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Microalgae with high growth rates represent a potential source of carotenoids including fucoxanthin. For commercial fucoxanthin production, choosing the cultivation system is a critical parameter where the final biomass must contain a high content of the target product. To realize this, the reaction system must allow the use of stress conditions that induce the synthesis of these compounds. In this study, oxidative stress was applied to the diatom Amphora capitellata by the formation of reactive oxygen species in the culture medium through chemical reactions which generate. The effect of this oxidative stress on the amount of fucoxanthin and specific growth rate of A. capitellata was investigated. In the presence of H2O2/NaOCl, fucoxanthin content was 41.83 ± 0.92 mg g−1 as determined by HPLC–DAD a 2.20-fold increase compared with the control group. For the purification of fucoxanthin, preparative HPLC using a semi-prep C30 carotenoid column (10 × 250 mm, 5 µm) was used for the first time with an isocratic elution of 75:25 (methanol:acetonitrile) mobile phase at a flow rate of 4 mL min−1. Liquid chromatography tandem mass spectrometry (LC–MS/MS) was employed for the confirmation of fucoxanthin. The developed method has potential to obtain highly pure fucoxanthin for food and pharmaceutical applications using A. capitellata as a commercial source of fucoxanthin, particularly after its enhancement via oxidative stress. [ABSTRACT FROM AUTHOR]

Phycobiliproteins, light-harvesting pigments found in cyanobacteria and in some eukaryotic algae, have numerous commercial applications in food, cosmetic, and pharmaceutical industries. Colorant production from cyanobacteria offers advantages over their production from higher plants, as cyanobacteria have fast growth rate and high photosynthetic efficiency and require less space. In this study, three cyanobacteria strains were studied for phycobiliprotein production and the influence of sodium nitrate, potassium nitrate and ammonium chloride on the growth and phycobiliprotein composition of the strains were evaluated. In the batch culture period of 12 days, Phormidium sp. and Pseudoscillatoria sp. were able to utilize all tested nitrogen sources; however, ammonium chloride was the best nitrogen source for both strains to achieve maximum growth rate μ = 0.284 ± 0.03 and μ = 0.274 ± 0.13 day−1, chlorophyll a 16.2 ±  0.5 and 12.2 ±  0.2 mg L−1, and phycobiliprotein contents 19.38 ± 0.09 and 19.99 ± 0.14% of dry weight, whereas, for Arthrospira platensis, the highest growth rate of μ = 0.304 ± 0.0 day−1, chlorophyll a 19.1 ± 0.5 mg L−1, and phycobiliprotein content of 22.27 ± 0.21% of dry weight were achieved with sodium nitrate. The phycocyanin from the lyophilized cyanobacterial biomass was extracted using calcium chloride and food grade purity (A620/A280 ratio > 0.7) was achieved. Furthermore, phycocyanin was purified using two-step chromatographic method and the analytical grade purity (A620/A280 ratio > 4) was attained. SDS-PAGE demonstrated the purity and presence of two bands corresponding to α- and β-subunits of the C-phycocyanin. The results showed that Phormidium sp. and Pseudoscillatoria sp. could be good candidates for phycocyanin production. [ABSTRACT FROM AUTHOR]

Agricultural by-products are becoming an attractive substrate for bioethanol production. The aim of this study was to evaluate the effects of regional differences in the rice hulls using Escherichia coli KO11 for bioethanol production. The rice hulls coded Edirne were obtained from Thrace Region, and the rice hulls coded Izmir were obtained from Aegean Region in Turkey. Rice hulls were treated by dilute acid before using them as substrates. The cells were incubated on an orbital shaker at 160 rpm under 30 °C during 96 h of the fermentation period. It was found that the maximum yield of ethanol from sugar (0.44 g ethanol/g reducing sugar) was obtained with the substrate C/N ratio of 29.16 in Izmir medium. The main difference was the dominant carbon source available as a substrate. It was detected that glucose concentration was about 2.5 times higher in Izmir medium, whereas xylose concentration was about two times higher in Edirne medium. The different results obtained with rice hulls from different origins could depend on the type of paddy as well as different cultivation conditions. These findings provide a valuable indicator for identifying suitable agricultural waste materials to be used as substrates for bioethanol production. [ABSTRACT FROM AUTHOR]