JBB : Journal of Bioscience and Bioengineering

JBB Vol. 125表紙  

JBB 新着20報



  • Cultivation of microalgae Chlorella zofingiensis on municipal wastewater and biogas slurry towards bioenergy
    Publication date: Available online 23 May 2018
    Source:Journal of Bioscience and Bioengineering

    Author(s): Weizheng Zhou, Zhongming Wang, Jingliang Xu, Longlong Ma

    The high cost of large-scale cultivation of microalgae has limited their industrial application. This study investigated the potential use of mixed biogas slurry and municipal wastewater to cultivate microalgae. Pig biogas slurry as the sole nutrient supplement, was assessed for the cultivation of Chlorella zofingiensis in municipal wastewater. Batch culture of various ratios of pig biogas slurry and municipal wastewater were compared. The characteristics of algal growth and lipid production were analyzed, and the removal rates of nitrogen and phosphate were examined. Results indicate that 8% pig bio-gas slurry in municipal wastewater, had a significant effect on microalgal growth. C. zofingiensis, with 2.5 g L−1 biomass, 93% total nitrogen and 90% total phosphorus removal. Lipid content was improved by 8% compared to BG11 medium. These findings show that mixing pig biogas slurry and municipal wastewater, without additional nutrition sources, allows efficient cultivation of C. zofingiensis. This is of high research and industrial significance, allowing cultivation of C. zofingiensis in mixed waste culture solution without additional nutrition sources.





  • Protein kinase C-dependent cell damage by unsaturated carbonyl compounds in vascular cells
    Publication date: Available online 22 May 2018
    Source:Journal of Bioscience and Bioengineering

    Author(s): Tsunehito Higashi, Yosuke Mai, Yuichi Mazaki

    Unsaturated carbonyl compounds, such as acrolein (ACR) and methyl vinyl ketone (MVK), are known as the environmental pollutants, and are contained in smoke, automobile exhaust, and heated oil. Although they can enter the circulation through the alveolar epithelium, the details of their effects on the vascular system remain to be clarified. We have recently reported that ACR and MVK induce protein kinase C (PKC) activation and cell damage mediated by intracellular Ca2+ in rat glioma cells (Higashi et al., J. Biosci. Bioeng., 124, 680–684, 2017). In this study, we have attempted to elucidate the effects of ACR and MVK on the vascular system, because blood vessels are easily exposed to these compounds. The rat aorta smooth muscle cells A7r5 were highly sensitive to ACR and MVK, whereas the human umbilical vein endothelial cells EA.hy926 were resistant to them. The ACR- and MVK-induced cell damage in A7r5 cells was PKC-dependent. In A7r5 cells, PKCα, PKCδ, PKCε, and PKCι were expressed. ACR and MVK induced PKCα and PKCδ translocation to the cell membrane. PKC activity was enhanced in A7r5 cells by ACR and MVK. These results indicate that the unsaturated carbonyl compounds might affect the vascular system by damaging smooth muscle cells via PKC activation.





  • Production of giant unilamellar vesicles by the water-in-oil emulsion-transfer method without high internal concentrations of sugars
    Publication date: Available online 21 May 2018
    Source:Journal of Bioscience and Bioengineering

    Author(s): Gakushi Tsuji, Takeshi Sunami, Norikazu Ichihashi

    Giant unilamellar vesicles (GUVs) are large vesicles bounded by a single lipid bilayer, which have been used in various applications as artificial, cell-like compartments. The water-in-oil (w/o) emulsion-transfer method has been attracting attention as a method to prepare GUVs that can efficiently encapsulate macromolecules. For efficient GUV production by this method, non-physiological, high concentrations of sugars are usually required in the inner solution of the GUVs. These sugars limit the utility of the GUVs for a wide range of applications. In this study, we investigated various compositions of the inner and outer solutions to achieve efficient production without high concentrations of sugars through the w/o emulsion-transfer method. Firstly, we adjusted the osmotic pressure and density of the outer solution with NaCl and succeeded in increasing the proportion of GUVs and the absolute number in the prepared liposome population. Secondly, we increased the density of the inner solution with cytochrome c, but the proportion of GUVs and absolute number of vesicles did not increase. Thirdly, we increased the density of the inner and outer solutions with glycerol, which is membrane permeable and can be removed from GUVs, and succeeded in increasing the GUV proportion. These results provide useful information for the efficient preparation of GUVs that enclose a physiologically-relevant environment by the w/o emulsion-transfer method.





  • Deciphering synergistic characteristics of redox mediators-stimulated echinenone production of Gordonia terrae TWIH01
    Publication date: Available online 18 May 2018
    Source:Journal of Bioscience and Bioengineering

    Author(s): Bin Xu, Bor-Yann Chen, Kuan-Chieh Huang, Qing-Jiang Sun, John Chi-Wei Lan

    This first-attempt study tended to decipher synergistic interactions of model redox mediators (RMs) to echinenone production for electrochemically-steered fermentation (ESF). The findings indicated that supplement of RMs could significantly stimulate the production performance of fermentation (e.g., 36% for 4-aminophenol) which was parallel with stimulation of bioelectricity generation in microbial fuel cells (MFCs) as prior studies mentioned. Although redox mediators could usually enhance electron transport extracellular compartment, the mechanisms of bioelectricity generation in MFCs and echinenone production in ESF were very likely functioned in the extracellular and the intracellular compartment, respectively. In MFCs, electron transfer towards biofilm anode for bioelectricity generation must be taken place. However, for ESF echinenone accumulation was very likely occurred in the intracellular compartment, thus electron transfer was predominantly implemented in the intracellular, not the extracellular compartment.

    Graphical abstract

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  • 3D-printed scaffolds with calcified layer for osteochondral tissue engineering
    Publication date: Available online 16 May 2018
    Source:Journal of Bioscience and Bioengineering

    Author(s): Zhengyu Li, Shuaijun Jia, Zhuo Xiong, Qianfa Long, Shaorong Yan, Fu Hao, Jian Liu, Zhi Yuan

    Treating full-layer injury of bone and cartilage is currently a significant challenge in orthopedic trauma repair. Joint damage typically includes chondral defects, and the underlying subchondral defect sites are difficult to repair. Tissue engineering technology could potentially be used to treat such injuries; however, results to date been unsatisfactory. The aim of this study was to design a multilayer composite scaffold containing cartilage, bone, and calcified layers to simulate physiological full-thickness bone-cartilage structure. The cartilage layer was created using an improved temperature-gradient thermally induced crystallization technology. The bone and calcified layers were synthesized using 3D printing technology. We examined the scaffold by using scanning electron microscope (SEM), X-ray diffraction (XRD), fluorescence staining, and micro computed tomography (Micro-CT), and observed clearly oriented structures in the cartilage layer, overlapping structures in the bone scaffold, and a compressed calcified layer. Biomechanical performance testing showed that the scaffolds were significantly stronger than scaffolds without a calcified layer (traditional scaffolds) in maximum tensile strength and maximum shear strength (P < 0.05). After inoculating cells onto the scaffolds, we observed similar cell adherence and proliferation to that observed in traditional scaffolds, likely because of the high porosity of the whole scaffold. Our scaffolds could be used in bone and cartilage full-thickness injury repair methods, as well as applications in the field of tissue engineering.





  • Effectiveness of cross-linked enzyme aggregates of cellulolytic enzymes in hydrolyzing wheat straw
    Publication date: Available online 11 May 2018
    Source:Journal of Bioscience and Bioengineering

    Author(s): Shuddhodana, Munishwar N. Gupta, Virendra S. Bisaria

    Development of industrially potent cellulolytic enzymes is one of the greatest challenges faced in lignocellulosic feed-stock based bio-refining. In the current work cross-linked enzyme aggregates (CLEAs) of commercial cellulase mix were successfully prepared and their performance to be used as potential industrial enzymes in terms of stability and wheat straw hydrolysis was evaluated. The CLEAs were more stable compared to native enzymes with half-lives being 2.30-, 1.56-, 3.07- and 1.67-fold higher at 70°C for filter paper activity (FPA), endoglucanase, β-glucosidase and xylanase, respectively. CLEAs retained 77.4% of endoglucanase and 85.9% of xylanase activity after five cycles of hydrolysis of soluble substrates such as carboxymethyl cellulose and xylan, respectively. A maximum saccharification yield of 31.8% by soluble enzymes and 32.9% by CLEAs were obtained when alkali-pretreated wheat straw was subjected to hydrolysis. On repeated batch hydrolysis for five consecutive cycles of 24 h each, the CLEAs showed an overall higher saccharification yield of 43.3% compared to 31.8% with soluble enzymes.





  • Application of the biotin-labeled toxin mutant for affinity isolation of associated proteins in the mammalian cells
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Ju-Gyeong Yoon, Hye-Jeong Hwang, Jin Ah Cho

    Cholera toxin (CT), one of the AB5 bacterial toxin families, is produced by Vibrio cholerae, breeches the intestinal epithelial barrier and enters host epithelial cells to cause the massive secretory diarrhea. This study focused on understanding the retro-translocation machinery of the bacterial toxin using biotin-avidin technology to explain toxin trafficking from the endoplasmic reticulum (ER) to the cytosol. Because the association between the A1 chain of CT and other components of the retro-translocation machinery is likely transient or very weak, the successful bioengineering of such a mutant to be trapped as an intermediate in ER is essential for affinity isolation and further analysis. Here, we prepared a mutant toxin that 15 amino acid Biotin Acceptor Peptide (BAP) was fused to the C-terminal of A1 chain of CT. Biotinylation efficiency of the BAP-inserted cholera toxin (BT) was nearly 100%. Moreover, BT was functionally toxic and successfully pulled down by NeutrAvidin in vitro and in vivo. However, NeutrAvidin-bound biotinylated BT was not toxic. These results suggest the possibility of a plug effect of the biotin-NeutrAvidin-BT complex stuck in the ER without retro-translocation to the cytosol. Therefore, this model might identify the interacting proteins with A1 chain of CT in the host cells by holding the moment of retro-translocation of the bacterial toxin. In conclusion, this study established the model using biotin-avidin technology to elucidate the molecular basis for retro-translocation of bacterial toxin from within the lumen of ER to the cytosol.





  • Identification of EayjjPB encoding a dicarboxylate transporter important for succinate production under aerobic and anaerobic conditions in Enterobacter aerogenes
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Keita Fukui, Kei Nanatani, Yoshihiko Hara, Mitsunori Tokura, Keietsu Abe

    Enterobacter aerogenes, a gram-negative, rod-shaped bacterium, is an effective producer of succinate from glucose via the reductive tricarboxylic acid cycle under anaerobic conditions. However, to date, succinate-exporter genes have not been identified in E. aerogenes, although succinate exporters have a large impact on fermentative succinate production. Recently, we genetically identified yjjP and yjjB, as genes encoding a succinate transporter in Escherichia coli. Evaluation of the yjjPB homologs in E. aerogenes ( EayjjPB genes) showed that succinate accumulation increased from 4.1 g L−1 to 9.1 g L−1 when the EayjjPB genes were expressed under aerobic conditions. Under anaerobic conditions, succinate yield increased from 53% to 60% by EayjjPB expression and decreased to 48% by deletion of EayjjPB. Furthermore, the production levels of fumarate and malate, which are intermediates of the succinate-biosynthesis pathway, were also increased by EayjjPB expression. A complementation assay conducted in Corynebacterium glutamicum strain AJ110655ΔsucE1 demonstrated that both EaYjjP and EaYjjB are required for the restoration of succinate production. Taken together, these results suggest that EaYjjPB function as a dicarboxylate transporter in E. aerogenes and that the products of both genes are required for dicarboxylate transport.





  • Effect of acids produced from carbohydrate metabolism in cryoprotectants on the viability of freeze-dried Lactobacillus and prediction of optimal initial cell concentration
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Shumao Cui, Feng Hang, Xiaoming Liu, Zhiyuan Xu, Zhenmin Liu, Jianxin Zhao, Hao Zhang, Wei Chen

    For the industrial production of probiotics powder, various sugars have been used as cryoprotectants to preserve probiotics during freeze-drying. Some of these sugars can be metabolized by Lactobacillus with the production of acids during the mix. In this study, we investigated the effect of acids on ATPase, β-galactosidase, lactate dehydrogenase (LDH), integrity and fluidity of cell membrane and the survival rate of Lactobacillus during freeze-drying. In the presence of Lactobacillus, acids were produced from cryoprotectants containing fermentable sugars before freezing, resulting in a decrease in the pH of the bacterial suspension to below 5.0. During freeze-drying, the acids caused a loss of viability of Lactobacillus due to aggravated damage to ATPase, β-galactosidase and cell membrane fluidity, but not LDH and cell membrane integrity. This finding implied that cryoprotectants that do not lead to the production of acids are effective in improving the survival rate of freeze-dried Lactobacillus. Here, a new formula was proposed for a protectant containing whey protein isolate (WPI) and rhamnose, which were not metabolized. In addition, linear-regression analyses were performed on the proportion of cryoprotectants (M) against cell paste (m), total cell count (N), total surface area (S t ) and total volume (V t ) of bacteria for 100% survival rate. The total surface areas of bacteria were found to be highly correlated with the amount of proposed cryoprotectant. The following prediction equation was established for the optimal initial cell concentration for a 100% survival rate of freeze-dried Lactobacillus: N (4πr2 +2πl)=(0.66±0.03)M.





  • Valerate production by Megasphaera elsdenii isolated from pig feces
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Shota Yoshikawa, Ryosuke Araoka, Yu Kajihara, Toshiyuki Ito, Hirokuni Miyamoto, Hiroaki Kodama

    Megasphaera elsdenii is able to produce several short-chain fatty acids (SCFAs), such as acetate, propionate, butyrate, and valerate. These SCFAs serve as an energy source for host animals and play an important role in gut health. In this study, M. elsdenii was isolated from pig feces that had been collected from two farms located in distinct areas of Japan. These M. elsdenii isolates were genotyped, and 7 representative strains were selected. When these 7 strains and M. elsdenii JCM 1772T were cultured with lactate for 24 h, all 7 strains produced valerate as a predominant SCFA. Therefore, the valerate-producing M. elsdenii inhabits a wide area of Japan. In contrast, M. elsdenii JCM 1772T produced acetate, propionate, butyrate, and valerate at similar levels. When the Y2 strain, one of the 7 representative strains, was cultured without lactate, low levels of valerate accumulated. In contrast, in a time course of lactate fermentation by the Y2 strain, lactate was rapidly consumed, and acetate and propionate were produced after 6 h of incubation. Thereafter, acetate and propionate were consumed from 6 to 12 h after the start of the incubation, and valerate and butyrate were produced. In most of the previously described M. elsdenii strains, valerate was not a predominant SCFA. Therefore, the M. elsdenii Y2 strain showed an unique metabolism in which valerate was produced as a primary end product of lactate fermentation.





  • Metabolic dependent and independent pH-drop shuts down VirSR quorum sensing in Clostridium perfringens
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Keika Adachi, Kaori Ohtani, Michio Kawano, Ravindra Pal Singh, Basit Yousuf, Kenji Sonomoto, Tohru Shimizu, Jiro Nakayama

    Clostridium perfringens produces various exotoxins and enzymes that cause food poisoning and gas gangrene. The genes involved in virulence are regulated by the agr-like quorum sensing (QS) system, which consists of a QS signal synthesis system and a VirSR two-component regulatory system (VirSR TCS) which is a global regulatory system composed of signal sensor kinase (VirS) and response regulator (VirR). We found that the perfringolysin O gene (pfoA) was transiently expressed during mid-log phase of bacterial growth; its expression was rapidly shut down thereafter, suggesting the existence of a self-quorum quenching (sQQ) system. The sQQ system was induced by the addition of stationary phase culture supernatant (SPCS). Activity of the sQQ system was heat stable, and was present following filtration through the ultrafiltration membrane, suggesting that small molecules acted as sQQ agents. In addition, sQQ was also induced by pure acetic and butyric acids at concentrations equivalent to those in the stationary phase culture, suggesting that organic acids produced by C. perfringens were involved in sQQ. In pH-controlled batch culture, sQQ was greatly diminished; expression level of pfoA extended to late-log growth phase, and was eventually increased by one order of magnitude. Furthermore, hydrochloric acid induced sQQ at the same pH as was used in organic acids. SPCS also suppressed the expression of genes regulated by VirSR TCS. Overall, the expression of virulence factors of C. perfringens was downregulated by the sQQ system, which was mediated by primary acidic metabolites and acidic environments. This suggested the possibility of pH-controlled anti-virulence strategies.





  • Evaluation of the impact of dissolved oxygen concentration on biofilm microbial community in sequencing batch biofilm reactor
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Jingyin Wang, Hongwei Rong, Chaosheng Zhang

    The effect of dissolved oxygen concentration (DO) during simultaneous nitrification and denitrification (SND) was investigated in a sequencing batch biofilm reactor (SBBR). In addition, the removal rates of nitrogen and bacterial communities were investigated under different concentrations of DO (1.5, 3.5, and 4.5 mg/L). When the SND rate was 95.22%, the chemical oxygen demand and nitrogen removal was 92.22% and 84.15%, respectively, at 2.5 mg/L DO. The denitrification was inhibited by the increase of oxygen concentration. Microelectrode measurements showed that the thickness of oxygen penetration increased from 1.0 mm to 2.7 mm when the DO concentration increased from 1.5 mg/L to 5.5 mg/L. The current location of the aerobic and anaerobic layers in the biofilm was determined for analysis of the microbial community. High-throughput sequencing analysis revealed the communities of the biofilm approached similar structure and composition. Uliginosibacterium species, biofilm-forming bacteria Zoogloea species and Acinetobacter species were dominant. In the aerobic layer, phyla Betaproteobacteria and Saprospirae were predominant, the major phyla were shifted from Proteobacteria followed by Firmicutes and Bacteroidetes, which comprised 82% of the total sequences during the SND period. Anaerolineae was dominated in the anaerobic layer. The high abundance of Nitrospira in the aerobic biofilm provides evidence of the SND system performing better at ammonia oxidization. In addition, real-time PCR indicated that the amount of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) matched the Nitrospirales and Nitrosomonadales abundance well. Collectively, this study demonstrated the dynamics of key bacterial communities in the SND system were highly influenced by the DO concentration.





  • Comparative study of reactor performance and microbial community in psychrophilic and mesophilic biogas digesters under solid state condition
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Suzhen Wei, Yanfei Guo

    Psychrophilic (15°C) and mesophilic (35°C) reactor performance and microbial community dynamics were compared when the biogas fermenters were performed at high altitude and solid state condition using animal manure and highland barley straw as substrate. Longer biogas fermentation time, higher peak methane content and lower volatile fatty acids (VFA) accumulation were found at psychrophilic condition compared to that of at mesophilic condition although the biogas production in both temperature conditions was similar. The cumulative biogas production at 35°C and 15°C were 246 (±5) and 225 (±7) ml/g volatile solids, respectively. The highest total VFA concentration under 35°C was 10,796 (±310) mg/kg total solid, while it only reached to 2346 (±87) mg/kg total solid at the condition of 15°C. Additionally, the variation of pH, soluble chemical oxygen demand and total ammonia nitrogen during the anaerobic digestion under psychrophilic condition were much smaller than that of under mesophilic condition. Polymerase chain reaction and denaturing gradient gel electrophoresis analysis followed by 16S rDNA sequencing showed that bacteria of genera Bacillus and Clostridium and archaea of genera Methanosarcina and Methanosaeta played a pivotal role during the biogas production.





  • Characterization of newly isolated Pseudonocardia sp. N23 with high 1,4-dioxane-degrading ability
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Norifumi Yamamoto, Yuji Saito, Daisuke Inoue, Kazunari Sei, Michihiko Ike

    This study was conducted to elucidate the 1,4-dioxane degradation characteristics of a newly isolated 1,4-dioxane-degrading bacterial strain and evaluate the applicability of the strain to biological 1,4-dioxane removal from wastewater. A bacterial strain (designated strain N23) capable of degrading 1,4-dioxane as the sole carbon and energy source was isolated from an enrichment culture prepared from 1,4-dioxane-contaminated groundwater. Strain N23 was phylogenetically identified as belonging to the genus Pseudonocardia, based on 16S rRNA gene sequencing. 1,4-Dioxane degradation experiments revealed that strain N23 is capable of constitutive 1,4-dioxane degradation. Further, this strain exhibited the highest specific 1,4-dioxane degradation rate of 0.230 mg-1,4-dioxane (mg-protein)−1 h−1 among 1,4-dioxane-degrading bacteria with constitutively expressed degrading enzymes reported to date. In addition, strain N23 was shown to degrade up to 1100 mg L−1 of 1,4-dioxane without significant inhibition, and to maintain a high level of 1,4-dioxane degradation activity under a wide pH (pH 3.8–8.2) and temperature (20–35 °C) range. In particular, the specific 1,4-dioxane degradation rate, even at pH 3.8, was 83% of the highest rate at pH 7.0. In addition, strain N23 was capable of utilizing ethylene glycol and diethylene glycol, which are both considered to be present in 1,4-dioxane-containing industrial wastewater, as the sole carbon source. The present results indicate that strain N23 exhibits the potential for 1,4-dioxane removal from industrial wastewater.





  • Biohydrogen fermentation of galactose at various substrate concentrations in an immobilized system and its microbial correspondence
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Periyasamy Sivagurunathan, Arivalagan Pugazhendhi, Gopalakrishnan Kumar, Jong-Hun Park, Sang-Hyoun Kim

    The effects of substrate concentration on fermentative hydrogen production from galactose at a fixed hydraulic retention time of 12 h were investigated in an immobilized continuously stirred tank reactor. Peak hydrogen production rate and hydrogen yield of 9.57 L/L-d and 1.10 mol/mol galactoseadded, respectively, were obtained at a feed substrate concentration of 30 g/L and an organic loading rate of 60 L/L-d. Quantitative polymerase chain reaction analysis showed that the variations in the performance resulted primarily from metabolic alterations within the metabolism of the established microbial community rather than modifications in the population. The results obtained showed that optimal substrate concentration is essential for the efficient, continuous production of hydrogen from galactose.





  • Bacterial communities adapted to higher external resistance can reduce the onset potential of anode in microbial fuel cells
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Kei Suzuki, Yutaka Kato, Arashi Yui, Shuji Yamamoto, Syota Ando, Owen Rubaba, Yosuke Tashiro, Hiroyuki Futamata

    We investigated how bacterial communities adapted to external resistances and exhibited the performance of electricity production in microbial fuel cells (MFCs) with external resistance of 10 Ω (LR-MFC) and 1000 Ω (HR-MFC). The HR-MFC exhibited better performance than the LR-MFC. The power densities of the LR-MFC and the HR-MFC were 5.2 ± 1.6 mW m−2 and 28 ± 9.6 mW m−2 after day 197, respectively. Low-scan cyclic voltammetry analyses indicated that the onset potential of the HR-MFC was more negative than that of the LR-MFC, suggesting that the higher external resistance led to enrichment of the highly current producing bacteria on the anode surface. All clones of Geobacter retrieved from the LR-MFC and the HR-MFC were members of the Geobacter metallireducens clade. Although the population density of Geobacter decreased from days 366–427 in the HR-MFC, the current density was almost maintained. Multidimensional scaling analyses based on denaturing gradient gel electrophoresis profiles indicated that the dynamics of the biofilm and anolytic communities changed synchronously in the two MFCs, but the dynamics of the bacterial communities in the LR-MFC and the HR-MFC were different from each other, reflecting different processes in adaptation to the different external resistances. The results suggest that the microbial community structure was formed by adapting to higher external resistance, exhibiting more negative onset potential and higher performance of the HR-MFC through collaborating with anode-respiring bacteria and fermenters.





  • Mutations responsible for alcohol tolerance in the mutant of Synechococcus elongatus PCC 7942 (SY1043) obtained by single-cell screening system
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Yasutaka Hirokawa, Yu Kanesaki, Sayuri Arai, Fumiko Saruta, Kayoko Hayashihara, Akio Murakami, Kazunori Shimizu, Hiroyuki Honda, Hirofumi Yoshikawa, Taizo Hanai

    The production of alcohols directly from carbon dioxide by engineered cyanobacteria is an attractive technology for a sustainable future. Enhanced tolerance to the produced alcohols would be a desirable feature of the engineered cyanobacterial strains with higher alcohol productivity. We have recently obtained the mutant strains of Synechococcus elongatus PCC 7942 with higher tolerance to isopropanol using a single-cell screening system (Arai et al., Biotechnol. Bioeng., 114, 1771–1778, 2017). Among the mutant strains, SY1043 showed the highest isopropanol tolerance. Interestingly, SY1043 also showed higher tolerance to other alcohols such as ethanol and 1-butanol, however, the mechanisms involved in enhancing this alcohol tolerance were unclear. To reveal the alcohol tolerance mechanism of SY1043, we investigated the relationship between alcohol tolerance and four mutations found in SY1043 by genome resequencing analysis. Isopropanol tolerance was enhanced by amino acid substitution (Leu285Pro) in a hypothetical protein encoded by Synpcc7942_0180 of the wild type strain TA1297. TA4135, into which this mutation was introduced, showed a same tendency of tolerance to other alcohols (ethanol and 1-butanol).





  • Production and characterization of ectoine using a moderately halophilic strain Halomonas salina BCRC17875
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Wei-Chuan Chen, Ching-Cha Hsu, John Chi-Wei Lan, Yu-Kaung Chang, Li-Fen Wang, Yu-Hong Wei

    This study attempted to utilize Halomonas salina BCRC17875 to produce ectoine by optimizing the agitation speed and medium composition. In addition, the chemical structure of ectoine produced by H. salina BCRC17875 was determined. The results indicate that ectoine production reached 3.65 g/L at 38 h of cultivation when the agitation rate and NaCl concentration were fixed at 200 rpm and 2.0 M, respectively. It reached 9.20 g/L at 44 h of cultivation when the major medium components were yeast extract (56 g/L), glutamate (74.40 g/L), and ammonium sulfate (14 g/L). After the nitrogen concentration had been evaluated, evaluation of the nitrogen concentration revealed that the ectoine production reached 11.80 g/L at 44 h of cultivation when 56 g/L of yeast extract and 28 g/L of ammonium sulfate were used. Ectoine production reached 13.96 g/L at 44 h of cultivation when the carbon/nitrogen ratio was fixed at 3/1 using 84 g/L of yeast extract and 28 g/L of ammonium sulfate. Furthermore, the identification of ectoine were identified and characterized by fast atom bombardment mass spectrometry (FAB-MS) and 1H NMR. The results demonstrated a fermentation strategy was successful in increasing ectoine production, and that the fermentation medium of ectoine had commercialization potential.





  • Direct recovery of Bacillus subtilis xylanase from fermentation broth with an alcohol/salt aqueous biphasic system
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Hui Suan Ng, Cindy Xin Yi Chai, Yin Hui Chow, Wai Leng Carmen Loh, Hip Seng Yim, Joo Shun Tan, John Chi-Wei Lan

    Xylanase enzyme degrades linear polysaccharide β-1,4 xylan and the hemicellulose of the plant cell wall. There is a growing demand in finding a cost-effective alternative for industrial scale production of xylanase with high purity for pharmaceutical applications. In this study, an alcohol/salt aqueous biphasic system (ABS) was adopted to recover xylanase from the Bacillus subtilis fermentation broth. The effects of several ABS parameters such as types and concentrations of alcohols and salts (i.e., sulphate, phosphate, and citrate), amount of crude loading and pH of the system on the recovery of xylanase were investigated. Partition coefficient of xylanase (KE), selectivity (S) and yield (YT) of xylanase in top phase of the ABS were measured. Highest KE (6.58 ± 0.05) and selectivity (4.84 ± 0.33) were recorded in an ABS of pH 8 composed of 26% (w/w) 1-propanol, 18% (w/w) ammonium sulphate. High YT of 71.88% ± 0.15 and a purification fold (PFT) of 5.74 ± 0.33 were recorded with this optimum recovery of xylanase using alcohol/salt ABS. The purity of xylanase recovered was then qualitatively verified with sodium dodecyl sulphate (SDS) gel electrophoresis. The SDS profile revealed the purified xylanase was successfully obtained in the top phase of the one-step 1-propanol/sulphate ABS with a distinct single band.

    Graphical abstract

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  • Evaluating new bio-hydrogen producers: Clostridium perfringens strain JJC, Clostridium bifermentans strain WYM and Clostridium sp. strain Ade.TY
    Publication date: May 2018
    Source:Journal of Bioscience and Bioengineering, Volume 125, Issue 5

    Author(s): Yee Meng Wong, Ta Yeong Wu, Tau Chuan Ling, Pau Loke Show, Sze Ying Lee, Jo-Shu Chang, Shaliza Ibrahim, Joon Ching Juan

    Three newly discovered H2 producing bacteria namely Clostridium perfringens strain JJC, Clostridium bifermentans strain WYM and Clostridium sp. strain Ade.TY originated from landfill leachate sludge have demonstrated highly efficient H2 production. The maximum H2 production attained from these isolates are in the descending order of strain C. perfringens strain JJC > C. bifermentans strain WYM > Clostridium sp. strain Ade.TY with yield of 4.68 ± 0.12, 3.29 ± 0.11, and 2.87 ± 0.10 mol H2/mol glucose, respectively. The result has broken the conventional theoretical yield of 4 mol H2/mol glucose. These isolates were thermodynamically favourable with Gibbs free energy between −33 and −35 kJ/mol (under process conditions: pH 6, 37 °C and 5 g/L glucose). All three isolates favour butyrate pathway for H2 production with the ratio of acetate and butyrate of 0.77, 0.65 and 0.80 for strain JJC, WYM and Ade.TY, respectively. This study reported provides a new insight on the potential of unique bacteria in H2 production.