ISOLATION AND CHARACTERIZATION OF POLYCYCLIC AROMATIC HYDROCARBON-DEGRADING MICROORGANISMS UNDER METHANOGENIC CONDITIONS

Polycyclic aromatic hydrocarbons (PAHs) are among the most widely distributed organic contaminants in aquatic sediments due to their presence in coal and petroleum. While it has been demonstrated that PAHs are degraded under anaerobic conditions, little is known about the microorganisms responsible for PAH degradation. This study demonstrates not only the first isolations of naphthalene (NAP)- and phenanthrene (PHE)-degrading microorganisms under methanogenic conditions by utilizing modified plating methods but also the first identification and isolation of a fermentative bacterium responsible for initiating a syntrophic PHE-degradation. Molecular characterization of PAH-degrading methanogenic cultures via comparative 16S rDNA sequence analysis was employed to monitor the microbial community structure and consequently to design isolation strategies for the possible microbial species responsible for PAH-degradation. To isolate PAH-degrading microbes under anaerobic conditions, a modified plating method was first developed for detecting microorganisms degrading solid PAHs on the agar-overlay plate. It was also verified that this method was not only applicable for the isolation of both aerobic and anaerobic PAH-degrading microorganisms but also effective to solve problems existing with other previous isolation methods. By employing the modified plating method, PHE-degrading microorganisms under methanogenic conditions were successfully isolated from the enrichment cultures. The degradation of PHE was partially inhibited by 2-bromoethanesulfonic acid; however, no 14CH4 was detected when [9-14C] PHE was employed, indicating partial mineralization of PHE. One species of bacterium was isolated and identified as an initial microbial catalyst for PHE-degradation. NAP-degrading microorganisms under methanogenic conditions were also isolated by employing an agar-overlay containing evenly dispersed fine particles of NAP. One species of the bacteria was identified to be the same microorganism as a fermentative bacterium initiating a syntrophic PHE-degradation, and the other one showed a syntrophic relationship with methanogen species. The results presented here will likely contribute to the development of the isolation techniques and the identification of microbial consortia for the biodegradation of PAHs under anaerobic conditions

Co-culturing a novel Bacillus strain with Clostridium tyrobutyricum ATCC 25755 to produce butyric acid from sucrose

Background: Currently, the most promising microorganism used for the bio-production of butyric acid is Clostridium tyrobutyricum ATCC 25755(T); however, it is unable to use sucrose as a sole carbon source. Consequently, a newly isolated strain, Bacillus sp. SGP1, that was found to produce a levansucrase enzyme, which hydrolyzes sucrose into fructose and glucose, was used in a co-culture with this strain, permitting C. tyrobutyricum ATCC 25755(T) to ferment sucrose to butyric acid. Results: B. sp. SGP1 alone did not show any butyric acid production and the main metabolite produced was lactic acid. This allowed C. tyrobutyricum ATCC 25755(T) to utilize the monosaccharides resulting from the activity of levansucrase together with the lactic acid produced by B. sp. SGP1 to generate butyric acid, which was the main fermentative product within the co-culture. Furthermore, the final acetic acid concentration in the co-culture was significantly lower when compared with pure C. tyrobutyricum ATCC 25755(T) cultures grown on glucose. In fed-batch fermentations, the optimum conditions for the production of butyric acid were around pH 5.50 and a temperature of 37 degrees C. Under these conditions, the final butyrate concentration was 34.2 +/- 1.8 g/L with yields of 0.35 +/- 0.03 g (butyrate)/g (sucrose) and maximum productivity of 0.3 +/- 0.04 g/L/h. Conclusions: Using this co-culture, sucrose can be utilized as a carbon source for butyric acid production at a relatively high yield. In addition, this co-culture offers also the benefit of a greater selectivity, with butyric acid constituting 92.8% of the acids when the fermentation was terminated.open2

Comment on "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581"

This document is the Accepted Manuscript Version of the following article: Guillem Anglada-Escude and Mikko Tuomi, 'Comment on "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581"', Science, Vol 347 (6226), 2015, the final, published version is available online at doi: 10.1126/science.1260796. © 2015 The American Association for the Advancement of Science. All rights reserved.Robertson et al. (Reports, 25 July 2014, p. 440) claimed that activity-induced variability is responsible for the Doppler signal of the proposed planet candidate GJ 581d. We point out that their analysis using periodograms of residual data is inappropriate and promotes inadequate tools. Because the claim challenges the viability of the method to detect exo-Earths, we encourage reanalysis and a deliberation on what the field-standard methods should be.Peer reviewedFinal Accepted Versio

Exploring islands of stability in the design space of cylindrical shell structures

<p><b>Fed-batch fermentation of glucose by <i>R</i>. <i>ornithinolytica</i> B6 with an agitation speed of 200 rpm;</b> (a) without pH control; (b) with pH maintained at 7.0; (c), pH controlled at 5.5 after pH dropped to 5.5 from the initial pH of 7.0.; ■, glucose; □, growth; ♢, ethanol; ●, acetoin; ○, 2,3-BD; ♦, acetic acid; ▲, succinic acid; △, lactic acid; +, butyric acid.</p

Perspectives for biocatalytic lignin utilization: cleaving 4-O-5 and C??-C?? bonds in dimeric lignin model compounds catalyzed by a promiscuous activity of tyrosinase

Background: In the biorefinery utilizing lignocellulosic biomasses, lignin decomposition to value-added phenolic derivatives is a key issue, and recently biocatalytic delignification is emerging owing to its superior selectivity, low energy consumption, and unparalleled sustainability. However, besides heme-containing peroxidases and laccases, information about lignolytic biocatalysts is still limited till date. Results: Herein, we report a promiscuous activity of tyrosinase which is closely associated with delignification requiring high redox potentials (&gt;1.4 V vs. normal hydrogen electrode [NHE]). The promiscuous activity of tyrosinase not only oxidizes veratryl alcohol, a commonly used nonphenolic substrate for assaying ligninolytic activity, to veratraldehyde but also cleaves the 4-O-5 and C??-C?? bonds in 4-phenoxyphenol and guaiacyl glycerol-??-guaiacyl ether (GGE) that are dimeric lignin model compounds. Cyclic voltammograms additionally verified that the promiscuous activity oxidizes lignin-related high redox potential substrates. Conclusion These results might be applicable for extending the versatility of tyrosinase toward biocatalytic delignification as well as suggesting a new perspective for sustainable lignin utilization. Furthermore, the results provide insight for exploring the previously unknown promiscuous activities of biocatalysts much more diverse than ever thought before, thereby innovatively expanding the applicable area of biocatalysis

Succinate production from CO2-grown microalgal biomass as carbon source using engineered Corynebacterium glutamicum through consolidated bioprocessing

The potential for production of chemicals from microalgal biomass has been considered as an alternative route for CO2 mitigation and establishment of biorefineries. This study presents the development of consolidated bioprocessing for succinate production from microalgal biomass using engineered Corynebacterium glutamicum. Starch-degrading and succinate-producing C. glutamicum strains produced succinate (0.16 g succinate/g total carbon source) from a mixture of starch and glucose as a model microalgal biomass. Subsequently, the engineered C. glutamicum strains were able to produce succinate (0.28 g succinate/g of total sugars including starch) from pretreated microalgal biomass of CO2-grown Chlamydomonas reinhardtii. For the first time, this work shows succinate production from CO2 via sequential fermentations of CO2-grown microalgae and engineered C. glutamicum. Therefore, consolidated bioprocessing based on microalgal biomass could be useful to promote variety of biorefineries

Novel NAD-independent D-lactate dehydrogenases from Acetobacter aceti and Acidocella species MX-AZ02 as potential candidates for in vitro biocatalytic pyruvate production

Pyruvate is a significant platform chemical widely used in the agrochemical and pharmaceutical industries. We discovered FAD-containing lactate dehydrogenases (LDHs) from Acetobacter aceti (Aa-LDH) and Acidocella species MX-AZ02 (As-LDH), expressed them in Escherichia coil, optimized their FAD reconstitution, and characterized the recombinants as NAD-independent D-LDHs that are capable of the in vitro biocatalytic production of pyruvate from lactate. Instead of NAD, both Aa-LDH and As-LDH utilized various organic dyes as the electron acceptor. In addition, Aa-LDH and As-LDH exhibited substrate specificity for D-lactate only. Activity was optimized at pH 7.0 and 65 degrees C. The kinetic parameters of Aa-LDH and As-LDH were examined and both enzymes exhibited higher catalytic efficiency (k(cat)/K-m) for 2,6-dichlorophenolindophenol (DCIP), one of the electron acceptors, than D-lactate due to higher binding affinities. When using 10 mM D-lactate as the substrate with stepwise DCIP and D-LDH feeding, Aa-LDH and As-LDH produced 5.48 and 4.09 mM pyruvate, respectively, and the conversion was proportional to the DCIP concentration.clos

Asticcacaulis solisilvae sp nov., isolated from forest soil

An obligately aerobic, chemoheterotrophic, mesophilic prosthecate bacterium, designated strain CGM1-3EN(T), was isolated from the enrichment cultures of forest soil from Cheonggyesan Mountain, Republic of Korea. Cells were Gram-reaction-negative, motile rods (1.3-2.4 mu m long by 0.30-0.75 mu m wide) with single flagella. The strain grew at 10-37 degrees C (optimum 25-30 degrees C) and at pH 4.5-9.5 (optimum 5.0-7.0). The major cellular fatty acids were C-16:0, C-18:1 omega 7c 11-methyl, C-12:1 3-OH and summed feature 8 (comprising C-18:1 omega 7c/C-18:1 omega 6c). The genomic DNA G + C content of strain CGM1-3EN(T) was 63.7 mol%. The closest phylogenetic neighbour to strain CGM1-3EN(T) was identified as Asticcacaulis biprosthecium DSM 4723(T) (97.2 % 16S rRNA gene sequence similarity) and the DNA-DNA hybridization value between strain CGM1-3EN(T) and A. biprosthecium DSM 4723(T) was less than 24.5 %. Strain CGM1-3EN(T) used D-glucose, D-fructose, sucrose, maltose, trehalose, D-mannose, D-mannitol, D-sorbitol, D-galactose, cellobiose, lactose, raffinose, fumarate, pyruvate, DL-alanine and glycerol as carbon sources. Based on data from the present polyphasic study, the forest soil isolate CGM1-3EN(T) is considered to represent a novel species of the genus Asticcacaulis, for which the name Asticcacaulis solisilvae sp. nov. is proposed. The type strain is CGM1-3EN(T) (=AIM0088(T)=KCTC 32102(T)=JCM 18544(T)).OAIID:oai:osos.snu.ac.kr:snu2013-01/102/0000002410/17SEQ:17PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:0000002410ADJUST_YN:YEMP_ID:A002014DEPT_CD:458CITE_RATE:2.112DEPT_NM:화학생물공학부SCOPUS_YN:YCONFIRM: