Heterotrophic cultivation of Euglena gracilis was carried out on synthetic (Hutner medium) and complex cultivation media in order to optimize production of β-1,3-glucan (paramylon). For preparation of complex media, various industrial by-products (e.g., molasses, corn steep solid, yeast extract, and beef extract) were used with or without addition of pure compounds [glucose, galactose, fructose, lactose, maltose, sucrose, and (NH4)2HPO4]. Heterotrophic cultivation of E. gracilis was performed in Erlenmeyer flasks and additionally confirmed during research in the stirred tank bioreactor. The results clearly show that E. gracilis can easily metabolize glucose and fructose as carbon sources and corn steep solid as complex nitrogen and growth factors source for biomass growth and paramylon synthesis. Furthermore, it was also proved that addition of (NH4)2HPO4, beef extract, or gibberellic acid did not have positive effect on the biomass growth and paramylon synthesis. After optimization of complex medium composition and verification in the stirred tank bioreactor, it was concluded that medium composed of glucose (20 g/L) and corn steep solid (30 g/L) is the most suitable complex medium for industrial cultivation of E. gracilis and paramylon production.

No abstract

The effect of zinc gluconate on the corrosion inhibition of carbon steel DIN RSt 37-2 in various water types has been evaluated using Tafel polarization and scanning electron microscopy techniques. Experiments were performed using 6 types of water, namely, soft tap water from Dubrovnik region, hard tap water from Zagreb region, 3.5% sodium chloride solution, sea water from Dubrovnik region, biologically inert sea water from Dubrovnik region and demineralized water. The concentration of zinc gluconate varied from 0.1 to 3 gl -1 . The results show that substantial corrosion inhibition using zinc gluconate can be obtained with low concentrations in tap waters along with demineralized water and with moderate concentrations in 3.5% sodium chloride solution and sea waters. EDX analysis confirmed the presence of zinc ions which are incorporated in the protective layer of carbon steel specimen. The corrosion inhibition is predominately obtained by anodic mechanism.Keywords: carbon steel / corrosion inhibition / zinc gluconate / sea water / tap water / Die Wirkung von Zinkgluconat auf die Korrosionsinhibierung des Kohlenstoffstahls DIN RSt 37-2 in verschiedenen Wasserarten anhand der Tafel Polarisation und der Rasterelektronenmikroskopie wurde untersucht. Die Experimente wurden unter Verwendung von 6 Arten von Wasser durchgeführt, nämlich: weiches Leitungswasser der Dubrovnik Region, hartes Leitungswasser der Zagreb Region, eine 3,5% Natriumchloridlösung, Meerwasser der Dubrovnik Region, biologisch inertes Meerwasser der Dubrovnik Region und demineralisiertes Wasser. Die Konzentration von Zinkgluconat variierte von 0,1 -3 bis gl -1 . Die Ergebnisse zeigten, dass schon bei niedrigen Konzentrationen von Zinkgluconat in Leitungswasser und demineralisiertem Wasser eine erhebliche Korrosionsinhibierung erreicht werden kann, während für die Inhibierung im Meereswasser, inerten Wasser und in einer 3,5% Natriumchloridlösung, eine etwas höhere Konzentration des Zinkgluconat erforderlich ist. Die EDX-Analyse bestätigte die Anwesenheit von Zink Ionen, die vermutlich in der Schutzschicht des Kohlenstoffstahles inkorporiert sind. Die Korrosionsinhibierung wird überwiegend durch einen anodischen Mechanismus hervorgerufen.

This work investigates the methodology of producing a 3D-printed microreactor from the acrylic resin by PolyJet Matrix process. The PolyJet Matrix technology employs different materials or their combinations to generate 3D-printed structures, from small ones to complex geometries, with different material properties. Experimental and numerical methods served for the evaluation of the geometry and production of the microreactor and its hydrodynamic characterization. The operational limits of the single-phase flow in the microchannels, further improvements and possible applications of the microreactor were assessed based on the hydrodynamic characterization.

Paramylon is a valuable intracellular product of the microalgae Euglena gracilis, and it can accumulate in Euglena cells according to the cultivation conditions. For the sustainable production of paramylon and appropriate cell growth, different bioreactor processes and industrial byproducts can be considered as substrates. In this study, a complex medium with corn steep solid (CSS) was used, and various bioreactor processes (batch, fed batch, semicontinuous and continuous) were performed in order to maximize paramylon production in the microalgae Euglena gracilis. Compared to the batch, fed batch and repeated batch bioprocesses, during the continuous bioprocess in a stirred tank bioreactor (STR) with a complex medium containing 20 g/L of glucose and 25 g/L of CSS, E. gracilis accumulated a competitive paramylon content (67.0%), and the highest paramylon productivity of 0.189 g/Lh was observed. This demonstrated that the application of a continuous bioprocess, with corn steep solid as an industrial byproduct, can be a successful strategy for efficient and economical paramylon production.