Production of soluble sugar from cellulosic materials by repeated use of a reversibly soluble-autoprecipitating cellulase

A reversibly soluble-autoprecipitating cellulase was prepared by covalently immobilizing Meicelase on an enteric coating polymer (AS-L, hydroxypropyl methylcellulose acetate succinate). The immobilized enzyme (M-AS) was reversibly soluble-insoluble depending on the pH of the reaction medium. Moreover, the enzymatic activity of M-AS, in a soluble state, for microcrystalline cellulose was higher than that of the conventional solid immobilized enzyme. On the other hand, M-AS, in an insoluble state, and good properties of self-sedimentation, and a large portion of M-AS spontaneously precipitated for about 15 min at pH 3.8. In the repeated hydrolysis of rice straw, delignified with sodium hydroxide using a bioreactor with a conical bottom, M-AS was separated batchwise from a production solution by self-sedimentation in a conical bottom of the bioreactor. When delignified, rice straw was hydrolyzed repeatedly by reuse of M-AS; the total amount of soluble sugar produced from 5 g of delignified rice straw was 2.7 g. Further, by the hydrolysis method with repeated removal of reaction inhibitors (soluble sugar), the time required for converting the same amount of delignified rice straw to soluble sugar was significantly reduced, as compared with that by the standard reaction method.     

纤维素酶水解稻草生产单细胞蛋白（SCP）：Ⅱ.稻草酶解液生产SCP的研究

从18株酵母和2株白地霉中选得两株酵母它们能较好地利用稻草酶解液生产单细胞蛋白,其菌名和编号为皮状丝孢酵母(Trichosporon cutaneum)AS 1.374,假丝酵母(Candida sp.)Y002对这两株菌的生长条件进行了研究,在pH5.0、30—32℃、糖浓度1.5—2.0％、培养36h的条件下,SCP对糖的产率可达66.6％。     

结冷胶固定化保加利亚乳杆菌及在玉米秸秆连续发酵d-乳酸中的应用

秸秆生物炼制化学品是解决秸秆资源利用附加值低、减轻秸秆焚烧带来的环境污染的主要方法之一。本研究制备了结冷胶固定化保加利亚乳酸杆菌(Lactobacillus bulgaricus)T15凝胶珠(结冷胶-T15凝胶珠),并对其性质进行表征,建立了结冷胶-T15凝胶珠固定化细胞循环连续发酵产D-乳酸发酵工艺。结冷胶-T15凝胶珠的断裂应力为(91.68±0.11) kPa,较海藻酸钙固定化T15凝胶珠(海藻酸钙-T15凝胶珠)提高了125.12%,表明结冷胶-T15凝胶珠的强度更强。以结冷胶-T15凝胶珠为出发菌株,葡萄糖为发酵基质,10批次循环(720h)发酵,其D-乳酸最高批次产量为(72.90±2.79)g/L,较海藻酸钙-T15凝胶珠提高了33.85%,较游离T15提高了37.70%。将葡萄糖更换为玉米秸秆酶解液,使用结冷胶-T15凝胶珠进行10批次循环(240 h)发酵,D-乳酸生产强度可达(1.74±0.79)g/(L·h),远高于游离菌。10批次循环发酵后结冷胶-T15凝胶珠磨损率小于5%,表明结冷胶是一种细胞固定化的良好载体,可广泛应用于细胞固定化工业发酵领域。本研究为细胞...     

生物发酵稻秸对湖羊消化道上皮形态及微生物区系的影响

【目的】本研究旨在通过显微观察和16SrRNA基因高通量测序技术来探究饲喂生物发酵稻秸对湖羊肠道上皮形态及微生物区系的影响。【方法】试验选择70日龄、体重相近(25.15±0.47)kg的湖羊公羔21只,根据饲粮中粗饲料的组成随机分为3组：稻秸组、生物发酵稻秸组和苜蓿干草组,饲粮精粗比为6:4,试验持续7周,其中适应期3周,正试期4周,结束后屠宰取样,采集瘤胃、空肠和结肠上皮组织进行观察测量,收集对应肠段内容物用于微生物区系和代谢产物测定。【结果】与稻秸组相比,饲喂生物发酵稻秸显著提高湖羊瘤胃中纤维杆菌(Fibrobacteres)的相对丰度和挥发性脂肪酸(volatile fatty acids, VFA)的含量,促进瘤胃上皮的发育;显著提高湖羊空肠中厚壁菌门(Firmicutes)和疣微菌门(Verrucomicrobia)的相对丰度,改变空肠微生物菌群结构,促进空肠上皮组织的发育;改变湖羊结肠微生物菌群结构。【结论】饲喂生物发酵稻秸有利于湖羊肠道上皮的发育,并增加消化道内的微生物多样性。     

Cereal straw and pure cellulose as carbon sources for growth and production of plant cell-wall degrading enzymes by Sporotrichum thermophile

Sporotrichum thermophile grew well and produced plant cell-wall degrading enzymes on straw (barley and wheat) of different particle sizes and Avicel as carbon sources. Comparable activities of endoglucanase, Avicelase and cellobiase were produced on each substrate. In contrast, activities of xylanase, aryl--glucosidase, -xylosidase, esterase and -l-arabinofuranosidase were higher on straw (either wheat or barley) than on Avicel. The enzyme systems produced on barley straw of different particle sizes degraded finely milled barley straw in vitro more rapidly and to a greater extent than those produced on Avicel. In contrast, the enzyme systems produced on Avicel and very coarse barley straw hydrolysed Avicel to about the same extent while that produced on fine barley straw was slightly less effective. The main hydrolysis product in all cases was glucose. Isoelectric focusing revealed that the plant cell-wall degrading enzyme system produced by S. thermophile on barley straw was qualitatively and quantitatively superior to that produced on Avicel.C. Sugden was and M.K. Bhat is with the Department of Protein Engineering, Institute of Food Research, Reading Laboratory, Earley Gate, Whiteknights Road, Reading RG6 2EF, UK; C. Sugden is now with the Department of Biochemistry, University of York, Heslington, York YO1 5DD, UK.     

Biomethanation of rice and wheat straw

When rice or wheat straw was added to cattle dung slurry and digested anaerobically, daily gas production increased from 176 to 331 l/kg total solids with 100% rice straw and to 194 l/kg total solids with 40% wheat straw. Not only was methane production enhanced by adding chopped crop residues but a greater biodegradability of organic matter in the straws was achieved.The authors are with the Microbiology and Molecular Genetics Unit, Tata Energy Research Institute, 158 Jor Bagh, New Delhi 110 003, India     

白腐真菌对稻草秸秆的降解及其有关酶活性的变化*

以稻草秸秆加20%棉籽壳为培养基质,接种侧耳Z17、921、1024菌株,在不同生长阶段,测定培养物的主要化学成分和有关酶活的变化。结果表明,从接种到子实体形成,所试菌株培养物的纤维素、木质素等呈持续不断的下降趋势,水份、粗蛋白含量却逐渐升高。基质中漆酶酶活性在菌丝生长初期呈迅速上升趋势,后稍降低,而愈创木酚酶活性在菌丝生长初期及子实体形成时达到高峰,后有所降低或消失。     

High-yield spore production from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> by solid state fermentation

Bacillus licheniformis was grown for 48 h at 37°C in solid state fermentation; a maximum of 1.7 × 10¹¹ spores/g dry substrate were obtained using rice straw powder (300 g/kg) and wheat bran (700 g/kg) supplemented with glucose (40 g/kg), peptone (20 g/kg), yeast extract (20 g/kg), KH₂PO₄ (10 g/kg) and CaO (5 g/kg) with an initial moisture content of 65%.     

Management of an ornamental pond as a conservation site for a threatened native fish species, crucian carp Carassius carassius

Ornamental ponds are important sites for conserving threatened native fish species (e.g. crucian carp Carassius carassius L.), but pond management plans rarely include considerations of native fishes. We developed and implemented a management plan for a small (0.8 h), ornamental estate pond in Hertfordshire (England) using historical information (aquatic plant and animal surveys) and a 9-year data set on climatic variables and crucian carp body condition. Crucian carp growth was not correlated with climatic variables, but body condition decreased with increasing temperature (in degree-days), which suggests that temperature influences on growth are counter-balanced by environmental factors. Management included the removal of one fish species (to eliminate hybridization with another species) and the introduction of two native species (to re-balance the fish assemblage), a reduction in floating aquatic plants (to reduce shading of the sediments) as well as the use of a chemical agent to compact the pond’s fine sediments and barley straw to enhance invertebrate habitat and thus fish prey production. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli and S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Comparison of SHF and SSF processes from steam-exploded wheat straw for ethanol production by xylose-fermenting and robust glucose-fermenting Saccharomyces cerevisiae strains

In this study, bioethanol production from steam-exploded wheat straw using different process configurations was evaluated using two Saccharomyces cerevisiae strains, F12 and Red Star. The strain F12 has been engineerically modified to allow xylose consumption as cereal straw contain considerable amounts of pentoses. Red Star is a robust hexose-fermenting strain used for industrial fuel ethanol fermentations and it was used for comparative purposes. The highest ethanol concentration, 23.7 g/L, was reached using the whole slurry (10%, w/v) and the recombinant strain (F12) in an SSF process, it showed an ethanol yield on consumed sugars of 0.43 g/g and a volumetric ethanol productivity of 0.7 g/L h for the first 3 h. Ethanol concentrations obtained in SSF processes were in all cases higher than those from SHF at the same conditions. Furthermore, using the whole slurry, final ethanol concentration was improved in all tests due to the increase of potential fermentable sugars in the fermentation broth. Inhibitory compounds present in the pretreated wheat straw caused a significantly negative effect on the fermentation rate. However, it was found that the inhibitors furfural and HMF were completely metabolized by the yeast during SSF by metabolic redox reactions. An often encountered problem during xylose fermentation is considerable xylitol production that occurs due to metabolic redox imbalance. However, in our work this redox imbalance was counteracted by the detoxification reactions and no xylitol was produced.