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<jats:title>Abstract</jats:title><jats:p>Biocementation, driven by ureolytic bacteria and their biochemical activities, has evolved as a powerful technology for soil stabilization, crack repair, and bioremediation. Ureolytic bacteria play a crucial role in calcium carbonate precipitation through their enzymatic activity, hydrolyzing urea to produce carbonate ions and elevate pH, thus creating favorable conditions for the precipitation of calcium carbonate. While extensive research has explored the ability of ureolytic bacteria isolated from natural environments or culture conditions, bacterial synergy is often unexplored or under-reported. In this study, we isolated bacterial strains from the local eutrophic river canal and evaluated their suitability for precipitating calcium carbonate polymorphs. We identified two distinct bacterial isolates with superior urea degradation ability (conductivity method) using partial 16 S rRNA gene sequencing. Molecular identification revealed that they belong to the <jats:italic>Comamonas</jats:italic> and <jats:italic>Bacillus</jats:italic> genera. Urea degradation analysis was performed under diverse pH (6,7 and 8) and temperature (15 °C,20 °C,25 °C and 30 °C) ranges, indicating that their ideal pH is 7 and temperature is 30 °C since 95% of the urea was degraded within 96 h. In addition, we investigated these strains individually and in combination, assessing their microbially induced carbonate precipitation (MICP) in silicate fine sand under low (14 ± 0.6 °C) and ideal temperature 30 °C conditions, aiming to optimize bio-mediated soil enhancement. Results indicated that 30 °C was the ideal temperature, and combining bacteria resulted in significant (<jats:italic>p</jats:italic> ≤ 0.001) superior carbonate precipitation (14–16%) and permeability (&gt; 10<jats:sup>− 6</jats:sup> m/s) in comparison to the average range of individual strains. These findings provide valuable insights into the potential of combining ureolytic bacteria for future MICP research on field applications including soil erosion mitigation, soil stabilization, ground improvement, and heavy metal remediation.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The β-fructofuranosidase enzyme from <jats:italic>Aspergillus niger</jats:italic> has been extensively used to commercially produce fructooligosaccharides from sucrose. In this study, the native and an engineered version of the β-fructofuranosidase enzyme were expressed in <jats:italic>Pichia pastoris</jats:italic> under control of the glyceraldehyde-3-phosphate dehydrogenase promoter, and production was evaluated in bioreactors using either dissolved oxygen (DO-stat) or constant feed fed-batch feeding strategies. The DO-stat cultivations produced lower biomass concentrations but this resulted in higher volumetric activity for both strains. The native enzyme produced the highest volumetric enzyme activity for both feeding strategies (20.8% and 13.5% higher than that achieved by the engineered enzyme, for DO-stat and constant feed, respectively). However, the constant feed cultivations produced higher biomass concentrations and higher volumetric productivity for both the native as well as engineered enzymes due to shorter process time requirements (59 h for constant feed and 155 h for DO-stat feed). Despite the DO-stat feeding strategy achieving a higher maximum enzyme activity, the constant feed strategy would be preferred for production of the β-fructofuranosidase enzyme using glycerol due to the many industrial advantages related to its enhanced volumetric enzyme productivity.</jats:p>

<jats:title>Abstract</jats:title><jats:p>In this study, it was aimed to investigate bacterial contamination in apheresis platelet suspensions (APS) by automated blood culture system and flow cytometry method (FCM).</jats:p><jats:p>33 spiked APS each using 11 bacterial strains (5 standard strains, 6 clinical isolates), were prepared in three different dilutions (1–10, 10–50, 50-100 cfu/mL), incubated in two different temperatures (35–37 °C and 22–24 °C) and different incubation times (18–96 h) evaluated by FCM. This three different dilutions were also inoculated into special platelet culture bottles (BacT/ALERT® BPA) and loaded into the blood culture system. Additionally 80 APSs routinely prepared in the Transfusion Center were evaluated by both FCM and the blood culture system. Platelets were lysed by freeze-thaw method.</jats:p><jats:p>All spiked samples were positive with BacT/ALERT® BPA in 12–18 h. In 96 h incubation at 22–24 °C, the presence of bacteria was detected by FCM in all other samples (31/33) except low dilutions (1–10 and 10–100 CFU/ml) of <jats:italic>K.pneumoniae</jats:italic> standard strain. In the 35–37 °C, the presence of bacteria was detected by FCM in all samples (33/33) after 48 h of incubation. In routine APS one sample detected as positive (<jats:italic>Bacillus simplex</jats:italic>) with BacT/ALERT® BPA and no positivity was detected by FCM.</jats:p><jats:p>The freeze-thaw method, which we have optimized for the lysis of platelets, is very practical and can be easily applied. The BacT/ALERT® system has been found to be very sensitive in detecting bacterial contamination in PSs. Flow cytometry method has been found to be successful, fast, easy to use and low cost in detecting bacterial contamination in PSs.</jats:p>