Enhanced continuous biohydrogen production using dynamic membrane with conductive biofilm supporter.

The present study investigated the effect of a conductive biofilm supporter on continuous production of biohydrogen in a dynamic membrane bioreactor (DMBR). Two lab-scale DMBRs were operated: one with a nonconductive polyester mesh (DMBR I) and the other with a conductive stainless-steel mesh (DMBR II). The highest average hydrogen productivity and the yield were 16.8% greater in DMBR II than in DMBR I, with values of 51.64 ± 0.66 L/L-d and 2.01 ± 0.03 mol H2/mol hexoseconsumed, respectively. The improved hydrogen production was concurrent with a higher NADH/NAD+ ratio and a lower ORP (Oxidation-reduction potential). Metabolic flux analysis implied that the conductive supporter promoted H2-producing acetogenesis and repressed competitive NADH-consuming pathways, such as homoacetogenesis and lactate production. Microbial community analysis revealed that electroactive Clostridium sp. were the dominant H2 producers in DMBR II. Conclusively, conductive meshes may be useful as biofilm supporters of dynamic membranes during H2 production for selectively enhancing H2-producing pathways.

Effect of bioaugmentation using Clostridium butyricum on the start-up and the performance of continuous biohydrogen production.

This study aimed to mitigate the instability in the start-up and continuous performance of dark fermentative biohydrogen production using heat-treated sludge by the addition of an exogenous H2-producing strain. Continuous fermentation augmented with Clostridium butyricum showed the highest average biohydrogen production rate (HPR) as 50.35 ± 2.56 and 58.57 ± 5.03 L/L-d with H2-producing butyric and acetic acid pathways, whereas the fermenters without bioaugmentation showed the termination of biohydrogen production in 3 days of continuous operation with non H2-producing lactic acid pathway and H2-consuming propionic acid pathway. The bioaugmentation blocked the growth of the competitors for hexose such as Streptococcus, Lactobacillus and Megasphaera, and provided H2-producer dominated microbiome with not only Clostridium butyricum, but also Clostridium puniceum and Clostridium neuense originated from heat-treated sludge. Bioaugmentation of a H2-producing strain would be a reliable dissemination strategy for dark fermentative biohydrogen production by minimizing the influence of seed sludge population.

Biohydrogen and biomethane production from food waste using a two-stage dynamic membrane bioreactor (DMBR) system.

This study examined a two-stage dynamic membrane bioreactor (DMBR) system for biohydrogen and biomethane production from food waste (FW) in mesophilic condition. The two-stage DMBR system enabled high-rate H2 and CH4 production from particulate feedstock by enhanced microorganism retention. Chemical energy in FW was recovered up to 79% as renewable energy. The highest average hydrogen production rate of 7.09 ± 0.42 L/L-d was observed at a hydraulic retention time (HRT) of 8 h in the H2-DMBR, while the highest CH4 average production rate of 0.99 ± 0.02 L/L-d was observed at an HRT of 6 d in the CH4-DMBR. The high specific methanogenic activity of 71.7 mL CH4/g VSS-d was maintained at the short HRT, which also contributed to the high MPR. The genus Clostridium was dominant in the H2-DMBR, while bacterial and archaeal populations in the CH4-DMBR were dominated by the class Clostridia and genera Methanobacterium and Methanosaeta, respectively.

High-rate biohydrogen production from xylose using a dynamic membrane bioreactor.

This study aimed a high-rate dark fermentative H2 production from xylose using a dynamic membrane module bioreactor (DMBR) with a 444-µm pore polyester mesh. 20 g xylose/L was fed continuously to the DMBR at different hydraulic retention times (HRTs) from 12 to 3 h at 37 °C. The maximum average H2 yield (HY) and H2 production rate (HPR) at 3 h HRT were found to be 1.40 ± 0.07 mol H2/mol xyloseconsumed and 30.26 ± 1.19 L H2/L-d, respectively. The short HRT resulted in the maximum suspended biomass concentration (8.92 ± 0.40 g VSS/L) along with significant attached biomass retention (7.88 ± 0.22 g VSS/L). H2 was produced by both butyric and acetic acid pathways. Low HY was concurrent with lactic acid production. The bacterial population shifted from non-H2 producers, such as Lactobacillus and Sporolactobacillus spp., to Clostridium sp., when HY increased. Thus, xylose from lignocellulose is a feasible substrate for dark fermentative H2 production using DMBR.

Effect of genus Clostridium abundance on mixed-culture fermentation converting food waste into biohydrogen.

This study examined the effect of various inocula on mixed-culture dark fermentative H2 production from food waste. Heat-treated and frozen H2-producing granular sludge (HPG) grown with monomeric sugars showed a higher H2 yield, production rate, and acidogenic efficiency along with a shorter lag phase than heat-treated methanogenic sludge. Among three different methods of methanogenic sludge inoculation, inoculation after centrifugation showed better H2 production performance. Propionic acid production and homoacetogenesis were regarded as major H2-consuming pathways when methanogenic sludge was used, whereas only homoacetogenesis was found in HPG-inoculated fermentation. During fermentation, the abundance of Clostridium increased greater than 48-fold for methanogenic sludge and greater than 108-fold for HPG, respectively. The initial abundance of Clostridium showed a linear relationship with the H2 production rate and lag-phase time. The use of inoculum with a high abundance of Clostridium is essential for H2 production from food waste.

Dynamic membrane bioreactor for high rate continuous biohydrogen production from algal biomass.

This study aimed to achieve continuous biohydrogen production from red algal biomass using a dynamic membrane bioreactor (DMBR). The DMBR was continuously fed with pretreated Echeuma spinosum containing 20 g/L hexose. The highest average hydrogen production rate (HPR) of 21.58 ± 1.59 L/L-d was observed at HRT 3 h, which was higher than previous reports for continuous H2 production from biomass feedstock. Metabolic flux analysis revealed that butyric acid and propionic acid were the major by-products of the H2-producing and H2-consuming pathways, respectively, of the algal biomass fermentation. Hydrogen consumption by propionic acid pathway could not be prevented completely by heat treatment. PICRUSt2 analysis predicted that Clostridium sp., Anaerostipes sp., and Caproiciproducens sp. might significantly contribute to the expression of both ferredoxin hydrogenase and propionate CoA-transferase. This study would provide the design and operational information on high-rate bioreactor for continuous hydrogen production using biomass.

High-rate mesophilic hydrogen production from food waste using hybrid immobilized microbiome.

This study examined the feasibility of dark fermentative biohydrogen production from food waste using hybrid immobilization in mesophilic condition. Among four different organic loading rates (OLRs), the highest average hydrogen production rate (HPR) of 9.82 ± 0.30 L/L-d was found at an OLR of 74.7 g hexose/L-d, which was higher than reported values from particulate feedstock in mesophilic condition. The average hydrogen yield (HY) at the condition was 1.25 ± 0.04 mol H2/mol hexoseconsumed. Whereas the average HPR and HY at an OLR 80 g hexose/L-d were 5.82 ± 0.12 L/L-d and 0.64 ± 0.02 mol H2/mol hexoseconsumed, respectively. Metabolic flux analysis showed the low HY was concurrent with the highest propionic acid and homoacetogenis. Bacterial population was shift from Clostridium sp. to non-hydrogen producers including Bifidobacterium, Bacteriodes, Olsenella, Dysgonomonas, and Dialister sp.

Effect of shear velocity on dark fermentation for biohydrogen production using dynamic membrane.

This study examined the effect of shear velocity on biohydrogen producing dynamic membrane bioreactor (DMBR) containing 50 µm polyester mesh as supporting material. Increase of shear velocity up to 6.75 m/h enhanced hydrogen production performance as well as biomass retention in both suspended and attached forms, while wash-out was found at a shear velocity of 11.69 m/h. The highest average HPR, HY, suspended biomass, and attached biomass were 26.56 ± 1.49 L/L-d, 1.78 ± 0.10 mol H2/mol glucoseadded, 9.99 ± 0.11 g VSS/L, and 8.82 g VSS/L, respectively, at a shear velocity of 6.75 m/h. Flux balance analysis showed homoacetogenic pathway decreased at the shear velocity of 4.70 m/h with the increase of hydrogen yield based on consumed substrate. The highest copy numbers of Clostridium butyricum was found at the optimum shear velocity. Shear velocity would be a critical operational criteria for continuous biohydrogen production using DMBR.

Usefulness of diffusion tensor imaging findings as biomarkers for amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease. However, no reliable biomarkers have been identified to represent the clinical status. This study aimed to investigate whether diffusion tensor imaging (DTI) findings are useful imaging biomarkers to indicate the clinical status of ALS patients. Ninety-six probable or definite ALS cases and 47 age- and sex-matched, normal controls were enrolled. Demographic and clinical data were collected at the time of DTI. DTI data were acquired using a 3-Tesla magnetic resonance imaging scanner and analysed by voxel-wise statistical analyses for fractional anisotropy, axial diffusivity, radial diffusivity, mean diffusivity, and mode of anisotropy. Compared with the healthy control group, the ALS group had significant differences in DTI scalars in the diffuse tracts of the brain, which was predominant in the corticospinal tract at the brainstem and cerebellar peduncle area. Furthermore, the DTI values correlated with the ALS functional rating scale-revised (ALSFRS-R) scores and the delta ALSFRS-R score representing the rate of disease progression. The subgroup analysis revealed a more severe and widespread brain degeneration was observed in rapidly progressive ALS. Therefore, our results suggest that DTI findings are useful as imaging biomarkers for evaluating the clinical severity and rate of disease progression in ALS.

Automated Subfield Volumetric Analysis of Hippocampus in Patients with Drug-Naïve Nondementia Parkinson's Disease.

Several studies used automated segmentation of hippocampal subfield (ASHS) for detailed measurements of anatomic subregions of the hippocampus, especially in the field of neurodegenerative disorders. In this study, we investigated the hippocampal subfield volume of patients with early-stage nondementia PD compared with normal healthy subjects using the ASHS method. A total of 32 subjects were enrolled in this study (sixteen patients with drug naive nondementia PD and sixteen healthy controls). All subjects were scanned with a 1.5 tesla MRI. The volumes of the seven subfields were calculated separately, and then, the whole hippocampal volume was calculated by the summing of CA1, CA2-3, CA4-DG, subiculum, presubiculum, and fimbria, excluding the hippocampal fissure. There were significant diagnosis-by-hemisphere interactive effects on the total hippocampal volume (F = 5.197; p=0.031) and the subfield volume of CA2-3 (F = 7.586; p=0.010) and CA4-DG (F = 7.403; p=0.011). The volumes of CA2-3 (F = 19.911; p < 0.001), CA4-DG (F = 20.273; p < 0.001), and total hippocampus (F = 10.573; p=0.005) in the left hemisphere were reduced compared to the right hemisphere. We suggest that the hippocampal volume asymmetry, especially in CA4-DG and CA2-3, could be observed in drug-naïve PD patients even in the early stage of the disease.

Formation of a dynamic membrane altered the microbial community and metabolic flux in fermentative hydrogen production.

This study aimed to investigate the relationship among dynamic membrane (DM) formation, metabolic flux, and microbial community population in dark fermentative hydrogen production. A continuously stirred tank reactor was equipped with an external submerged polyester screen mesh and inoculated with heat-treated anaerobic sludge without immobilization. DM was successfully developed on the polyester mesh and provided high-rate hydrogen production at 60.5 L H2/L.d and 2.39 mol H2/mol glucoseadded. DM formation was along with tightly bound extracellular polymeric substances. Flux balance analysis revealed that formation of DM altered the metabolic pathways for acetic acid production from homoacetogenesis to hydrogenesis. Bacterial community analysis suggested that Sporolactobacillaceae would contributed to this metabolic pathway shift. Nevertheless, lactic acid was not accumulated and assumed to be consumed by hydrogen producers including Clostridia.

Kinetic modeling and microbial community analysis for high-rate biohydrogen production using a dynamic membrane.

This study investigated the kinetic parameters of high-rate continuous performance and biofilm layer formation in a H2-producing dynamic membrane bioreactor, composed of a continuously stirred tank reactor along with an external module containing polyester mesh with a pore size of 100 µm. A maximum H2 production rate of 48.9 L/L-day and hydrogen yield of 2.8 mol/mol glucoseadded were attained at a hydraulic retention time of 3 h. The maximum specific growth rate and Monod constant were estimated as 14.92 d-1 and 1.02 g COD/L, respectively. During the entire operation without backwashing, the transmembrane pressure remained below 1.7 kPa, while tightly bound extracellular polymeric substances increased as the dynamic membrane was developed. Fluorescent in situ hybridization and quantitative polymerase chain reaction assays revealed that Clostridium butyricum was dominant in all samples; however, the biofilm had a higher proportion of Prevotella spp. than the fermentation liquor.

Influence of FKBP5 polymorphism and DNA methylation on structural changes of the brain in major depressive disorder.

A single nucleotide polymorphism of rs1360780 in the FKBP5 gene is associated with a predisposition to developing major depressive disorder (MDD). We investigated the interactive effects of FKBP5 rs1360780 allelic variants, DNA methylation, and the diagnosis of MDD on structural changes of the entire brain. One hundred and fourteen patients with MDD and eighty-eight healthy controls underwent T1-weighted structural magnetic resonance imaging and FKBP5 rs1360780 genotyping, including DNA methylation of intron 7. We analyzed the volume of cortical and subcortical regions and cortical thickness using FreeSurfer. Significant genotype-by-diagnosis interactions were observed for volumes of the left pars triangularis, supramarginal gyrus, superior parietal lobule, right frontomarginal, and posterior midcingulate gyrus. The T allele was associated with significant volume reductions in these brain regions only in the MDD group except for the right posterior midcingulate gyrus. FKBP5 DNA methylation showed a positive correlation with the thickness of the right transverse frontopolar gyrus in the C allele homozygote group. Our findings suggest that the FKBP5 gene and its epigenetic changes could have influence on morphologic changes of several brain regions involved in emotion regulation, and that this process may be associated with the development of MDD.

Alterations in the brainstem volume of patients with major depressive disorder and their relationship with antidepressant treatment.

BACKGROUND: Morphologic changes of the brainstem in major depressive disorder (MDD) have rarely been reported in neuroimaging studies, even though, monoaminergic neurotransmitters are synthesized in several brainstem regions. We aimed to investigate volume changes in each region of the brainstem and their association with antidepressant use or the remission status of MDD. METHODS: A total of 126 patients with MDD and 101 healthy controls underwent T1-weighted structural magnetic resonance imaging. We analyzed volumes of each brainstem region, including the medulla oblongata, pons, midbrain, and superior cerebellar peduncle, and the volume of the whole brainstem using the FreeSurfer. RESULTS: The patients with MDD had significantly greater midbrain volumes (P=0.013) compared to healthy controls. In particular, drug-naïve patients with MDD had significantly greater brainstem volumes compared to healthy controls (P=0.007), while no significant findings were observed between the antidepressant treatment group and healthy controls. The remitted patient group had reduced pons (P=0.002) and midbrain (P=0.005) volumes compared to healthy controls, while the non-remitted MDD patient group had significantly greater midbrain volumes compared to the healthy controls (P=0.017). LIMITATIONS: We could not distinguish gray versus white matter volumes changes in our analysis. CONCLUSIONS: We observed that the midbrain is enlarged in patients with a current depressive episode, who are not undergoing antidepressant treatment. This volume then returns to normal after antidepressant treatment, and is even reduced, when the patient is in remission. Further studies are needed to confirm our observations.

Hippocampal subfield analysis in medication-naïve female patients with major depressive disorder.

BACKGROUND: Hippocampal volume loss is known as the best-replicated finding of structural brain imaging studies on major depressive disorder (MDD). Several evidences suggest localized mechanisms of hippocampal neuroplasticity lead the brain imaging studies on the hippocampus and MDD to perform analyses in the subfield level. The aim of this study was to investigate the differences in total and subfield hippocampal volumes, between medication-naïve female MDD patients and healthy controls, through automated segmentation and volumetric methods. METHODS: Twenty medication-naïve female patients diagnosed with MDD and 21 age-matched healthy controls, underwent T1-weighted structural magnetic resonance scanning. Total volumes of both hippocampi and subfield regions were calculated by the automated procedure for volumetric measures implemented in FreeSurfer and automated segmentation method by Van Leemput et al. RESULTS: We observed patients to have significantly smaller volumes of the left hippocampus, subiculum, cornu ammonis 2-3, cornu ammonis 4-dentate gyrus, and right subiculum compared to healthy controls. There were no significant predictors for these subfield region volumes among the illness burden-related parameters including duration of illness, number of depressive episodes, severity of depressive symptoms and memory performances. LIMITATIONS: Our findings relied on the data of only female participants. CONCLUSIONS: We found significant volume reductions in several hippocampal subfield regions in medication-naïve female MDD patients. Our results are consistent with neurobiological evidences on hippocampal neuroplasticity in MDD, and replicate previous findings that suggest morphologic changes of hippocampal subfields in MDD patients.