeasts and other microorganisms has received much attention in microbial conversion of xylose to ethanol (Ghasem et al. 2004; Jeewon 1997; Palmqvist and Hahn-Hagerdal 2000)....
[...]
TL;DR: Improvement of the fermentation process is just one of several factor that needs to be fully optimized and integrated to generate a competitive lignocellulose ethanol plant.
Abstract: With industrial development growing rapidly, there is a need for environmentally sustainable energy sources. Bioethanol (ethanol from biomass) is an attractive, sustainable energy source to fuel transportation. Based on the premise that fuel bioethanol can contribute to a cleaner environment and with the implementation of environmental protection laws in many countries, demand for this fuel is increasing. Efficient ethanol production processes and cheap substrates are needed. Current ethanol production processes using crops such as sugar cane and corn are well-established; however, utilization of a cheaper substrate such as lignocellulose could make bioethanol more competitive with fossil fuel. The processing and utilization of this substrate is complex, differing in many aspects from crop-based ethanol production. One important requirement is an efficient microorganism able to ferment a variety of sugars (pentoses, and hexoses) as well as to tolerate stress conditions. Through metabolic engineering, bacterial and yeast strains have been constructed which feature traits that are advantageous for ethanol production using lignocellulose sugars. After several rounds of modification/evaluation/modification, three main microbial platforms, Saccharomyces cerevisiae, Zymomonas mobilis, and Escherichia coli, have emerged and they have performed well in pilot studies. While there are ongoing efforts to further enhance their properties, improvement of the fermentation process is just one of several factors-that needs to be fully optimized and integrated to generate a competitive lignocellulose ethanol plant.
991 citations
"Ethanol fermentation from biomass r..." refers background in this paper
...With the inevitable depletion of the world’s energy supply, there has been an increasing worldwide interest in alternative sources of energy (Aristidou and Penttila 2000; Jeffries and Jin 2000; John 2004; Kerr 1998; Wheals et al. 1999; Zaldivar et al. 2001)....
[...]