微藻与其他微生物共培养的研究进展及应用

化石燃料的挖掘和燃烧导致环境污染以及气候变化.与化石燃料相比,微藻被认为是一种更有前途的生物柴油生产原料,它具有生长速度快、含油量高、不占用耕地的特点.尽管微藻被认为是生产第三代生物燃料的最佳生产者之一,但单独培养微藻容易污染且采收成本高,与化石燃料和传统可再生能源相比缺乏竞争力.利用微藻与其他微生物共培养能够实现自絮...     

底栖生物影响下的潮滩微地貌演化数值模拟

潮滩是海岸带湿地的主要类型之一,其中分布的底栖生物对生态环境具有重要的调节作用。潮滩底栖微藻、泥沙与水动力之间存在相互作用,影响潮滩微地貌形态,明晰底栖生物对潮滩微地貌的演化机制至关重要。以黄河三角洲潮滩湿地为研究区,通过构建潮滩微地貌动力模型,探究底栖生物对微地貌格局演化的作用机制,分析底栖生物对微地貌系统稳定性的影响。结果表明(1)底栖微藻生长与泥沙扩散、水流再分配过程交互作用驱动下,潮滩上可形成底栖微藻覆盖的高丘与积水洼地交替分布的规则性微地貌斑图;(2)微地貌斑图的形成提高了潮滩生态系统初级生产力和泥沙淤积高度;(3)底栖微藻与泥沙、水流的交互作用使得潮滩微地貌系统对侵蚀扰动呈现非线性响应行为,系统存在临界点,且在一定侵蚀率范围内存在双稳态;(4)黄河口泥螺入侵使得微地貌系统抵抗侵蚀扰动能力减小,且系统稳定性随泥螺生物量的增加而降低。     

Botryococcus braunii: A Renewable Source of Hydrocarbons and Other Chemicals

ABSTRACT:?

Botryococcus braunii, a green colonial microalga, is an unusually rich renewable source of hydrocarbons and other chemicals. Hydrocarbons can constitute up to 75% of the dry mass of B. braunii. This review details the various facets of biotechnology of B. braunii, including its microbiology and physiology; production of hydrocarbons and other compounds by the alga; methods of culture; downstream recovery and processing of algal hydrocarbons; and cloning of the algal genes into other microorganisms. B. braunii converts simple inorganic compounds and sunlight to potential hydrocarbon fuels and feedstocks for the chemical industry. Microorganisms such as B. braunii can, in the long run, reduce our dependence on fossil fuels and because of this B. braunii continues to attract much attention.     

A METHOD TO IMPROVE THE SPATIAL RESOLUTION OF PHOTOSYNTHETIC RATES OBTAINED BY OXYGEN MICROSENSORS

To determine gross photosynthesis in benthic microalgal communities, oxygen microelectrodes were used to measure the rate of decrease within the first 4 s after extinction of light. Photosynthetic rates calculated from third-order polynomial fits to the curve of decreasing O₂ concentration were compared to the rates obtained by the traditional method, where rates were estimated from linear regression. When photosynthesis was calculated for the fitted initial rates of O₂ decrease, maximum rates in microbial mats were up to 32% higher, and the depth-integrated gross photosynthesis was 5%–10% higher than the rates determined by the traditional method. The determinations from fitted initial rates also resulted in a more detailed profile of photosynthetic rate than that normally obtained. Computer simulation based on diffusion models, where the estimated initial rates of O₂ decrease were assumed to represent actual photosynthesis rates, verified the validity of the curve-fitting procedure for obtaining high-resolution photosynthesis profiles.     

Secretion of Free Fatty Acids by Prokaryotic and Eukaryotic Algae at Optimal,Supraoptimal, and Suboptimal Growth Temperatures

The paper describes the composition of extracellular free fatty acids (FFAs) and intracellular fatty acids (FAs) in the enrichment cultures of the prokaryotic alga Spirulina platensisand the eukaryotic alga Chlorella vulgarisgrown at optimal, supraoptimal, and suboptimal growth temperatures. With increasing growth temperature, the degree of unsaturation of the intracellular FAs of both algae decreased, while that of the extracellular FFAs of S. platensisincreased. The composition of the extracellular FFAs of C. vulgarispractically did not depend on the growth temperature.     

Selectivity and competitive interactions between two benthic invertebrate grazers (Asellus aquaticus and Potamopyrgus antipodarum): an experimental study using 13C- and 15N-labelled diatoms

1. Tracer experiments with two diatoms labelled with ¹³C (Nitzschia palea) and ¹⁵N (Fragilaria crotonensis), were conducted to investigate feeding selectivity and interspecific competition between the grazers Asellus aquaticus (Isopoda, Crustacea) and Potamopyrgus antipodarum (Hydrobiidae, Gastropoda). Conventional methods, such as cell counts and estimated biovolume, were used first to detect feeding preferences within the different grazer treatments. 2. The results revealed a significant decline in algal biovolume in all grazer treatments and no indications of active selectivity were observed. In contrast to conventional methods, measurements based on isotope signatures showed strong differences in tracer uptake, thus indicating different degrees of assimilation and digestion by the two grazers. 3. The selectivity index Q, which provides information on the uptake ratio of ¹³C to ¹⁵N, showed a significant time effect for both grazer species and a significant difference between single‐ and mixed‐grazer treatments for P. antipodarum. Thus, this technique enabled the direct quantification of the uptake by grazers and, therefore, served as an ideal tool for the detection of passive selectivity. 4. Our results indicate a shift in feeding preferences related to between‐species competition and a potential divergence of trophic niches when species coexist.     

Isolation of disproportionating enzyme from halotolerant microalga Dunaliella parva (Volvocales, Chlorophyceae)

Starch metabolism in Dunaliella parva Lerche is regulated by the osmolarity of the surrounding solute. Two isozymes showing amylolytic activity were obtained after purification by gel filtration chromatography. The isozymes show disproportionating activity (D‐enzyme) that is specific for malto‐oligosaccharides as substrate. Properties of the D‐enzyme in D. parva are similar to those in higher plants. The activity of the D‐enzyme is also found in various Dunaliella and Chlamydomonas, indicating that the D‐enzyme is also important in the starch metabolism in algae.     

Phycological expertise in geological applications

Our knowledge about fossil algae has been biased for a long time towards groups with calcified tissues such as dasyclads and crustose rhodophytes. This picture has recently begun to change owing to the growing number of discoveries of silicified microbial fossils and fossil microbial endoliths. There is good evidence that both groups contain a large proportion of photosynthetic organisms, particularly algae. Silicified microbial fossils are best known from the Precambrian strata, while microbial endoliths, which apparently evolved during middle to late Precambrian times are common throughout the Phanerozoic including the present. Because of the small size of these fossils, it is possible to study and morphometrically evaluate entire populations rather than individual specimens or body fragments. Thus, we are able to approach fossil taxa using largely biological rather than strictly paleontological criteria and to apply interpretations and reconstructions of biological species. Phycologists entering this field can contribute to the interpretation of such fossils by applying comparisons with modern algae, their life cycles, cellular organization, and cell division patterns. However, they have to learn to deal with post-mortem degradation and diagenetic changes, and to recognize algal remains from mineral features that surround and often obliterate the fossils. This work is often similar to that of a detective or coroner where the use of intuition and imagination is just as dangerous as it is necessary. Detection of microfossils between and within single carbonate grains in otherwise unfossiliferous rocks can provide valuable information for applied geology including petroleum exploration.     

The algal microflora of the salt works of Tarquinia (Italy)

The microflora and benthic microbial mats of the salt works of Tarquinia (Italy) are described. From 144 samples, 111 species and varieties of microalgae were identified. Diatoms prevailed up to 110. S. They were substituted by Cyanophyta at higher salinities. The microbial mats consisted of Cyanophyta, Beggiatoa spp., purple sulphur bacteria, and diatoms. Information on hypertonic resistance in some euryhaline species is given.     

Algal biotechnology products and processes — matching science and economics

Several microalgae, such as species ofChlorella, Spirulina andDunaliella, are grown commercially and algal products such as -carotene and phycocyanin are available. The main focus of algal biotechnology continues to be on high value fine chemicals and on algae for use as aquaculture feeds. This paper provides the outline for a rational approach in evaluating which algae and which algal products are the most likely to be commercially viable. This approach involves some simple market analysis followed by economic modelling of the whole production process. It also permits an evaluation of which steps in the production process have the greatest effect on the final production cost of the alga or algal product, thus providing a guide as to what area the research and development effort should be directed to. An example of this approach is presented and compared with other models. The base model used here gives a production cost of microalgal biomass at about AS 14 to 15 kg^–1, excluding the costs of further processing, packaging and marketing. The model also shows that some of the key factors in microalgal production are productivity, labor costs and harvesting costs. Given the existing technology, high value products such as carotenoids and algal biomass for aquaculture feeds have the greatest commercial potential in the short term.This paper was presented at the Symposium on Applied Phycology at the Fourth International Phycological Congress, Duke University.