基于GLM模型和神经网络研究芳烃化合物对藻类毒性

工业的快速发展和溢油事故的频繁发生所产生的大量芳烃化合物正威胁海洋生态系统的健康,建立芳烃化合物物化性质与小球藻急性毒性间的非线性模型,是预测未知芳烃化合物对藻类毒性的主要手段之一.本研究以实验获取的25种芳烃化合物对小球藻96h的毒性数据为基础,采用密度泛函理论(DFT)中的B3LYP方法,在6-311G**基组上全优化计算25种芳烃化合物结构参数和热力学参数,通过逐步广义线性回归(GLM)、小波神经网络(WNN)和T-S模糊神经网络(T-SFNN)等方法,对芳烃化合物物化性质和藻类抑制毒性的非线性关系进行拟合和逼近.F检验表明,逐步GLM方程是显著的(p<0.001).配对t检验表明,GLM、WNN、T-SFNN3种模型都是可信的;决定系数(R2>0.96)表明3个模型具有很高的精确性.上述结果证明本文建立的模型具有良好的拟合度和解释能力,可以预测未知芳烃化合物对小球藻的急性毒性.模型误差计算结果表明,WNN的精度最高(mse=0.0076,mae=0.0533),采用WNN方法进行建模,预测未知芳烃化合物对小球藻的急性毒性是最合适的.     

营养条件对污水中小球藻生长及产能效应的影响

以过滤的富营养化的鱼塘废水为培养液,添加外源的碳、氮、磷元素,考察污水中不同的外源无机碳浓度、总氮浓度、总磷浓度对小球藻(Chlorella vulgaris)的生长、油脂含量和烃类含量的影响。在25℃、光照强度为4 500 Lux、光暗比为12L:12D的条件下培养10 d。单因子方差分析和多重比较结果表明:(1)以Na2CO3做碳源,小球藻生物量和烃类含量在外源无机碳浓度为6 mg/L时最高,油脂含量在外源无机碳浓度为12 mg/L最高。(2)以KNO3做氮源,小球藻生物量在总氮浓度为25 mg/L时最高,油脂含量在总氮浓度为15 mg/L时最高,烃含量在总氮浓度为20 mg/L时最高。(3)以KH2PO4做磷源,小球藻生物量和烃类含量在总磷浓度为2 mg/L时最高,油脂含量在总磷浓度为1.5 mg/L时最高。     

共生细菌对盐生小球藻亚砷酸盐代谢的影响

为探讨共生细菌对盐生小球藻（Chlorella salina）亚砷酸盐（As（III））富集和形态转化的影响,从C.salina培养液中分离培养出一株共生细菌,并采用抗生素处理C.salina获得无菌藻,设置0,75,150,300,750 μg/LAs（III）溶液处理带菌和无菌的C.salina,7d后测定C.salina对As（III）的吸收、吸附和富集量,以及培养液和藻细胞内As的形态,计算带菌和无菌C.salina对As（III）的氧化率和去除率;使用不同浓度的As（III）处理共生细菌7d,并以300μg/L的As（III）处理共生细菌不同时间,计算两种情况下共生细菌对培养液中As（III）的氧化率和去除率.结果表明：C.salina的共生细菌为根癌农杆菌（Agrobacterium tumefaciens WB-1）;与无菌C.salina相比,带菌C.salina生长更快、对As（III）的耐性更强.带菌C.salina对As（III）的富集量为103.10~448.12mg/kg、氧化率为78.93%~96.88%、去除率为18.92%~55.21%,显著高于无菌C.salina的富集量（11.68~91.39mg/kg）、氧化率（14.46%~26.39%）和去除率（12.82%~29.15%）,也高于A.tumefaciens WB-1对As（III）的氧化率（4.51%~30.61%）和去除率（1.86%~16.19%）.此外,带菌C.salina胞内还检测到少量的As（III）和甲基砷,而在无菌C.salina胞内没有甲基砷存在.共生细菌促进了盐生小球藻对As（III）的富集和形态转化.     

微藻无机氮利用过程中的稳定氮同位素分馏

选用两种δ15N差异显著的铵态氮和硝态氮,分别设置不同浓度的铵态氮和硝态氮来处理莱茵衣藻和蛋白核小球藻,通过分析微藻的稳定氮同位素组成变化,来研究微藻利用不同浓度、不同形态无机氮过程中的稳定氮同位素分馏特征。结果显示,在未添加无机氮的条件下,微藻利用有机氮时,生长缓慢,稳定氮同位素基本上不存在分馏;在添加低浓度无机氮(≤20 mmol/L)时,微藻的生长和稳定氮同位素分馏都随着无机氮浓度的增加而增加;而添加高浓度无机氮(20 mmol/L)时,微藻的生长趋于稳定,铵态氮条件下的微藻稳定氮同位素分馏继续加大,而硝态氮条件下的微藻稳定氮同位素分馏反而减小,可能与此时微藻硝酸还原酶的活力减小有关。     

不同碳源及光照对小球藻生长和产油脂的影响

考察了3种碳源(葡萄糖、NaHCO3和乙酸钠)在不同初始质量浓度和光照条件下对小球藻(Chlorella vulgaris)生长和产油脂的影响。采用OD680和生物量来评价小球藻的生长情况;以溶剂浸提法提取生物油脂,并以油脂质量分数和油脂产量来描述产油脂特性。结果表明,经过9 d的培养,3种碳源中葡萄糖是最佳有机碳源。由其培养的小球藻生长速率最快,由NaHCO3培养的小球藻的生长效果不如葡萄糖,而乙酸钠不利于小球藻的生长。随着光照的增强,小球藻光合效率提高,生物量逐渐提高,5 000 lx最利于小球藻的生长,而1 600 lx最利于小球藻油脂的积累。研究表明,光照5 000 lx下,初始质量浓度为15 g/L的葡萄糖作为碳源是小球藻适宜的生长和产油条件,获得了3.17 g/L的最大生物量和1.025 g/L的最大油脂产量。     

Effects of cultivation strategies on the cultivation of Chlorella sp. HQ in photoreactors

Heterotrophic cultivation caused high level of ROS and high lipids accumulation. HMTC is the best culture strategy for improving the microalgal biomass. Chlorella sp. HQ had great nutrient removal capacity under five culture strategies. The effects of cultivation strategies (including autotrophic cultivation (AC), heterotrophic cultivation (HC), fed-batch cultivation (FC), heterotrophic+ autotrophic two-stage cultivation (HATC), and heterotrophic+ mixotrophic two-stage cultivation (HMTC)) on the growth and lipid accumulation of Chlorella sp. HQ and its total nitrogen (TN) and total phosphorus (TP) removal in secondary effluent were investigated in column photoreactors. The results showed that the TN and TP removal rates ranged between 93.72%–95.82% and 92.73%–100%, respectively, under the five different strategies. The microalgal growth potential evaluated by the maximal growth rate (R_max) was in the order of HMTC>HC>FC>AC>HATC. The values of biomass, total lipid yield, triacylglycerols (TAGs) yield, and total lipid content of the microalga cultivated in the last 5 d increased significantly, but the TAGs productivities of the five strategies were lower than those in the first 7 d. Compared with all the other cultivation strategies, the TAGs productivity and yield after 12 d of cultivation under the heterotrophic condition reached the highest values accompanying the highest level of intracellular reactive oxygen species (ROS), in which the TAGs yield reached 40.81 mg/L at the end of the cultivation period. The peaks in TAGs yield and ROS level suggested that HC was beneficial for lipids accumulation via regulating the cellular redox status and exerting ROS stress on microalgal cells. In summary, HMTC was the best cultivation strategy for improving the microalgal biomass and HC was the best strategy for microalgal TAGs accumulation to produce biodiesel.     

普通小球藻和铜绿微囊藻与粘土颗粒凝聚沉降行为研究

本研究结果表明,不同的藻类和不同的粘土颗粒均使藻类与粘土颗粒的凝聚沉降发生变化。结果还表明,溶液中[Cu~(2+)]浓度超过10~(-5)mol后,加快了小球藻与高龄土的凝聚沉降。使80％以上的小球藻和高岭土在不到10min内即凝聚沉降。在最后结合实验结果讨论了利用藻类与粘土的凝聚沉降治理水体污染。     

改进的硫酸盐-聚乙烯醇法包埋藻菌脱氮除磷研究

采用改进的硫酸盐-PVA固定化法将藻与菌混合固定。在三种不同藻菌比的情况下，固定化系统对氮去除均可达100％，但是去除速度与固定的细菌量有关，细菌量越大，对氮的去除速度越快；对磷的去除随实验进行，最大去除率逐步下降，其下降速度与固定藻的量有关，藻量越大，下降速度越慢。由此说明脱氮的主要贡献者是细菌，而藻对除磷起了主要作用。为达到有效的脱氮除磷，应适当提高固定化藻的浓度，藻菌比应大于2：1。透射电镜照片显示，在聚乙烯醇载体上，藻类的生长没有受到限制。     

Early stage toxicity of excess copper to photosystem II of Chlorella pyrenoidosa–OJIP chlorophyll a fluorescence analysis

Acute toxicity of excess Cu on the photosynthetic performance of Chlorella pyrenoidosa was examined by using chlorophyll a fluorescence transients and JIP-test after exposure to elevated Cu concentrations for a short time period. High Cu concentration resulted in a significant suppression in photosynthesis and respiration. The absorption flux (ABS/RC) per PSII reaction center increased with increasing Cu concentration, but the electron transport flux (ET₀/RC) decreased. Excess Cu had an insignificant effect on the trapping flux (TR₀/RC). The decline in the efficiency, with which a trapped exciton can move an electron into the electron transport chain further than Q_A−(Ψ₀), the maximal quantum yield of primary photochemistry (?_P0), and the quantum yield of electron transport (?_E0) were also observed. The amount of active PSII reaction centers per excited cross section (RC/CS) was also in consistency with the change of photosynthesis when cells were exposed to excess Cu concentration. JIP-test parameters had a good linear relationship with photosynthetic O₂ evolution. These results suggested that the decrease of photosynthesis in exposure to excess Cu may be a result of the inactivation of PSII reaction centers and the inhibition of electron transport in the acceptor side.     

三峡库区水华优势藻类生长动力学的普适性研究

从蓝绿藻中选取绿藻门的普通小球藻(Chlorella vulgaris,CV藻)为研究对象,应用Monod方程考察氮、磷营养盐对CV藻生长的影响,分别计算出CV藻对TP、TN的半饱和常数KSP和KSN结果表明KSN>>KSP,说明TP对CV藻生长的影响明显大于TN.CV藻生长速率对磷质量浓度反应很灵敏:与空白值相比,在0.002 mg·L-1的低浓度下u就有提高,而浓度到0.2 mg.L-1时,u明显增大;但在0.000-0.050 mg·L-1氮浓度范围内u几乎没有变化.通过系统比较CV藻与优势蓝绿藻,甚至海水藻的生长动力学特征,探讨了CV藻与其它蓝绿藻的动力学普适性和共同性,证实这些藻类都具有非常类似的生长动力学和生态学特征.因此,推测CV藻生长动力学模型可以从整体上反映和代表库区优势蓝绿藻的生长行为.同时分析和归纳了蓝绿藻生长模型的相似性和规律性,得出三峡库区优势藻类生长行为存在普遍一致性的初步结论.