Sustainable carbon sources for microbial organic acid production with filamentous fungi

Background: The organic acid producer Aspergillus oryzae and Rhizopus delemar are able to convert several alternative carbon sources to malic and fumaric acid. Thus, carbohydrate hydrolysates from lignocellulose separation are likely suitable as substrate for organic acid production with these fungi. Results: Before lignocellulose hydrolysate fractions were tested as substrates, experiments with several mono- and disaccharides, possibly present in pretreated biomass, were conducted for their suitability for malic acid production with A. oryzae. This includes levoglucosan, glucose, galactose, mannose, arabinose, xylose, ribose, and cellobiose as well as cheap and easy available sugars, e.g., fructose and maltose. A. oryzae is able to convert every sugar investigated to malate, albeit with different yields. Based on the promising results from the pure sugar conversion experiments, fractions of the organosolv process from beechwood (Fagus sylvatica) and Miscanthus giganteu s were further analyzed as carbon source for cultivation and fermentation with A. oryzae for malic acid and R. delemar for fumaric acid production. The highest malic acid concentration of 37.9 ± 2.6 g/L could be reached using beechwood cellulose fraction as carbon source in bioreactor fermentation with A. oryzae and 16.2 ± 0.2 g/L fumaric acid with R. delemar. Conclusions: We showed in this study that the range of convertible sugars for A. oryzae is even higher than known before. We approved the suitability of fiber/cellulose hydrolysate obtained from the organosolv process as carbon source for A. oryzae in shake flasks as well as in a small-scale bioreactor. The more challenging hemicellulose fraction of F. sylvatica was also positively evaluated for malic acid production with A. oryzae

A Low Concentration Receiver Concept for Cost Effective Crystalline Back Contact Cells

A versatile interconnection and receiver concept for back contact low concentrating crystalline solar cells is presented. The key feature is the AP-C-MWT cell which allows for any cell formats as a multiple of 22.5 × 10 mm2. We demon-strate the feasibility of an adequate receiver concept and show the electrical optimization steps for a given concentration. The steps include the electrical finite-element-method (FEM) simula-tion of the interconnector conductivity and an analytical model to derive the optimal geometric design. Finally measured efficiency data for a built prototype are reported, showing a receiver effi-ciency based on string area of 19.2% (C=9.9) and a cell to receiv-er efficiency of 99.3%

CPV module with fresnel lens primary optics and homogenizing secondary optics

In this work CPV modules based on Fresnel lenses and using refractive secondary optical elements (SOEs) are investigated. Pure silicone as well as glass SOEs glued on top of the solar cells are explored in prototype modules. They are differently manufactured in respect to how the secondary optics was assembled. For example, units with secondary silicone optics directly casted to solar cells are manufactured. For a design of glued glass optics and Fresnel lenses, the thermal design and optimum cell-lens distance are analyzed. Moreover, the long term stability has been intensively tested by accelerated aging tests and outdoor experiments. Here, the focus was on the used silicone material and the adhesion of the silicone to the glass interface