Interactions between rumen amylolytic and lactate-utilizing bacteria in growth on starch

The growth and metabolism of the rumen amylolytic bacteria Streptococcus bovis, Butyrivibrio fibrisolvens and Bacteroides ruminicola , growing in pure cultures and co-cultures with the rumen lactilytic bacteria Megasphera elsdenii and Veillonella alcalescens were followed. The interaction of amylolytic bacteria with V. alcalescens represents a simple food chain. The interaction with M. elsdenii is more complex, since there is a simultaneous competition for products of the starch degradation.     

Effect of pH on growth rates of rumen amylolytic and lactilytic bacteria.

The relationship between the pH of the medium and specific growth rates, in well-buffered media at 38.5 degrees C, was determined for three strains of Butyrivibrio fibrisolvens and for one strain each of Streptococcus bovis, Selenomonas ruminantium subsp. lactilytica. Megasphaera elsdenii, Veillonella alcalescens, and Propionibacterium acnes. The pH optima for growth were between 6.1 and 6.6 for all six species, and the upper pH limits were between 7.3 and 7.8. The lower limit pH values for growth on glucose were 5.4 for B. fibrisolvens, near 5.0 for V. alcalescens, and between 4.4 and 4.8 for the other four species. These values fall within the minimum pH ranges found when these species are grown in poorly buffered medium with nonlimiting glucose concentrations. Acid sensitivity per se could cause the washout of B. fibrisolvens, but not of the other five species, from the rumens of animals on high-starch diets.     

Stoichiometry of glucose and starch splitting by strains of amylolytic bacteria from the rumen and anaerobic digester

The stoichiometry of glucose and starch splitting by the amylolytic bacteria Streptococcus bovis, Selenomonas ruminantium, Butyrivibrio fibrisolvens, Eubacterium ruminantium and Clostridium sp. was followed. There were many differences in the ratios of metabolites and in growth yields, as well as in the cell composition, between the growth on glucose and starch. The bacteria employ different nutritional strategies with respect to both energy sources.     

Stoichiometry of glucose and starch splitting by strains of amylolytic bacteria from the rumen and anaerobic digester

The stoichiometry of glucose and starch splitting by the amylolytic bacteria Streptococcus bovis, Selenomonas ruminantium, Butyrivibrio fibrisolvens, Eubacterium ruminantium and Clostridium sp. was followed. There were many differences in the ratios of metabolites and in growth yields, as well as in the cell composition, between the growth on glucose and starch. The bacteria employ different nutritional strategies with respect to both energy sources.     

Interactions between rumen bacteria and ciliate protozoa in their attachment to barley straw

The attachment of ¹⁴C-choline-labelled mixed rumen protozoa to barley straw in vitro was not significantly affected when bacteria prepared from rumen fluid were added to the incubation mixture. There was similarly little effect on protozoal attachment when the straw had already been colonized by a bacterial population for 24 h. In contrast, it was deduced from measurements of enzyme activities associated with straw that bacterial attachment was reduced if protozoa were present. Bacteria that had colonized the straw for 25 h beforehand were less susceptible to predation by protozoa.     

Batch fermentations on synthetic mixed sugar and starch medium with amylolytic lactic acid bacteria

The green crop drying industry in Denmark uses Italian rye grass, clover, and alfalfa as raw materials for the production of green pellets. The green crop drying industry solves its energy economical problems by heating and pressing of the green crop before drying. The produced sidestream is called brown juice. Brown juice was shown to be an excellent medium for lactic acid fermentation. The aim of this study was to investigate the utilisation of brown juice in the production of polylactic acid, where wheat starch would be added to increase the lactic acid yield and, thus, the feasibility of the process. A number of amylolytic lactic acid bacteria have been identified, and in this work, six different strains were tested for their ability to produce α-amylase and to utilise all sugars with high lactic acid yield in a medium with a complex composition of free sugars (brown juice) and starch. Lactobacillus plantarum A6 was the only strain that showed both a good lactic acid production and utilisation of starch in this medium. The growth rate of this strain was approximately 0.4 h⁻¹ and the lactic acid yield was 0.7.     

Different restriction and modification phenotypes in ruminal lactate-utilizing bacteria

Analysis of restriction and modification activities in lactate-utilizing bacteria belonging to the Megasphaera elsdenii and Mitsuokella multiacida species revealed the presence of GATC-specific, MboI isospecific, restriction-modification (R-M) systems in all strains tested. While restriction endonucleases isolated from M. elsdenii strains were found to be sensitive to Dam methylation, enzymes from M. multiacida cleaved DNA irrespective of Dam methylation. The comparison of type II R-M systems specificities in three closely related lactate-utilizing ruminal bacterial species indicated complete lack of restriction and/or modification enzymes previously characterized from Selenomonas ruminantium in tested M. elsdenii and M. multiacida strains. R-M systems are believed to represent the main defense tool against phage infection. Based on the results of our experiments it could be assumed that M. elsdenii and M. multiacida use the different strategy for bacteriophage protection compared to S. ruminantium.     

Genetic transfer of lactate-utilizing ability in the rumen bacterium Selenomonas ruminantium

M. GILMOUR, W.J. MITCHELL AND H.J. FLINT. 1996. Matings between the lactate-utilizing, tetracycline-sensitive Selenomonas ruminantium strains 5521Cl and 5934e and the lactate-non-utilizing, tetracycline-resistant strain FB322 resulted in putative recombinant strains capable of growth on lactate. Analysis of total protein by SDS-PAGE and chromosomal DNA by hybridization, indicated that the recombinants were derived from strain FB322. DNA hybridization produced no evidence that plasmid transfer occurred, leaving chromosomal DNA transfer as the most likely mechanism for the altered phenotype. Analysis of strains 5934e, FB322 and the resulting recombinant TC3 indicated that all three strains contained D-nLDH and L-nLDH activities. In addition strains 5934e and TC3 possessed D-iLDH activity when grown on DL-lactate. The ability of strain FB322 to grow on pyruvate but not lactate suggested that the lactate-utilizing recombinant had acquired the ability to synthesize D-iLDH.     

一株瘤胃源乳酸利用菌的分离鉴定及其体外代谢特性

【目的】从饲喂高精料的本地山羊瘤胃内分离到一株利用乳酸并能产生大量丙酸的菌株L9,并进一步研究了该菌在调控瘤胃微生物发酵中的作用。【方法】采用厌氧培养技术,结合形态、生理生化特性和16SrRNA基因序列分析结果。【结果】该菌株被鉴定为反刍兽新月形单胞菌（Selenomonas ruminantium）。该菌株体外代谢特性研究表明,L9可利用乳酸作为唯一碳源,该菌在24h内可对90mmol／L的乳酸完全降解。体外摸拟瘤胃急性酸中毒的发酵试验结果表明,以淀粉为底物时,与对照组相比,添加菌株L9可显著降低瘤胃微生物体外培养体系中乳酸浓度,提高pH值,提高总挥发性脂肪酸和丙酸浓度,并显著降低乙酸与丙酸的浓度比（P〈0．05）。【结论】结果显示,菌株L9是一株可代谢乳酸,促进丙酸生成,提高总挥发性脂肪酸浓度的有益瘤胃细菌。     

Interactions between amino-acid-degrading bacteria and methanogenic bacteria in anaerobic digestion

The degradation of amino acids in anaerobic digestion was examined in terms of the interactions between amino-acid-degrading bacteria and methanogenic bacteria. Certain amino acids were degraded oxidatively by dehydrogenation, with methanogenic bacteria acting as H(2) acceptors. The inhibition of methanogenesis by chloroform also inhibited the degradation of these amino acids and/or caused variations in the composition of volatile acids produced from them. The presence of glycine reduced the inhibitory effect caused by chloroform, probably because glycine acted as an H(2) acceptor in place of methanogenic bacteria. This fact suggested that the coupled oxidation-reduction reactions between two amino acids-one acting as the H(2) donor and the other acting as the H(2) acceptor-may occur in the anaerobic digestion of proteins or amino-acid mixtures. The conversion of some proteins to volatile acids was not affected when methanogenesis was inhibited by chloroform. This suggested that the component amino acids of proteins may be degraded by the coupled oxidation-reduction reactions and that the degradation of proteins may not be dependent on the activity of methanogenic bacteria as H(2) acceptors.     

Effect of fatty acids on growth of conjugated-linoleic-acids-producing bacteria in rumen

Microorganisms with high activity of linoleic acid delta12-cis,delta11-trans-isomerase were isolated from the digestive tract of ruminants and characterized. The isolate with the highest isomerase activity was identified as Pseudobutyrivibrio ruminis. The susceptibility of this strain to 3 fatty acids added to the grow medium was determined. A significant inhibition of bacterial growth (during a 3-d period) by linoleic acid (0.1 %) and oleic acid (5 ppm) was observed; no inhibition was found in the presence of stearic acid.     

New amylolytic yeast strains for starch and dextrin fermentation

Yeast strains capable of fermenting starch and dextrin to ethanol were isolated from samples collected from Brazilian factories in which cassava flour is produced. Considerable alcohol production was observed for all the strains selected. One strain (DI-10) fermented starch rapidly and secreted 5 times as much amylolytic enzyme than that observed for Schwanniomyces alluvius UCD 54-83. This strain and three other similar isolates were classified as Saccharomyces cerevisiae var. diastaticus by morphological and physiological characteristics and molecular taxonomy.