Fermentation patterns of forage sorghum ensiled under different environmental conditions

The effects of temperature, aerobic and anaerobic conditions in the silo and plant characteristics [water-soluble carbohydrate (WSC) contents, growing season] on the fermentation characteristics of a tropical forage species, Sorghum bicolor cv. sugar-drip, were investigated. Silages fermented in oxygen-impermeable bags were well preserved and had low pH (3.7), high lactic acid [72 g kg^–1 dry matter (DM) 80% of total acids], and low butyric acid (0.12 g kg^–1 DM) and ammonia nitrogen (NH₃–N) (57 g kg^–1 total nitrogen contents. Conversely, the use of oxygen-permeable bags as silos allowed aerobic decomposition of the ensiled forages. Increasing the incubation temperature lowered the population of lactic acid bacteria, reduced lactic acid production and caused the pH to rise. The heterofermentative Leuconostoc spp. predominated on fresh forages but homofermentative Lactobacillus plantarum began to dominate after 5 and 8 days of fermentation. Heterofermentative lactobacilli, notably Lactobacillus brevis, were dominant among the isolates obtained from 100-day silages. Varying the WSC contents, by crushing and/or chopping the forage, and growing season did not significantly affect the fermentation quality of the resulting silages. It was concluded that the maintenance of anaerobic conditions is essential if good quality silage is to be produced from tropical forage species.     

Characteristics of aerobic,solid substrate fermentation of swine waste-corn mixtures

Summary Aerobic fermentation of swine waste combined with corn produced differences in microbial and biochemical patterns dependent on use of fresh or stored excrement. Lactic acid fermentation and odor control resulted with either waste. Homofermentative lactic acid bacteria were present initially at 10⁷ organisms/dry g with stored waste-corn cultures and total microflora amounted to 10⁸ organisms/dry g. Fresh waste-corn fermentations initially yielded heterofermentative lactic acid bacteria at 10⁷ organisms/dry g and total viable population was 10⁹ organisms/dry g. These respective groups of lactic acid bacteria dominated from 12 through 144 h in cultures with either waste, and acid production (0.2 meq/dry g) decreased pH by 2 units to 4.5. The major acid component with stored waste-corn was lactic acid, whereas fresh waste-corn fermentation produced both lactic and homologous fatty acids from acetic through valeric acid. Coliform bacteria present initially at 10⁵ organisms/dry g in stored waste-corn cultures were not detected after 36 h; coliform bacteria in fresh waste-corn fermentations persisted at 10⁶ organisms/dry g. A silage-like fermentation product resulted which may have use in animal feed formulations.     

Fermentation of swine waste-corn mixtures for animal feed: Pilot-plant studies

Summary Aerobic culture with solid substrates of fresh swine waste combined with corn resulted in lactic acid fermentation with odor control. Heterofermentative lactic acid bacteria produced lactic and homologous tatty acids from acetic through valeric acid (0.1 meq/dry g) to reduce pH 2 units to 4.2 to 4.6. During the fermentation, lactic acid organisms increased from 10⁷ to 10⁹/dry g. Coliform organisms remained steady in number at 10⁶ organisms/dry g. Pilot-plant scale fermentation produced a product with 21 to 39% more methionine than corn but was still limiting for this amino acid as well as lysine for young pigs. Fermentation product from fresh waste-corn cultures was fed as the major dietary component to young pigs, hens, and sheep. Pigs showed gain and gain/feed diminished by one-third in 13-day trials. Laying hens performed comparably to controls in a 21-day test, and sheep did not discriminate against fermentation product.     

Influence of a Probiotic Enterococcus Faecium Strain on Selected Bacterial Groups in the Small Intestine of Growing Turkey Poults

A feeding trial was carried out with turkey poults, which were fed a diet containing 10¹⁰ viable probiotic E. faecium NCIB 10415 cells/kg feed. Samples of the intestinal tract were analyzed for lactate, colony forming units of total anaerobic bacteria, lactic acid bacteria, enterobacteria and enterococci. Furthermore, metabolic activity of total eubacterial, lactobacilli and enterococci was recorded in selected RNA-extracts with specific ribosomal RNA oligonucleotide probes. Animals fed the probiotic diet showed continously increasing lactate concentrations throughout the sampling period up to day 42 of life. No correlation was found for colony forming units (cfu) of lactic acid bacteria, but metabolic activity of lactobacilli showed very close relation to continously increasing lactate concentrations. Throughout the feeding trial, enterococci in the control group continously increased to a maximum of 10⁴ cfu/g wet weight, but 10-fold higher enterococci cfu were generally found in the treated group. However, rRNA content as measure for metabolic activity showed a drastic decline in both groups after high metabolic activities on day 7. This study shows that E. faecium NCIB 10415 (E. faecium SF68) stimulates other lactic acid bacteria in the small intestine, especially lactobacilli.     

Survival of <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> in Wilted and Additive-Treated Grass Silage

Grass was field-dried to 3 different dry matter (DM) levels (200, 430 and 540 g/kg) and inoculated with 10⁶–10⁷ cfu/g of a Listeria monocytogenes strain sharing a phagovar occasionally involved in food-borne outbreaks of listeriosis. Formic acid (3 ml/kg) or lactic acid bacteria (8·10⁵/g) with cellulolytic enzymes were applied only to forages with low and intermediate DM levels. Forages were ensiled in laboratory silos (1700 ml) and were stored at 25°C for 30 or 90 days. After 90 days of storage, L. monocytogenes could not be detected in any silo, except one with the high dry matter grass without additive. After 30 days of storage, between 10² and 10⁶ cfu L. monocytogenes/g silage were isolated from the untreated silages. Increasing the DM content from 200 to 540 g/kg did not reduce listeria counts possibly because of the lower production of fermentation acids (higher pH). In silages treated with additives, counts of L. monocytogenes were always lower than in silages without additive. In wet silages (DM 200 g/kg) both additives were effective, but in the wilted silages (DM 430 g/kg) only the bacterial additive reduced listeria counts below detection level. Listeria counts were highly correlated to silage pH (r = 0.92), the concentration of lactic acid (r = -0.80) and the pooled amount of undissociated acids (r = -0.83).     

Variations in bacterial communities in laboratory-scale and big bale silos assessed by fermentation products, colony counts and denaturing gradient gel electrophoresis profiles

Aims: To assess the variation in bacterial communities in laboratory‐scale and big bale silos. Methods and Results: Wilted Italian ryegrass (628 g dry matter kg^?1) was ensiled in vacuum‐packed plastic pouches and big bales. Silos were opened after 3 months, and the fermentation products, colony counts and denaturing gradient gel electrophoresis (DGGE) profiles were determined. Eight samples were collected separately from a big bale, while one representative sample was taken from a plastic pouch. Significant variation was found between big bales in dry matter, ethanol, lactic acid, acetic acid and ammonia‐N contents. No differences were shown between plastic pouches and big bales, except that more ethanol was produced in the former air‐tight silos. Plastic pouches could resemble a specific silo and outer sampling sites of big bales based on fermentation products and DGGE profiles respectively. Conclusions: Considerable variation in fermentation products may exist between big bale silos. Plastic pouches can serve as a model of big bale silos, although they do not provide information on the heterogeneity within and between bales. Significance and Impact of the Study: Assessment of bacterial communities associated with ensiling can differ according to the criteria of fermentation products, colony counts and DGGE profiles.     

Types and Distribution of Anaerobic Bacteria in the Large Intestine of Pigs

An examination was made of various sites along the length of the swine large intestine, using strictly anaerobic culture methods. Sites were separated by differential washing into fractions described as lumenal content, lumenal surface layer, and intestinal wall tissue. Direct microscopic clump counts averaged 13.3 × 10¹⁰ organisms per g (dry weight) of material in the lumenal content, 14.0 × 10¹⁰ in the surface layer, and 5.1 × 10¹⁰ in the intestinal wall tissue. Both direct microscopic counts and viable culture counts were higher from the lumenal content and surface layer than from the intestinal tissue at all sites sampled in the intestine. Cultural counts averaged 56.2% of the direct microscopic counts in lumenal content and surface layer and 20.2% in intestinal tissue. Over 90% of the bacteria isolated were gram positive and consisted mainly of gram-positive cocci, lactobacilli, eubacteria, and clostridia. Of 192 isolates recovered, only 124 could be assigned to recognized species.     

Dynamics of orange peel fermentation during ensilage

The dynamics of fermentation during ensilage were studied on orange peel (variety Shamouti) ensiled in 50 plastic containers, 10 kg in each, with an outlet for seepage. At predetermined intervals the containers were weighed and samples were taken from three of them for chemical and microbial analysis. Fermentation losses amounted to up to ca one-third of the fresh peel dry matter (DM) content. Most losses occurred within 10 d of commencement of fermentation, and were attributable to gas release. The major fermentation products were ethanol, lactic and acetic acids (16, 3 and 3% of DM, respectively). The dominant microbial populations were lactobacilli and yeasts. Tests are in progress to inhibit the yeasts and thereby reduce fermentation losses.     

Microbiology of Lebanon Bologna

Various aspects of the microbiology of the Lebanon bologna process were studied. Manufacture of Lebanon bologna appeared to be similar to that of summer sausage and other fermented sausages and consisted of a lactic acid fermentation by lactobacilli accompanied by the production of cured meat color from the reduction of nitrate by micrococci. The traditional process consists of aging coarse ground beef at 5 C for several days. Aging the beef for about 10 days was necessary to allow development of lactic acid bacteria; for successful fermentation, the concentration of lactic acid producers must be 10(4)/g or more. At least 3% NaCl was necessary to suppress the development of pseudomonads during the aging period; higher concentrations of salt suppress the development of the lactic acid-producing flora. During aging, in the presence of salt, the predominant flora developing on the meat consisted of catalase-positive, gram-positive rods and cocci; during fermentation at 35 C, the predominant flora became catalase-negative, gram-positive rods with characteristics of lactobacilli. Lebanon bologna could be made from frozen beef if the meat was thawed, salted, and aged. However, bolognas could not be made from unaged beef unless a lactic acid starter culture was used. The microflora of several commercial bolognas is reported also.     

Monitoring the bacterial community of maize silage stored in a bunker silo inoculated with Enterococcus faecium, Lactobacillus plantarum and Lactobacillus buchneri

Aims: To monitor variations in the bacterial community and fermentation products of maize silage within and between bunker silos. Methods and Results: Silage samples were collected in 2008 and 2009 from three dairy farms, wherein the farmers arranged for a contractor to produce maize silage using bunker silos. Silage was prepared using a lactic acid bacteria (LAB) inoculant consisting of Enterococcus faecium, Lactobacillus plantarum and Lactobacillus buchneri. Eight samples were collected from each bunker silo; 4 ‘outer’ and 4 ‘inner’ samples were collected from near the top and the bottom of the silo. The dry matter, lactic acid, acetic acid, ethanol, 1‐propanol and 1,2‐propanediol contents differed between bunker silos in both sampling years. Higher acetic acid, 1‐propanol and 1,2‐propanediol contents were found in the bottom than the top layers in the 2008 samples, and higher lactic acid content was found in the top than the bottom layers in the 2009 samples. The bacterial community varied more between bunker silos than within a bunker silo in the 2008 samples, whereas differences between the top and the bottom layers were seen across bunker silos in the 2009 samples. The inoculated LAB were uniformly distributed, while several nonconventional silage bacteria were also detected. Lactobacillus acetotolerans, Lactobacillus panis and Acetobacter pasteurianus were detected in both years. Stenotrophomonas maltophilia was detected in the 2008 samples, and Lactobacillus reuteri, Acinetobacter sp. and Rahnella sp. were detected in the 2009 samples. Conclusions: Although differences were seen within and between bunker silos, the bacterial community may indicate a different relationship between bunker silos and sampling locations within a bunker silo from that indicated by the fermentation products. Significance and Impact of the Study: Analysis of bacterial community can help understand how diverse non‐LAB and LAB species are involved in the ensiling process of bunker‐made maize silage.     

Metabolic profile of ginkgo kernel juice fermented with lactic aicd bacteria: A potential way to degrade ginkgolic acids and enrich terpene lactones and phenolics

In this paper, the influence of lactic acid fermentation on the metabolic profile of ginkgo kernel juice was studied. For this purpose, three lactic acid bacteria (LAB), Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus casei, were selected. The results showed that all the lactobacilli grew well in ginkgo kernel juice with viable cell counts exceeding 8.0 Log CFU/mL. The organic acid contents underwent dynamic changes, and the lactic acid production reached more than 3 g/L. The consumption of sugars and free amino acids by LAB was evident. Meanwhile, more than 70% of the ginkgolic acids were degraded by LAB, and the final concentrations in ginkgo kernel juice were below 1 mg/L after 48 h of fermentation. In contrast, the terpene lactones contents in fermented ginkgo kernel juice exceed 20 mg/L, which was 1.6-fold higher than that in the unfermented juice. Certain phenolics were significantly enriched, and the total phenolic content increased by approximately 9% through fermentation. In addition, lactic acid fermentation significantly enhanced the antioxidant and antimicrobial activities of ginkgo kernel juice. Overall, the results indicated that lactic acid fermentation can effectively improve the nutritional value and safety of ginkgo kernel juice.     

The role of nisin in fuel ethanol production with Saccharomyces cerevisiae

Aims: To investigate the effects of nisin on lactobacilli contamination of yeast during ethanol fermentation and to determine the appropriate concentration required to control the growth of selected lactobacilli in a YP/glucose media fermentation model. Methods and Results: The lowest concentration of nisin tested (5 IU ml^?1) effectively controlled the contamination of YP/glucose media with 10⁶ CFU ml^?1 lactobacilli. Lactic acid yield decreased from 5·0 to 2·0 g l^?1 and potential ethanol yield losses owing to the growth and metabolism of Lactobacillus plantarum and Lactobacillus brevis were reduced by 11 and 7·8%, respectively. Approximately, equal concentrations of lactic acid were produced by Lact. plantarum and Lact. brevis in the presence of 5 and 2 IU ml^?1 nisin, respectively, thus demonstrating the relatively higher nisin sensitivity of Lact. brevis for the strains in this study. No differences were observed in the final ethanol concentrations produced by yeast in the absence of bacteria at any of the nisin concentrations tested. Conclusions: Metabolism of contaminating bacteria was reduced in the presence of 5 IU ml^?1 nisin, resulting in reduced lactic acid production and increased ethanol production by the yeast. Significance and Impact of the Study: Bacteriocins represent an alternative to the use of antibiotics for the control of bacterial contamination in fuel ethanol plants and may be important in preventing the emergence of antibiotic‐resistant contaminating strains.     

Changes in microbial population during fermentation of feedlot waste with corn

A new process for recycling feedlot waste involves the fermentation of liquid from this waste combined with corn. Changes in the flora of this silage-like fermentation were followed. The fermentation was dominated by lactobacilli and yeasts, which initially constitute 1% or less of the natural flora. The species of yeasts and lactics involved were characterized. The fermentation has two phases. A single heterolactic species multiplied rapidly for the first 24 h until it represented 95% of the lactobacilli and more than 90% of the total microflora. It displaced the betabacterium predominant among lactics of the original waste; the acid produced killed coliforms and other organisms in feedlot waste; and the acetic acid produced probably caused the death of the dominant native yeast Trichosporon cutaneum (de Beurm., Gougerot et Vaucher) Ota. The peak lactobacillus count remained constant (about 2 × 10⁹ organisms/g [wet weight]) throughout the rest of the fermentation. Homolactics dominated the later phase and yeasts increased to 9.5 × 10⁷ organisms/g (wet weight). At 6 days, a stable mixture of three lactobacilli was present, one streptobacterium, one thermobacterium, and one betabacterium. Similarly, yeasts stabilized as a mixture of two Candida sp. and one Pichia sp. The dominant species of lactics were characterized. Information on the sequence of microorganisms provides a basis for enhanced protein synthesis in the fermentation.     

Anaerobic Conversion of Lactic Acid to Acetic Acid and 1,2-Propanediol by Lactobacillus buchneri

The degradation of lactic acid under anoxic conditions was studied in several strains of Lactobacillus buchneri and in close relatives such as Lactobacillus parabuchneri, Lactobacillus kefir, and Lactobacillus hilgardii. Of these lactobacilli, L. buchneri and L. parabuchneri were able to degrade lactic acid under anoxic conditions, without requiring an external electron acceptor. Each mole of lactic acid was converted into approximately 0.5 mol of acetic acid, 0.5 mol of 1,2-propanediol, and traces of ethanol. Based on stoichiometry studies and the high levels of NAD-linked 1,2-propanediol-dependent oxidoreductase (530 to 790 nmol min⁻¹ mg of protein⁻¹), a novel pathway for anaerobic lactic acid degradation is proposed. The anaerobic degradation of lactic acid by L. buchneri does not support cell growth and is pH dependent. Acidic conditions are needed to induce the lactic-acid-degrading capacity of the cells and to maintain the lactic-acid-degrading activity. At a pH above 5.8 hardly any lactic acid degradation was observed. The exact function of anaerobic lactic acid degradation by L. buchneri is not certain, but some results indicate that it plays a role in maintaining cell viability.     

Use of Lactobacillus plantarum LPCO10, a Bacteriocin Producer, as a Starter Culture in Spanish-Style Green Olive Fermentations

Bacteriocin-producing Lactobacillus plantarum LPCO10 and its non-bacteriocin-producing, bacteriocinimmune derivative, L. plantarum 55-1, were evaluated separately for growth and persistence in natural Spanish-style green olive fermentations. Both strains were genetically marked and selectively enumerated using antibiotic-containing media. Plasmid profile and bacteriocin production (bac⁺) were used as additional markers. When olive brines were inoculated at 10⁵ CFU/ml, the parent strain, LPCO10, proliferated to dominate the epiphytic microflora, sharing high population levels with other spontaneously occurring lactobacilli and persisting throughout the fermentation (12 weeks). In contrast, the derivative strain could not be isolated after 7 weeks. Stability of both plasmid profile and bac⁺ (LPCO10 strain) or bac^- (55-1 strain) phenotype was shown by L. plantarum LPCO10 and L. plantarum 55-1 isolated throughout the fermentation. Bacteriocin activity could be found in the L. plantarum LPCO10-inoculated brines only after ammonium sulfate precipitation and concentration (20 times) of the final brine. Spontaneously occurring lactobacilli and lactic coccus populations, which were isolated from each of the fermenting brines studied during this investigation, were shown to be sensitive to the bacteriocins produced by L. plantarum LPCO10 when tested by the drop diffusion test. The declines in both pH and glucose levels throughout the fermentative process were similar in L. plantarum LPCO10- and in L. plantarum 55-1-inoculated brines and were comparable to the declines in the uninoculated brines. However, the final concentration of lactic acid in L. plantarum LPCO10-inoculated brines was higher than in the L. plantarum 55-1-inoculated brines and uninoculated brines. These results indicated that L. plantarum LPCO10 may be useful as a starter culture to control the lactic acid fermentation of Spanish-style green olives.     

Effect of yeast inoculation rate on the metabolism of contaminating lactobacilli during fermentation of corn mash

Two separate 4 (bacterial concentrations)×6 (yeast concentrations) full factorial experiments were conducted in an attempt to identify a novel approach to minimize the effects caused by bacterial contamination during industrial production of ethanol from corn. Lactobacillus plantarum and Lactobacillus paracasei, commonly occurring bacterial contaminants in ethanol plants, were used in separate fermentation experiments conducted in duplicate using an industrial strain of Saccharomyces cerevisiae, Allyeast Superstart. Bacterial concentrations were 0, 1×10⁶, 1×10⁷ and 1×10⁸ cells/ml mash. Yeast concentrations were 0, 1×10⁶, 1×10⁷, 2×10⁷, 3×10⁷, and 4×10⁷ cells/ml mash. An increased yeast inoculation rate of 3×10⁷ cells/ml resulted in a greater than 80% decrease (P<0.001) and a greater than 55% decrease (P<0.001) in lactic acid production by L. plantarum and L. paracasei, respectively, when mash was infected with 1×10⁸ lactobacilli/ml. No differences (P>0.25) were observed in the final ethanol concentration produced by yeast at any of the inoculation rates studied, in the absence of lactobacilli. However, when the mash was infected with 1×10⁷ or 1×10⁸ lactobacilli/ml, a reduction of 0.7–0.9% v/v (P<0.005) and a reduction of 0.4–0.6% v/v (P<0.005) in the final ethanol produced was observed in mashes inoculated with 1×10⁶ and 1×10⁷ yeast cells/ml, respectively. At higher yeast inoculation rates of 3×10⁷ or 4×10⁷ cells/ml, no differences (P>0.35) were observed in the final ethanol produced even when the mash was infected with 1×10⁸ lactobacilli/ml. The increase in ethanol corresponded to the reduction in lactic acid production by lactobacilli. This suggests that using an inoculation rate of 3×10⁷ yeast cells/ml reduces the growth and metabolism of contaminating lactic bacteria significantly, which results in reduced lactic acid production and a concomitant increase in ethanol production by yeast.     

Populations of Anaerobic Phototrophic Bacteria in a Spartina alterniflora Salt Marsh

Habitat-simulating media were used with the Hungate anaerobic roll tube technique to enumerate culturable anaerobic photosynthetic bacteria in sediment, tidal waters, and Spartina alterniflora plant samples collected from the salt marsh at Sapelo Island, Ga. No phototrophs were detected in samples of creekside (low marsh) sediment or in tidal waters in creekside regions. In the high marsh region, 90% of anaerobic phototrophic bacteria occurred in the top 5 mm of sediment and none were detected below 6 mm. There was a seasonal variation, with maximal populations occurring in summer and fall (mean, 4.4 × 10⁵ phototrophs g of dry sediment⁻¹) and minimal numbers occurring in winter (mean, 3.9 × 10³ phototrophs g of dry sediment⁻¹). During winter and late spring, phototrophs had a patchy distribution over the high marsh sediment surface. In contrast, during late summer they had a random uniform distribution. Tidal water collected over high marsh sediment contained an average of 8.7 × 10² phototrophs ml⁻¹, with no significant seasonal variation. Anaerobic phototrophic bacteria were also cultured from the lower stem tissue of S. alterniflora growing in both the high (4.3 × 10⁴ phototrophs g of dry tissue⁻¹) and creekside (4.9 × 10⁴ phototrophs g of dry tissue⁻¹) marsh regions. Chromatium buderi, Chromatium vinosum, Thiospirillum sanguineum, Rhodospirillum molischianum, and Chlorobium phaeobacteroides were the predominant anaerobic phototrophic species cultured from high marsh sediment. The two Chromatium species were dominant.     

耐乙酸乳杆菌的筛选及其产乳酸特性

【背景】耐受乙酸的乳酸菌是传统谷物醋醋酸发酵过程中产生乳酸及其风味衍生物的重要功能微生物。【目的】从镇江香醋醋醅中分离鉴定具有耐乙酸特性的乳酸菌,并评价不同条件下该菌株的产乳酸能力。【方法】利用4%(体积比)乙酸含量的MRS培养基分离耐乙酸乳酸菌;对其进行16S rRNA基因鉴定、基因组测序、形态观察以及生理生化特性研究;考察不同乙酸浓度、葡萄糖浓度、发酵温度和时间对菌株产乳酸能力的影响。【结果】分离得到一株可耐受6%乙酸的乳杆菌Lactobacillus sp. JN500903;在厌氧静置、接种量5%、乙酸浓度5%、葡萄糖浓度40 g/L、发酵温度37°C、发酵时间10 d条件下,该菌株乳酸产量为16.1 g/L。【结论】乳杆菌JN500903能够耐受6%乙酸浓度,具有在酸性环境下合成乳酸的能力,有一定的应用潜力。     

Lactic fermentation of poultry droppings with molasses and wheat straw

The pH of wastelage inoculated with Lactobacillus plantarum and Streptococcus faecalis was more than 5.4 and the off-flavour of poultry droppings, at 51% of dry matter, was not completely removed after 20 days' fermentation. By varying the amount of poultry droppings from 15 to 45% in the pre-mix and by including wheat straw, the pH and total volatile fatty acid production were increased, lactic acid synthesis decreased, and the off-flavour was completely abolished. Poultry droppings can be included in a pre-mix at less than 25% of total dry matter provided 10% molasses is added to give good quality wastelage.The authors are with the Microbiology Section, Animal Nutrition Division, Indian Veterinary Research Institute, Izatnagar 243122, India.     

Characterization of intestinal lactobacilli as putative probiotic candidates

AIMS: To use antioxidative activity and antagonistic properties of lactobacilli against selected pathogens and members of the normal microflora as a basis for screening probiotic candidates. METHODS AND RESULTS: Antagonistic activity of lactobacilli against target bacteria in both microaerobic and anaerobic environments was tested. Production of antagonistic metabolites (ethanol, hydrogen peroxide (H2O2), acetic, lactic and succinic acid) by lactobacilli as well as their total antioxidative activity were assessed. In general, the lactobacilli tested were most effective against Gram-negative bacteria and their antagonistic activity was strain-specific. However, obligately heterofermentative lactobacilli had the strongest activity when tested in a microaerobic environment. Additionally, facultatively heterofermentative lactobacilli were equally effective in either milieu and produced significant levels of acetic and lactic acid. Moreover, obligately homofermentative lactobacilli had high H2O2 production and total antioxidative activity but weak antagonistic activity. CONCLUSIONS: Antioxidative and antagonistic activity of intestinal lactobacilli is strain-specific but typically can be related to their fermentation type which may be used for rapidly screening large numbers of lactobacilli for probiotic candidates. SIGNIFICANCE AND IMPACT OF THE STUDY: This study represents the first report on the utilization of group characteristics to screen lactobacilli intended for specific probiotic use. Such uses include the targeting of particular gut niches and pathogens as well as allowing for long-term benefits to the host.