Understanding and modeling retention of mammalian cells in fluidized bed centrifuges

Within the last decade, fully disposable centrifuge technologies, fluidized‐bed centrifuges (FBC), have been introduced to the biologics industry. The FBC has found a niche in cell therapy where it is used to collect, concentrate, and then wash mammalian cell product while continuously discarding centrate. The goal of this research was to determine optimum FBC conditions for recovery of live cells, and to develop a mathematical model that can assist with process scaleup. Cell losses can occur during bed formation via flow channels within the bed. Experimental results with the kSep400 centrifuge indicate that, for a given volume processed: the bed height (a bed compactness indicator) is affected by RPM and flowrate, and dead cells are selectively removed during operation. To explain these results, two modeling approaches were used: (i) equating the centrifugal and inertial forces on the cells (i.e., a force balance model or FBM) and (ii) a two‐phase computational fluid dynamics (CFD) model to predict liquid flow patterns and cell retention in the bowl. Both models predicted bed height vs. time reasonably well, though the CFD model proved more accurate. The flow patterns predicted by CFD indicate a Coriolis‐driven flow that enhances uniformity of cells in the bed and may lead to cell losses in the outflow over time. The CFD‐predicted loss of viable cells and selective removal of the dead cells generally agreed with experimental trends, but did over‐predict dead cell loss by up to 3‐fold for some of the conditions. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1520–1530, 2016     

瓦氏马尾藻规模化繁育技术研究

研究了瓦氏马尾藻(Sargassum vachellianum)规模化育苗及海区养殖技术。采集海区成熟藻体, 室内催熟放散受精卵, 收集并喷洒于水泥板、棕绳、木板3种附着基, 进行受精卵附着、萌发及苗体生长等实验, 发现棕绳育苗效果最佳。受精卵喷洒10d后, 3种附着基的出苗率分别为 85.5%、80.2%和91.3%, 平均株高约1.3 mm。前20天木板幼苗密度最高, 达8.2株/cm2, 但幼苗均生长缓慢。第30天, 幼苗出现明显分枝, 生长率增大到前20天的1.6倍, 其中棕绳幼苗株高最大, 幼苗存活率分别为83.6%、79.7%和75.6%。第60天棕绳幼苗密度及平均株高均最大。将附有幼苗的水泥板(藻礁)、棕绳放入海区进行养殖, 发现幼苗在浪大流急海区生长较快, 4周后平均株高分别达98.7和103.1 mm, 是对照组的1.5倍, 但棕绳脱苗严重。藻礁较适合海区规模化投放养殖, 是藻场修复和重建的理想材料。     

Bioaerosol biomonitoring: Sampling optimization for molecular microbial ecology

Bioaerosols (or biogenic aerosols) have largely been overlooked by molecular ecologists. However, this is rapidly changing as bioaerosols play key roles in public health, environmental chemistry and the dispersal ecology of microbes. Due to the low environmental concentrations of bioaerosols, collecting sufficient biomass for molecular methods is challenging. Currently, no standardized methods for bioaerosol collection for molecular ecology research exist. Each study requires a process of optimization, which greatly slows the advance of bioaerosol science. Here, we evaluated air filtration and liquid impingement for bioaerosol sampling across a range of environmental conditions. We also investigated the effect of sampling matrices, sample concentration strategies and sampling duration on DNA yield. Air filtration using polycarbonate filters gave the highest recovery, but due to the faster sampling rates possible with impingement, we recommend this method for fine ‐scale temporal/spatial ecological studies. To prevent bias for the recovery of Gram‐positive bacteria, we found that the matrix for impingement should be phosphate‐buffered saline. The optimal method for bioaerosol concentration from the liquid matrix was centrifugation. However, we also present a method using syringe filters for rapid in‐field recovery of bioaerosols from impingement samples, without compromising microbial diversity for high ‐throughput sequencing approaches. Finally, we provide a resource that enables molecular ecologists to select the most appropriate sampling strategy for their specific research question.     

山东东营和烟台潮间带海草床食物网结构特征

为了探明海草床内主要生物类群间的营养关系以及食物网结构, 作者于2018年8月分别在东营黄河口潮间带和烟台西海岸潮间带海草床采集大型底栖生物样品, 采用δ ¹³C和δ ¹⁵N稳定同位素方法, 对生物样品的碳、氮同位素组成进行了测定和分析。结果表明: 东营海草床内生物的δ ¹³C、δ ¹⁵N值范围分别为-21.99‰至-12.13‰和5.23‰-11.05‰, 烟台海草床内生物的δ ¹³C、δ ¹⁵N值范围分别为-18.11‰至-14.06‰和6.60‰-10.22‰。东营海草床主要生物的营养级范围为2.00-3.85, 烟台海草床主要生物的营养级范围为2.00-3.15。根据δ ¹⁵N值计算所得的营养级图分析可知两区域海草床内初级消费者主要为滤食性双壳类和多毛类, 次级消费者为植食性或杂食性甲壳类,肉食性鱼类和腹足类。与近海海域大型底栖生物食物网相比, 海草床内底栖生物的营养级均值普遍较低。     

Studies on the structure of human coronary vasculature

Based on morphometric data, we calculate the structural parameters of the coronary vasculature as an optimal branching bed. We show (i) significant correlations between the diameters of the larger daughter and the parent vessel and between the diameter of the smaller daughter vessel and the asymmetry coefficient; (ii) differences in the structural parameters for two types of artery that deliver and distribute blood in the cardiac muscle; and (iii) the length-diameter relationships for different arteries. The coronary vasculature is characterized by asymmetrical branching and thus should be modeled with self-similar asymmetrical tree-like systems.     

Vibrational and electronic circular dichroism study of the interactions of cationic porphyrins with (dG-dC)10 and (dA-dT)10

The interactions of two different porphyrins, without axial ligands-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin-Cu(II) tetrachloride (Cu(II)TMPyP) and with bulky meso substituents-5,10,15,20-tetrakis(N,N,N-trimethylanilinium-4-yl)porphyrin tetrachloride (TMAP), with (dG-dC)10 and (dA-dT)10 were studied by combination of vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopy at different [oligonucleotide]/[porphyrin] ratios, where [oligonucleotide] and [porphyrin] are the concentrations of oligonucleotide per base-pair and porphyrin, respectively. The combination of VCD and ECD spectroscopy enables us to identify the types of interactions, and to specify the sites of interactions: The intercalative binding mode of Cu(II)TMPyP with (dG-dC)(10), which has been well described, was characterized by a new VCD "marker" and it was shown that the interaction of Cu(II)TMPyP with (dA-dT)10 via external binding to the phosphate backbone and major groove binding caused transition from the B to the non-B conformer. TMAP interacted with the major groove of (dG-dC)10, was semi-intercalated into (dA-dT)10, and caused significant variation in the structure of both oligonucleotides at the higher concentration of porphyrin. The spectroscopic techniques used in this study revealed that porphyrin binding with AT sequences caused substantial variation of the DNA structure. It was shown that VCD spectroscopy is an effective tool for the conformational studies of nucleic acid-porphyrin complexes in solution.     

Anaerobic methanethiol degradation in upflow anaerobic sludge bed reactors at high salinity (> or =0.5 M Na(+))

The feasibility of anaerobic methanethiol (MT) degradation at elevated sodium concentrations was investigated in a mesophilic (30 degrees C) lab-scale upflow anaerobic sludge bed (UASB) reactor, inoculated with estuarine sediment originating from the Wadden Sea (The Netherlands). MT was almost completely degraded (>95%) to sulfide, methane and carbon dioxide at volumetric loading rates up to 37 mmol MT x L(-1) x day(-1), 0.5 M sodium (NaCl or NaHCO(3)) and between pH 7.3 and 8.4. Batch experiments revealed that inhibition of MT degradation started at sodium (both NaCl and NaHCO(3)) concentrations exceeding 0.8 M. Sulfide inhibited MT degradation already around 3 mM (pH 8.3).