Optimization of fermentation conditions of bacterium Pseudoxanthomonas indica H32.

Pseudoxanthomonas indica H32, constitutes the active component of a promising bioproduct candidate with biopesticide and biofertilizing activities. However, suitable fermentation conditions should be established to manufacture this product. Accordingly, the aim of this study was to optimize the fermentation conditions of bacterium Pseudoxanthomonas indica H32 in a 3 L bioreactor. The relevant parameters for strain growth, temperature (25-40 °C) and pH (6-9), were optimized using the response surface methodology (RSM). Additionally, the influence of air flow (0.5-1.5 vvm) and impeller stirrer speed (4.17-14.17 s - 1) in the volumetric oxygen transfer coefficient (KLa) were evaluated and then, in the P. indica H32 growth. The response variables were dry cell weight (DCW) and specific growth rate (µ). The results showed that P. indica H32 growth was significantly affected by the culture medium pH (p < 0.005). The optimum pH and temperature values were found at 7.4 and 34 °C, respectively. The conditions that increased KLa, were 12.17 s - 1 and 1.5 vvm, with a KLa value of 0.104 s - 1. This conditions ensured optimum strain growth of 5.496 g/L of DCW (5.E1010 CFU/mL), whereas µ was 0.403 h - 1. The findings of this study are a step forward in the development of P. indica H32 as biopesticide and biofertilizer.

Novel chimeric E2CD154 subunit vaccine is safe and confers long lasting protection against classical swine fever virus.

E2CD154 is a vaccine candidate against classical swine fever (CSF) based on a chimeric protein composed of the E2 glycoprotein fused to porcine CD154 antigen, and formulated in the oil adjuvant Montanide™ ISA 50 V2. This vaccine confers early protection in pigs and prevents vertical transmission in pregnant sows. The objectives of this study were to assess the safety of this immunogen in piglets, to compare several doses of antigen in the formulation, and to study the duration of the immunity provided by this vaccine for up to 9 months. Three trials were conducted by immunizing pigs with a two-dose regime of the vaccine. Challenge experiments were carried out with the highly pathogenic Margarita strain. No local or systemic adverse effects were documented, and neither macroscopic nor microscopic pathological findings were observed in the vaccinated animals. The three antigen doses explored were safe and induced CSF protective neutralizing antibodies. The dose of 50 µg was selected for further development because it provided the best clinical and virological protection. Finally, this protective immunity was sustained for at least 9 months. This study demonstrates that E2CD154 vaccine is safe; defines a vaccine dose of 50 µg antigen, and evidences the capacity of this vaccine to confer long term protection from CSFV infection for up to 9 months post- vaccination. These findings complement previous data on the evaluation of this vaccine candidate, and suggest that E2CD154 is a promising alternative to modified live vaccines in CSF endemic areas.

Design of a culture medium for optimal growth of the bacterium Pseudoxanthomonas indica H32 allowing its production as biopesticide and biofertilizer.

Culture medium composition is one of the most important parameters to analyze in biotechnological processes with industrial purposes. The aim of this study was to design of a culture medium for optimal growth of the bacterium Pseudoxanthomonas indica H32 allowing its production as biopesticide and biofertilizer. The influence of several carbon and nitrogen sources and their molar ratios on P. indica H32 growth was investigated. The effect of different micronutrients such as mineral salts and vitamin on P. indica H32 growth was determined as well. A mixture design based on Design-Expert 10.0 Software was performed to optimize the culture medium concentration. Finally, in the designed medium, an attribute of the biological mechanism of action of the P. indica H32 against nematodes, was evaluated: the hydrogen sulfide production. It was found that tested carbon/nitrogen ratios were not a significant influence on P. indica H32 growth. Growth of P. indica H32 was favored with use of sucrose, yeast extract and phosphate buffer without the addition of any tested micronutrients. An optimal concentration of 10 g/L sucrose and 5 g/L yeast extract were obtained at a cost of 0.10 $/L. In this concentration, the specific growth rate (µ) and maximal optical density (Xmax) were equal to 0.439 h- 1 and 8.00 respectively. It was evidenced that under the culture conditions used, P. indica H32 produced hydrogen sulfide. The designed medium led to a 1.08 $/L reduction of costs in comparison to LB medium. These results were critical to carry on with biotechnological development of P. indica H32 as a bioproduct.