Biotechnological potential of immobilized algae for wastewater N, P and metal removal: A review

This presentation comprises a review on the use of immobilized algae for wastewater nitrogen, phosphorus and metal removal purposes. Details of the use of immobilized algae, the techniques of immobilization and the effects of immobilization on cell function are included. Particularly relevant in their use for heavy metal removal from wastewaters; upon enriching the biomass in metal, can be recoverd, thereby providing economic advantages. The use of immobilized microalgae in these processes is very adequate and offers significant advantages in bioreactors. The future of this area of algal cell biotechnology is considered.     

Effect of dissolved oxygen concentration on differentiation of somatic embryos of Coffea arabica cv. Catimor 9722

The effect of two different dissolved oxygen (DO) concentrations (50 and 80%) on differentiation of somatic embryos (SE) from cell suspensions of coffee (Coffea arabica cv. Catimor 9722) was analyzed. Two bioreactors CMF-100 (CHEMAP AG) designed for the culture of cells, with 2-l glass vessels and a maximum work volume of 1.8 l were used. Each one was equipped with a gas blending unit (air, O₂, N₂, CO₂) for the control of DO concentration. The inoculation density of embryogenic cells was 1.0 gram of fresh weight per liter (g FW l^–1). The number of somatic embryos was greater (71 072 SE l^–1) with 80% DO, but the major proportion were globular and heart shaped SE (66 399 SE l^–1) and only 6.6% with regard to total was torpedo shaped SE. However, the 50% DO produced the higher number in the torpedo shaped SE (7389 SE l^–1) what represented 20.0% with regard to total. Thus, higher concentrations of DO induced globular and heart shaped SE differentiation, but for production of torpedo shaped SE lower concentrations DO are needed. The somatic embryos obtained in the bioreactor with 50% DO showed similar behavior to the somatic embryos obtained in the rotary shaker. After 8 weeks of culture, 49.2% germination was obtained, which allowed a total of 1725 plantlet to be transferred to conditions ex vitro. After 6 months of culture, 89.2% of conversion was achieved and 1539 plants obtained were transferred to field conditions.     

应用基因工程生产一次性使用的常规种子

美国公布的“植物基因表达调控”的专利技术,使经遗传改变的植物生产的下一代种子不能发芽。农民买了此一次性种子后,产量不受影响但不能留种用。种子公司把此技术作为开发新品种的一种手段。     

凝血因子Ⅶ及其重组表达新进展

凝血因子Ⅶ是一种维生素K依赖型的单链糖蛋白,在凝血过程中发挥着极其重要的作用,在临床上有广泛的应用,可用于伴有抑制物的血友病、先天性FⅦ缺乏症、血小板无力症及外科手术或严重外伤导致的创伤出血等止血用途.基因重组技术提供了能够大规模制备人凝血因子Ⅶ的有效途径,近年来已尝试并建立了多种人凝血因子Ⅶ的重组表达系统.对重组人凝...     

Enhancement of PCB degradation by Burkholderia xenovorans LB400 in biphasic systems by manipulating culture conditions

Two-phase partitioning bioreactors (TPPBs) can be used to biodegrade environmental contaminants after their extraction from soil. TPPBs are typically stirred tank bioreactors containing an aqueous phase hosting the degrading microorganism and an immiscible, non-toxic and non-bioavailable organic phase functioning as a reservoir for hydrophobic compounds. Biodegradation of these compounds in the aqueous phase results in thermodynamic disequilibrium and partitioning of additional compounds from the organic phase into the aqueous phase. This self-regulated process can allow the delivery of large amounts of hydrophobic substances to degrading microorganisms. This paper explores the reactor conditions under which the polychlorinated biphenyl (PCB) degrader Burkholderia xenovorans LB400 can degrade significant amounts of the PCB mixture Aroclor(R) 1242. Aroclor(R) degradation was found to stall after approximately 40 h if no carbon source other than PCBs was available in the reactor. Sodium pyruvate was found to be a suitable carbon source to maintain microbial activity against PCBs and to function as a substrate for additional cell growth. Both biphenyl (while required during the inoculum preparation) and glucose had a negative effect during the Aroclor(R) degradation phase. Initial Aroclor(R) 1242 degradation rates in the presence of pyruvate were high (6.2 mg L(-1) h(-1)) and 85% of an equivalent concentration of 100 mg Aroclor(R) 1242 per L aqueous phase could be degraded in 48 h, which suggest that solvent extraction of PCBs from soil followed by their biodegradation in TPPBs might be a feasible remediation option.     

Hydrodynamic behaviors in fermentative hydrogen bioreactors by pressure fluctuation analysis

Three bioreactor configurations were employed in these investigations, which consisted of working volumes of 10, 1.2 and 1.2 L. Power spectrum diagrams of bed pressure fluctuation were used with hydraulic retention times (HRT) and geometric factors to identify the flow regimes in the bioreactors, where HRT varied from 8 to 1 h. It was found that the flow regimes in the bioreactors changed from a dispersed regime to coalesced and slugging regimes, when the biogas production rate (BPR) increased, as a result of decreasing the operating HRT. The flow regime was a dispersed bubble regime when the HRT was higher than 4 h in the bioreactor, whereas when the HRT was 2 h the coalesced bubble phenomena occurred in the bioreactor. A slugging regime was found when the HRT was lower than 1 h in thinner bioreactor.     

废气生物处理设施排放的微生物气溶胶逸散特征、影响因素与暴露风险研究进展

生物处理技术因其具有高效、成本低廉、操作简便、清洁、无二次污染等特点,已被广泛应用于废气处理方面,但微生物气溶胶会作为二次污染物从废气处理设施排放到周围空气中。由于携带和传播有害微生物,微生物气溶胶对人体健康造成潜在危害和风险。废气生物处理设施既是微生物气溶胶的“汇”,也是微生物气溶胶的“源”。本文阐述了废气生物处理设施微生物气溶胶的逸散水平、群落结构和粒径分布特征,分析了其形成原因、主要来源、影响因素和暴露风险,为废气生物处理设施产生的微生物气溶胶的识别和控制技术研究提供科学依据和参考。     

Intracellular pH-based controlled cultivation of yeast cells: II. cultivation methodology

Intracellular pH (pH(i)) was measured on-line in a bioreactor using a fluorescent pH(i) indicator, 9-aminoacridine, and controlled fed-batch cultivations of yeast cells based on pH(i) (FB-pH(i)) were performed. In FB-pH(i) cultivations, automated glucose additions were made to the culture in response to culture pH(i). The average ethanol (an-aerobic product) yield was significantly lower [0.12 g g(-1) glucose in fed-batch pH(i) cultivations with 100 ppm glucose additions (FB-pH(i)-100 cultivation) vs. 0.48 g g(-1) glucose in batch] and cell yield was higher (0.54 g g(-1) glucose in FB-pH(i)-100 cultivation vs. 0.3 g g(-1) glucose in batch) compared to batch cultivation. An expression has been derived to calculate changes in pH(i) from measured fluorescence values when the cell concentration increases during growth. Cultivations based on pH(i), performed with different magnitudes of glucose addition (100, 50, and 10 ppm additions), showed that lower magnitudes of glucose addition resulted in lower ethanol yields while cell yield remained unaffected. The ratio of specific oxygen uptake rate to specific glucose uptake rate (OUR/GUR) increased with decreased in magnitude of glucose additions in FB-pH(i) cultivations, suggesting that the culture aerobic state was higher when the magnitude of glucose addition was lower. The average cell productivity in FB-pH(i) cultivations was 29% higher than in batch cultivation. Cells were also cultivated at high OUR conditions, and the results are compared with other cultivations. (c) 1993 John Wiley & Sons, Inc.     

Toward a control of lignin and manganese peroxidases hypersecretion by Phanerochaete chrysosporium in agitated vessels: Evidence of the superiority of pneumatic bioreactors on mechanically agitated bioreactors

Phanerochaete chrysosporium and cultivated both mechanically agitated and pneumatic bioreactors. In the pneumatic devices, the yields of lignin and manganese peroxidases as well as extracellular protein, were considerably increased as compared with mechanically agitated bioreactors. Lignin peroxidase and manganese peroxidase activities as high as 4500 U . L(-1) and 1812 U . L(-1) respectively, were produced in an airlift bioreactor. By using enzyme markers, the secretion pathway and the respiration were shown to be dramatically activated in pneumatic bioreactors. The general metabolism of the fungus, when cultivated in the conventional fermentors, is oriented toward the synthesis of biomass at the expense of the synthesis of peroxidases. The use of pneumatic devices for the production of extracellular peroxidases by P. chrysosporium, avoids shear effects due to turbine agitator in the conventional fermentors, and provides a good example for the production of shear-sensitive metabolites. (c) 1993 John Wiley & Sons, Inc.     

Prediction of gas-liquid mass transfer coefficient in sparged stirred tank bioreactors

Oxygen mass transfer in sparged stirred tank bioreactors has been studied. The rate of oxygen mass transfer into a culture in a bioreactor is affected by operational conditions and geometrical parameters as well as the physicochemical properties of the medium (nutrients, substances excreted by the micro-organism, and surface active agents that are often added to the medium) and the presence of the micro-organism. Thus, oxygen mass transfer coefficient values in fermentation broths often differ substantially from values estimated for simple aqueous solutions. The influence of liquid phase physicochemical properties on kLa must be divided into the influence on k(L) and a, because they are affected in different ways. The presence of micro-organisms (cells, bacteria, or yeasts) can affect the mass transfer rate, and thus kLa values, due to the consumption of oxygen for both cell growth and metabolite production. In this work, theoretical equations for kLa prediction, developed for sparged and stirred tanks, taking into account the possible oxygen mass transfer enhancement due to the consumption by biochemical reactions, are proposed. The estimation of kLa is carried out taking into account a strong increase of viscosity broth, changes in surface tension and different oxygen uptake rates (OURs), and the biological enhancement factor, E, is also estimated. These different operational conditions and changes in several variables are performed using different systems and cultures (xanthan aqueous solutions, xanthan production cultures by Xanthomonas campestris, sophorolipids production by Candida bombicola, etc.). Experimental and theoretical results are presented and compared, with very good results.