Search Results (2)

High-temperature ethanol fermentation (HTEF) using high-potential thermotolerant ethanologenic microorganisms is a promising platform for ethanol production in tropical or subtropical areas. This study aims to evaluate the ethanol production potential of recombinant Zymomonas mobilis R301 overexpressing groESL genes under normal and high-temperature conditions and the expression of genes involved in the heat shock response and ethanol production pathway during ethanol fermentation using sweet sorghum juice (SSJ) as feedstock. Growth characterization analysis revealed that the recombinant Z. mobilis R301 exhibited multi-stress tolerance toward heat, acetic acid, and furfural. Based on the statistical experimental design, the optimum conditions for ethanol production from SSJ by the recombinant R301 at 30 °C were a sugar concentration of 171.67 g/L, cell concentration of 9.42% (v/v), and yeast extract concentration of 10.89 g/L, while those at 40 °C were a sugar concentration of 199.48 g/L, yeast extract concentration of 10.88 g/L, MgSO₄ concentration of 1.05 g/L, and initial pH of 6.8. The maximum ethanol concentrations and productivities achieved in this study were 63.26 g/L and 1.17 g/L.h at 30 °C and 58.62 g/L and 1.22 g/L.h at 40 °C. The overexpression of the groES and groEL genes and upregulation of other heat shock-responsive genes at 40 °C enhanced cell growth, viability, and fermentation capacity of recombinant Z. mobilis R301 under heat stress. The current study demonstrated that recombinant Z. mobilis R301 exhibited high potential for ethanol production from SSJ or other sugar-based raw materials under high-temperature conditions. Full article

Ehrlichia chaffeensis, a tick-transmitted intraphagosomal bacterium, is the causative agent of human monocytic ehrlichiosis. The pathogen also infects several other vertebrate hosts. E. chaffeensis has a biphasic developmental cycle during its growth in vertebrate monocytes/macrophages and invertebrate tick cells. Host- and vector-specific differences in the gene expression from many genes of E. chaffeensis are well documented. It is unclear how the organism regulates gene expression during its developmental cycle and for its adaptation to vertebrate and tick host cell environments. We previously mapped promoters of several E. chaffeensis genes which are recognized by its only two sigma factors: σ³² and σ⁷⁰. In the current study, we investigated in assessing five predicted E. chaffeensis transcription regulators; EcxR, CtrA, MerR, HU and Tr1 for their possible roles in regulating the pathogen gene expression. Promoter segments of three genes each transcribed with the RNA polymerase containing σ⁷⁰ (HU, P28-Omp14 and P28-Omp19) and σ³² (ClpB, DnaK and GroES/L) were evaluated by employing multiple independent molecular methods. We report that EcxR binds to all six promoters tested. Promoter-specific binding of EcxR to several gene promoters results in varying levels of gene expression enhancement. This is the first detailed molecular characterization of transcription regulators where we identified EcxR as a gene regulator having multiple promoter-specific interactions. Full article