The impact of probiotic Clostridium butyricum MIYAIRI 588 on murine gut metabolic alterations.

INTRODUCTION: Clostridium butyricum MIYAIRI 588 (CBM 588) is a probiotic bacterium used in antidiarrheal medicine in Japan. A few studies analyzed the changes in gut microbiome in patients treated with antimicrobials based on metagenomics sequencing. However, the impact of CBM 588 on gut metabolic alterations has not been fully elucidated. This study was to reveal the impact of CBM 588 on gut metabolic alterations. MATERIAL AND METHODS: In this in vivo study, mice were divided into four groups and CBM 588, clindamycin (CLDM), and normal saline (control) was orally administered (1. CLDM, 2. CBM 588, 3. CBM 588 + CLDM, 4. water) for 4 days. Fecal samples were collected to extract DNA for metagenomics analysis. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to obtain relative Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway abundance information derived from metagenomics data. RESULTS: CLDM treatment resulted in a dramatic increase in Firmicutes phylum compared to non-CLDM-treated groups (control and CBM 588-treated group). Then, the CBM 588 + CLDM-treated group showed a trend similar in many metabolic pathways to the CLDM-treated group. On the other hand, the CBM 588 + CLDM-treated group showed higher relative abundance compared to the CLDM-treated group especially in starch and sucrose metabolism. DISCUSSION: We concluded that CBM 588 caused a gut microbiome functional shift toward increased carbohydrate metabolism. These results support the hypothesis that CBM 588 treatment modulates gut microbiome under dysbiosis conditions due to antimicrobials.

Stability of probiotics with antibiotics via gastric tube by simple suspension method: An in vitro study.

Data on the stability of probiotics with antibiotics delivered via gastric tube using the simple suspension method (SSM) are limited. Therefore, we investigated bacterial survivability in probiotics treated with antibiotics prepared by the SSM in vitro. Probiotics and antibiotics were suspended in 20 mL of sterilized hot water (55 °C) and then 1-mL of the suspensions were taken each at 10, 60, 120, 180 and 360 min. Thereafter, the samples were inoculated on 3 media and cultured at 37 °C for 24 h. Survival of probiotic strains was measured in colony-forming units. The growth of Clostridium butyricum did not change without antibiotics at all experimental times, but in the case of Enterococcus faecium tended to increase. On the other hand, the viable bacterial number of C. butyricum was decreased significantly by treatment with cefdinir, tosufloxacin, clarithromycin, or azithromycin, but was not altered by levofloxacin, minocycline, or vancomycin. The viable bacterial number of E. faecium was significantly decreased by treatment with tosufloxacin, levofloxacin, minocycline, vancomycin, or azithromycin, and was significantly increased by clarithromycin. In conclusion, our results suggest that the efficacy of probiotic therapies might be reduced by the SSM when specific antibiotics are used. Moreover, antibiotics might inhibit probiotic growth, although some probiotics are spore-forming and have high minimum inhibitory concentrations. Additionally, early administration of non-spore-forming bacteria might be desirable. Therefore, when patients are administered therapy combining probiotics and antibiotics by the SSM, we should consider the characteristics of the probiotics and the administration times.

Metabolic profiles analysis of 1,3-propanediol production process by Clostridium butyricum through repeated batch fermentation coupled with activated carbon adsorption.

1,3-propanediol production by Clostridium butyricum is a low productivity process due to the long time seed cultivation and thus hinders its industrial scale production. In the present study, repeated batch fermentation coupled with activated carbon adsorption strategy was first established which conduced not only to saving the time of seed cultivation and enhancing the productivity, but also to reducing the costs for the seed cultivation to achieve the purpose of 1,3-propanediol continuous production. The concentration of 1,3-propanediol from first to fourth cycle was 42.89, 45.78, 44.48, 42.39 (g/L), and the corresponding volumetric productivity was 2.14, 1.91, 1.85, 2.12 (g/L · h-1 ) respectively. More importantly, a relatively complete schematic diagram of the proposed metabolic pathways was firstly mapped out based on the intracellular metabolites analysis through GC-MS. At the same time, metabolic pathway and principal components analyses were carried out to give us deep insight into metabolic state. Many metabolites occurred to response to the stress in Cycle II. Even resting body formed and lipid accumulated owing to the worsening environment in the group without activated carbon in Cycle III. Thus, it demonstrated that activated carbon provided a favorable microenvironment for Clostridium butyricum in the repeated batch fermentation process to achieve the purpose of 1,3-propanediol continuous production.

Clostridium butyricum partially regulates the development of colitis-associated cancer through miR-200c.

Colitis-associated cancer (CAC), one form of colorectal cancer (CRC),is an increasing concern worldwide. Both diagnosis and current therapy are challenging and bottlenecked. The aim of this study is to investigate novel mechanisms by which the therapeutic C. butyricum regulates colitis-induced oncogenesis. Mouse models of CAC were established with 2,4,6-Trinitrobenzenesulfonic acid (TNBS)and azoxymethane (AOM), following by biochemical, clinical and histological analysis. The integrity of epitheliumwas examined by electron microscopy (EM). The epithelial barrier function was evaluated with Ussing chamber. Real time PCR and fluorescent in situ hybridization (FISH) were performed to characterize the effect of C. butyricum on miR-200c; cell proliferation assays (MTT) were performed to study the role ofC. butyricum on epithelial cell proliferation mediated by miR-200c inhibitor; finally, we quantified the proinflammatory cytokines TNF-α and interleukin (IL)-12 by real time PCR. C. butyricum ameliorates clinical, histological and biochemical manifestations in colitis-induced CAC models. Further mechanistic studies demonstrated that C. Butyricum could lengthen epithelial microvillus and increase TER by decreasing the transepithelial permeability. We also showed that C. butyricum facilitates the expression of miR-200c, by which increase the proliferation rate. Finally, we found that C. butyricum can regulate the production of proinflammatory cytokines TNF-α and IL-12 through miR-200c. C. butyricum may regulate epithelial barrier function through miR-200c, then to be involved in the process of inflammation-associated cancers.

Inhibited growth of Clostridium butyricum in efficient H2-producing co-culture with Rhodobacter sphaeroides.

Cell number of Clostridium butyricum and Rhodobacter sphaeroides in co-culture was measured using q-PCR approach. During efficient H2 photoproduction from starch (6.2 mol H2/mol glucose), Clostridia growth and starch-hydrolyzing activity was partly suppressed. Apparently, the effect of R. sphaeroides towards C. butyricum was not attributed to altered Eh or pH values in the presence of purple bacteria. Further, disk-diffusion test proved that R. sphaeroides was capable of producing inhibitors against another purple bacterium, Rhodospirillum rubrum, but not against C. butyricum. We suggested that at initial cell number ratio C. butyricum:R. sphaeroides 1:1 purple bacteria outcompeted C. butyricum for yeast extract at its low concentration (80 mg/L). Under these conditions, the H2 yield was rather high (5.7 mol/mol). When the yeast extract concentration increased to 320 mg/L, this process was replaced by the low-yield H2 production (1.8 mol/mol) characteristic of Clostridia. However, increased percentage of purple bacteria in inoculum under these conditions prevented this shift. The outcome of competition depended on both the yeast extract concentration and cell number ratio. Apparently, the competition for yeast extract helped to maintain balance between fast-growing C. butyricum and slower-growing R. sphaeroides for efficient H2 photoproduction.

Effect of 1,3-propanediol, organic acids, and ethanol on growth and metabolism of Clostridium butyricum DSP1.

Knowledge of tolerance of bacteria to toxic stress is important, especially for processes targeted at high final titers of product. Information on environmental limits and stress responses may help during selection of strains or design and control of processes. The influence of the main product and its co-products on the process of 1,3-propanediol (PD) synthesis was determined. Adaptation to toxic compounds was noticed as Clostridium butyricum DSP1 was less sensitive to the addition of these factors during its exponential growth on glycerol than when the factor was present in the medium before inoculation. It was also shown that the response of the tested strain to the toxicity of 1,3-propanediol (1,3-PD) has different proteomic profiles depending on the stage of culture when this substance is introduced. Relatively satisfactory activity of the analyzed strain was sustained up to a concentration of 1,3-PD of 40 g/L while 80 g/L of this metabolite was lethal to the bacterium. As for the by-products, acetic acid was determined to be the most toxic among the acids excreted during the process.

The functional dlt operon of Clostridium butyricum controls the D-alanylation of cell wall components and influences cell septation and vancomycin-induced lysis.

Clostridium butyricum is a Gram-positive bacterium involved in the development of necrotizing enterocolitis (NEC) in preterm infants. To colonize the digestive tract, components of the cell wall of C. butyricum must interact with the intestinal mucosa. The D-alanylation of cell wall components such as teichoic acids results in a net positive charge on the cell wall, which is important for many functions of Gram-positive bacteria. Notably, D-alanylation mediates resistance to antimicrobial peptides and antibiotics. Here, we show that the dlt operon of C. butyricum encodes the enzymes responsible for the D-alanylation of cell wall components and influences the surface properties of the cell wall. We show that the D-alanylation of cell wall components controls the septation of C. butyricum, which is an essential mechanism during vegetative growth. Furthermore, we find that D-alanylation is involved in the resistance of C. butyricum to some cationic antimicrobial peptides (CAMPs) and lysozyme. Finally, we show that the D-alanylation of cell wall components influences vancomycin-induced lysis.

Outcome of oral provocation test in egg-sensitive children receiving semi-fat hard cheese Grana Padano PDO (protected designation of origin) containing, or not, lysozyme.

PURPOSE: Lysozyme, obtained from egg white, is a potential food allergen used in the dairy industry to prevent late blowing of the loaf caused by the outgrowth of clostridial spores (Cl. butyricum and Cl. tyrobutyricum) during cheese aging. The aim of this study was to evaluate the possible correlation between egg protein allergy in pediatric age and sensitization to egg lysozyme, used for the preparation of Grana Padano cheese. METHODS: The tolerability of Grana Padano cheese has been evaluated in pediatric patients allergic to egg proteins through an oral provocation test with increasing amounts of cheese containing, or not, lysozyme at 12 and 24 months of aging. RESULTS: When lysozyme-sensitized children received 12-months aged and lysozyme-containing cheese, several immediate and late adverse reactions such as itching, abdominal pain, vomiting, nausea, dermatitis, rhinitis, bronchial asthma, urticaria, and angioedema were seen in 5 out of 21 subjects; only 1 out of 21 children showed an adverse reaction after challenge with 24-months-ripened lysozyme-containing cheese. CONCLUSIONS: There is a possible relationship between the severity of allergic reactions and the lysozyme-specific IgE level in blood. In particular vomiting, hypotension, and abdominal pain were present when IgE level was higher than 7 kU/L. A ripening time of 24 months may reduce allergy problems when lysozyme-containing cheese is given to sensitized subjects, probably due to the hydrolysis of antigenic epitopes during aging.

Immunological response in egg-sensitive adults challenged with cheese containing or not containing lysozyme.

OBJECTIVE: Lysozyme is an enzyme that hydrolyzes bacterial peptidoglicans. For this reason, it is used in cheese manufacturing in order to prevent a defect of long-ripened hard cheese called "late blowing" due to the outgrowth of spores of Clostridium tyrobutyricum and Clostridium butyricum. Moreover, germination of Listeria monocytogenes spores into vegetative cells is also sensitive to lysozyme. The enzyme can be an allergenic molecule, and for this reason there are concerns about its use in food industry. The immunological and clinical response of consumption of lysozyme-containing cheese has been evaluated in 25 egg-sensitive subjects with or without lysozyme sensitization. METHODS: A total of 25 egg-sensitive subjects were enrolled in this study. All the subjects were already treated for egg-sensitization and presented a positive skin prick test. All the subjects had a body mass index ≤ 25 kg/m(2) and were in the age range of 20-50 years. Each subject was studied twice and received randomly 30 g of Grana Padano (containing lysozyme) or TrentinGrana cheese (lysozyme-free) of two different aging periods: 16 or 24 months. A washout period of 1 week between each cheese intake was adopted. Blood samples were taken in fasting conditions and 1 hour after cheese intake and IgA, total IgE, and lysozyme-, ovomucoid-, and ovalbumin-specific IgE were measured. RESULTS: No adverse reactions were observed in both groups of patients after cheese samples were given. Lysozyme did not determine any variation of specific IgE compared with basal level. In lysozyme-sensitive patients a significant relationship between IgA and lysozyme-specific IgE was observed when lysozyme-containing cheese was given, confirming that lysozyme can pass the gut barrier. CONCLUSIONS: Neither adverse events nor immunological responses were observed after ingestion of cheese containing lysozyme. However, the immunological properties of peptides deriving from cheese protein hydrolysis need to be clarified, as does the effect of lysozyme on bacterial proteolytic activity.

High-level production of 1,3-propanediol from crude glycerol by Clostridium butyricum AKR102a.

The aim of this study was to optimize a biotechnological process for the production of 1,3-propanediol (1,3-PD) based on low-quality crude glycerol derived from biodiesel production. Clostridium butyricum AKR102a was used in fed-batch fermentations in 1-L and 200-L scale. The newly discovered strain is characterized by rapid growth, high product tolerance, and the ability to use crude glycerol at the lowest purity directly gained from a biodiesel plant side stream. Using pure glycerol, the strain AKR102 reached 93.7 g/L 1,3-PD with an overall productivity of 3.3 g/(L*h). With crude glycerol under the same conditions, 76.2 g/L 1,3-PD was produced with a productivity of 2.3 g/(L*h). These are among the best results published so far for natural producers. The scale up to 200 L was possible. Due to the simpler process design, only 61.5 g/L 1,3-PD could be reached with a productivity of 2.1 g/(L*h).

Adaptation dynamics of Clostridium butyricum in high 1,3-propanediol content media.

Aim of the present study was to evaluate the effect of exogenous additions of 1,3-propanediol (1,3-PDO) on microbial growth and metabolites production of Clostridium butyricum VPI 1718 strain, during crude glycerol fermentation. Preliminary batch cultures in anaerobic Duran bottles revealed that early addition of 1,3-PDO caused growth cessation in rather low quantities (15 g/L), while 1,3-PDO additions during the middle exponential growth phase up to 70 g/L resulted in an almost linear decrease of the specific growth rate (µ), accompanied by reduced glycerol assimilation, with substrate consumption being used mainly for energy of maintenance requirements. During batch trials in a 3-L bioreactor, the strain proved able to withstand more than 70 g/L of both biologically produced and externally added 1,3-PDO, whereas glycerol assimilation and metabolite production were carried on at a lower rate. Adaptation of the strain in high 1,3-PDO concentration environments was validated during its continuous cultivation with pulses of 1,3-PDO in concentrations of 31 and 46 g/L, where no washout phenomena were noticed. As far as C. butyricum cellular lipids were concerned, during batch bioreactor cultivations, 1,3-PDO addition was found to favor the biosynthesis of unsaturated fatty acids. Also, fatty acid composition was studied during continuous cultures, in which additions of 1,3-PDO were performed at steady states. Lipids were globally more saturated compared to batch cultures, while by monitoring of the transitory phases, it was noticed that the gradual diol washout had an evident impact in the alteration of the fatty acid composition, by rendering them more unsaturated.

An improved screening method for microorganisms able to convert crude glycerol to 1,3-propanediol and to tolerate high product concentrations.

A new screening method was developed and established to find high-performance bacteria for the conversion of crude glycerol to 1,3-propanediol. Three soil samples from palm oil-rich habitats were investigated using crude glycerol of a German biodiesel plant. Nine promising 1,3-propanediol producers could be found. Because of a special pH buffer system, a fast evaluation on microscale and high 1,3-propanediol concentrations up to 40 g L⁻¹ could be achieved. Three strains demonstrated very high product tolerance and were identified as Clostridium butyricum. Two strains, AKR91b and AKR102a, grew and produced 1,3-propanediol in the presence of 60 g L⁻¹ initial 1,3-propanediol, the strain AKR92a even in the presence of 77 g L⁻¹ 1,3-propanediol. The strains AKR91b and AKR102a tolerated up to 150 g L⁻¹ crude glycerol and produced 80% of the 1,3-propanediol attained from pure glycerol of the same concentration. Further criteria for the choice of a production strain were the pathogenicity (risk class), ability to grow on low-cost media, e.g., with less yeast extract, and robustness, e.g., process stability after several bioconversions. Overall, the strain C. butyricum AKR102a was chosen for further process optimization and scale-up due to its high productivity and high final concentration in a pH-regulated bioreactor.

Gaseous CO2 signal initiates growth of butyric-acid-producing Clostridium butyricum in both pure culture and mixed cultures with Lactobacillus brevis.

Microbial strains produce numerous volatile substances in the anaerobic conditions of the human intestines. The availability of CO(2) is known to be a prerequisite for bacterial growth in general. In experiments with anaerobic Lactobacillus brevis and Clostridium butyricum bacteria in the Portable Microbial Enrichment Unit (PMEU) it was shown that these strains interact; this interaction being mediated by CO(2) emission. CO(2) promoted clostridial growth in pure cultures and mixed cultures with lactobacilli. The growth of C. butyricum in pure cultures was much delayed or did not start at all without CO(2) from outside. Conversely, the onset of growth was provoked by a short (15 min) CO(2) burst. In mixed cultures the presence of lactobacilli in equal numbers speeded up the onset of clostridial growth by 10 h. If C. butyricum cultures designated as PMEU 1, 2, and 3 in cultivation syringes were chained by connecting the gas flow thereby allowing the volatiles of the preceding syringe culture to bubble to the next one, the growth started in 20, 10, or 6 h, respectively. This effect of gaseous emissions from other cultures speeding up the bacterial growth initiation was abolished if the gas was passed through sodium hydroxide to remove the CO(2). The positive contribution of lactobacilli to the growth of butyric-acid-producing clostridia documented in this simulation experiment with PMEU has in vivo implications and indicates molecular communication between the species. CO(2) is a necessary signal for the growth of clostridia, and lactobacilli can promote clostridial growth in mixed cultures where both bacteria grow well with mutual benefit.

Effect of probiotics on serum bile acids in patients with ulcerative colitis.

BACKGROUND/AIMS: Evaluation of bile acids (BA) is useful for assessing the changes of intestinal flora in patients with ulcerative colitis (UC). During enterohepatic circulation, the intestinal micro flora cause 7 alpha-dehydroxylation of cholic acid (CA) and chenodeoxycholic acid (CDCA), yielding deoxycholic acid(DCA) and lithocholic acid, respectively. The aim of the present study was to investigate the effects of probiotics in patients with UC by examining changes of the serum BA profile. METHODOLOGY: Twenty-seven patients were divided into the following 2 groups based on endoscopic findings: Fifteen patients with distal UC (dUC group) and 12 patients with pancolitis (pUC group). After treatment with mesalazine or salazosulfapyridine (5-ASA), all patients achieved remission. Then they were given 5-ASA plus the probiotic Clostridium butyricum Miyairi (3.0 g/day) for 4 weeks. RESULTS: After 4 weeks of probiotic treatment, %CDCA was significantly higher and %DCA was significantly lower in the pUC group than in the HV group. In contrast, the dUC group showed no significant differences of %CDCA or %DCA from the HV group after 4 weeks. CONCLUSIONS: Probiotic therapy restored intestinal flora involved in 7 alpha-dehydroxylation in the dUC group, but not in the pUC group.

The future of butyric acid in industry.

In this paper, the different applications of butyric acid and its current and future production status are highlighted, with a particular emphasis on the biofuels industry. As such, this paper discusses different issues regarding butyric acid fermentations and provides suggestions for future improvements and their approaches.

Long-term effect of inoculum pretreatment on fermentative hydrogen production by repeated batch cultivations: homoacetogenesis and methanogenesis as competitors to hydrogen production.

Long-term effects of inoculum pretreatments (heat, acid, loading-shock) on hydrogen production from glucose under different temperatures (37 °C, 55 °C) and initial pH (7 and 5.5) were studied by repeated batch cultivations. Results obtained showed that it was necessary to investigate the long-term effect of inoculum pretreatment on hydrogen production since pretreatments may just temporarily inhibit the hydrogen consuming processes. After long-term cultivation, pretreated inocula did not enhance hydrogen production compared to untreated inocula under mesophilic conditions (initial pH 7 and pH 5.5) and thermophilic conditions (initial pH 7). However, pretreatment could inhibit lactate production and lead to higher hydrogen yield under thermophilic conditions at initial pH 5.5. The results further demonstrated that inoculum pretreatment could not permanently inhibit either methanogenesis or homoacetogenesis, and methanogenesis and homoacetogenesis could only be inhibited by proper control of fermentation pH and temperature. Methanogenic activity could be inhibited at pH lower than 6, both under mesophilic and thermophilic conditions, while homoacetogenic activity could only be inhibited under thermophilic condition at initial pH 5.5. Microbial community analysis showed that pretreatment did not affect the dominant bacteria. The dominant bacteria were Clostridium butyricum related organisms under mesophilic condition (initial pH 7 and 5.5), Thermoanaerobacterium sp. related organisms under thermophilic condition (initial pH 7), and Thermoanaerobacterium thermosaccharolyticum related organisms under thermophilic condition (initial pH 5.5). Results from this study clearly indicated that the long-term effects of inoculum pretreatments on hydrogen production, methanogenesis, homoacetogenesis and dominant bacteria were dependent on fermentation temperature and pH.

Production of 1,3-propanediol by Clostridium butyricum growing on biodiesel-derived crude glycerol through a non-sterilized fermentation process.

The aim of the present study was to investigate the production of 1,3-propanediol (PDO) under non-sterile fermentation conditions by employing the strain Clostridium butyricum VPI 1718. A series of batch cultures were performed by utilizing biodiesel-derived crude glycerol feedstocks of different origins as the sole carbon source, in various initial concentrations. The strain presented similarities in terms of PDO production when cultivated on crude glycerol of various origins, with final concentrations ranging between 11.1 and 11.5 g/L. Moreover, PDO fermentation was successfully concluded regardless of the initial crude glycerol concentration imposed (from 20 to 80 g/L), accompanied by sufficient PDO production yields (0.52-0.55 g per gram of glycerol consumed). During fed-batch operation under non-sterile culture conditions, 67.9 g/L of PDO were finally produced, with a yield of 0.55 g/g. Additionally, the sustainability of the bioprocess during a continuous operation was tested; indeed, the system was able to run at steady state for 16 days, during which PDO effluent level was 13.9 g/L. Furthermore, possible existence of a microbial community inside the chemostat was evaluated by operating a polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, and DGGE results revealed the presence of only one band corresponding to that of C. butyricum VPI 1718. Finally, non-sterile continuous cultures were carried out at different dilution rates (D), with inlet glycerol concentration at 80 g/L. Maximum PDO production was achieved at low D values (0.02 h(-1)) corresponding to 30.1 g/L, while the elaboration of kinetic data from continuous cultures revealed the stability of the bioprocess proposed, with global PDO production yield corresponding to 0.52 g/g.

Oral administration of Clostridium butyricum for modulating gastrointestinal microflora in mice.

This study aimed to evaluate the safety of Clostridium butyricum and to investigate the effect of C. butyricum on mice ecosystem in the intestinal tract by way of examining the population of different microorganisms isolated from caecal contents. We firstly evaluated the safety of C. butyricum using acute toxicity test and Ames test. Then forty male BALB/c mice were divided into the following four treatment groups, each consisting of ten mice: normal group, low-dose group, medium-dose group and high-dose group. Caecal contents were removed aseptically, immediately placed into an anaerobic chamber, and dissolved in sterile pre-reduced PBS. The determination of Enterococcus spp., Enterobacter spp., Lactobacillus spp., Bifidobacterium spp. and Clostridium perfringens was analyzed by the spread plate method, cell morphologies and biochemical profiles. The results showed the oral maximum tolerated dose of C. butyricum was more than 10 g/kg body weight in mice and no mutagenicity judged by negative experimental results of Ames test. And in medium- and high-dose groups, the populations of Bifidobacterium spp. and Lactobacillus spp. increased in caecum, as well as the ratios of Bifidobacterium spp. and Lactobacillus spp. to Clostridium perfringens (P < 0.01) as compared with the normal group. This research showed the intake of C. butyricum significantly improved the ecosystem of the intestinal tract in BALB/c mice by increasing the amount of probiotics and reducing the populations of unwanted bacteria.

Growth of bifidobacteria and clostridia on human and cow milk saccharides.

For healthy infants, which were born normally and fully breastfed, the dominant component of the intestinal microflora are bifidobacteria. However, infants born by caesarean section possess clostridia as a dominant intestinal bacterial group. The aim of the present study was to determine whether bifidobacteria and clostridia are able to grow on human milk oligosaccharides (HMOs) and other carbon sources - lactose, cow milk (CM) and human milk (HM). Both bifidobacteria and clostridia grew on lactose and in CM. Bifidobacteria grew in HM and on HMOs. In contrast, 3 out of 5 strains of clostridia were not able to grow in HM. No clostridial strain was able to utilise HMOs. While both bifidobacterial strains were resistant to lysozyme, 4 out of 5 strains of clostridia were lysozyme-susceptible. It seems that HMOs together with lysozyme may act as prebiotic-bifidogenic compounds inhibiting intestinal clostridia.

Metabolic modelling of syntrophic-like growth of a 1,3-propanediol producer, Clostridium butyricum, and a methanogenic archeon, Methanosarcina mazei, under anaerobic conditions.

Clostridium butyricum can convert glycerol into 1,3-propanediol, thereby generating unfortunately a high amount of acetate, formate and butyrate as inhibiting by-products. We have proposed a novel mixed culture comprising C. butyricum and a methane bacterium, Methanosarcina mazei, to relieve the inhibition and to utilise the by-products for energy production. In order to examine the efficiency of such a mixed culture, metabolic modelling of the culture system was performed in this work. The metabolic networks for the organisms were reconstructed from genomic and physiological data. Several scenarios were analysed to examine the preference of M. mazei in scavenging acetate and formate under conditions of different substrate availability, including methanol as a co-substrate, since it may exist in glycerol solution from biodiesel production. The calculations revealed that if methanol is present, the methane production can increase by 130%. M. mazei can scavenge over 70% of the acetate secreted by C. butyricum.