Isolation and Characterization of a Yellow Xanthophyll Pigment-Producing Marine Bacterium, Erythrobacter sp. SDW2 Strain, in Coastal Seawater

Xanthophylls, a yellow pigment belonging to the carotenoid family, have attracted much attention for industrial applications due to their versatile nature. We report the isolation of a homo xanthophyll pigment-producing marine bacterium, identified as the Erythrobacter sp. SDW2 strain, from coastal seawater. The isolated Erythrobacter sp. SDW2 strain can produce 263 ± 12.9 mg/L (89.7 ± 5.4 mg/g dry cell weight) of yellow xanthophyll pigment from 5 g/L of glucose. Moreover, the xanthophyll pigment produced by the SDW2 strain exhibits remarkable antioxidative activities, confirmed by the DPPH (73.4 ± 1.4%) and ABTS (84.9 ± 0.7%) assays. These results suggest that the yellow xanthophyll pigment-producing Erythrobacter sp. SDW2 strain could be a promising industrial microorganism for producing marine-derived bioactive compounds with potential for foods, cosmetics, and pharmaceuticals.

Unjukkerja Electrolyzer tipe Dry Cell Terhadap Variasi Konsentrasi Elektrolit dan Arus Listrik pada Mesin PEM Fuel Cell Skala Kecil untuk Pembangkit Listrik

<p>Seiring peningkatan kebutuhan listrik di Indonesia serta menipisnya jumlah energi fosil dilakukan pengembangan energi baru terbarukan yang bebas polusi salah satunya yakni pemanfaatan energi hidrogen. Mesin fuel cell merupakan aplikasi pengembangan energi hidrogen yang dapat mengubah energi kimia menjadi energi listrik. Proton Exchange Membrane (PEM) fuel cell merupakan salah satu jenis fuel cell yang mampu beroperasi pada temperatur rendah dan menghasilkan efisiensi sekitar 40-60%. Pada penelitian sebelumnya kinerja dari mesin PEM fuel cell kurang maksimal, sehingga perlu dilakukan modifikasi pada bagian komponen HHO generator yakni dengan mengubah dari tipe wet cell menjadi dry cell. Pengubahan ini didasari kelemahan tipe wet cell dimana hasil debit gas hidrogen rentan tercampur dengan uap air akibat kenaikan temperatur pada larutan elektrolit sehingga menyebabkan terjadinya penguapan. Hasil dari modifikasi ini yakni debit gas hidrogen yang mana setelah dilakukan modifikasi pada arus masukan 20 A dan konsentrasi KOH 0,5 M terjadi peningkatan debit sebesar 0,306 mL/s, kemudian pada 1 M terjadi peningkatan debit sebesar 1,434 mL/s, serta pada 1,5 M meningkat sebesar 5,439 mL/s. Namun demikian meski debit HHO generator, yang mana daya masukan fuel cell, meningkat efisiensi dari fuel cell justru menurun karena maksimum tegangan keluaran fuel cell sesuai spesifikasi hanya mencapai 2,3 V - 3 V, sehingga daya input masukan fuel cell tinggi namun daya keluaran fuel cell tetap sesuai dengan spesifikasi yang tentunya mengakibatkan nilai efisiensi fuel cell menurun. Secara keseluruhan hasil tertinggi efisiensi dari HHO generator mencapai 85,86% sedangkan efisiensi fuel cell mencapai 4,6%.</p>

Influence of the total concentration and the profile of volatile fatty acids on polyhydroxyalkanoates (PHA) production by mixed microbial cultures

Polyhydroxyalkanoates (PHAs) production from lignocellulosic biomass using mixed microbial cultures (MMC) is a potential cheap alternative for reducing the use of petroleum-based plastics. In this study, an MMC adapted to acidogenic effluent from dark fermentation (DF) of exhausted sugar beet cossettes (ESBC) has been tested in order to determine its capability to produce PHAs from nine different synthetic mixtures of volatile fatty acids (VFAs). The tests consisted of mixtures of acetic, propionic, butyric, and valeric acids in the range of 1.5–9.0 g/L of total acidity and with three different valeric:butyric ratios (10:1, 1:1, and 1:10). Experimental results have shown a consistent preference of the MMC for the butyric and valeric acids as carbon source instead other shorter acids (propionic or acetic) in terms of PHA production yield (estimated in dry cell weight basis), with a maximum value of 23% w/w. Additionally, valeric-rich mixtures have demonstrated to carry out a fast degradation process but with poor final PHA production compared with high butyric mixtures. Finally, high initial butyric and valeric concentrations (1.1 g/L and 4.1 g/L) have demonstrated to be counterproductive to PHA production.

Overexpression of Shinorhizobium Meliloti Flavohemoglobinefficiently Improved Cell Growth and Fatty Acid Biosynthesis in Oleaginous Fungus Mucor Circinelloides

Oxygen availability is a limiting factor for lipid biosynthesis in eukaryotic microorganisms. Two bacterial hemoglobins from Vitreoscilla sp. (VHb) and Shinorhizobium meliloti (SHb), which could deliver the oxygen to the respiratory chain to produce more ATP, were introduced into Mucor circinelloides to alleviate oxygen limitation, thereby improving cell growth and fatty acid production. VHb and SHb genes were integrated into the M. circinelloides MU402 genome through homologous recombination, and their protein expression was verified by carbon monoxide difference spectrum (CO-difference spectrum)analysis. SHb-expressing strain showed higher biomass than VHb-expressing strain. The biomass of the SHb-expressing strain was increased by about 50% and the total fatty acid (TFA) content was as high as 15.7% of the dry cell weight which was about 40% higher than that of the control strain in flask conditions. In the fermenter, the maximum biomass and TFA content was obtained in SHb-expressing strains, with the biomass being 12.1 g/L and the TFA being 21.1% of the dry cell weight. VHb and SHb expression also affected the fatty acid composition with the proportion of polyunsaturated fatty acids being increased. Over-expression of bacterial hemoglobins, especially SHb increased cell growth and TFA content in M. circinelloides at low and high aeration, suggesting that SHb is better than VHb in improving the fatty acid production in oleaginous microorganisms.

Rapid and concise quantification of mycelial growth by microscopic image intensity model and application to mass cultivation of fungi

The microbial food fermentation industry requires real-time monitoring and accurate quantification of cells. However, filamentous fungi are difficult to quantify as they have complex cell types such as pellet, spores, and dispersed hyphae. In this study, numerous data of microscopic image intensity (MII) were used to develop a simple and accurate quantification method of Cordyceps mycelium. The dry cell weight (DCW) of the sample collected during the fermentation was measured. In addition, the intensity values were obtained through the ImageJ program after converting the microscopic images. The prediction model obtained by analyzing the correlation between MII and DCW was evaluated through a simple linear regression method and found to be statistically significant (R2 = 0.941, p < 0.001). In addition, validation with randomly selected samples showed significant accuracy, thus, this model is expected to be used as a valuable tool for predicting and quantifying fungal growth in various industries.

The synthesis of polyhydroxyalkanoates from low carbon wastewater under anaerobic-microaerobic process: effects of pH and nitrogen and phosphorus limitation

Polyhydroxyalkanoate (PHA) is a new type of bio-polyester which is expected to replace traditional petroleum-based plastics. The experiment was carried out based on anaerobic-microaerobic process. Firstly, the PHA accumulation capacity of activated sludge under different pH conditions was discussed, and then the batch test of nitrogen and phosphorus limitation was carried out under the condition of optimal pH. Moreover, the content of PHA monomer under nutrient restriction was also studied. The experimental results showed that when pH was not controlled (7.5~8.5), C:N and C:P weight ratio was equal to 150, the maximum content of PHA accounted for 50.39% and 36.07% of the dry cell weight, respectively. Besides, it was found that increasing the C:N weight ratio was beneficial to increasing the proportion of polyhydroxyvalerate (PHV) monomer in PHA.

Effect of the Concentration of Extracellular Polymeric Substances (EPS) and Aeration Intensity on Waste Glycerol Valorization by Docosahexaenoic Acid (DHA) Produced in Heterotrophic Culture of Schizochytrium sp.

The study aimed to determine the effectiveness of docosahexaenoic acid (DHA) production by Schizochytrium sp. biomass fed with waste glycerol depending on the concentration of extracellular polymeric substances (EPS) in the culture medium and medium aeration effectiveness. The microalgae from the genus Schizochytrium sp. were proved to be capable of producing EPS composed of glucose, galactose, mannose, fucose, and xylose. The highest EPS concentration, reaching 8.73 ± 0.09 g/dm3, was determined at the stationary growth phase. A high EPS concentration caused culture medium viscosity to increase, contributing to diminished oxygen availability for cells, lower culture effectiveness, and reduced waste glycerol conversion to DHA. The Schizochytrium sp. culture variant found optimal in terms of the obtained technological effects and operating costs was performed at the volumetric oxygen mass transfer coefficient of kLa = 600 1/h, which enabled obtaining dry cell weight (DCW) of 147.89 ± 4.77 g/dm3, lipid concentration of 69.44 ± 0.76 g/dm3, and DHA concentration in the biomass reaching 29.44 ± 0.36 g/dm3. The effectiveness of waste glycerol consumption in this variant reached 3.76 ± 0.31 g/dm3·h and 3.16 ± 0.22 g/gDCW.

Rapid and Concise Quantification of Mycelial Growth by Microscopic Image Intensity Model and Application to Mass Cultivation of Fungi

The microbial food fermentation industry requires real-time monitoring and accurate quantification of cells. However, filamentous fungi are difficult to quantify as they have complex cell types such as pellet, spores, and dispersed hyphae. In this study, numerous data of microscopic image intensity (MII) were used to develop a simple and accurate quantification method of Cordyceps mycelium. The dry cell weight (DCW) of the sample collected during the fermentation was measured. In addition, the intensity values were obtained through the ImageJ program after converting the microscopic images. The prediction model obtained by analyzing the correlation between MII and DCW was evaluated through a simple linear regression method and found to be statistically significant (R2 = 0.941, p <0.001). In addition, validation with randomly selected samples showed significant accuracy, thus, this model is expected to be used as a valuable tool for predicting and quantifying fungal growth in various industries.