Seasonal Variation on Microbial Community and Methane Production during Anaerobic Digestion of Cattle Manure in Brazil.

Anaerobic digestion is an alternative method for the treatment of animal manure and wastewater. The anaerobic bioconversion of biomass requires a multi-step biological process, including microorganisms with distinct roles. The diversity and composition of microbial structure in pilot-scale anaerobic digestion operating at ambient temperature in Brazil were studied. Influence of the seasonal and temporal patterns on bacterial and archaeal communities were assessed by studying the variations in density, dynamic and diversity and structure. The average daily biogas produced in the summer and winter months was 18.7 and 16 L day(-1), respectively, and there was no difference in the average methane yield. Quantitative PCR analysis revealed that no differences in abundances and dynamics were found for bacterial communities and the total number of Archaea in different seasons. Analysis of bacterial clone libraries revealed a predominance of Firmicutes (54.5 %/summer and 46.7 %/winter) and Bacteroidetes (31.4 %/summer and 44.4 %/winter). Within the Archaea, the phylum Euryarchaeota was predominant in both digesters. Phylogenetic distribution showed changes in percentage between the phyla identified, but no alterations were recorded in the quality and amount of produced methane or community dynamics. The results may suggest that redundancy of microbial groups may have occurred, pointing to a more complex microbial community in the ecosystem related to this ambient temperature system.

Characterization of rumen bacterial strains isolated from enrichments of rumen content in the presence of propolis.

Propolis presents many biological properties, including antibacterial activities, and has been proposed as an additive in ruminant nutrition. Twenty bacterial strains, previously isolated from enrichments of Brazilian cow rumen contents in the presence of different propolis extracts (LLOS), were characterized using phenotyping and 16S rRNA identification. Seven strains were assigned to Streptococcus sp., most likely S. bovis, and were all degrading starch. One amylolytic lactate-utilizing strain of Selenomonas ruminantium was also found. Two strains of Clostridium bifermentans were identified and showed proteolytic activity. Two strains were assigned to Mitsuokella jalaludinii and were saccharolytic. One strain belonged to a Bacillus species and seven strains were affiliated with Escherichia coli. All of the 20 strains were able to use many sugars, but none of them were able to degrade the polysaccharides carboxymethylcellulose and xylans. The effect of three propolis extracts (LLOS B1, C1 and C3) was tested on the in vitro growth of four representative isolates of S. bovis, E. coli, M. jalaludinii and C. bifermentans. The growth of S. bovis, E. coli and M. jalaludinii was not affected by the three propolis extracts at 1 mg ml(-1). C. bifermentans growth was completely inhibited at this LLOS concentration, but this bacterium was partially resistant at lower concentrations. LLOS C3, with the lower concentration of phenolic compounds, was a little less inhibitory than B1 and C1 on this strain.

Antimicrobial activity of Brazilian propolis extracts against rumen bacteria in vitro.

The antimicrobial activity of three Brazilian propolis extracts was evaluated on bacterial strains representing major rumen functional groups. The extracts were prepared using different concentrations of propolis and alcohol, resulting in different phenolic compositions. The propolis extracts inhibited the growth of Fibrobacter succinogenes S85, Ruminococcus flavefaciens FD-1, Ruminococcus albus 7, Butyrivibrio fibrisolvens D1, Prevotella albensis M384, Peptostreptococcus sp. D1, Clostridium aminophilum F and Streptococcus bovis Pearl11, while R. albus 20, Prevotella bryantii B14 and Ruminobacter amylophilus H18 were resistant to all the extracts. The inhibited strains showed also different sensitivity to propolis; the hyper-ammonia-producing bacteria (C. aminophilum F and Peptostreptococcus sp. D1) being the most sensitive. Inhibition of hyper-ammonia-producing bacteria by propolis would be beneficial to the animal. The extract containing the lowest amount of phenolic compounds (LLOS C3) showed the lowest antimicrobial activity against all the bacteria. The major phenolic compounds identified in the propolis extracts (naringenin, chrysin, caffeic acid, p-coumaric acid and Artepillin C) were also evaluated on four sensitive strains. Only naringenin showed inhibitory effect against all strains, suggesting that naringenin is one of the components participating to the antibacterial activity of propolis.

Efeito de diferentes doses de enxofre no consumo voluntário e nas populações de protozoários do rúmen de novilhas mestiças alimentadas com capim-elefante de baixa qualidade / Effect of different doses of sulfur on voluntary intake of low-quality elephant grass and estimates of ruminal protozoa populations in crossbred heifers

O experimento foi conduzido no Campo Experimental de Coronel Pacheco - MG da EMBRAPA Gado de Leite. O efeito de doses de enxofre (sulfato de amônio, 0,15; 0,31; 0,46 e 0,92 por cento de S na matéria verde / dia) na população de protozoários ruminais, foi avaliado utilizando-se quatro novilhas 7/8 Holandês X Zebu, arranjadas em um quadrado latino de 4 x 4. Forneceu-se diariamente capim-elefante de baixa qualidade (76,1 por cento FDN na MS), picado, com correção do teor de PB para 7 por cento com uréia, mais mistura mineral sem enxofre fornecida diretamente no rúmen. Foram feitas amostragens do conteúdo ruminal, uma hora após a alimentação. A estimativa das populações microbianas ruminais foi realizada por microscópica direta. Os resultados foram transformados para logaritmos decimais e avaliados estatisticamente. Não houve diferença significativa entre os tratamentos para microrganismos. O tratamento 0,92 por centoS apresentou o menor consumo de matéria seca e ainda, causou início de intoxicação em dois animais. De acordo com esses resultados, doses de 0,31 por cento de enxofre adicionadas a dieta promoveram o incremento das populações de microganismos ruminais e com isso um maior consumo voluntário.

The experiment was carried out in the Experimental Field of Coronel Pacheco belonging to EMBRAPA Dairy Cattle, Minas Gerais. The effects of the doses of sulfur (ammonium sulfate, 0.15 percent, 0.31 percent, 0.46 percent and 0.92 percentS fresh matter/day) on the ruminal protozoa population was evaluated by utilizing four 7/8 Holstein x Zebu, heifers arranged in 4 x 4 Latin square. Low quality elephant grass (76.1 percent NDF in DM) , chopped with correction of the CP content to 7 percent with urea plus a mineral mixture without sulfur given directly into the rumen. Samplings of the ruminal content were done, one hour after feeding. The estimate of the ruminal microbial populations was done by means of the direct microscopy. The results were transformed to decimal logarithm and evaluated statistically. There were no significant differences among the treatments for microorganisms. The 0.92 percentS treatment presented the least dry matter intake and, in addition, caused start of intoxication in two animals. According to those results, doses of 0.31 percent of sulfur added to the diet promoted the increase of the ruminal microorganism populations and hence a greater voluntary intake.