Search

Abstract Desmodesmus spp. are one of the most dominant components of phytoplankton, which are present in most water bodies. However, identification of the species based only on morphological data is challenging. The aim of the present study was to provide a comprehensive understanding of the actual distribution of the Desmodesmus species in Saga City, Saga Prefecture, Japan. In the present study, 38 water bodies were surveyed between June 2017 and March 2023. A total of 86 culture strains were established from the samples collected from the 21 sites, and identified by molecular phylogenetic analysis, comparison of ITS2 rRNA secondary structures, and observation of surface microstructure. In total, four new species, including D. notatus Demura sp. nov., D. lamellatus Demura sp. nov., D. fragilis Demura sp. nov., and D. reticulatus Demura sp. nov. were proposed and 17 Desmodesmus species were identified as described species. The present study revealed > 20 Desmodesmus species, exhibiting high genetic diversity in a small area.

Fish sauce is produced at high salt concentrations (>20%) to inhibit the growth of harmful microorganisms. The salt-reduced fish sauce (10% salt) was prepared under pressurized CO2 (pCO2) conditions at 30 °C and 5 MPa for 3 months (FSCO2), from Sardinops melanostictus, Odontamblyopus lacepedii, Trachurus japonicus, Konosirus punctatus, and their collective mixture, as well as unused fish mixture obtained from the Ariake Sea in Japan. FSCO2 exhibited significantly better microbial quality and free amino acid content, lighter color, standardized odor (dashi-like odor), and umami richness qualities compared to fish sauces prepared using the conventional method (FScon) (20% salt), as previously demonstrated, after a fermentation period of 2 months. Bacterial flora analysis implied that the standardization of odor and umami richness may not be the result of specific microbial metabolism. Even when using previously unused fish, it was possible to produce FSCO2 equivalent to that produced by conventional sardines and other fish. These results indicate that the quality of fish sauce can be improved. The flavor of FSCO2 became similar regardless of the type of fish and fermentation period using pCO2 during fermentation, leading to the effective utilization of unutilized fish as a resource for high-quality salt-reduced fish sauce.

Microalgae are now known as potential microorganisms in the production of chemicals, fuel, and food. Since microalgae live in the sea and the river, they need to be harvested and separated and cultured for further usage. In this study, to separate microalgae, a bed of magnetite-containing gel (Mag gel, 190 µm) was packed in the column by the application of a magnetic field for the separative elution of injected microalgae (including mainly four species), cultured at Saga University in Japan. The applied magnetic field was set at a constant and dynamic-convex manner. At a constant magnetic field of 0.4–1.1 T, the elution percentage of the microalgae at less than 5 µm was 30–50%. At 1.1 T, the larger-sized microalgae were eluted at a percentage of 20%, resulting in the structural change of the bed by the applied magnetic field. In a convex-like change of the magnetic field at 1.1 T ⇄ 0.4 T, the smaller-sized microalgae were selectively eluted, whereas at 1.1 T ⇄ 0.8 T, the larger-sized microalgae were eluted. Dynamic convex-like changes by the magnetic field selectively eluted the microalgae, leading to the separation and the extraction of potential microalgae.

In this study, the effects of an ethanolic extract of Aurantiochytrium mangrovei 18W-13a strain (AM18W-13a) on lipopolysaccharide (LPS)-induced inflammatory responses in RAW264 murine macrophages were studied. Pre-treatment with the AM18W-13a extract significantly suppressed the LPS-induced production of nitric oxide and pro-inflammatory cytokines. RAW264 cells treated with the AM18W-13a extract for 1 and 24 h were subjected to DNA microarray analyses for detecting the differentially expressed genes. The treatment of RAW264 cells with the AM18W-13a extract for 24 h significantly suppressed the expression of several genes associated with inflammation or chemotaxis. Furthermore, treatment with the AM18W-13a extract for 1 h suppressed the expression of Pde4b, but induced the expression of Egr2 and Egr3 in RAW264 cells. Additionally, the AM18W-13a extract significantly enhanced the expression of certain anti-inflammatory mediators. This study is the first report of the anti-inflammatory effects of the AM18W-13a extract and its mechanism of action in LPS-stimulated murine macrophages.

This article presents an engineering study of an integrated system to produce bio-oil from microalgae biomass. The analysis is based on a pilot plant located at Minami-soma Fukushima, Japan, which further simulates 1 ha based-cultivation. Municipal wastewater and flue gases were utilized as nutrient sources for the microalgae culture of the proposed design. A flow sheet diagram of the integrated plant was synthesized by process engineering software to allow simulation of a continuous system. The design and sizing of the process equipment were performed to obtain a realistic estimation of possible production cost. The results demonstrated that nutrient savings was achieved by wastewater and CO2 utilization to the polyculture of native microalgae. Process simulation gave an estimated CO2 sequestration of 82.77 to 140.58 tons ha−1year−1 with 63 to 107 tons ha−1year−1 of potential biomass production. The integrated process significantly improved the energy balance and economics of biofuel production and also the wastewater treatment plant (WWTP). The economic analysis confirmed that higher biomass production and technology improvement were required to achieve operational feasibility and profitability of the current microalgae-based bio-oil production.

Microalgae is a promising next-generational energy. In this research, we focus on oil-extracted Botryococcus braunii residues collected by adding polysilicato-iron (PSI) as a flocculant followed by carbonization under argon atmosphere. We conducted carbonization at various temperatures as a first attempt to reveal the fundamental properties of the carbonization process of the microbes. The carbons thus obtained by heat treatment at 900 °C present a unique magnetic behavior due to reduced magnetite (Fe3O4) inclusion, which is produced from polysilicato iron (Fe2O3) during the heating process. Experimental results suggest that this carbonic material can be applied as a heavy metal-capturing carbon and magnetic porous substrate catalyst. The effective use of the waste may open a new avenue for an energy-microbiology-materials system.

This study investigates the potential of microalgae oil production as an alternative renewable energy source, in a pilot project located at Minamisoma City in the Fukushima Prefecture of Japan. The algal communities used in this research were the locally mixed species, which were mainly composed of Desmodesmus collected from the Minamisoma pilot project. The microalgae oil-production processes in Minamisoma consisted of three stages: cultivation, dewatering, and extraction. The estimated theoretical input-energy requirement for extracting oil was 137.25 MJ to process 50 m3 of microalgae, which was divided into cultivation 15.40 MJ, centrifuge 13.39 MJ, drum filter 14.17 MJ, and hydrothermal liquefaction (HTL) 94.29 MJ. The energy profit ratio (EPR) was 1.41. The total energy requirement was highest in the HTL process (68%) followed by cultivation (11%) and the drum filter (10%). The EPR value increased along with the yield in the cultivation process. Using HTL, the microalgae biomass could be converted to bio-crude oil to increase the oil yield in the extraction process. Therefore, in the long run, the HTL process could help lower production costs, due to the lack of chemical additions, for extracting oil in the downstream estimation of the energy requirements for microalgae oil production.

Phycobiliprotein (PB), which is produced by cyanobacteria, has potential applications as a valuable pharmaceutical product. In this study, PB was separated by using a nonwoven-fabric membrane (Rx-1) that contained quaternary amino groups. PB was extracted from a Nostoc commune, which is a type of microalga, by disrupting the cell walls by a freeze–thaw method. Two types of biomolecules, namely PB and other biomolecules X, were identified by gel permeation chromatography. Permeation of the PB-containing solution through Rx-1 increased the purity of the PB in the filtrate from 0.25 to 0.45. The adsorption constant (Kp) and maximum adsorbed amount of each protein on Rx-1 (qmax) were determined by fitting the experimental data to a mathematical model. The obtained values for Kp and qmax were used to simulate scaled-up treatment of a PB-containing solution. Permeation of a PB-containing solution (3.0 L at 1.2 × 10−3 m³/h) through Rx-1 (volume of scale-up membrane, 8.0 × 10−4 m³) enabled PB separation for 26 h. Further PB purification could be achieved by using the Rx-1 membrane in combination with precipitation with ammonium sulfate solution and an ultrafiltration membrane. [ABSTRACT FROM AUTHOR]

We assessed changes in the microbial communities in ballast water during a trans-Pacific voyage from Japan to Australia that included a mid-ocean ballast-water exchange. Uncultured (i.e., total) and culturable bacteria were counted and were characterized by using denaturing gradient gel electrophoresis (DGGE). There was a clear decrease over time in numbers of uncultured microorganisms, except for heterotrophic nanoflagellates, whereas the abundance of culturable bacteria initially decreased after the ballast-water exchange but then increased. The increase, however, was only up to 5.34% of the total number of uncultured bacteria. Cluster analysis showed that the DGGE profiles of uncultured bacteria clearly changed after the exchange. In contrast, there was no clear change in the DGGE profiles of culturable bacteria after the exchange. Multidimensional scaling analysis showed changes in microbial communities over the course of the voyage. Although indicator microbes as defined by the International Convention for the Control and Management of Ships' Ballast Water and Sediments were occasionally detected, no coliform bacteria were detected after the exchange.

Fish sauce is a liquid condiment prepared by fermenting fish at room temperature and high salt concentration (> 20 %) for more than six months. We examined whether the application of pressurized CO2 (pCO2), mild heating, and acid protease (1 %) would produce reduced-salt fish sauce in a short fermentation period. Optimal fermentation temperature and NaCl concentration were determined to be 45ºC and 7%, respectively, at a fixed fermentation period (one week). Treatment with pCO2 (1 MPa), mild heating (45 °C), and acid protease (ORYENTASE AY) decreased biogenic amine content, increased free amino acid content, and enriched umami flavor. This treatment did not induce bacterial growth, and the changes in organic acid content and smell were minimal. In the presence of protease, browning was suppressed under pCO2 compared to atmospheric pressure. Thus, the application of pCO2 and protease with mild heating enabled reduced-salt fish sauce production in a short fermentation period. [ABSTRACT FROM AUTHOR]

Algae have been recognized as important resources providing functional components due to their capacity to exert beneficial effects on health. Therefore, there is increasing interest in investigating the biological activity of algae. In this study, we evaluated the antidepressant-like effect of the administration of 100 mg/kg/day of the ethanol extract of colonial green alga Botryococcus braunii (EEB) for 14 consecutive days in the forced swimming test (FST)-induced depression in imprinting control region (ICR) mice. Imipramine, a commercial antidepressant drug, was used as a positive control. In addition, we investigated the molecular mechanisms underlying the effect of EEB by measuring ATP production and by assessing any change in gene expression at the end of the treatment using real-time polymerase chain reaction (PCR) and microarray assays. We showed that the immobility time in the water-administered control (FST stress) group gradually increased from day 1 to day 14. However, treatment with EEB caused a significant decrease of immobility time in the FST compared with that in the FST stress group. Microarray and real-time PCR results revealed that EEB treatment induced variation in the expression of several genes associated with neurogenesis, energy metabolism, and dopamine synthesis. Interestingly, we revealed that only EEB treatment enhanced the promotion of energy production, while treatment with imipramine was ineffective. Our study provides the first evidence that B. braunii enhances energy production, which may contribute to the modulation of neurogenesis and to the enhancement of dopaminergic function, in turn potentially underlying the antistress- and antidepressant-like effects that we observed. [ABSTRACT FROM AUTHOR]