Characterization of an aerated submerged hollow fiber ultrafiltration device for efficient microalgae harvesting

The present work characterizes a submerged aerated hollow fiber polyvinylidene fluorid (PVDF) membrane (0.03 μm) device (Harvester) designed for the ultrafiltration (UF) of microalgae suspensions. Commercial baker\u27s yeast served as model suspension to investigate the influence of the aeration rate of the hollow fibers on the critical flux (CF, J$_{c}$) for different cell concentrations. An optimal aeration rate of 1.25 vvm was determined. Moreover, the CF was evaluated using two different Chlorella cultures (axenic and non-axenic) of various biomass densities (0.8–17.5 g DW/L). Comparably high CFs of 15.57 and 10.08 L/m/$^{2}$/h were measured for microalgae concentrations of 4.8 and 10.0 g DW/L, respectively, applying very strict CF criteria. Furthermore, the J$_{c}$-values correlated (negative) linearly with the biomass concentration (0.8–10.0 g DW/L). Concentration factors between 2.8 and 12.4 and volumetric reduction factors varying from 3.5 to 11.5 could be achieved in short-term filtration, whereat a stable filtration handling biomass concentrations up to 40.0 g DW/L was feasible. Measures for fouling control (aeration of membrane fibers, periodic backflushing) have thus been proven to be successful. Estimations on energy consumption revealed very low energy demand of 17.97 kJ/m$^{3}$ treated microalgae feed suspension (4.99 × 10$^{-3}$ kWh/m$^{3}$) and 37.83 kJ/kg treated biomass (1.05 × 10$^{-2}$ kWh/kg), respectively, for an up-concentration from 2 to 40 g DW/L of a microalgae suspension

Evaluation of Downstream Processing, Extraction, and Quantification Strategies for Single Cell Oil Produced by the Oleaginous Yeasts Saitozyma podzolica DSM 27192 and Apiotrichum porosum DSM 27194

Single cell oil (SCO) produced by oleaginous yeasts is considered as a sustainable source for biodiesel and oleochemicals since its production does not compete with food or feed and high yields can be obtained from a wide variety of carbon sources, e.g., acetate or lignocellulose. Downstream processing is still costly preventing the broader application of SCO. Direct transesterification of freeze-dried biomass is widely used for analytical purposes and for biodiesel production but it is energy intensive and, therefore, expensive. Additionally, only fatty acid esters are produced limiting the subsequent applications. The harsh conditions applied during direct esterification might also damage high-value polyunsaturated fatty acids. Unfortunately, universal downstream strategies effective for all yeast species do not exist and methods have to be developed for each yeast species due to differences in cell wall composition. Therefore, the aim of this study was to evaluate three industrially relevant cell disruption methods combined with three extraction systems for the SCO extraction of two novel, unconventional oleaginous yeasts, Saitozyma podzolica DSM 27192 and Apiotrichum porosum DSM 27194, based on cell disruption efficiency, lipid yield, and oil quality. Bead milling and high pressure homogenization (HPH) were effective cell disruption methods in contrast to sonification. By combining HPH (95% cell disruption efficiency) with ethanol-hexane-extraction 46.9 +/- 4.4% lipid/CDW of S. podzolica were obtained which was 2.7 times higher than with the least suitable combination (ultrasound + Folch). A. porosum was less affected by cell disruption attempts. Here, the highest disruption efficiency was 74% after BM and the most efficient lipid recovery method was direct acidic transesterification (27.2 +/- 0.5% fatty acid methyl esters/CDW) after freeze drying. The study clearly indicates cell disruption is the decisive step for SCO extraction. At disruption efficiencies of >90%, lipids can be extracted at high yields, whereas at lower cell disruption efficiencies, considerable amounts of lipids will not be accessible for extraction regardless of the solvents used. Furthermore, it was shown that hexane+ethanol which is commonly used for extraction of algal lipids is also highly efficient for yeasts

Investigating the dynamics of recombinant protein secretion from a microalgal host

Lauersen KJ, Huber I, Wichmann J, et al. Investigating the dynamics of recombinant protein secretion from a microalgal host. Journal of Biotechnology. 2015;215:62-71

An advanced finite element model for BiCMOS process oriented ultra-thin wafer deformation

A process-oriented wafer-scale finite element model is developed and validated. The model is used to study the relationship between the in-plane residual stress and the deformation of state-of-the-art 0.13- μ m SiGe BiCMOS fully processed 8-inch wafers. Based on the in-situ wafer bow measurement results, the residual stress values are extracted regarding each deposited material per process step. The extracted material residual stress values are integrated into the in-plane stresses of each back-end redistribution layer by knowing the material densities, greatly reducing the computational effort. An advanced finite element model composed of these integrated redistribution layers is therefore developed by exploiting the first order shear deformation theory. The model is validated using analytical solutions and is used to characterize the wafer thickness-deflection non-linear relationship. As a comparison, 8 fully processed BiCMOS wafers from the same lot are thinned to different thicknesses ranging from 50 μ m to 600 μ m for bow measurement. After taking the gravity-induced deflection and grinding effect into consideration, the wafer bow predicted by the finite element model deviates less than 20% from the measurement results for all the thickness values

Imbalanced nutrient recycling in a warmer ocean driven by differential response of extracellular enzymatic activities

10 pages, 4 tables, supporting information https://dx.doi.org/10.1111/gcb.13779, database is available in https://doi.org/10.5281/zenodo.583989Ocean oligotrophication concurrent with warming weakens the capacity of marine primary producers to support marine food webs and act as a CO sink, and is believed to result from reduced nutrient inputs associated to the stabilization of the thermocline. However, nutrient supply in the oligotrophic ocean is largely dependent on the recycling of organic matter. This involves hydrolytic processes catalyzed by extracellular enzymes released by bacteria, which temperature dependence has not yet been evaluated. Here, we report a global assessment of the temperature-sensitivity, as represented by the activation energies (E), of extracellular β-glucosidase (βG), leucine aminopeptidase (LAP) and alkaline phosphatase (AP) enzymatic activities, which enable the uptake by bacteria of substrates rich in carbon, nitrogen, and phosphorus, respectively. These E were calculated from two different approaches, temperature experimental manipulations and a space-for-time substitution approach, which generated congruent results. The three activities showed contrasting E in the subtropical and tropical ocean, with βG increasing the fastest with warming, followed by LAP, while AP showed the smallest increase. The estimated activation energies predict that the hydrolysis products under projected warming scenarios will have higher C:N, C:P and N:P molar ratios than those currently generated, and suggest that the warming of oceanic surface waters leads to a decline in the nutrient supply to the microbial heterotrophic community relative to that of carbon, particularly so for phosphorus, slowing down nutrient recycling and contributing to further ocean oligotrophication.This is a contribution to the MALASPINA Expedition 2010 project, funded by the CONSOLIDER-Ingenio 2010 program from the Spanish Ministry of Economy and Competitiveness (Ref. CSD2008-00077). NA was supported by a grant from the Basque Government (Ref. BFI-2010-130)Peer Reviewe