木质纤维素资源生物精炼技术研究进展

开发利用可再生性的木质纤维素资源来生产液体燃料和大宗化学品,对于解决人类发展面临的资源与环境危机具有重要的意义。然而,作为其代表性工艺的纤维素乙醇生产却因为经济上无法过关而迟迟不能真正实现产业化。采用生物精炼技术,充分利用木质纤维素材料中各种组分,生产包括部分高值产品的多种产品,是克服其转化技术产业化经济可行性问题的有效措施。综述了木质纤维素原料生物精炼技术的研究发展现状,着重阐述了玉米芯的生物精炼技术产业化进展,并对木质纤维素的生物精炼前景进行了展望。     

能源植物芒草研究进展与综合利用现状

芒草是一类多年生的C4草本植物,因其具有生物量大、纤维素含量高、灰分低、热值高、适应性强、生产成本低等诸多优点被认为是目前最具开发潜力的高产纤维类能源植物之一,因而成为国内外关注和研究的热点。综述了国内外能源芒草的研究进展与综合利用现状,并展望了今后的发展前景。     

生物质能源四十年

为应对1973年全球石油危机而发展起来的现代生物质能源已渐趋成熟,在对化石能源的替代中发挥着越来越突出的作用。回顾了生物质能源40年的发展历程,对液体生物燃料、生物天然气和固体生物燃料与发电作了专门叙述。就生物质能源与中国,以及中国发展生物质能源方略发表了自己的见解。     

Relationship between functional diversity and productivity in meadow and marsh plant communities

功能多样性-生产力关系研究结果支持质量比假说和多样性假说, 但对于这两种假说的适用条件尚有争议。通过对吉林省西部草甸和沼泽植物群落的地上生物量、2个物种多样性指标(物种丰富度和Shannon-Weaver指数)、7种植物性状的两类功能多样性指标(群落权重均值和Rao二次熵), 以及土壤环境因子进行调查测量, 研究了群落功能多样性与生产力的关系。结果表明: 1)功能多样性与生产力的关系比物种多样性与生产力的关系更为密切; 2)功能群落权重均值解释生产力变异的能力好于Rao二次熵, 即优势物种对群落生产力的影响作用更大; 3)水淹条件影响着功能多样性与生产力的关系, 以群落权重均值为基础的质量比假说适于解释草甸群落功能多样性与生产力的关系, 而以Rao二次熵为基础的多样性假说适于解释有强烈环境筛(水淹)的沼泽群落功能多样性与生产力的关系。     

Effects of Temperature and pH on Cell Growth of a Flocculating Microalga (Chlorella vulgaris) JSC-7

微藻是可广泛用于健康食品及水产养殖的饵料,同时,微藻细胞内积累的油脂可作为可再生生物燃料,因此微藻的生长和代谢受到广泛关注。温度和pH对微藻的生物量积累有很大影响,考察不同温度和pH条件下微藻细胞的生长有助于寻找最佳的条件进行微藻的培养。自絮凝小球藻JSC-7（Chlorella vulgaris JSC-7）可实现自沉降采收,有利于降低微藻生产成本,优化其生长条件对更好地利用该微藻具有重要意义。考察了温度（22∽40℃）及pH（6.0∽10.0）对其细胞生长、叶绿素含量和油脂产量的影响。在所选取的温度及pH范围内,JSC-7细胞均可生长,显示该藻种可以适应广泛的温度和pH条件。适合细胞生长的温度依次为31℃〉28℃〉35℃〉25℃,pH依次为7.0〉8.0〉6.0。pH 8.0时生物量和油脂的积累量最多,说明该藻株在弱碱条件下更适合生长和产油。当温度为31℃、pH为7.0时,可获得最高的生长量（OD690=0.941）、叶绿素含量（19 mg/L）及油脂产量（39.07%/克干重）。     

Microbial Communities Associated with Tree Bark Foliose Lichens: A Perspective on their Microecology

Tree‐bark, foliose lichens occur widely on a global scale. In some locales, such as forests, they contribute a substantial amount of biomass. However, there are few research reports on microbial communities including eukaryotic microbes associated with foliose lichens. Lichens collected from tree bark at 11 locations (Florida, New York State, Germany, Australia, and the Arctic) were examined to determine the density and C‐biomass of bacteria and some eukaryotic microbes, i.e. heterotrophic nanoflagellates (HNF) and amoeboid protists. A rich microbial diversity was found, including large plasmodial slime molds, in some cases exceeding 100 μm in size. The densities of HNF and amoeboid protists were each positively correlated with densities of bacteria, r = 0.84 and 0.80, respectively (p < 0.01, N = 11 for each analysis) indicating a likely bacterial‐based food web. Microbial densities (number/g lichen dry weight) varied markedly across the geographic sampling sites: bacteria (0.7–13.1 × 10⁸), HNF (0.2–6.8 × 10⁶) and amoeboid protists (0.4–4.6 × 10³). The ranges in C‐biomass (μg/g lichen dry weight) across the 11 sites were: bacteria (8.8–158.5), HNF (0.03–0.85), and amoeboid protists (0.08–540), the latter broad range was due particularly to absence or presence of large slime mold plasmodia.     

Growth characteristics of Nostoc flagelliforme at intermittent elevated CO2 concentrations

Algal cultivation is a potential candidate for CO₂ mitigation. CO₂ plays important roles in mass cultivation of algae, including supplying carbon source and adjusting medium pH. To assess the possibility of using edible cyanobacterium Nostoc flagelliforme as carbon storage device, the growth characteristics of N. flagelliforme batch cultured under elevated CO₂ concentrations (0, 2.5, 5, 20, and 40%) were investigated in this study. Results showed that the net photosynthetic rate, efficiency and carbon sequestration rate at 20% CO₂ were increased at a maximum of 121 μmol O₂ (mg chla)^?1 h^?1 8.40% and 0.17 g CO₂ L^?1 day^?1, and increased by 0.42, 1.03 and 1.13 folds compared with that of the control, respectively. Higher CO₂ concentration resulted in the declines in photosynthetic rate, efficiency and carbon sequestration rate because of medium pH reduction. Accordingly, the dry cell weight, amount of exopolysaccharides and protein content of N. flagelliforme cells at 20% CO₂ were obtained at a maximum of 1.45 g L^?1, 54.98 mg L^?1 and 57.75%, increased by 0.93, 0.29 and 0.8 folds compared with that of the control, respectively. These results provided important information for CO₂ mitigation by N. flagelliforme and would shed more light on elucidating the mechanisms of CO₂ tolerance in cyanobacterium.     

Changes in forest biomass and linkage to climate and forest disturbances over Northeastern China

The forests of northeastern China store nearly half of the country's total biomass carbon stocks. In this study, we investigated the changes in forest biomass by using satellite observations and found that a significant increase in forest biomass took place between 2001 and 2010. To determine the possible reasons for this change, several statistical methods were used to analyze the correlations between forest biomass dynamics and forest disturbances (i.e. fires, insect damage, logging, and afforestation and reforestation), climatic factors, and forest development. Results showed that forest development was the most important contributor to the increasing trend of forest biomass from 2001 to 2010, and climate controls were the secondary important factor. Among the four types of forest disturbance considered in this study, forest recovery from fires, and afforestation and reforestation during the past few decades played an important role in short‐term biomass dynamics. This study provided observational evidence and valuable information for the relationships between forest biomass and climate as well as forest disturbances.     

Transformation and stabilization of pyrogenic organic matter in a temperate forest field experiment

Pyrogenic organic matter (PyOM) decomposes on centennial timescale in soils, but the processes regulating its decay are poorly understood. We conducted one of the first studies of PyOM and wood decomposition in a temperate forest using isotopically labeled organic substrate, and quantified microbial incorporation and physico‐chemical transformations of PyOM in situ. Stable‐isotope (¹³C and ¹⁵N) enriched PyOM and its precursor wood were added to the soil at 2 cm depth at ambient (N0) and increased (N+) levels of nitrogen fertilization. The carbon (C) and nitrogen (N) of added PyOM or wood were tracked through soil to 15 cm depth, in physically separated soil density fractions and in benzene polycarboxylic acids (BPCA) molecular markers. After 10 months in situ, more PyOM‐derived C (>99% of initial ¹³C‐PyOM) and N (90% of initial ¹⁵N‐PyOM) was recovered than wood derived C (48% of ¹³C‐wood) and N (89% under N0 and 48% under N+). PyOM‐C and wood‐C migrated at the rate of 126 mm yr^?1 with 3–4% of PyOM‐C and 4–8% of wood‐C recovered below the application depth. Most PyOM C was recovered in the free light fraction (fLF) (74%), with 20% in aggregate‐occluded and 6% in mineral associated fractions – fractions that typically have much slower turnover times. In contrast, wood C was recovered mainly in occluded (33%) or dense fraction (27%). PyOM addition induced loss of native C from soil (priming effect), particularly in fLF (13%). The total BPCA‐C content did not change but after 10 months the degree of aromatic condensation of PyOM decreased, as determined by relative contribution of benzene hexa‐carboxylic acid (B6CA) to the total BPCA C. Soil microbial biomass assimilated 6–10% of C from the wood, while PyOM contributions was negligible (0.14–0.18%). The addition of N had no effect on the dynamics of PyOM while limited effect on wood.