酸解纤维素酒精发酵的毒性问题

目前 ,纤维素的酒精发酵主要有两种方法 :一种是酸水解法 ,另一种是酶解法。虽然经过 2 0多年研究 ,在纤维素的酶法水解方面有了一定进展[1,2 ] ,但是与酸法水解发酵相比较 ,仍存在很多不足之处 ,如 :纤维素的酶解效率不高 ,原料没有被充分利用 ,生产周期长 ,成本高。因此 ,纤维素酒精发酵在目前仍以酸法水解工艺为主。这一工艺已经比较成熟 ,目前生产中存在的主要问题就是关于水解产物对发酵微生物的“毒性问题” ,近年来 ,在这方面的研究较多 ,也取得了一定进展。1　纤维素酸解产物对发酵微生物的抑制作用1 1　纤维素类原料水解过程中各物…     

产纤维素体菌厌氧降解纤维素制乙醇的研究进展

纤维素(植物细胞壁的主要成分)是自然界最丰富的一种可再生资源,但是极难降解利用。纤维素体是一种多酶复合体,能够高效降解纤维素,降解产物能够被某些厌氧微生物利用发酵产乙醇。综述了近年来产纤维素体菌厌氧降解纤维素制乙醇的研究进展,报道了纤维素体结构和功能、重组设计型纤维素体、代谢工程、混菌培养等研究方向的最新成果和思路,并对其前景作了展望。可以预期,随着研究的深入,生物质制乙醇必将日益显示出其强大的市场竞争力。     

黑曲霉HS—16纤维素糖化菌的选育及在酒精发酵中的应用研究

本试验以有一定纤维素酶活力的黑曲霉Ａ．ｎｉｇｅｒＨＳ－００为出发菌株,经紫外光、激光、亚硝基胍复合诱变,选育出糖化稻草纤维素性能优良的Ａ．ｎｉｇｅｒＨＳ－１６菌株,其分解稻草纤维素产生还原糖的能力是出发菌株的５倍,还原糖生成率可达２８％。利用其稻草纤维素糖化液进行酒精发酵,酒化率为８４．８％。本试验还系统研究了影响稻草纤维素糖化的因素,确定了糖化用固体稻草培养基的最佳配方,分析了不同营养对酒精发酵     

纤维素生物转化过程工程的研究

虽有上百年的研究历史，但至今木质纤维素原料的低成本、大规模生物转化仍没有实现。导致这一问题的主要原因在于：纤维素生物转化涉及多个学科，是一个系统工程，目前往往从单一学科或单一技术的角度来研究，缺乏与原料相适应的集成工程技术。     

纤维素类物质生产酒精的技术进展

世界上第二次石油危机的出现引起了各国对未来能源供应不足的担心。虽然原子能和煤炭可以作为能源供应的一个途径,但是,对于某些用途的液体燃烧还急待开发新的来源。作为耗能巨大而又缺乏能源的日本,对这一领域的技术开发极为重视。     

脉冲耦合神经网络的并行加速优化算法研究

并行编程技术可以有效提高算法的执行效率。文中分别利用CPU的单指令多数据流扩展指令集（Streaming SIMD Extensions,SSE）技术和多核并行编程技术,对脉冲耦合神经网络（Pulse Coupled Neural Network,PCNN）分割算法进行并行编程优化,以减少算法的运行时间。实验结果表明,SSE技术以及多核并行编程技术大大加快了PCNN分割算法的运行速度,有效提高了算法的执行效率,在一定程度上解决了该方法计算量大、耗时多的问题,具有应用于医学图像处理的潜在价值。     

木质纤维素生物炼制的国际发展态势分析

木质纤维素是地球上最丰富的可再生资源之一,蕴藏着巨大的生物质能。它不仅来源广泛。而且转化产品丰富。根据产品与原料组成的不同,其生物炼制方法主要包括化学法、发酵法、直接生物转化法等。本文以Web of Science和Derwent Innovation Index作为数据源,     

决胜纤维素

<正>纤维素乙醇的产业化受到全球越来越多的国家的重视,其原因、其目的不言而喻。以粮食和油料作为原料生产第一代生物燃料的产业,正受到政府机构、环境保护主义者以及广大消费者越来越多的指责。与玉米等粮食为原料的第一代生物燃料形成对比的是,用稻草、秸秆等植物纤维为原料生产的第二代生物燃料,具有原料不与粮食竞争而且整个生产过程排放的CO_2量少等优势。     

纤维素乙醇气化发酵研究取得进展

在美国提出的2022年生产1360亿L生物燃料目标计划中,纤维素生物燃料的研发将发挥巨大作用。近10a来,美国俄克拉何马州立大学的生物燃料交叉学科研究小组在纤维素乙醇的气化发酵过程研究中取得了进展。该项工艺主要利用低成本、未处理过的生物质原料,如多年生牧草和作物秸秆,能够获取生物乙醇和其他增值产品。该研究小组正在进行进一步的整体分析研究,     

Simultaneous Bioconversion of Cellulose and Hemicellulose to Ethanol

ABSTRACT:?

Lignocellulosic materials containing cellulose, hemicellulose, and lignin as their main constituents are the most abundant renewable organic resource present on Earth. The conversion of both cellulose and hemicellulose for production of fuel ethanol is being studied intensively with a view to develop a technically and economically viable bioprocess. The fermentation of glucose, the main constituent of cellulose hydrolyzate, to ethanol can be carried out efficiently. On the other hand, although bioconversion of xylose, the main pentose sugar obtained on hydrolysis of hemicellulose, to ethanol presents a biochemical challenge, especially if it is present along with glucose, it needs to be fermented to make the biomass-to-ethanol process economical. A lot of attention therefore has been focussed on the utilization of both glucose and xylose to ethanol. Accordingly, while describing the advancements that have taken place to get xylose converted efficiently to ethanol by xylose-fermenting organisms, the review deals mainly with the strategies that have been put forward for bioconversion of both the sugars to achieve high ethanol concentration, yield, and productivity. The approaches, which include the use of (1) xylose-fermenting yeasts alone, (2) xylose isomerase enzyme as well as yeast, (3) immobilized enzymes and cells, and (4) sequential fermentation and co-culture process are described with respect to their underlying concepts and major limitations. Genetic improvements in the cultures have been made either to enlarge the range of substrate utilization or to channel metabolic intermediates specifically toward ethanol. These contributions represent real significant advancements in the field and have also been adequately dealt with from the point of view of their impact on utilization of both cellulose and hemicellulose sugars to ethanol.     

纤维素乙醇基因工程研究进展

天然微生物代谢木质纤维素生成乙醇的途径和能力各不相同,通过基因工程的手段,将不同菌种的优良基因加以重组和改造,提高乙醇产率及降低成本,是当前纤维素乙醇研究的重要课题。综述了已发现的能够代谢纤维素产乙醇的天然微生物的种类、特性、代谢机理及构建重组菌株的方法和研究进展,并对基因工程开发纤维素乙醇工程菌的前景和存在的问题进行分析。     

纤维素在不同介质中的吸附碱的研究

文中研究了纤维素在不同介质(水、乙醇、吡啶及N,N-二甲基乙酰胺)中吸附碱测定情况并通过对比总结出了纤维素对氢氧化钠随用碱量及介质变化规律:纤维素的吸附碱量随着介质及用碱量不同而有所变化,用水作碱化介质比用有机溶剂/水作碱化介质时的吸附碱量少;在用有机溶剂/水作碱化介质时,纤维素对碱吸附表现出大致相同的变化趋势。     

Coupling of Fermentation and Esterification: Microbial Esterification of Decanoic Acid with Ethanol Produced via Fermentation

Two different kinds of bioprocess, ethanol fermentation and subsequent microbial esterification, were coupled using Issatchenkia terricola IFO 0933 in an interface bioreactor. The strain produced ethyl decanoate (Et-DA) by esterification of exogenous decanoic acid (DA) with ethanol produced via fermentation. The efficiency of the new coupling system depended on the concentration of glucose in a carrier and DA in an organic phase (decane) in an agar plate interface bioreactor. Optimum glucose content and DA concentration were 4% and 29 mM, respectively.     

Bioconversion of phytosterols to androstanes by mycobacteria growing on sugar cane mud

Direct sterol conversion of sugar cane mud (residue) by Mycobacterium sp. was demonstrated to be possible technologically, thus avoiding sugar cane oil extraction and further processes of extraction and purification of phytosterols from this oil. Indeed, mycobacterial cells were able to convert phytosterols from sugar cane mud into 4-androstene-dione (AD) and 1,4 androsta-diene-3,17-dione (ADD). For the various concentrations assayed, concomitant higher yields for both androstanes were achieved at 20% (w/w) sugar cane mud in media. Furthermore, conversions were similar to those from other substrates, such as a mixture of phytosterols. The results suggest that the mycobacterial cell is able to easily access and bioconvert sugar cane mud phytosterols.     

Bioconversion of lignocellulosic biomass to hydrogen: Potential and challenges

No comprehensive review on the bioconversion of lignocellulosic biomass to hydrogen is presented. This paper provides an up-to-date review on recent research development in biotechnology-based lignocellulosic biomass-to-H₂ conversion. Bioconversion of lignocellulosic prehydrolysate, hydrolysate or cellulose to hydrogen was discussed in terms of the involved microorganisms and the bioaugmentation tactics. To achieve fully the utilization of biomass, the integrated approaches composed of coupled dark–photo fermentation and the dark fermentation and bioelectrohydrogenesis were sketched. Additionally, this review sheds light on the perspectives on the lignocellulosic biomass conversion to hydrogen, and on the scientific and technical challenges faced for the lignocelluloses bioconversion.     

兼性厌氧复合菌群H纤维素降解和产乙醇能力及生态组成初探

通过限制性培养条件和连续继代培养,筛选获得了一组具有高效稳定降解纤维素能力的复合菌群H。该菌群在传代30代以上仍能保持各项性状稳定,其工作pH为6～9,3 d可以完全降解置于100 mL PCS缓冲液培养基中的滤纸,发酵液中能够检出1.54 g/L乙醇。通过16S rDNA扩增和DGGE的方法,对菌群在不同阶段的微生物组成进行了研究,确定了琥珀酸嗜热梭菌Clostridium thermo succinogene、产气荚膜梭菌Clostridium straminisolvens和紫色板蓝根梭菌Clostridium isatidis等多种可直接实现纤维素到乙醇转化的菌株。菌群通过菌种之间的协同作用,共同维持了体系的稳定及降解能力的稳定。明确菌系的组成,对于进一步研究菌群降解机理、优化菌群和提高乙醇产率意义重大。     

利用乙醇系统RP－HPLC分析PTC－氨基酸

首次报道了用乙醇作梯度洗脱有机相分离PTC－氨基酸的新方法.同乙腈相比,乙醇毒害性小、价廉、易得.在优化的色谱条件下,乙醇洗脱分辨率、灵敏度、准确度均佳,可成为PTC－氨基酸分析的一种极有前途的新方法.     

利用乙醇系统RP－HPLC分析PTC－氨基酸

首次报道了用乙醇作梯度洗脱有机相分离ＰＴＣ－氨基酸的新方法同乙腈相比,乙醇毒害性小,价廉、易得。在优化的色谱条件下,乙醇洗脱分辨率,灵敏度,准确度均佳,可成为ＰＴＣ－氨基酸分析的一种极有前途的新方法。     

Bioconversion of carbon dioxide to methane using hydrogen and hydrogenotrophic methanogens

Biogas produced from organic wastes contains energetically usable methane and unavoidable amount of carbon dioxide. The exploitation of whole biogas energy is locally limited and utilization of the natural gas transport system requires CO₂ removal or its conversion to methane. The biological conversion of CO₂ and hydrogen to methane is well known reaction without the demand of high pressure and temperature and is carried out by hydrogenotrophic methanogens. Reducing equivalents to the biotransformation of carbon dioxide from biogas or other resources to biomethane can be supplied by external hydrogen. Discontinuous electricity production from wind and solar energy combined with fluctuating utilization cause serious storage problems that can be solved by power-to-gas strategy representing the production of storable hydrogen via the electrolysis of water. The possibility of subsequent repowering of the energy of hydrogen to the easily utilizable and transportable form is a biological conversion with CO₂ to biomethane. Biomethanization of CO₂ can take place directly in anaerobic digesters fed with organic substrates or in separate bioreactors. The major bottleneck in the process is gas-liquid mass transfer of H₂ and the method of the effective input of hydrogen into the system. There are many studies with different bioreactors arrangements and a way of enrichment of hydrogenotrophic methanogens, but the system still has to be optimized for a higher efficiency. The aim of the paper is to gather and critically assess the state of a research and experience from laboratory, pilot and operational applications of carbon dioxide bioconversion and highlight further perspective fields of research.