The Bacillus megaterium LVN01 species native to Colombia has demonstrated the ability to metabolize different coproducts or industrial waste (such as fique juice, cane molasses, and residual glycerol) and accumulate polyhydroxybutyrate (PHB), giving it potential in the bioplastics industry. In this research, the potential of liquid digestate as a carbon source for the production of PHA polymers in fermentation processes with this bacterial strain was evaluated. Favorably, it was found that B. megaterium utilizes the nutrients from this residual substrate to multiply appropriately and efficiently synthesize poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Bench-scale aerobic batch fermentation, under the operational conditions of this research [volume: 3 L; temperature: 30.8 °C; agitation: 400 rpm; pH: 7.0 ± 0.2; dissolved oxygen: 100% saturation; antifoam: 10% (v/v)], generated maximum values of dry cell weight (DCW) (0.56 g cell L⁻¹) at 60 h, while the maximum PHBV yield (360 mg PHBV L⁻¹) occurred at 16 h, which is very favorable for sustainable degradable bioplastics production. Additionally, GC–MS and NMR analyses confirmed that the PHBV copolymer synthesized by B. megaterium is made up of the monomers 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). Furthermore, the thermal properties determined by TGA (Tonset = 283.1 °C; Tendset = 296.98 °C; Td = 290.114 °C) and DSC (Tm = °C 155.7 °C; ΔHf = 19.80 J g⁻¹; Xcr = 18.17%) indicate that it is a thermally stable biopolymer with low percentages of crystallinity, providing flexibility that facilitates molding, adaptation, and application in various industrial sectors.

El principal objetivo de este estudio es determinar el nivel de cuantificación necesario para detectar Escherichia coli O157 enterohemorrágica utilizando la reacción en cadena de la polimerasa (PCR). Se desarrolla la validación de PCR convencional evaluando sus genes de mayor virulencia: stx₁, stx₂ y rfbE. Los resultados de sensibilidad de PCR indican un límite de detección entre 0,011 y 0,33 ng µL^-1 de ADN para stx₁ y stx₂ y de 0,0037 ng µL^-1 de ADN para rfbE. El límite de corte inferior varía entre 0,033 y 0,099 ng µL^-1 de ADN para stx₁ y stx₂, para rfbE es de 0,033 ng µL^-1 de ADN. La selectividad (inclusividad y exclusividad) y la robustez son del 100% para los tres genes, demostrando la reproducibilidad del PCR para distinguir E. coli O157 de otros serotipos. Se concluye que la PCR convencional es una técnica que permite monitorear la presencia de E. coli O157 mediante sus genes de mayor virulencia (stx1, stx2 y rfbE).

Escherichia coli serotype O157:H7 is a diarrheal agent and a significant cause of hemorrhagic colitis and the development of hemolytic uremic syndrome (HUS), mainly in infants. Early detection of contaminated food and water using reliable and fast tests is one of the strategies to prevent infections from E. coli O157:H7. Methods: Four quantitative polymerase chain reaction protocols (SYBR Green qPCR) were developed and validated to determine the presence of the bacteria according to its rfbE, stx₁, and stx₂ genes. Results: The results of the efficiencies were between 80% and 97% with a high linearity (R² 0.99). The cut-off limits for each primer sequence were 3.1667 × 10⁻² ng µL⁻¹ for two sequences of the serogroup O157 (primers rfbE and O157), 1.7228 × 10⁻³ ng µL⁻¹ for stx₁, and 3.5185 × 10⁻³ ng µL⁻¹ for stx₂. The inclusivity and the exclusivity of each gene, as well as the analytical precision and the positive and negative predictive value, were 100%. A contaminated meat matrix was evaluated, detecting up to 4 CFU g⁻¹. Conclusions: SYBR Green qPCR protocols could be implemented to trace the presence of E. coli O157 in a routine analysis of ground beef or as an easy, rapid, sensitive, and specific diagnostic test while still considering microbiological tests to validate any inconclusive results.

The Bacillus megaterium LVN01 species native to Colombia has demonstrated the ability to metabolize different co-products or industrial waste (such as fique juice, cane molasses, residual glycerol) and accumulate polyhydroxybutyrate (PHB), giving it potential in the bioplastics industry. In this research, the potential of liquid digestate as a carbon source for the production of PHA in fermentation processes with this bacterial strain was evaluated. Favorably, it was found that B. megaterium utilizes the nutrients from this residual substrate to multiply appropriately and efficiently synthesize poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV). Bench scale aerobic batch fermentation, under the operational conditions of this research [Volume: 3L; Temperature: 30.8°C; Agitation: 400 rpm; pH: 7.0 ± 0.2; Disolved Oxygen: 100% saturation; Antifoam 10% (v/v)], generated maximum values of DCW (0.56 g cell L-1) at 60 h, while the maximum PHB yield (360 mg PHB L-1) occurred at 16 h, which is very favorable for sustainable degradable bioplastics production. Additionally, GC-MS and NMR analyses confirmed that the PHBV copolymer synthesized by B. megaterium is made up of the monomers 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). Furthermore, the thermal properties determined by TGA (Tonset=283.1 ºC, Tendset= 296.98 ºC. Td =290.114 °C) and DSC (Tm= ºC155.7 °C, ΔHf= 19.80 J g-1, Xcr = 18.17%), indicate that it is a thermally stable biopolymer with low percentages of crystallinity, providing flexibility that facilitates molding, adaptation, and application in various industrial sectors.