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1.
The influence of aeration and hemicellulosic sugars on xylitol production by Candida tropicalis 总被引:11,自引:0,他引:11
The influence of other hemicellulosic sugars (arabinose, galactose, mannose and glucose), oxygen limitation, and initial xylose concentration on the fermentation of xylose to xylitol was investigated using experimental design methodology. Oxygen limitation and initial xylose concentration had considerable influences on xylitol production by Canadida tropicalis ATCC 96745. Under semiaerobic conditions, the maximum xylitol yield was 0.62 g/g substrate, while under aerobic conditions, the maximum volumetric productivity was 0.90 g/l h. In the presence of glucose, xylose utilization was strongly repressed and sequential sugar utilization was observed. Ethanol produced from the glucose caused 50% reduction in xylitol yield when its concentration exceeded 30 g/l. When complex synthetic hemicellulosic sugars were fermented, glucose was initially consumed followed by a simultaneous uptake of the other sugars. The maximum xylitol yield (0.84 g/g) and volumetric productivity (0.49 g/l h) were obtained for substrates containing high arabinose and low glucose and mannose contents. 相似文献
2.
The biocatalytic reduction of d-xylose to xylitol requires separation of the substrate from l-arabinose, another major component of hemicellulosic hydrolysate. This step is necessitated by the innate promiscuity of xylose reductases, which can efficiently reduce l-arabinose to l-arabinitol, an unwanted byproduct. Unfortunately, due to the epimeric nature of d-xylose and l-arabinose, separation can be difficult, leading to high production costs. To overcome this issue, we engineered an E. coli strain to efficiently produce xylitol from d-xylose with minimal production of l-arabinitol byproduct. By combining this strain with a previously engineered xylose reductase mutant, we were able to eliminate l-arabinitol formation and produce xylitol to near 100% purity from an equiweight mixture of d-xylose, l-arabinose, and d-glucose. 相似文献
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Niu Hao Li Ruirui Liang Quanfeng Qi Qingsheng Li Qiang Gu Pengfei 《Journal of industrial microbiology & biotechnology》2019,46(1):55-65
Journal of Industrial Microbiology & Biotechnology - l-Tryptophan is an important aromatic amino acid that is used widely in the food, chemical, and pharmaceutical industries. Compared with the... 相似文献
5.
Exacerbation of climate change and air pollution around the world have emphasized the necessity of replacing fossil fuels with clean and sustainable energy. Metabolic engineering has provided strategies to engineer diverse organisms for the production of biofuels from renewable carbon sources. Although some of the processes are commercialized, there has been continued effort to produce advanced biofuels with higher efficiencies. In this article, metabolic engineering strategies recently exploited to enhance biofuel production and facilitate utilization of non-edible low-value carbon sources are reviewed. The strategies include engineering enzymes, exploiting new pathways, and systematically optimizing metabolism and fermentation processes, among others. In addition, metabolic and bioprocess engineering strategies to achieve competitiveness of current biofuel production systems compared with fossil fuels are discussed. 相似文献
6.
Sofia Ferreira Rui Pereira S. A. Wahl Isabel Rocha 《Biotechnology and bioengineering》2020,117(8):2571-2587
The global market of butanol is increasing due to its growing applications as solvent, flavoring agent, and chemical precursor of several other compounds. Recently, the superior properties of n-butanol as a biofuel over ethanol have stimulated even more interest. (Bio)butanol is natively produced together with ethanol and acetone by Clostridium species through acetone-butanol-ethanol fermentation, at noncompetitive, low titers compared to petrochemical production. Different butanol production pathways have been expressed in Escherichia coli, a more accessible host compared to Clostridium species, to improve butanol titers and rates. The bioproduction of butanol is here reviewed from a historical and theoretical perspective. All tested rational metabolic engineering strategies in E. coli to increase butanol titers are reviewed: manipulation of central carbon metabolism, elimination of competing pathways, cofactor balancing, development of new pathways, expression of homologous enzymes, consumption of different substrates, and molecular biology strategies. The progress in the field of metabolic modeling and pathway generation algorithms and their potential application to butanol production are also summarized here. The main goals are to gather all the strategies, evaluate the respective progress obtained, identify, and exploit the outstanding challenges. 相似文献
7.
Optimal experimental condition for hemicellulosic hydrolyzate treatment with activated charcoal for xylitol production 总被引:1,自引:0,他引:1
Rice straw was hydrolyzed into a mixture of sugars using diluted H(2)SO(4). During hydrolysis, a variety of inhibitors was also produced, including acetic acid, furfural, hydroxymethylfurfural, and lignin degradation products (several aromatic and phenolic compounds). To reduce the toxic compounds concentration in the hydrolyzate and to improve the xylitol yield and volumetric productivity, rice straw hemicellulosic hydrolyzate was treated with activated charcoal under different pH values, stirring rates, contact times, and temperatures, employing a 2(4) full-factorial design. Fermentative assays were conducted with treated hydrolyzates containing 90 g/L xylose. The results indicated that temperature, pH, and stirring rate strongly influenced the hydrolyzate treatment, temperature and pH interfering with all of the responses analyzed (removal of color and lignin degradation products, xylitol yield factor, and volumetric productivity). The combination of pH 2.0, 150 rpm, 45 degrees C, and 60 min was considered an optimal condition, providing significant removal rates of color (48.9%) and lignin degradation products (25.8%), as well as a xylitol production of 66 g/L, a volumetric productivity of 0.57 g/L.h, and a yield factor of 0.72 g/g. 相似文献
8.
Toivari MH Ruohonen L Miasnikov AN Richard P Penttilä M 《Applied and environmental microbiology》2007,73(17):5471-5476
Recombinant Saccharomyces cerevisiae strains that produce the sugar alcohols xylitol and ribitol and the pentose sugar D-ribose from D-glucose in a single fermentation step are described. A transketolase-deficient S. cerevisiae strain accumulated D-xylulose 5-phosphate intracellularly and released ribitol and pentose sugars (D-ribose, D-ribulose, and D-xylulose) into the growth medium. Expression of the xylitol dehydrogenase-encoding gene XYL2 of Pichia stipitis in the transketolase-deficient strain resulted in an 8.5-fold enhancement of the total amount of the excreted sugar alcohols ribitol and xylitol. The additional introduction of the 2-deoxy-glucose 6-phosphate phosphatase-encoding gene DOG1 into the transketolase-deficient strain expressing the XYL2 gene resulted in a further 1.6-fold increase in ribitol production. Finally, deletion of the endogenous xylulokinase-encoding gene XKS1 was necessary to increase the amount of xylitol to 50% of the 5-carbon sugar alcohols excreted. 相似文献
9.
M G A Felipe M Vitolo I M Mancilha S S Silva 《Journal of industrial microbiology & biotechnology》1997,18(4):251-254
The bioconversion of xylose to xylitol by Candida guilliermondii FTI 20037 cultivated in sugar cane bagasse hemicellulosic hydrolyzate was influenced by cell inoculum level, age of inoculum
and hydrolyzate concentration. The maximum xylitol productivity (0.75 g L−1 h−1) occurred in tests carried out with hydrolyzate containing 54.5 g L−1 of xylose, using 3.0 g L−1 of a 24-h-old inoculum. Xylitol productivity and cell concentration decreased with hydrolyzate containing 74.2 g L−1 of xylose.
Received 02 February 1996/ Accepted in revised form 15 November 1996 相似文献
10.
Kinetic behavior of Candida guilliermondii yeast during xylitol production from Brewer's spent grain hemicellulosic hydrolysate 总被引:4,自引:0,他引:4
Brewer's spent grain, the main byproduct of breweries, was hydrolyzed with dilute sulfuric acid to produce a hemicellulosic hydrolysate (containing xylose as the main sugar). The obtained hydrolysate was used as cultivation medium by Candidaguilliermondii yeast in the raw form (containing 20 g/L xylose) and after concentration (85 g/L xylose), and the kinetic behavior of the yeast during xylitol production was evaluated in both media. Assays in semisynthetic media were also performed to compare the yeast performance in media without toxic compounds. According to the results, the kinetic behavior of the yeast cultivated in raw hydrolysate was as effective as in semisynthetic medium containing 20 g/L xylose. However, in concentrated hydrolysate medium, the xylitol production efficiency was 30.6% and 42.6% lower than in raw hydrolysate and semisynthetic medium containing 85 g/L xylose, respectively. In other words, the xylose-to-xylitol bioconversion from hydrolysate medium was strongly affected when the initial xylose concentration was increased; however, similar behavior did not occur from semisynthetic media. The lowest efficiency of xylitol production from concentrated hydrolysate can be attributed to the high concentration of toxic compounds present in this medium, resulting from the hydrolysate concentration process. 相似文献
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Hemicellulosic hydrolyzate obtained from rice straw was evaluated to determine if it was a suitable fementation medium for
the production of xylitol byCandida mogii ATCC 18364. To obtain xylose selectively from rice straw, it is important to establish rapid hydrolysis conditions that yield
xylose-rich substrates. The results of hydrolysis experiments indicated that the optimal reaction conditions for the recovery
of xylose from rice straw hemicellulose were obtained using a sulfuric acid concentration of 1.5%, a reaction temperature
of 130°C, a reaction time of 20 min and a solid to liquid ratio of 1∶10. Because the fermentation of concentrated acid hydrolyzates
can be inhibited by compounds present in the raw material or produced during the hydrolysis process, various methods were
tested to determine if they could detoxify the hydrolyzates and thus improve xylitol production. The greatest xylitol yield
(0.53 g/g) and volumetric productivity (0.38 g/L·h) were obtained when an overlimed hydrolyzate was treated with activated
charcoal. 相似文献
13.
Although the potential for biofuel production from microalgae via photosynthesis has been intensively investigated, information on the selection of a suitable operation strategy for microalgae-based biofuel production is lacking. Many published reports describe competitive strains and optimal culture conditions for use in biofuel production; however, the major impediment to further improvements is the absence of effective engineering strategies for microalgae cultivation and biofuel production. This comprehensive review discusses recent advances in understanding the effects of major environmental stresses and the characteristics of various engineering operation strategies on the production of biofuels (mainly biodiesel and bioethanol) using microalgae. The performances of microalgae-based biofuel-producing systems under various environmental stresses (i.e., irradiance, temperature, pH, nitrogen depletion, and salinity) and cultivation strategies (i.e., fed-batch, semi-continuous, continuous, two-stage, and salinity-gradient) are compared. The reasons for variations in performance and the underlying theories of the various production strategies are also critically discussed. The aim of this review is to provide useful information to facilitate development of innovative and feasible operation technologies for effectively increasing the commercial viability of microalgae-based biofuel production. 相似文献
14.
Metabolic engineering strategies for the improvement of cellulase production by Hypocrea jecorina 总被引:1,自引:0,他引:1
Christian P Kubicek Marianna Mikus André Schuster Monika Schmoll Bernhard Seiboth 《Biotechnology for biofuels》2009,2(1):19-14
Hypocrea jecorina (= Trichoderma reesei) is the main industrial source of cellulases and hemicellulases used to depolymerise plant biomass to simple sugars that are
converted to chemical intermediates and biofuels, such as ethanol. Cellulases are formed adaptively, and several positive
(XYR1, ACE2, HAP2/3/5) and negative (ACE1, CRE1) components involved in this regulation are now known. In addition, its complete
genome sequence has been recently published, thus making the organism susceptible to targeted improvement by metabolic engineering.
In this review, we summarise current knowledge about how cellulase biosynthesis is regulated, and outline recent approaches
and suitable strategies for facilitating the targeted improvement of cellulase production by genetic engineering. 相似文献
15.
Batch xylitol production from wheat straw hemicellulosic hydrolysate using Candida guilliermondii in a stirred tank reactor 总被引:3,自引:0,他引:3
Batch production of xylitol from the hydrolysate of wheat straw hemicellulose using Candida guilliermondii was carried out in a stirred tank reactor (agitation speed of 300 rpm, aeration rate of 0.6 vvm and initial cell concentration of 0.5 g l–1). After 54 h, xylitol production from 30.5 g xylose l–1 reached 27.5 g l–1, resulting in a xylose-to-xylitol bioconversion yield of 0.9 g g–1 and a productivity of 0.5 g l–1 h–1. 相似文献
16.
This study develops a system for the efficient valorisation of hemicellulosic hydrolysates of vineshoot trimmings. By connecting two reactors of 2L and 10L, operational conditions were set up for the sequential production of lactic acid and xylitol in continuous fermentation, considering the dependence of the main metabolites and fermentation parameters on the dilution rate. In the first bioreactor, Lactobacillus rhamnosus consumed all the glucose to produce lactic acid at 31.5°C, with 150rpm and 1L of working volume as the optimal conditions. The residual sugars were employed for the xylose to xylitol bioconversion by Debaryomyces hansenii in the second bioreactor at 30°C, 250rpm and an air-flow rate of 2Lmin(-1). Several steady states were reached at flow rates (F) in the range of 0.54-5.33mLmin(-1), leading to dilution rates (D) ranging from 0.032 to 0.320h(-1) in Bioreactor 1 and from 0.006 to 0.064h(-1) in Bioreactor 2. The maximum volumetric lactic acid productivity (Q(P LA)=2.908gL(-1)h(-1)) was achieved under D=0.266h(-1) (F=4.44mLmin(-1)); meanwhile, the maximum production of xylitol (5.1gL(-1)), volumetric xylitol productivity (Q(P xylitol)=0.218gL(-1)h(-1)), volumetric rate of xylose consumption (Q(S xylose)=0.398gL(-1)h(-1)) and product yield (0.55gg(-1)) were achieved at an intermediate dilution rate of 0.043h(-1) (F=3.55mLmin(-1)). Under these conditions, ethanol, which was the main by-product of the fermentation, was produced in higher amounts (1.9gL(-1)). Finally, lactic acid and xylitol were effectively recovered by conventional procedures. 相似文献
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Víctor E Balderas-Hernández Andrea Sabido-Ramos Patricia Silva Natividad Cabrera-Valladares Georgina Hernández-Chávez José L Báez-Viveros Alfredo Martínez Francisco Bolívar Guillermo Gosset 《Microbial cell factories》2009,8(1):19-12
Background
Anthranilate is an aromatic amine used industrially as an intermediate for the synthesis of dyes, perfumes, pharmaceuticals and other classes of products. Chemical synthesis of anthranilate is an unsustainable process since it implies the use of nonrenewable benzene and the generation of toxic by-products. In Escherichia coli anthranilate is synthesized from chorismate by anthranilate synthase (TrpED) and then converted to phosphoribosyl anthranilate by anthranilate phosphoribosyl transferase to continue the tryptophan biosynthetic pathway. With the purpose of generating a microbial strain for anthranilate production from glucose, E. coli W3110 trpD9923, a mutant in the trpD gene that displays low anthranilate producing capacity, was characterized and modified using metabolic engineering strategies. 相似文献19.
Global energy and environmental problems have stimulated increasing efforts toward synthesizing liquid biofuels as transportation energy. Compared to the traditional biofuel, ethanol, advanced biofuels should offer advantages such as higher energy density, lower hygroscopicity, lower vapor pressure, and compatibility with existing transportation infrastructure. However, these fuels are not synthesized economically using native organisms. Metabolic engineering offers an alternative approach in which synthetic pathways are engineered into user-friendly hosts for the production of these fuel molecules. These hosts could be readily manipulated to improve the production efficiency. This review summarizes recent progress in the engineering of Escherichia coli to produce advanced biofuels. 相似文献
20.
Metabolic engineering strategies for acetoin and 2,3-butanediol production: advances and prospects 总被引:1,自引:0,他引:1
Taowei Yang Xian Zhang Meijuan Xu Zhenghong Xu Shang-Tian Yang 《Critical reviews in biotechnology》2017,37(8):990-1005
Acetoin and 2,3-butanediol (2,3-BD) have a large number of industrial applications. The production of acetoin and 2,3-BD has traditionally relied on oil supplies. Microbial production of acetoin and 2,3-BD will alleviate the dependence on oil. Acetoin and 2,3-BD are neighboring metabolites in the 2,3-BD metabolic pathway of bacteria. This review summarizes metabolic engineering strategies for improvement of microbial acetoin and 2,3-BD production. We also propose enhancements to current acetoin and 2,3-BD production strategies, by offering a metabolic engineering approach that is guided by systems biology and synthetic biology. 相似文献