Taxonomy of obligately homofermentative and facultatively heterofermentative lactobacilli in pig faeces

AIMS: Identification and characterization of obligately homofermentative and facultatively heterofermentative strains of Lactobacillus spp. isolated from the faeces of pigs that had been raised under different conditions. METHODS AND RESULTS: The phenotypic relatedness of the isolated strains and reference strains were determined by numerical analysis of total soluble cell protein patterns and simple physiological and biochemical tests. Of the 23 strains isolated from faeces, nine were obligately homofermentative and 14 facultatively heterofermentative. The strains clustered at r > or = 0.61 with Lactobacillus amylovorus (seven strains), Lactobacillus crispatus (one strain), Lactobacillus plantarum (14 strains) and Lactobacillus intestinalis (one strain). CONCLUSIONS: Results obtained from the physiological and biochemical tests confirmed the identity of the isolates as determined by numerical analysis of total soluble cell protein profiles. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the association of Lact. crispatus and Lact. intestinalis with the gastro-intestinal tract of pigs.     

Citrate utilization by homo- and heterofermentative lactobacilli

Citrate utilization by several homo- and heterofermentative lactobacilli was determined in Kempler and McKay and in calcium citrate media. The last medium with glucose permitted best to distinguish citrate-fermenting lactobacilli. Lactobacillus rhamnosus ATCC 11443, Lactobacillus zeae ATCC 15820 and Lactobacillus plantarum ATCC 8014 used citrate as sole energy source, whereas in the other strains, glucose and citrate were cometabolized. Some lactobacilli strains produced aroma compounds from citrate. Citrate transport experiments suggested that all strains studied presented a citrate transport system inducible by citrate. The levels of induction were variable between several strains. Dot blot experiment showed that lactobacilli do not present an equivalent plasmid coding for citrate permease.     

Homo- and heterofermentative lactobacilli differently affect sugarcane-based fuel ethanol fermentation

Bacterial contamination during industrial yeast fermentation has serious economic consequences for fuel ethanol producers. In addition to deviating carbon away from ethanol formation, bacterial cells and their metabolites often have a detrimental effect on yeast fermentative performance. The bacterial contaminants are commonly lactic acid bacteria (LAB), comprising both homo- and heterofermentative strains. We have studied the effects of these two different types of bacteria upon yeast fermentative performance, particularly in connection with sugarcane-based fuel ethanol fermentation process. Homofermentative Lactobacillus plantarum was found to be more detrimental to an industrial yeast strain (Saccharomyces cerevisiae CAT-1), when compared with heterofermentative Lactobacillus fermentum, in terms of reduced yeast viability and ethanol formation, presumably due to the higher titres of lactic acid in the growth medium. These effects were only noticed when bacteria and yeast were inoculated in equal cell numbers. However, when simulating industrial fuel ethanol conditions, as conducted in Brazil where high yeast cell densities and short fermentation time prevail, the heterofermentative strain was more deleterious than the homofermentative type, causing lower ethanol yield and out competing yeast cells during cell recycle. Yeast overproduction of glycerol was noticed only in the presence of the heterofermentative bacterium. Since the heterofermentative bacterium was shown to be more deleterious to yeast cells than the homofermentative strain, we believe our findings could stimulate the search for more strain-specific antimicrobial agents to treat bacterial contaminations during industrial ethanol fermentation.     

Identification of heterofermentative lactobacilli isolated from pig faeces by numerical analysis of total soluble cell protein patterns and RAPD-PCR

AIMS: The study deals with a number of heterofermentative Lactobacillus strains isolated from pig faeces and their identification. METHODS AND RESULTS: SDS-PAGE of total soluble cell proteins and RAPD-PCR profiles were used to identify the strains isolated from pig faeces. Protein profiles obtained with SDS-PAGE revealed that 15 strains clustered at r >or= 0.78 with Lactobacillus buchneri and nine strains at r >or= 0.77 with two reference strains of Lactobacillus reuteri. The identity of the strains was confirmed with RAPD-PCR. CONCLUSIONS: Numerical analysis of protein profiles and RAPD-PCR proved valuable in the differentiation of Lactobacillus spp. isolated from pig faeces. SIGNIFICANCE: This is the first report on the association of Lact. buchneri with pig faeces.     

Esterase activities of cell-free extracts from 'wild' strains of leuconostocs and heterofermentative lactobacilli isolated from traditional Greek cheese

Cell-free extracts from strains of leuconostocs and heterofermentative lactobacilli were tested for esterase activities using synthetic substrates. Results showed that esterases from both lactic acid bacteria groups preferentially degraded short-chain fatty acids. Moreover, even though some similarities between strains of the same species were recorded, the observed differences were not strong enough to distinguish between species and therefore commend this technique as a tool for taxonomy of either leuconostocs or heterofermentative lactobacilli.     

Development and potential of starter lactobacilli resulting from exploration of the sourdough ecosystem

Lactic acid bacteria are widely used as starter organisms in food fermentations. The development of such cultures as organisms fulfilling all metabolic, technical and handling requirements is the result of a multidisciplinary approach, i.e. to analyse, follow and direct the microbial ecology in food fermentations by molecular biology tools, gene cloning, biochemical and physiological analyses, pilot trials and modelling of behaviour and metabolism. The possibilities and restrictions of such an approach is given for cereal fermentations, namely sourdoughs. In this environment highly adapted lactobacilli are predominant, sharing the environment with yeasts present in traditional preparations. The competitiveness of these lactobacilli and their contribution to flavour, machineability and prebiosis of doughs and bread relies on their maltose and amino acid metabolism, use of electron acceptors and EPS formation. Their reactions on environmental stresses can be used to embed these recalcitrant organisms into starter culture preparations. Beyond the cereal environment the described strategy can be generally applied to understand ecosystems in food fermentations and finally control them. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nucleic acid studies on some heterofermentative lactobacilli: Description of Lactobacillus malefermentans sp.nov. and Lactobacillus parabuchneri sp.nov.

Chemotaxonomic studies were performed on some heterofermentative lactobacilli of uncertain taxonomic position. Two strains from beer and six strains from a variety of habitats were found to be distinct from each other and all other Lactobacillus species examined on the basis of DNA-DNA hybridizations and warrant new species for which the names L. malefermentans and L. parabuchneri , respectively, are proposed.     

Growth effects and metabolism of arginine in stationary and rapidly-dividing sugarcane cell suspensions

The effect of 300 μ M arginine on growth of sugarcane cell suspensions was studied. Cells transferred to defined media in the stationary growth stage showed a greater requirement for exogenous arginine than cells similarly transferred in the rapidly dividing stage. Cell arginine levels, rates of arginine synthesis, and enzymes of arginine synthesis all decreased in cells entering the stationary stage. It is concluded that stationary stage cells are deficient in their ability to synthesize arginine and are therefore dependent upon an exogenous supply to resume growth in fresh media.     

Growth and fine structure of monolayers derived from adult rat adenohypophyseal cell suspensions

Summary Primary monolayer cell cultures of trypsin-dispersed adult rat adenohypophyses are capable of synthetizing deoxyribonucleic acid and are able to divide at least for 3 weeks. Most cells contain secretory granules in the absence of hypothalamic extracts. It seems possible that granules are formed which mature and are released in vitro.     

Characterization of cell envelope-associated proteinases of thermophilic lactobacilli

D. FIRA, M. KOJIC, A. BANINA, I. SPASOJEVIC, I. STRAHINIC AND L. TOPISIROVIC. 2001 . The proteolytic activities of two natural isolates of thermophilic lactobacilli, Lactobacillus acidophilus BGRA43 and Lact. delbrueckii BGPF1, and Lact. acidophilus CH2 (Chr. Hansen's strain) and Lact. acidophilus V74 (Visby's strain), were compared. Results revealed that optimal pH for all four proteinases is 6·5, whereas temperature optimum varied among proteinases. Determination of caseinolytic activity done under optimal conditions for each strain revealed that the CH2 and V74 proteinases completely hydrolysed both α_S1-casein and β-casein, showing very low activity towards κ-casein. The BGPF1 proteinase completely hydrolysed only β-casein. The BGRA43 proteinase completely hydrolysed all three casein fractions. The proteolytic activities of whole cells were inhibited by serine proteinase inhibitors, suggesting that all four strains produce serine proteinases. DNA–DNA hybridization and PCR analysis showed that BGPF1 contains the prtB -like proteinase gene. Characterized thermophilic strains BGPF1 and BGRA43 were successfully used as starter cultures for production of yoghurt and acidophilus milk, respectively.     

Short-term radiorespirometry of cell suspensions

1. An apparatus and method are described with which the oxidation of labelled substrates to (14)CO(2) by cell suspensions may be examined. 2. The use of high-specific-radioactivity substrates at low concentration together with frequent quantitative collection of CO(2) permit a more detailed analysis of the appearance of various substrate carbon atoms as CO(2) than is possible by existing techniques. 3. Typical experiments with various cell types are reported, in which pathways of glucose oxidation are examined.     

Characterization of cell envelope-associated proteinases of thermophilic lactobacilli

The proteolytic activities of two natural isolates of thermophilic lactobacilli, Lactobacillus acidophilus BGRA43 and Lact. delbrueckii BGPF1, and Lact. acidophilus CH2 (Chr. Hansen's strain) and Lact. acidophilus V74 (Visby's strain), were compared. Results revealed that optimal pH for all four proteinases is 6.5, whereas temperature optimum varied among proteinases. Determination of caseinolytic activity done under optimal conditions for each strain revealed that the CH2 and V74 proteinases completely hydrolysed both alphaS1-casein and beta-casein, showing very low activity towards kappa-casein. The BGPF1 proteinase completely hydrolysed only beta-casein. The BGRA43 proteinase completely hydrolysed all three casein fractions. The proteolytic activities of whole cells were inhibited by serine proteinase inhibitors, suggesting that all four strains produce serine proteinases. DNA-DNA hybridization and PCR analysis showed that BGPF1 contains the prtB-like proteinase gene. Characterized thermophilic strains BGPF1 and BGRA43 were successfully used as starter cultures for production of yoghurt and acidophilus milk, respectively.