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Feather degrading bacteria from birds' nests were characterized to find safe bacterial strains that could be utilized to convert feathers into soluble form and bacterial biomass for feed purposes. Of all tested 571 isolates 122 were keratinolytic. Partial sequencing of the 16S rRNA gene revealed that the keratinolytic isolates represented Proteobacteria (genera Pseudomonas and Stenotrophomonas) and Firmicutes (genera Bacillus, Exiguobacterium, Paenibacillus, Rummeliibacillus, and Sporosarcina). Bacillus cereus group and gram-negative bacterial isolates were not further characterized due to safety concerns related to potential pathogenicity or potential exposure of animals or workers to endotoxins (lipopolysaccharide part of the gram-negative cell wall). Keratinolytic strains showed clear differences in their ability to solubilize feathers with feather weight losses up to 30%. Amino acid composition of feather hydrolysates shifted from feather composition towards more bacterial-like composition. Especially the levels of lysine could be increased in the feather hydrolysate with bacterial fermentation. Feathers can be effectively hydrolyzed with non-pathogenic bacteria without any additional nutrients. The resulting feather hydrolysate is easier to digest than feather material and it has an improved amino acid composition regarding some limiting amino acids. The amino acid content of the final product can be tailored by varying the fermentation time and thus the ratio of bacterial cells to the feather hydrolysate.

OBJECTIVES: Human breast milk contains a high quantity of oligosaccharides (HMOs) which are not digested by infants but are selectively utilized by beneficial gut microbes such as Bifidobacterium species. The gut microbiome in breast-fed infants is dominated by Bifidobacterium species, whereas formula-fed infants have a higher representation of Bacteroides and Enterobacteria species. The aim of this study was to evaluate the ability of various potentially pathogenic bacteria and commercially available probiotic strains to grow using the HMOs 2’-fucosyllactose (2’-FL) and 3-fucosyllactose (3-FL), glucose, lactose or galacto-oligosaccharide (GOS) as a sole carbon source. We also compared the production of short-chain fatty acids (SCFAs) and lactic acid during the fermentation of 2’-FL by B. infantis, B. bifidum and Bacteroides strains. METHODS: Bacterial growth was monitored by measuring the absorbance at 600 nm every 30 min for 24 h using the automatic Bioscreen(©) C system under anaerobic conditions in culture media containing 1% 2’-FL, 3-FL, glucose, lactose or GOS as a sole carbon source. Metabolites were analyzed by chromatographic methods in spent culture media after over-night growth of bacterial strains with 1% 2’-FL. RESULTS: Only certain bifidobacteria strains, B. infantis and B. bifidum, were able to utilize 2’-FL and 3-FL, whereas other tested Lactobacillus and Bifidobacterium strains as well as pathogenic bacteria grew with all other carbon sources. We also confirmed that Bacteroides fragilis, B. thetaiotaomicron and B. vulgatus strains utilized HMO. Distinct SCFA and lactic acid quantities were observed between Bifidobacterium and Bacteroides strains in 2’-FL fermentation. For instance, acetic and lactic acids were produced at much higher levels in Bifidobacterium than in Bacteroides, and propionic acid was produced at low level only in Bacteroides. CONCLUSIONS: These results show the selectivity of 2’-FL and 3-FL utilization in certain Bifidobacterium and Bacteroides strains, which is translated to differences in metabolite production between these individual HMO-utilizing bacteria. Further studies will enlighten the role and potential benefits of HMOs as a selective substrate for gut microbes, as well as for competition and cross-feeding of microbial metabolites among gut species. FUNDING SOURCES: This research was funded by DuPont Nutrition and Health.

We investigated the effects of oral therapy with doxycycline, a tetracycline group antibiotic, on the gastrointestinal (GI) survival and tetracycline susceptibility of probiotic strains Lactobacillus acidophilus LaCH-5 and Bifidobacterium animalis subsp. lactis Bb-12. In addition, the influence of doxycycline therapy on the diversity of the predominant faecal microbiota was evaluated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Faecal samples from the antibiotic group (receiving antibiotics and probiotics) and the control group (receiving probiotics only) were analysed for anaerobically and aerobically growing bacteria, bifidobacteria and lactic acid bacteria as well as for the dominant microbiota. Although doxycycline consumption did not have a large impact on GI survival of the probiotics, it had a detrimental effect on the bifidobacteria and on the diversity of the dominant faecal microbiota. A higher proportion of tetracycline-resistant anaerobically growing bacteria and bifidobacteria was detected in the antibiotic group than in the control group. Several antibiotic group subjects had faecal B. animalis subsp. lactis Bb-12-like isolates with reduced tetracycline susceptibility. This was unlikely to be due to the acquisition of novel tetracycline resistance determinants, since only tet(W), which is also present in the ingested B. animalis subsp. lactis Bb-12, was found in the resistant isolates. Thus, concomitant ingestion of probiotic L. acidophilus LaCH-5 and B. animalis subsp. lactis Bb-12 with the antibiotic did not generate a safety risk regarding the possible GI transfer of tetracycline resistance genes to the ingested strains.

In the present study various combinations of metabolic indicators were used in viability studies of foodborne spoilage and pathogenic organisms. Various metabolic stains were tested in pure culture suspensions of Pseudomonas fragi and Listeria monocytogenes containing only viable cells, both viable and dead cells or only dead cells. In addition, foodborne monospecies biofilms of L. monocytogenes and P. fragi were studied. The biofilms were grown on stainless steel (AISI 304, 2B) surfaces. The results showed that both the LIVE/DEAD Bac Light Viability Kit (LIVE/DEAD) and the 5-cyano-2,3-ditolyl tetrazolium chloride (CTC)-4′,6-diamidino-2-phenylindole (DAPI) staining procedures offer a rapid, easy and reliable method for metabolic investigation of bacteria in suspension and swabbed biofilm bacteria. Assessment of replicate samples using luciferin–luciferase-based ATP measurement and conventional cultivation corroborated the results of swabbed biofilm bacteria obtained by staining. LIVE/DEAD staining cannot be used for direct staining of biofilms on surfaces, due to interference between the stain and polysaccharides of the biofilm matrix and slime. Staining by CTC-DAPI is suitable for studying viability of cells both in suspension and in biofilms attached to surfaces. The other staining procedures tested were not satisfactory or only slightly satisfactory in distinguishing between viable and dead cells.