Binding effect of proline-rich-proteins (PRPs) on in vitro antimicrobial activity of the flavonoids

The interaction of the cyanidin, pelargonidin, catechin, myrecetin and kaempferol with casein and gelatin, as proline rich proteins (PRPs), was studied. The binding constants calculated for both flavonoid-casein and flavonoid-gelatin were fairly large (105–107 M−1) indicating strong interaction. Due to higher proline content in gelatin, the binding constants of flavonoid-gelatin (2.5 × 105–6.2 × 107 M−1) were found to be higher than flavonoid-casein (1.2 × 105–5.0 × 107 M−1). All the flavonoids showed significant antibacterial activity against the tested strains. Significant loss in activity was observed due to the complexation with PRPs confirming that binding effectively reduced the concentration of the free flavonoids to be available for antibacterial activity. The decline in activity was corresponding to the values of the binding constants. Though the activities of free catechin and myrecetin were higher compared to pelargonidin, cyanidin and kaempferol yet the decline in activity of catechin and myrecetin due to complexation with casein and gelatin was more pronounced.

Separation of polyhydroxyalkanoates-producing bacterial strains using PHA synthase gene and their evaluation for PHA deposition

In this study, a variety of samples were screened for the presence of PHA synthase gene. Results showed that 16 out of 102 isolated were positive for PHA respective genes. The highest prevalence was observed in Pseudomonas aeruginosa. The capability of PHA production was also shown by growing these strains on the defined medium and subsequent analysis using intracellular granules staining and Fourier transform infrared spectroscopy (FT-IR). The microscopic analysis showed that the positive strains accumulated PHA in the cell. The FT-IR analysis showed the presence of PHA peaks in the dried cells as well as in extraction product. P aeruginosa strain P7 showed higher concentration of PHA compared to the others as demonstrated by the highest respective peaks in FT-IR.