Increased water content in bacterial cellulose synthesized under rotating magnetic fields.

The current study describes properties of bacterial cellulose (BC) obtained from Komagataeibacter xylinus cultures exposed to the rotating magnetic field (RMF) of 50 Hz frequency and magnetic induction of 34 mT for controlled time during 6 days of cultivation. The experiments were carried out in the customized RMF exposure system adapted for biological studies. The obtained BC displayed an altered micro-structure, degree of porosity, and water-related parameters in comparison to the non-treated, control BC samples. The observed effects were correlated to the duration and the time of magnetic exposure during K. xylinus cultivation. The most preferred properties in terms of water-related properties were found for BC obtained in the setting, where RMF generator was switched off for the first 72 h of cultivation and switched on for the next 72 h. The described method of BC synthesis may be of special interest for the production of absorbent, antimicrobial-soaked dressings and carrier supports for the immobilization of microorganisms and proteins.

Staphylococci isolated from ready-to-eat meat - Identification, antibiotic resistance and toxin gene profile.

The aim of this study was to analyse the staphylococci isolated from ready-to-eat meat products, including pork ham, chicken cold cuts, pork sausage, salami and pork luncheon meat, sliced in the store to the consumer's specifications, along with species identification and determination of antibiotic resistance. Genes encoding staphylococcal enterotoxins, staphylococcal enterotoxin-like proteins, exfoliative toxins, and toxic shock syndrome toxin 1 were also investigated. From the 41 samples, 75 different staphylococcal isolates were obtained. Based on PCR-RFLP analysis of the gap gene using AluI and HpyCH4V restriction enzymes, the isolates were identified as Staphylococcus equorum (28%), S. vitulinus (16%), S. carnosus (14%), S. succinus (11%), S. xylosus (11%), S. saprophyticus (9%), S. warneri (9%), S. haemolyticus (1%) and S. pasteuri (1%). The incidence and number of resistances to antimicrobials was found to be species but not source of isolation dependent. All S. xylosus, S. saprophyticus, S. haemolyticus and S. pasteuri isolates showed antibiotic resistance. A lower percentage of resistance was recorded for S. warneri (71%) and S. vitulinus (58%), followed by S. equorum (57%), S. carnosus (50%) and S. succinus (50%). The most frequent resistance was observed to fusidic acid (43%). The mecA gene was amplified in 4% of the staphylococci. However, phenotypic resistance to methicillin was not confirmed in any of these isolates. On the other hand, the mecA gene was not detected in any of 9% of the isolates resistant to cefoxitin. It was also found that among 75 isolates, 60 (80%) harbored from 1 to 10 out of 21 analyzed superantigenic toxin genes. The most prevalent genes were: sei (36% isolates) among enterotoxins, seln (32% isolates) among enterotoxin-like proteins and eta encoding exfoliative toxin A (37% isolates). The findings of this study further extend previous observations that, when present in food, not only S. aureus but also other species of staphylococci could be of public health significance.

Wet and Dry Forms of Bacterial Cellulose Synthetized by Different Strains of Gluconacetobacter xylinus as Carriers for Yeast Immobilization.

The present study aimed to explore and describe the properties of bacterial cellulose (BC) membranes obtained from three different strains of Gluconacetobacter xylinus for 72, 120, and 168 h, used as a carrier support for the immobilization of Saccharomyces cerevisiae. The experiments also included the analysis of glucose consumption and alcohol production during the fermentation process displayed by yeasts immobilized on the BC surface. The results of the present study demonstrate that the number of immobilized yeast cells is dependent on the type of cellulose-synthesizing strain, cellulose form, and duration of its synthesis. The BC in the form of wet membranes obtained after 3 days of synthesis displayed the most favorable properties as a carrier for yeast immobilization. The immobilization of yeast cells on BC, regardless of its form, increased the amount of the produced alcohol as compared to free cells. The yeast cells immobilized in BC were able to multiply on its surface during the fermentation process.

Modification of bacterial cellulose through exposure to the rotating magnetic field.

The aim of the study was to assess the influence of rotating magnetic field (RMF) on production rate and quality parameters of bacterial cellulose synthetized by Glucanacetobacter xylinus. Bacterial cultures were exposed to RMF (frequency f=50Hz, magnetic induction B=34mT) for 72h at 28°C. The study revealed that cellulose obtained under RMF influence displayed higher water absorption, lower density and less interassociated microfibrils comparing to unexposed control. The application of RMF significantly increased the amount of obtained wet cellulose pellicles but decreased the weight and thickness of dry cellulose. Summarizing, the exposure of cellulose-synthesizing G. xylinus to RMF alters cellulose biogenesis and may offer a new biotechnological tool to control this process. As RMF-modified cellulose displays better absorbing properties comparing to non-modified cellulose, our finding, if developed, may find application in the production of dressings for highly exudative wounds.