青藏高原北部库赛湖沉积柱中长链烯酮的分布特征及古环境意义

长链烯酮不饱和度指标U37K或U37K′已被广泛应用于古海洋表层水温的重建,但用于恢复湖泊古温度的研究则相对很少。本文以青藏高原北部咸水湖泊库赛湖作为研究对象,对湖心一个5m沉积柱中的长链烯酮进行了测定分析,并通过分子生物学手段确定了其母源。结果表明该沉积柱的大部分层位存在长链烯酮,其C37/C38<1;DNA测序结果表明库赛湖中的定鞭藻为Isochrysis属,为长链烯酮的母源。根据已发表文献中的湖泊环境中长链烯酮不饱和度指标U37K与温度的经验公式估算出的古湖水温度接近于实测的现代夏季水温,且与甘油二烷基甘油四醚(Glycerol Dialkyl Glycerol Tetraethers,GDGT)重建的库赛湖古湖水温度范围基本一致。但是,用长链烯酮恢复的古湖水温度总体上稍高于由GDGT计算出的温度且波动更为强烈,这可能与这两种脂类的母源生物在湖中的栖息层位不同有关。     

非饱和土壤轻油污染多相流研究进展

轻油泄漏到地下后 ,在非饱和土壤中水、气、油三相相互作用、相互影响 ,共同构成多相流体系统。在简要分析轻油污染问题的产生、危害以及轻油泄漏在地表以下运移方式的基础上 ,介绍并总结了近些年来国内外土壤轻油污染有关的多相流研究方面的进展 ,包括国外的模型研究成果、国内外试验研究方法和研究成果 ,并指出目前研究中存在的问题和需要进一步探讨的方向     

长链烯酮不饱和度温标研究进展

长链烯酮不饱和度温标是古温度研究的重要替代指标。介绍了小样量、低长链烯酮样品的分析方法 ,长链烯酮的来源、分布 ,长链烯酮的不饱和度与温度的关系及其在古环境研究中的应用。介绍海洋中长链烯酮研究最新进展的同时 ,着重阐述了湖泊中长链烯酮研究现状及存在的主要问题。     

Cell-recycle fed-batch production of a highly unsaturated polyhydroxyalkanoate from 1,3-butanediol byPseudomonas sp. A33

The recently isolatedPseudomonas sp. A33 was investigated for the production of a highly unsaturated polyhydroxyalkanoate (PHA) containing various alkyl and alkenyl pendent groups from 1,3-butanediol in a cell-recycle fed-batch production mode. The monomer composition and degree of unsaturation in PHA were dependent on the environmental conditions. The production temperature markedly influenced the content, composition, and degree of unsaturation of PHA. As the production temperature decreased from 30 to 10°C, the degree of unsaturation and content of PHA were increased, while the mole percentage of 3-hydroxybutyrate (3HB) was decreased. These temperature effects on the composition of PHA imply that the production can be used as a control variable for the biosynthesis of a highly unsaturated PHA and for the specific regulation of the composition of PHA. The biosynthetic pathway for a highly unsaturated PHA which is based on de novo fatty acid biosynthetic pathway is proposed. For the enhanced production of this functional PHA, a high cell density was achieved by cell-recycle continuous culture at 30°C, and then a large amount of PHA was accumulated at 15°C by fed-batch addition of the feeding solution containing excess 1,3-butanediol. The structures of monomer constituents of polymer were confirmed by gas chromatography—mass spectrometric analysis of trimethylsiyl derivatives of 3-hydroxyalkanoic acids methyl esters.