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- ItemMulti-scale processes of beech wood disintegration and pretreatment with 1-ethyl-3-methylimidazolium acetate/water mixtures(London : BioMed Central, 2016) Viell, Jörn; Inouye, Hideyo; Szekely, Noemi K.; Frielinghaus, Henrich; Marks, Caroline; Wang, Yumei; Anders, Nico; Spiess, Antje C.; Makowski, LeeBackground: The valorization of biomass for chemicals and fuels requires efficient pretreatment. One effective strategy involves the pretreatment with ionic liquids which enables enzymatic saccharification of wood within a few hours under mild conditions. This pretreatment strategy is, however, limited by water and the ionic liquids are rather expensive. The scarce understanding of the involved effects, however, challenges the design of alternative pretreatment concepts. This work investigates the multi length-scale effects of pretreatment of wood in 1-ethyl-3-methylimidazolium acetate (EMIMAc) in mixtures with water using spectroscopy, X-ray and neutron scattering. Results: The structure of beech wood is disintegrated in EMIMAc/water mixtures with a water content up to 8.6 wt%. Above 10.7 wt%, the pretreated wood is not disintegrated, but still much better digested enzymatically compared to native wood. In both regimes, component analysis of the solid after pretreatment shows an extraction of few percent of lignin and hemicellulose. In concentrated EMIMAc, xylan is extracted more efficiently and lignin is defunctionalized. Corresponding to the disintegration at macroscopic scale, SANS and XRD show isotropy and a loss of crystallinity in the pretreated wood, but without distinct reflections of type II cellulose. Hence, the microfibril assembly is decrystallized into rather amorphous cellulose within the cell wall. Conclusions: The molecular and structural changes elucidate the processes of wood pretreatment in EMIMAc/water mixtures. In the aqueous regime with >10.7 wt% water in EMIMAc, xyloglucan and lignin moieties are extracted, which leads to coalescence of fibrillary cellulose structures. Dilute EMIMAc/water mixtures thus resemble established aqueous pretreatment concepts. In concentrated EMIMAc, the swelling due to decrystallinization of cellulose, dissolution of cross-linking xylan, and defunctionalization of lignin releases the mechanical stress to result in macroscopic disintegration of cells. The remaining cell wall constituents of lignin and hemicellulose, however, limit a recrystallization of the solvated cellulose. These pretreatment mechanisms are beyond common pretreatment concepts and pave the way for a formulation of mechanistic requirements of pretreatment with simpler pretreatment liquors. © 2016 Viell et al.
- ItemOptimized polymer-based glucose release in microtiter plates for small-scale E. coli fed-batch cultivations(London : BioMed Central, 2020) Keil, Timm; Dittrich, Barbara; Lattermann, Clemens; Büchs, JochenBackground: Small-scale cultivation vessels, which allow fed-batch operation mode, become more and more important for fast and reliable early process development. Recently, the polymer-based feeding system was introduced to allow fed-batch conditions in microtiter plates. Maximum glucose release rates of 0.35 mg/h per well (48-well-plate) at 37 °C can be achieved with these plates, depending on the media properties. The fed-batch cultivation of fluorescent protein-expressing E. coli at oxygen transfer rate levels of 5 mmol/L/h proved to be superior compared to simple batch cultivations. However, literature suggests that higher glucose release rates than achieved with the currently available fed-batch microtiter plate are beneficial, especially for fast-growing microorganisms. During the fed-batch phase of the cultivation, a resulting oxygen transfer rate level of 28 mmol/L/h should be achieved. Results: Customization of the polymer matrix enabled a considerable increase in the glucose release rate of more than 250% to up to 0.90 mg/h per well. Therefore, the molecular weight of the prepolymer and the addition of a hydrophilic PDMS-PEG copolymer allowed for the individual adjustment of a targeted glucose release rate. The newly developed polymer matrix was additionally invariant to medium properties like the osmotic concentration or the pH-value. The glucose release rate of the optimized matrix was constant in various synthetic and complex media. Fed-batch cultivations of E. coli in microtiter plates with the optimized matrix revealed elevated oxygen transfer rates during the fed-batch phase of approximately 28 mmol/L/h. However, these increased glucose release rates resulted in a prolonged initial batch phase and oxygen limitations. The newly developed polymer-based feeding system provides options to manufacture individual feed rates in a range from 0.24-0.90 mg/h per well. Conclusions: The optimized polymer-based fed-batch microtiter plate allows higher reproducibility of fed-batch experiments since cultivation media properties have almost no influence on the release rate. The adjustment of individual feeding rates in a wide range supports the early process development for slow, average and fast-growing microorganisms in microtiter plates. The study underlines the importance of a detailed understanding of the metabolic behavior (through online monitoring techniques) to identify optimal feed rates. © 2020 The Author(s).