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This study aimed to investigate the characteristics of hydrogen production by mixed cultures using Laminaria japonica hydrolysates. The hydrolysates of L. japonica were prepared by pretreatment methods, including heat (100°C or 121°C) and acid (HCl or H 2 SO 4 ) pretreatments. The mixed cultures could produce hydrogen using L. japonica as a substrate, with the highest cumulative hydrogen production of 825 ± 14 mL/L from HCl-pretreated L. japonica. High-throughput sequencing of the 16S rRNA gene revealed that the microbial community in the hydrolysate of HCl-pretreated L. japonica was the most diverse among all the samples, with a Shannon diversity index of 5.253. The mixed culture from HCl-pretreated L. japonica and those from heat-pretreated (100°C and 121°C) L. japonica occupied different regions in a principal component analysis (PCA) plot. The dominant population in the hydrolysate of HCl-pretreated L. japonica was represented by hydrogen-producing bacteria, Clostridium spp. and Bacillus spp. The results suggested that L. japonica was an optimal feedstock for hydrogen production. The acid (HCl) pretreatment method could effectively enhance the hydrogen production from L. japonica., (Copyright © 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

Unlabelled: Laminaria japonica--a widely used ingredient in seaweed kimchi--and lactic acid bacteria (LAB)--a main component of traditional fermented Korean food--may alter human intestinal microbiota composition and have a positive effect on various digestive problems. However, few clinical trials have investigated the potential benefits of L. japonica when combined with LAB for human intestinal microbiota. Therefore, this study was designed to evaluate the effects of L. japonica and representative LAB on the human intestine. Forty participants with no known digestive diseases were randomly assigned to one of the two combination groups: (1) L. japonica with LAB and (2) L. japonica with placebo LAB. The study agents were administered for 4 weeks with a 2-week follow-up period. The primary outcome measure was the number of each of the seven LAB species in the human intestine, and the secondary outcome measures included the Korean version of the Gastrointestinal Symptom Rating Scale, the World Health Organization Quality of Life, and bowel functions. The primary outcome was evaluated before and after administration of the study agents (0 and 4 weeks), and the secondary outcomes were evaluated at 0, 4, and 6 weeks. Four of the seven LAB species were found to be significantly increased in the L. japonica with the LAB group and five species were significantly different from those of the placebo group. The secondary outcome measures did not change significantly. In conclusion, L. japonica with LAB facilitated the proliferation of beneficial human intestinal microbiota. (, Trial Number: ClinicalTrials.gov NCT01651741).

The temperature effect on continuous dark fermentative hydrogen production from non-pretreated Laminaria japonica was investigated in the present study. In a preliminary step, the fermentors were continuously operated as an inoculation process at three different temperatures, 35, 50 and 65°C, to respectively represent mesophilic, thermophilic, and hyperthermophilic conditions. An optimization process was subsequently conducted with a range of organic loading rate (OLR) and cultivation pH. Among the various operation conditions, the maximum H2 yield, 61.3±2.0 mL H2/g TS, was observed under a mesophilic condition at OLR of 3.4 g COD/L/d and pH 5.5. From a PCR-DGGE analysis, it was found that an increase of temperature can reduce the microbial diversity and change the predominant species. Finally, total cellulase activity was measured, to investigate the effect of temperature on hydrolysis of L. japonica. The highest cellulase activity was 0.19±0.02 FPU/mL, observed at 35°C, coinciding with the maximum H2 yield., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Methane production by anaerobic digestion (AD) of macroalgae (seaweed) is a promising algal bioenergy option. Work presented here is primarily based on the AD of Laminaria hyperborea using batch and continuously stirred tank reactors. Extrapolation of data from batch studies to long term continuous reactors was unreliable. A conservative organic loading rate (OLR) of 1 g L(-1) d(-1) was used due to difficulties experienced in achieving steady state performance at an OLR of 1.5 g L(-1) d(-1). Biogas composition and methane yields (60-70%) were near to values expected from terrestrial feedstocks. Biomass washout, as imposed by the dilution rate (i.e., hydraulic residence), had considerable bearing on the biogas generation profile, particularly at >3 hydraulic residences. Inhibition of methanogen growth was linked to nutrient deficiency and potentially antimicrobial compounds associated with the feedstock. Anaerobic digestion of L. hyperborea proved feasible over extended operational periods., (Copyright © 2013. Published by Elsevier Ltd.)

Wild populations of brown marine algae (Phaeophyta) provide extensive surfaces to bacteria and epiphytic eukaryotes for colonization. On one hand, various strategies allow kelps prevent frond surface fouling which would retard growth by reducing photosynthesis and increasing pathogenesis. On the other hand, production and release of organic exudates of high energy value, sometimes in association with more or less selective control of settlement of epiphytic strains, allow bacteria to establish surface consortia not leading to macrofouling. Here, we present the analysis of adhesion and biofilm formation of bacterial isolates from the kelp Laminaria digitata and of characterized and referenced marine isolates. When they were grown in flow cell under standard nutrient regimes, all used bacteria, except one, were able to adhere on glass and then develop as biofilms, with different architecture. Then, we evaluated the effect of extracts from undisturbed young Laminaria thalli and from young thalli subjected to oxidative stress elicitation; this latter condition induced the production of defense molecules. We observed increasing or decreasing adhesion depending on the referenced strains, but no effects were observed against strains isolated from L. digitata. Such effects were less observed on biofilms. Our results suggested that L. digitata is able to modulate its bacterial colonization. Finally, mannitol, a regular surface active component of Laminaria exudates was tested individually, and it showed a pronounced increased on one biofilm strain. Results of these experiments are original and can be usefully linked to what we already know on the oxidative halogen metabolism peculiar to Laminaria. Hopefully, we will be able to understand more about the unique relationship that bacteria have been sharing with Laminaria for an estimated one billion years.