Exploring encapsulation strategies as a protective mechanism to avoid amensalism in mixed populations of Pseudomonas taetrolens and Lactobacillus casei

Bioprocess and Biosystems Engineering - Pseudomonas taetrolens constitutes an efficient platform for the biosynthesis of lactobionic acid, a potentially prebiotic compound. Unfortunately, an...     

Gels prepared from egg yolk and its fractions for tissue engineering

New biomaterials prepared from egg yolk and its main fractions (plasma and granules) have been developed for use in tissue engineering. Protein gels obtained via transglutaminase cross‐linking were characterized by rheometry, texturometry and scanning electron microscopy. All the gels exhibited suitable physical and mechanical characteristics for use as potential biomaterials in skin regeneration. Specifically, results showed that these materials presented a compact, uniform structure, with granular gel being found to be the most resistant as well as the most elastic material. Accordingly, these gels were subsequently evaluated as scaffolds for murine fibroblast growth. The best results were obtained with granule gels. Not only adhesion and cell growth were detected when using these gels, but also continuous coatings of cells growing on their surface. These findings can be attributed to the higher protein content of this fraction and to the particular structure of its proteins. Thus, granules have proved to be an interesting potential raw material for scaffold development. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1577–1583, 2016     

Selection method of pH conditions to establish Pseudomonas taetrolens physiological states and lactobionic acid production

Microbial physiological responses resulting from inappropriate bioprocessing conditions may have a marked impact on process performance within any fermentation system. The influence of different pH-control strategies on physiological status, microbial growth and lactobionic acid production from whey by Pseudomonas taetrolens during bioreactor cultivations has been investigated for the first time in this work. Both cellular behaviour and bioconversion efficiency from P. taetrolens were found to be negatively influenced by pH-control modes carried out at values lower than 6.0 and higher than 7.0. Production schemes were also influenced by the operational pH employed, with asynchronous production from damaged and metabolically active subpopulations at pH values lower than 6.0. Moreover, P. taetrolens showed reduced cellular proliferation and a subsequent delay in the onset of the production phase under acidic conditions (pH?<?6.0). Unlike cultivations performed at 6.5, both pH-shift and pH-stat cultivation strategies performed at pH values lower than 6.0 resulted in decreased lactobionic acid production. Whereas the cellular response showed a stress-induced physiological response under acidic conditions, healthy functional cells were predominant at medium operational pH values (6.5–7.0). P. taetrolens thus displayed a robust physiological status at initial pH value of 6.5, resulting in an enhanced bioconversion yield and lactobionic acid productivity (7- and 4-fold higher compared to those attained at initial pH values of 4.5 and 5.0, respectively). These results have shown that pH-control modes strongly affected both the physiological response of cells and the biological performance of P. taetrolens, providing key information for bio-production of lactobionic acid on an industrial scale.     

Mycorrhization between <Emphasis Type="Italic">Cistus ladanifer</Emphasis> L. and <Emphasis Type="Italic">Boletus edulis</Emphasis> Bull is enhanced by the mycorrhiza helper bacteria <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> Migula

Boletus edulis Bull. is one of the most economically and gastronomically valuable fungi worldwide. Sporocarp production normally occurs when symbiotically associated with a number of tree species in stands over 40 years old, but it has also been reported in 3-year-old Cistus ladanifer L. shrubs. Efforts toward the domestication of B. edulis have thus focused on successfully generating C. ladanifer seedlings associated with B. edulis under controlled conditions. Microorganisms have an important role mediating mycorrhizal symbiosis, such as some bacteria species which enhance mycorrhiza formation (mycorrhiza helper bacteria). Thus, in this study, we explored the effect that mycorrhiza helper bacteria have on the efficiency and intensity of the ectomycorrhizal symbiosis between C. ladanifer and B. edulis. The aim of this work was to optimize an in vitro protocol for the mycorrhizal synthesis of B. edulis with C. ladanifer by testing the effects of fungal culture time and coinoculation with the helper bacteria Pseudomonas fluorescens Migula. The results confirmed successful mycorrhizal synthesis between C. ladanifer and B. edulis. Coinoculation of B. edulis with P. fluorescens doubled within-plant mycorrhization levels although it did not result in an increased number of seedlings colonized with B. edulis mycorrhizae. B. edulis mycelium culture time also increased mycorrhization levels but not the presence of mycorrhizae. These findings bring us closer to controlled B. edulis sporocarp production in plantations.     

Lipopolysaccharide of Escherichia coli, polyamines, and acetic acid stimulate cell proliferation in intestinal epithelial cells

Summary Our aim was to examine whether lipopolysaccharide of Escherichia coli, polyamines of dietetic and/or bacterial origin, and products of the bacterial metabolism influence cell proliferation in epithelial cells from the colon and small intestine. Lipopolysaccharide of Escherichia coli 0111:B4 was incubated with cultures from human colonic mucosa. The mitoses were arrested with Vincristine and the total number of metaphases per crypt was counted. In addition, lipopolysaccharide was incubated with a human colonic epithelial cell line from adenocarcinoma (LS-123 cells) and with a nontransformed small intestinal cell line from germ-free rats (IEC-6 cells) for 24 h. In the last 4 h, the cells were labeled with tritiated thymidine. The cells were incubated with putrescine, cadaverine, and spermidine at 10⁻¹¹–10⁻³ M and with acetic acid (10⁻⁵–10⁻¹ M), acetaldehyde (10⁻¹⁰–10⁻⁴ M) and ammonium chloride (1–20 mM). Lipopolysaccharide of Escherichia coli increased the number of arrested metaphases in human colonic crypts and DNA synthesis in L-123 and IEC-6 cells (P<0.001). All polyamines increased DNA synthesis in the colonic and small intestinal cell lines, the effects being more marked for putrescine (P<0.001). The higher concentrations of acetic acid increased DNA synthesis in both epithelial cell lines (P<0.001). Acetaldehyde slightly decreased DNA synthesis in LS-123 cells at cytotoxic concentrations. Ammonium chloride did not significantly affect DNA synthesis. The final concentration of nonionized ammonia was less than 3%. It is concluded that lipopolysaccharides of Escherichia coli and intraluminal factors derived from microorganisms increase cell proliferation in human colonic crypts and intestinal epithelial cell lines.     

Rad21l1 cohesin subunit is dispensable for spermatogenesis but not oogenesis in zebrafish

During meiosis I, ring-shaped cohesin complexes play important roles in aiding the proper segregation of homologous chromosomes. RAD21L is a meiosis-specific vertebrate cohesin that is required for spermatogenesis in mice but is dispensable for oogenesis in young animals. The role of this cohesin in other vertebrate models has not been explored. Here, we tested if the zebrafish homolog Rad21l1 is required for meiotic chromosome dynamics during spermatogenesis and oogenesis. We found that Rad21l1 localizes to unsynapsed chromosome axes. It is also found between the axes of the mature tripartite synaptonemal complex (SC) in both sexes. We knocked out rad21l1 and found that nearly all rad21l1^-/- mutants develop as fertile males, suggesting that the mutation causes a defect in juvenile oogenesis, since insufficient oocyte production triggers female to male sex reversal in zebrafish. Sex reversal was partially suppressed by mutation of the checkpoint gene tp53, suggesting that the rad21l1 mutation activates Tp53-mediated apoptosis or arrest in females. This response, however, is not linked to a defect in repairing Spo11-induced double-strand breaks since deletion of spo11 does not suppress the sex reversal phenotype. Compared to tp53 single mutant controls, rad21l1^-/- tp53^-/- double mutant females produce poor quality eggs that often die or develop into malformed embryos. Overall, these results indicate that the absence of rad21l1^-/- females is due to a checkpoint-mediated response and highlight a role for a meiotic-specific cohesin subunit in oogenesis but not spermatogenesis.     

“Diffusion” of microorganisms in calcium alginate beads

Summary The leakage of Serratia marcescens cells immobilised in Ca-alginate beads was quantified and the experimental values fitted to the pore diffusion model in order to obtain the biomass diffusion coefficient (D _x). This coefficient was then determined, resulting a value of 0.45 10^–7 cm² s^–1 at the beginning of the fermentation process. The variation of this coefficient, together with the porosity of the particles (_i), were also determined all along the process.