Quorum sensing mediated response of Achromobacter denitrificans SP1 towards prodigiosin production under phthalate stress.

Quorum sensing is a density-dependent chemical process between bacteria, which may be intergenus or intragenus. N-acyl homoserine lactones (HSLs) are a type of small signaling molecules associated with Gram-negative bacteria for monitoring their own population density. The present study unveils the mechanism of HSLs in Achromobacter denitrificans SP1 while transforming di(2-ethylhexyl) phthalate (DEHP) into prodigiosin in a simple basal salt medium. The primary detection of HSLs was done by the colorimetric method. Fourier-transform infrared spectroscopy and liquid chromatography-mass spectrometry-quadrupole time-of-flight confirmed and identified the HSLs. The maximum production of HSLs was observed between 24 and 72 h of incubation, which is noted to be a peak time of DEHP degradation. A total of 57.2% of DEHP was degraded within 30 h and complete degradation was observed within 72 h of incubation. Regulation in the synthesis of various acyl-HSL molecules, viz. 3OC6-HSL in the initial stage of DEHP stress, 3OC8-HSL, and C10-HSL during the time of degradation and 3OC12-HSL on completion of degradation was noticed. The role of HSLs on the production of prodigiosin was confirmed using vanillin as an HSL inhibitor. Through the selective activation of HSL molecules, A. denitrificans SP1 sustain the changing stressful conditions. Supplementation of acyl-HSL signal molecules may boost up the efficacy of A. denitrificans SP1 in both DEHP degradation and prodigiosin production which offers great potential towards the management of DEHP containing plastic wastes.

Response surface optimization of prodigiosin production by phthalate degrading Achromobacter denitrificans SP1 and exploring its antibacterial activity.

The role of various parameters like temperature, pH, blood bag concentration, agitation and incubation that influence the production of prodigiosin by Achromobacter denitrificans SP1 was determined. The Plackett-Burman and Box-Behnken experimental designs were employed to statistically optimize and find out the best combinational effect of parameters for the better yield of prodigiosin using blood bag as sole carbon and energy source for the growth of A. denitrificans SP1. The maximum (1.314 mg/ml) prodigiosin production was attained at a temperature of 24 °C, pH (8.8), and blood bag (1 g) as optimum; while the predicted value was 1.319 mg/ml with a correlation coefficient of 0.987; which signifies the fitness of the model. Antimicrobial activity of the prodigiosin was also evaluated and found to be an effective agent against bacterial pathogens including Staphylococcus aureus and Proteus mirabilis. Utilization of the plasticizer di (2-ethylhexyl)phthalate (DEHP) in blood bag and the production of antibacterial prodigiosin makes A. denitrificans SP1, an effective competitor toward the pathogenic bacterial disinfection and wastewater treatment processes.