Novel Wild-Type Pediococcus and Lactiplantibacillus Strains as Probiotic Candidates to Manage Obesity-Associated Insulin Resistance.

As the food and pharmaceutical industry is continuously seeking new probiotic strains with unique health properties, the aim of the present study was to determine the impact of short-term dietary intervention with novel wild-type strains, isolated from various sources, on high-fat diet (HFD)-induced insulin resistance. Initially, the strains were evaluated in vitro for their ability to survive in simulated gastrointestinal (GI) conditions, for adhesion to Caco-2 cells, for bile salt hydrolase secretion, for cholesterol-lowering and cellular cholesterol-binding ability, and for growth inhibition of food-borne pathogens. In addition, safety criteria were assessed, including hemolytic activity and susceptibility to antibiotics. The in vivo test on insulin resistance showed that mice receiving the HFD supplemented with Pediococcus acidilactici SK (isolated from human feces) or P. acidilactici OLS3-1 strain (isolated from olive fruit) exhibited significantly improved insulin resistance compared to HFD-fed mice or to the normal diet (ND)-fed group.

Scale-up of thermally dried kefir production as starter culture for hard-type cheese making: an economic evaluation.

This paper concerns the effect of thermal-drying methodology on the investment cost for dried kefir cells production in order to be used as starter culture in cheese manufacturing. Kefir cells were produced at pilot plant scale using a 250-L bioreactor and whey as the main substrate. Kefir cells were subsequently dried in a thermal dryer at 38 degrees C and used as a starter culture in industrial-scale production of hard-type cheeses. The use of thermally dried kefir as starter culture accelerated ripening of cheeses by increasing both lipolysis and fermentation rate as indicated by the ethanol, lactic acid, and glycerol formation. Additionally, it reduced coliforms and enterobacteria as ripening proceeded. This constituted the basis of developing an economic study in which industrial-scale production of thermally dried kefir starter culture is discussed. The industrial design involved a three-step process using three bioreactors of 100, 3,000, and 30,000 L for a plant capacity of 300 kg of thermally dried kefir culture per day. The cost of investment was estimated at 238,000 euro, which is the 46% of the corresponding cost using freeze-drying methodology. Production cost was estimated at 4.9 euro/kg of kefir biomass for a 300-kg/day plant capacity, which is the same as with the corresponding cost of freeze-dried cells. However, the estimated added value is up to 10.8 x 10(9) euro within the European Union.

Molecular characterization and molasses fermentation performance of a wild yeast strain operating in an extremely wide temperature range.

Molasses fermentation performance by both a cryotolerant and a thermophilic yeast (strain AXAZ-1) isolated from grapes in Greece was evaluated in an extremely wide temperature range (3-40 degrees C). Sequence analysis of the 5.8S internal transcribed spacer and the D1/D2 ribosomal DNA (rDNA) regions assigned isolate to Saccharomyces cerevisiae. Restriction fragment length polymorphism of the mitochondrial DNA showed that strain AXAZ-1 is genetically divergent compared to other wild strains of Greek origin or commercial yeast starters. Yeast cells growing planktonically were capable of fermentation in a wide temperature spectrum, ranging from 3 degrees C to 38 degrees C. Immobilization of yeast on brewer's spent grains (BSG) improved the thermo-tolerance of the strain and enabled fermentation at 40 degrees C. Time to complete fermentation with the immobilized yeast ranged from 20 days at 3 to 38 h at 40 degrees C. The daily ethanol productivity reached maximum (58.1 g/L) and minimum (2.5 g/L) levels at 30 and 3 degrees C, respectively. The aroma-related compounds' profiles of immobilized cells at different fermentation temperatures were evaluated by using solid phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS). Molasses fermentation resulted in a high quality fermentation product due to the low concentrations of higher and amyl alcohols at all temperatures tested. Strain AXAZ-1 is very promising for the production of ethanol from low cost raw materials, as it was capable to perform fermentations of high ethanol concentration and productivities in both low and high temperatures.

Thermally-dried free and immobilized kefir cells as starter culture in hard-type cheese production.

In an attempt to seek for suitable dried cultures, thermally-dried kefir was employed as starter in hard-type cheese production and tested in cheeses ripened at 5, 18 and 22 degrees C. Both free and immobilised on casein kefir cells were used and compared to cheese made without starter culture. Cheese products made with free cells of kefir culture were characterized by longer preservation time, improved aroma, taste, texture characteristics and increased degree of openness. Volatile profiles obtained by GC/MS analysis revealed a 216% increase in total concentration of esters, organic acids, alcohols and carbonyl compounds between cheeses prepared with and without kefir culture.

Production of hard-type cheese using free or immobilized freeze-dried kefir cells as a starter culture.

This study provides a contribution to hard-type cheese starter culture production through the use of a freeze-dried culture in the ripening of hard-type cheeses. The effect of initial cell concentration, ripening temperature, and cell immobilization of kefir on the degree of openness, mold spoilage, microbial associations, physicochemical characteristics, and aroma-related compounds was studied. Use of kefir starter cultures resulted in cheese with an increased shelf life and resistance to spoilage as compared to control cheeses without kefir inoculants. Furthermore, the freeze-dried kefir culture improved aroma, taste, and texture characteristics while increasing the degree of openness in comparison to traditional hard-type cheese products. The kefir culture resulted in an increase in counts of total aerobic bacteria, yeasts and molds, lactococci, and lactobacilli until the 15th day of ripening. From then on, only lactobacilli counts increased, reaching levels up to 9.17 log CFU/g in cheeses ripened at 5 degrees C using freeze-dried kefir cells immobilized on casein. SPME-GC/MS analysis revealed major differences in volatile composition, especially with regard to alcohols (up to 75%), carbonyl compounds (up to 75%), and esters (up to 64%) between cheeses made with kefir cells and cheeses made without kefir inoculants.

Evaluation of the thermally dried immobilized cells of Lactobacillus delbrueckii subsp. bulgaricus on apple pieces as a potent starter culture.

The aim of the present study was to evaluate the impact of thermal drying of immobilized Lactobacillus delbrueckii subsp. bulgaricus on apple pieces on the use of the derived biocatalyst in whey fermentation. The thermally dried immobilized biocatalyst was compared to wet and freeze-dried immobilized cells, in respect to maintenance of cell viability and fermentation efficiency. The thermal drying process appeared to be more efficient on survival rate as an 84% of the cells used for immobilization survived the process, while the freeze-drying process led to a 78% rate. The thermally dried immobilized biocatalyst was used in 12 repeated batch fermentations of synthetic lactose medium and whey at 37, 45, and 50 degrees C in order to evaluate its metabolic activity. The high number of repeated batch fermentations showed a tendency for high operational stability. Fermentations continued for up to 2 months without any significant loss of metabolic activity. SPME GC/MS analysis of aroma-related compounds revealed the distinctive character of fermented whey produced by the thermally dried immobilized bacterium cells. The effect of storage at 4-6 degrees C for up to 165 days of the biocatalyst, held directly after drying and after repeated batch fermentations, on fermentation activity was also studied. After storage, reactivation in whey was immediate, and the immobilized biocatalyst was able to produce up to 51.7 g/L lactic acid at 37 degrees C. The potential of thermally dried immobilized L. delbrueckii as a starter culture for food production was subsequently evaluated.

Detection of phosphonoacetate degradation and phnA genes in soil bacteria from distinct geographical origins suggest its possible biogenic origin.

Phosphonoacetate is regarded as an antiviral xenobiotic whose mineralization can be catalysed by an enzyme, phosphonoacetate hydrolase, encoded by the phnA gene. To date the enzyme's activity has been detected in only a limited number of bacteria. Its expression has been shown to occur in a manner independent of the phosphate status of the cell, in direct contrast to the general rule of organophosphonate metabolism being under the control of the pho regulon. In this study the environmental occurrence of the phnA gene was evaluated by polymerase chain reaction amplification of DNA extracts obtained directly from various soil environments. Sensitivity of this method was improved such that a positive result was routinely obtained with soil spiked with as few as 6 colony-forming units (cfu) per gram of soil of Pseudomonas fluorescens 23F (phnA(+)). When total DNA from a variety of Northern Irish, Greek and Bolivian soils was tested, all were positive for phnA. Bacteria capable of utilizing phosphonoacetate as sole carbon, energy and phosphorus source, with the release of essentially equimolar concentrations of phosphate to the culture supernatant, were isolated from all soil samples tested. Analysis of three such isolates revealed all to be species of Pseudomonas sensu stricto, possessing phosphonoacetate hydrolase activity in cell-free extracts. Sequence determination of the phnA gene revealed a similarity of the putative protein sequences at levels of 98.3-99.3% between the Pseudomonas strains. This is the first study to use molecular methods to investigate the distribution of a gene encoding organophosphonate metabolism, and indicates that the phnA gene is ubiquitous within soils from geographically distinct regions. Such an observation supports the proposition that phosphonoacetate is a compound that may also have a biogenic origin.