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Summary In this work, we present the development and characterization of a strain of Pichia kudriavzevii (TY1322), with highly improved phytate‐degrading capacity. The mutant strain TY1322 shows a biomass‐specific phytate degradation of 1.26 mmol g−1 h−1 after 8 h of cultivation in a high‐phosphate medium, which is about 8 times higher compared with the wild‐type strain. Strain TY1322 was able to grow at low pH (pH 2), at high temperature (46°C) and in the presence of ox bile (2% w/v), indicating this strain's ability to survive passage through the gastrointestinal tract. The purified phytase showed two pH optima, at pH 3.5 and 5.5, and one temperature optimum at 55°C. The lower pH optimum of 3.5 matches the reported pH of the pig stomach, meaning that TY1322 and/or its phytase is highly suitable for use in feed production. Furthermore, P. kudriavzevii TY1322 tolerates ethanol up to 6% (v/v) and shows high osmotic stress tolerance. Owing to the phenotypic characteristics and non‐genetically modified organisms nature of TY1322, this strain show great potential for future uses in (i) cereal fermentations for increased mineral bioavailability, and (ii) feed production to increase the phosphate bioavailability for monogastric animals to reduce the need for artificial phosphate fortification.

Three Gram-stain-positive, non-spore-forming, microaerophilic and fructose-6-phosphate phosphoketolase positive strains were isolated from a faecal sample of an adult subject of the emperor tamarin (Saguinus imperator). Given that the isolates revealed identical BOX PCR profiles, strain TRI 5(T) was selected as a representative and characterized further. Comparative analysis of 16S rRNA gene sequence similarity revealed that strain TRI 5(T) was closely related to Bifidobacterium saguini DSM 23967(T) (96.4 %) and to Bifidobacterium longum subsp. longum ATCC 15708 (96.2 %). Multilocus sequence analyses of five housekeeping genes showed the close phylogenetic relatedness of this strain to Bifidobacterium breve DSM 20213(T) (hsp60 94.1 %), Bifidobacteriumsaguini DSM 23967(T) (clpC 91 %), Bifidobacterium avesanii DSM 100685(T) (dnaG 80.3 %), Bifidobacterium longumsubsp. infantis ATCC 15697(T) (dnaJ 85.3 %) and Bifidobacterium longumsubsp. longum ATCC 15708 (rpoB 93 %), respectively. The peptidoglycan type was A3β, with an interpeptide bridge comprising l-Orn (Lys) - l-Ser - l-Ala - l-Thr - l-Ala. The DNA G+C content of strain TRI 5(T) was 60.9 mol%. Based on the data provided, strain TRI 5(T) represents a novel species of the genus Bifidobacterium for which the name Bifidobacteriumcallitrichidarum sp. nov. is proposed. The type strain is TRI 5(T) (=DSM 103152(T)=JCM 31790(T)).

The present research was aimed to investigate the technological potentialities of seven strains of Bifidobacterium aesculapii, a species recently described, in terms of exopolysaccharide (EPS) production and as starter fermentation in soybean milk. The strain production of EPS was firstly evaluated in model system, using different carbon sources. Furthermore, the fermented products obtained by the seven strains of B. aesculapii were tested for their EPS content and strain cell loads, the volatile molecule profiles, the texture features and the overall acceptance. The data showed that all the B. aesculapii strains were able to produce EPS in vitro model in presence of 1.5% and 2% glucose while only four strains were able to produce EPS in presence of lactose 2%. When the strains were employed as fermentation starters in soybean milk, some showed a good growth potential, fermenting the substrate in 14 h and giving rise to fermented products with good firmness and viscosity indexes. Moreover, five strains out seven showed production of EPS (from 5 to 174 μg/mL) in soybean fermented milk.

This study monitored the biomass composition of Saccharina latissima during a potential harvesting season on the West coast of Sweden, in order to find suitable harvest times for biorefinery purposes. Specimens of S. latissima were sampled at three locations in June, August and October and the biomass was analysed for its macromolecular composition, as well as for the content of several specific compounds, e.g. sugars and fatty acids. PERMANOVA analyses showed that there was a significant difference in the biomass composition among time points. The total carbohydrate concentration was lowest in June and peaked at 360 mg g-1 dry weight in August, while the mannitol content was highest, 90 mg g-1, in June and decreased throughout the sampling period. Total protein and fatty acid concentrations were found to be approximately 80 and 3 mg g-1, respectively, with relatively little variation over time. Overall, there was little spatial variation in the macromolecular composition, although the concentration of some specific monosaccharides and fatty acids, as well as the total phenolic content, differed among localities. We discuss the implications of the observed variation in biomass composition of S. latissima for future biorefinery purposes.

The Yaghnob Valley in Tajikistan is inhabited by a small isolated human population. The area is geographically isolated, causing the inhabitant’s culture, food and lifestyle to remain uninfluenced by the rest of the world. Traditional methods of fermenting milk involve the use of indigenous microorganisms, leading to the production of a variety of fermented milk products. The people in Yaghnobi produce a fermented milk from goat, which constitutes one of their main foods. The aim of the current work was to determine which yeasts were present in the original Yaghnobi fermented milk as well as in the same product reproduced at home for three years with monthly reculturing in cow milk. Thirty yeasts have been isolated using different lab media such as M17, MRS, WL,YPD and YPD plus chloramphenicol, and colonies were re-cultivated until pure. Twenty isolates have been obtained from the original product and 10 from fermented milk reproduced at home. They were identified by Sanger sequencing of the amplified ribosomal Internal Transcribed Spacers (ITS1-4). Furthermore, RFLP analyses of the ITS1-4 region were performed when quality, coverage or similarity of ITS1-4sequences did not permitted the unambiguously identification of the yeast isolates. Only for Saccharomyces cerevisiae, identity was also confirmed with GTG5Rep PCR. The results showed the presence of Kluyveromycesmarxianus (11), Pichia fermentans (7) and Saccharomyces cerevisiae (10) in both products. However, Kluyveromyceslactis (1) was found in the original fermented milk sample and Kazachstaniaunispora(1) in home maintained fermented milk. Great attention has nowadays been devoted to microbial resources and the study of traditional fermented products can be a very interesting source of microbial biodiversity. This study provides for the first time data on yeast composition and characteristics in naturally Yaghnobi fermented milk, showing an unexpected richness in yeast communities leading to fermented milk production.

The geographically isolated region of the Yaghnob Valley, Tajikistan, has allowed its inhabitants to maintain a unique culture and lifestyle. Their fermented goat milk constitutes one of the staple foods for the Yaghnob population, and is produced by backslopping, i.e., using the previous fermentation batch to inoculate the new one. This study addresses the yeast composition of the fermented milk, assessing genotypic, and phenotypic properties. The 52 isolates included in this study revealed small species diversity, belonging to Kluyveromyces marxianus, Pichia fermentans, Saccharomyces cerevisiae, and one Kazachstania unispora. The K. marxianus strains showed two different genotypes, one of which never described previously. The two genetically different groups also differed significantly in several phenotypic characteristics, such as tolerance toward high temperatures, low pH, and presence of acid. Microsatellite analysis of the S. cerevisiae strains from this study, compared to 350 previously described strains, attributed the Yaghnobi S. cerevisiae to two different ancestry origins, both distinct from the wine and beer strains, and similar to strains isolated from human and insects feces, suggesting a peculiar origin of these strains, and the existence of a gut reservoir for S. cerevisiae. Our work constitutes a foundation for strain selection for future applications as starter cultures in food fermentations. This work is the first ever on yeast diversity from fermented milk of the previously unexplored area of the Yaghnob Valley.

Phytases are nutritionally important for increased bioavailability of dietary minerals and phosphate for monogastric animals including humans. Release of minerals and phosphate is accomplished by the enzymatic stepwise degradation of phytate (inositol hexaphosphate, IP6). Activity determinations of phytase is often based on analysis of total released phosphate (Pi), but phytase activity in its purest form represents released product per time from IP6 only. Microbial and plant preparations often also contain mixtures of phosphatases and organic phosphate compounds; hence some released phosphate in enzymatic assays may originate from non-phytase phosphatases degrading non-phytate molecules. Moreover, even purified enzyme extracts assessed via Pi release may result in errors, since commercial IP6 commonly contains contamination of lower inositol phosphates, and further, the products of phytase IP6 hydrolysis are also substrates for the phytase. These facts motivate a quantitative comparative study. We compared enzyme activity determination in phytase assay samples at four different time points, based on analyzing the substrate IP6 versus the product Pi using different selected methods. The calculated activities varied substantially. For example, at 15 min into enzymatic assay, variations from 152 mU/ml (by IP6 analysis on HPIC) to 275-586 mU/ml (by Pi analysis using several methods) was detected. Our work emphasizes the importance of defining the type of activity assessed, showing that phytase activity based on released Pi may yield false positive results and/or overestimations. We propose to differentiate between phytase activity, being the activity by which IP6 is degraded, and total inositol phosphatase activity, corresponding to total released phosphate during the enzymatic reaction.

Aims Mineral deficiencies cause several health problems in the world, especially for populations consuming cereal-based diets rich in the anti-nutrient phytate. Our aim was to characterize the phytate-degrading capacity of the yeast Pichia kudriavzevii TY13 and its secretion of phytase. Methods and Results The phytase activity in cell-free supernatants from cultures with 100% intact cells was 35–190 mU ml−1 depending on the media. The Km was 0·28 mmol l−1 and the specific phytase activity 0·32 U mg−1 total protein. The phytase activity and secretion of extracellular non-cell-bound phytase was affected by the medium phosphate concentrations. Further, addition of yeast extract had a clearly inducing effect, resulting in over 60% of the cultures total phytase activity as non-cell-bound. Conclusions Our study reveals that it is possible to achieve high extracellular phytase activity from the yeast P. kudriavzevii TY13 by proper composition of the growth medium. Significance and Impact of the Study TY13 could be a promising future starter culture for fermented foods with improved mineral bioavailability. Using strains that secrete phytase to the food matrix may significantly improve the phytate degradation by facilitating the enzyme-to-substrate interaction. The secreted non-cell-bound phytase activities by TY13 could further be advantageous in industrial production of phytase.

Phytases are nutritionally important for increased bioavailability of dietary minerals and phosphate for monogastric animals including humans. Release of minerals and phosphate is accomplished by the enzymatic stepwise degradation of phytate (inositol hexaphosphate, IP6). Activity determinations of phytase is often based on analysis of total released phosphate (Pi), but phytase activity in its purest form represents released product per time from IP6 only. Microbial and plant preparations often also contain mixtures of phosphatases and organic phosphate compounds; hence some released phosphate in enzymatic assays may originate from non-phytase phosphatases degrading non-phytate molecules. Moreover, even purified enzyme extracts assessed via Pi release may result in errors, since commercial IP6 commonly contains contamination of lower inositol phosphates, and further, the products of phytase IP6 hydrolysis are also substrates for the phytase. These facts motivate a quantitative comparative study. We compared enzyme activity determination in phytase assay samples at four different time points, based on analyzing the substrate IP6 versus the product Pi using different selected methods. The calculated activities varied substantially. For example, at 15 min into enzymatic assay, variations from 152 mU/ml (by IP6 analysis on HPIC) to 275-586 mU/ml (by Pi analysis using several methods) was detected. Our work emphasizes the importance of defining the type of activity assessed, showing that phytase activity based on released Pi may yield false positive results and/or overestimations. We propose to differentiate between phytase activity, being the activity by which IP6 is degraded, and total inositol phosphatase activity, corresponding to total released phosphate during the enzymatic reaction.