Syntrophomonas zehnderi sp. nov., an anaerobe that degrades long-chain fatty acids in co-culture with Methanobacterium formicicum

An anaerobic, mesophilic, syntrophic fatty-acid-oxidizing bacterium, designated strain OL-4T, was isolated as a co-culture with Methanobacterium formicicum DSM 1535NT from an anaerobic expanded granular sludge bed reactor used to treat an oleate-based effluent. Strain OL-4T degraded oleate, a mono-unsaturated fatty acid, and straight-chain fatty acids C4 : 0–C18 : 0 in syntrophic association with Methanobacterium formicicum DSM 1535NT. Even-numbered fatty acids were degraded to acetate and methane whereas odd-numbered fatty acids were degraded to acetate, propionate and methane. Branched-chain fatty acids were not degraded. The bacterium could not grow axenically with any other substrate tested and therefore is considered to be obligately syntrophic. Fumarate, sulfate, thiosulfate, sulfur and nitrate could not serve as electron acceptors for strain OL-4T to degrade oleate or butyrate. Cells of strain OL-4T were curved rods, formed spores and showed a variable response to Gram staining. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain OL-4T was most closely related to the fatty-acid-oxidizing, syntrophic bacterium Syntrophomonas sp. TB-6 (95% similarity), Syntrophomonas wolfei subsp. wolfei DSM 2245T (94% similarity) and Syntrophomonas erecta DSM 16215T (93% similarity). In addition to this moderate similarity, phenotypic and physiological characteristics, such as obligate syntrophy, spore formation and utilization of a broader substrate range, differentiated strain OL-4T from these Syntrophomonas species. Therefore strain OL-4T represents a novel species, for which the name yntrophomonas zehnderi sp. nov. is proposed. The type strain is OL-4T (=DSM 17840T=JCM 13948T).Fundação para a Ciência e a Tecnologia (FCT)( Fundo Social Europeu (FSE); Wageningen Institute for Environmental and Climate Research (WIMEK)

Perspectives on carbon materials as powerful catalysts in continuous anaerobic bioreactors

Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.watres.2016.06.004.The catalytic effect of commercial microporous activated carbon (AC) and macroporous carbon nanotubes (CNT) is investigated in reductive bioreactions in continuous high rate anaerobic reactors, using the azo dye Acid Orange 10 (AO10) as model compound as electron acceptor and a mixture of VFA as electron donor. Size and concentration of carbon materials (CM) and hydraulic retention time (HRT) are assessed. CM increased the biological reduction rate of AO10, resulting in significantly higher colour removal, as compared to the control reactors. The highest efficiency, 98%, was achieved with a CNT diameter (d) lower than 0.25 mm, at a CNT concentration of 0.12 g per g of volatile solids (VS), a HRT of 10 h and resulted in a chemical oxygen demand (COD) removal of 85%. Reducing the HRT to 5 h, colour and COD removal in CM-mediated bioreactors were above 90% and 80%, respectively. In the control reactor, thought similar COD removal was achieved, AO10 decolourisation was just approximately 20%, demonstrating the ability of CM to significantly accelerate the reduction reactions in continuous bioreactors. AO10 reduction to the correspondent aromatic amines was proved by high performance liquid chromatography (HPLC). Colour decrease in the reactor treating a real effluent with CNT was the double comparatively to the reactor operated without CNT. The presence of AC in the reactor did not affect the microbial diversity, as compared to the control reactor, evidencing that the efficient reduction of AO10 was mainly due to AC rather than attributed to changes in the composition of the microbial communities.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01- 0145-FEDER-006684). Raquel Pereira had a fellowship (SFRH/BD/ 72388/2010) and Luciana Pereira has the fellowship (SFRH/BPD/ 110235/2015) from FCT. The authors thank the FCT exploratory EXPL/AAG-TEC/0898/2013 project

Waste lipids to energy: how to optimize methane production from long-chain fatty acids (LCFA)

The position of high-rate anaerobic technology (HR-AnWT) in the wastewater treatment and bioenergy market can be enhanced if the range of suitable substrates is expanded. Analyzing existing technologies, applications and problems, it is clear that, until now, wastewaters with high lipids content are not effectively treated by HR-AnWT. Nevertheless, waste lipids are ideal potential substrates for biogas production, since theoretically more methane can be produced, when compared with proteins or carbohydrates. In this minireview, the classical problems of lipids methanization in anaerobic processes are discussed and new concepts to enhance lipids degradation are presented. Reactors operation, feeding strategies and prospects of technological developments for wastewater treatment are discussed. Long-chain fatty acids (LCFA) degradation is accomplished by syntrophic communities of anaerobic bacteria and methanogenic archaea. For optimal performance these syntrophic communities need to be clustered in compact aggregates, which is often difficult to achieve with wastewaters that contain fats and lipids. Driving the methane production from lipids/LCFA at industrial scale without risk of overloading and inhibition is still a challenge that has the potential for filling a gap in the existing processes and technologies for biological methane production associated to waste and wastewater treatment.Fundação para a Ciência e a Tecnologia (FCT) - project FAT-METHANE (POCTI/CTA/46328/2002), grants PRAXIS XXI/BD/20326/99, SFRH/BPD/14591/2003, SFRH/BD/24256/2005Instituto Nacional da Propriedade Industrial (INPI)Netherlands Science FoundationLettinga Associates Foundatio

Ecophysiology of syntrophic communities that degrade saturated and unsaturated long-chain fatty acids

Syntrophic relationships are the key for biodegradation in methanogenic environments. We review the ecological and physiological features of syntrophic communities involved in the degradation of saturated and unsaturated long-chain fatty acids (LCFA), as well as their potential application to convert lipids/fats containing waste to biogas. Presently, about 14 species have been described with the ability to grow on fatty acids in syntrophy with methanogens, all belonging to the families Syntrophomonadaceae and Syntrophaceae. The principle pathway of LCFA degradation is through β-oxidation, but the initial steps in the conversion of unsaturated LCFA are unclear. Communities enriched on unsaturated LCFA also degrade saturated LCFA, but the opposite generally is not the case. For efficient methane formation, the physical and inhibitory effects of LCFA on methanogenesis need to be considered. LCFA adsorbs strongly to biomass, which causes encapsulation of active syntrophic communities and hampers diffusion of substrate and products in and out of the biomass. Quantification of archaea by real-time PCR analysis suggests that potential LCFA inhibitory effect towards methanogens might be reversible. Rather, the conversion of adsorbed LCFA in batch assays was shown to result in a significant increase of archaeal cell numbers in anaerobic sludge samples.The authors thank J. Prosser for the invitation to write this minireview. We appreciated the critical reading of I.M. Head and of the anonymous reviewers, and we thank them for their constructive comments and suggestions. This work was possible through the financial support provided by the Portuguese Science Foundation (FCT) and European Social Fund (ESF) (grant SFRH/BD/8726/2002), and by the Wageningen Institute for Environmental and Climate Research (WIMEK)

Pathways and bioenergetics of anaerobic carbon monoxide fermentation

Carbon monoxide can act as a substrate for different modes of fermentative anaerobic metabolism. The trait of utilizing CO is spread among a diverse group of microorganisms, including members of bacteria as well as archaea. Over the last decade this metabolism has gained interest due to the potential of converting CO-rich gas, such as synthesis gas, into bio-based products. Three main types of fermentative CO metabolism can be distinguished: hydrogenogenesis, methanogenesis, and acetogenesis, generating hydrogen, methane and acetate, respectively. Here, we review the current knowledge on these three variants of microbial CO metabolism with an emphasis on the potential enzymatic routes and bio-energetics involved.The authors involved were financially supported by an ERC grant (project 323009) and the Gravitation grant (project 024.002.002) of the Netherlands Ministry of Education, Culture and Science and the Netherlands Science Foundation (NWO)

Escherichia coli mutants with a temperature-sensitive alcohol dehydrogenase

Mutants of Escherichia coli resistant to allyl alcohol were selected. Such mutants were found to lack alcohol dehydrogenase. In addition, mutants with temperature-sensitive alcohol dehydrogenase activity were obtained. These mutations, designated adhE, are all located at the previously described adh regulatory locus. Most adhE mutants were also defective in acetaldehyde dehydrogenase activity.</jats:p

VOLUME SIX Integrating Statistics with a Microbiology Laboratory Activity

Statistics is an important tool for microbiologists but is virtually absent from undergraduate laboratory activities. The variables in a stringent protocol, the antibiotic disk diffusion assay described by the National Committee for Clinical Laboratory Standards, were examined by the authors as a means for introducing hypothesis testing and the application of elementary statistical tools. After several experiments, a lab activity was developed where students examine the effect of cell concentration on antibiotic activity and analyze data with the t test. They also collect data independently from the same samples and compare their measurements using analysis of variance (ANOVA). The outcome of the activity, including an assessment tool, indicated that students learned the appropriate use of the t test and ANOVA, gained an appreciation for standardized protocols, and enjoyed the experience. Statistics is an important tool for microbiology. Statistical tools are used to collect, organize, analyze, and interpret numerical data. Descriptive statistics allow investigators to summarize large amounts of data to more understandable levels using numerical descriptors (e.g., mean, mode, median, or standard deviation) or graphical methods. Inferential statistics allow investigators to make generalizations an