Project description:The aim of the experiments was to determine the regulon of the Bacillus subtilis alternative sigma factor SigI. Biological relevance: To expand our knowledge about Bacillus subtilis transcriptional network under unfavorable conditions. Experimental workflow overview: Bacillus subtilis 168 trp+ (BaSysBio) was used as the genetic background. (i) sigI-rsgI knock-out, (ii) rsgI knock-out, and (iii) wr strains were cultured in LB medium to mid-exponential phase at 37°C and 52°C. Total RNA was isolated from 3 ml of the culture. rRNA was depleted from the samples with RiboMinus; subsequently RNA-seq libraries were prepared (Illumina compatible NEXTflex Rapid Directional RNA-Seq Kit, Bioo Scientific) and sequenced at the EMBL GeneCore facility. The experiment was performed in three independent replicates.
Project description:Halophilic microorganisms are potentially capable as platforms to produce low-cost biosurfactants. However, the robustness of bioprocesses is still a challenge and, therefore, it is essential to understand the effects of microbiological culture conditions through bioreactor engineering. Based on a design of experiments (DOE) and a response surface methodology (RSM) tailored and taken from the literature, the present work focuses on the evaluation of a composite central design (CCD) under batch cultures in stirred-tank bioreactors with the halophilic bacteria Salibacterium sp. 4CTb in order to determine the operative conditions that favor mass transfer and optimize the production of a lipopeptide. The results obtained showed profiles highlighting the most favorable culture conditions, which lead to an emulsification index (E24%) higher than 70%. Moreover, through the behavior of dissolved oxygen (DO), it was possible to experimentally evaluate the higher volumetric coefficient of mass transfer in the presence of lipopeptide (kLa = 31 1/h) as a key criterion for the synthesis of the biosurfactant on further cell expansion.
