Effect of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part I: biofilm growth and activity

Two similar anaerobic fixed-bed bioreactors which allowed the biomass to be periodically withdrawn were run in parallel. After feeding each digester with synthetic dairy wastes of different lipid content (Period I), both digesters were fed with increasing sodium oleate concentrations with skim milk as co-substrate (Period II) and oleate as the sole carbon source (Period III). In Period I, the digester fed with lipids was more effcient and exhibited lower levels of volatile fatty acids than the digester fed without lipids. The biofilm built up in the presence of lipids was thinner, but more resistant to the presence of oleate than the biofilm formed in the absence of lipids, which lost 53% of its solids after contacting with oleic acid. The specific methanogenic activity with butyrate as substrate was enhanced in the presence of lipids, but no significant effect was detected on the acetoclastic and hydrogenophilic activities, which remained similar for both digesters along the trial period

Influence of lipid acclimatization on the oleic acid toxicity towards methanogenic acetoclastic bacteria

Instituto de Biotecnologia e Química Fina (IBQF)

Effects of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part II : oleic acid toxicity and biodegradability

Oleic acid toxicity and biodegradability were followed during long-term operation of two similar anaerobic fixed-bed units. When treating an oleate based effluent, the sludge from the bioreactor that was acclimated with lipids during the first operation period, showed a higher tolerance to oleic acid toxicity (IC50=137 mg/l) compared with the sludge fed with a non-fat substrate (IC50=80 mg/l). This sludge showed also the highest biodegradation capacity of oleic acid, achieving maximum methane production rates between 33 and 46 mlCH4_(STP)/gVS.day and maximum percentages of methanization between 85 and 98% for the range of concentrations between 500 and 900 mg oleate/l. When oleate was the sole carbon source fed to both digesters, the biomass became encapsulated with organic matter, possibly oleate or an intermediate of its degradation, e.g. stearate that was degraded at a maximum rate of 99 mlCH4_(STP)/gVS.day. This suggests the possibility of using adsorption-degradation cycles for the treatment of LCFA based effluents. Both tolerance to toxicity and biodegradability of oleic acid were improved by acclimatization with lipids or oleate below a threshold concentration

Influence of lipid acclimatization on the support matrix colonisation in anaerobic filters treating oleic acid

Instituto de Biotecnologia e Química Fina (IBQF)

Effect of lipids on biomass development in anaerobic fixed-bed reactors treating a synthetic dairy waste

The aim of this work was to follow the evolution in quantity and quality of the biomass developed during the operation of two anaerobic fixed bed reactors treating a synthetic dairy waste with different lipid contents. The feasibility of a special reactor design that allowed the biomass withdrawal with minimum operation disturbances was tested. The HRT was maintained at 1.5 days and the influent concentration was gradually increased from 3 to 12 g COD/l. Initially, one reactor was loaded with skim milk and the other one with whole milk, with equal organic loading rates (OLR). The effect of lipids was evaluated in terms of reactor performance, total, adhered and entrapped biomass and evolution of biomass quality determined in batch assays by: (i) measuring of potential specific methanogenic activity against direct (acetate, H2/CO2) and indirect (propionate and butyrate) substrates; (ii) measuring of the resistance of acetoclastic bacteria to the presence of sodium oleate. The lipids reduced the adhered fraction of biomass. The methanogenic activity against butyrate was enhanced in the presence of lipids, but no significant effect was detected on the other measured activities. The biomass taken from the reactor fed with lipids was more susceptible to the presence of sodium oleate, but, over the operation period, this susceptibility was reduced

A new method to study interactions between biomass and packing material in anaerobic filters

A new anaerobic, random-packed, fixed-bed reactor, where the fixed bed matrix is distributed between up to 36 independent mini-bioreactors, has been developed to investigate biomass-support interactions in anaerobic filters. Glass, Plexiglas and polyvinyl chloride (PVC) of three sizes all gave similar results though entrapped biomass was maximal at 3 g/L of matrix void volume for the smallest size and a maximum of 1 g adhered biomass per m2 was obtained for the largest size. In a second run, by periodically removing 3 mini-bioreactors, potential specific methanogenic activities against individual substrates were determined along the time and a continuous growth of the adhered biomass was observed, achieving a maximum of 40% of the total biomass.Comunidade Europeia - Human Capital and Mobility grant

Pescadores artesanais e seguro defeso: reflexões sobre processos de constituição de identidades numa comunidade ribeirinha da Amazônia.

O objetivo deste artigo é analisar a influência de um programa de política pública motivado por preocupações ambientais ? o seguro-defeso ? no processo de constituição de uma identidade coletiva associada ao uso de recursos comuns (estoques pesqueiros). A pesquisa foi realizada por meio de um estudo de caso numa comunidade ribeirinha do estado do Pará no período de 2010 a 2011. Os procedimentos foram observações e entrevistas (totalizando 33 com lideranças, afiliados e não afiliados ao seguro-defeso). As principais conclusões mostram: i) a complexidade da execução de um programa de política pública destinado a segmentos sociais que desenvolvem diversas atividades simultaneamente; ii) o jogo dos atores que, em função dos seus interesses, dão novos sentidos às regras oficiais; iii) a superposição de identidades ante a possibilidade de ter a sua sobrevivência facilitada; iv) controvérsias quanto às iniciativas de conservação dos recursos naturais

The role of bacteria in pine wilt disease: insights from microbiome analysis.

Pine Wilt Disease (PWD) has a significant impact on Eurasia pine forests. The microbiome of the nematode (the primary cause of the disease), its insect vector, and the host tree may be relevant for the disease mechanism. The aim of this study was to characterize these microbiomes, from three PWD-affected areas in Portugal, using Denaturing Gradient Gel Electrophoresis, 16S rRNA gene pyrosequencing, and a functional inference-based approach (PICRUSt). The bacterial community structure of the nematode was significantly different from the infected trees but closely related to the insect vector, supporting the hypothesis that the nematode microbiome might be in part inherited from the insect. Sampling location influenced mostly the tree microbiome (P < 0.05). Genes related both with plant growth promotion and phytopathogenicity were predicted for the tree microbiome. Xenobiotic degradation functions were predicted in the nematode and insect microbiomes. Phytotoxin biosynthesis was also predicted for the nematode microbiome, supporting the theory of a direct contribution of the microbiome to tree-wilting. This is the first study that simultaneously characterized the nematode, tree and insect-vector microbiomes from the same affected areas, and overall the results support the hypothesis that the PWD microbiome plays an important role in the disease's development

Accumulation of long chain fatty acids onto anaerobic sludge under steady state and shock loading conditions: effect on acetogenic and methanogenic activity

Accumulation of substrate onto the biomass was quantified under steady-state and shock conditions in a fixed bed reactor fed with an oleic acid-based synthetic effluent. The accumulation of substrate onto the sludge was more dependent on oleic acid concentration than on oleic acid loading rate and decreased the acetogenic, acetoclastic and hydrogenophilic activity. However, even when the methanogenic activity measurements indicate a severe inhibition, the anaerobic sludge was able to methanise efficiently the accumulated substrate that was mainly adsorbed LCFA. Methanogenic activity measurements for a sludge loaded with 2,861 mg COD/gVSS as LCFA, revealed that only hydrogenophilic activity was detetcted, whereas the methanogenic activities with acetate, propionate and butyrate as substrates were null. However the methanogenic activity of the same sludge after allowing the depletion of the adsorbed LCFA were significantly enhanced in the presence of all substrates, except in propionate. A discussion about the relative importance of metabolic inhibition and transport limitations for the anaerobic degradation of LCFA is launched.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/20326/99

A new device to select microcarriers for biomass immobilization : application to an anaerobic consortium

Instituto de Biotecnologia e Química Fina (IBQF)