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The ability of the phototrophic bacterium Rhodopseudomonas palustris SP5212 to produce polyhydroxyalkanoates (PHAs), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] in particular was, assessed in acetate medium supplemented with hydroxybutyrate and valerate as cosubstrates. The isolate accumulated the polymer accounting for some 49.06% and 30% of cell dry weight when grown in hydroxybutyrate and valerate, respectively. PHA accumulation as well as 3HV monomer incorporation (30 mol%) was maximum at 0.1% hydroxybutyrate, while valerate at 0.1% and 0.3% was suitable for total polymer accumulation and 3HV monomer incorporation, respectively. Cosupplementation of hydroxybutyrate and valerate in the ratio of 3 : 1 led to the accumulation of PHA accounting for 54% of cell dry weight, which contained more than 50 mol% of 3HV monomer. Moreover, the biphasic cultivation conditions with hydroxybutyrate as cosubstrate have improved the quality as well as quantity of the accumulated copolymer significantly.

In the present study, 9 bacterial and 6 fungal endophytes were isolated from surface sterilized leaf, stem and root samples of the medicinal plant - Andrographis paniculata (Kalmegh). The endophytes were screened for plant growth promoting traits (IAA, phosphate solubilization and N2 fixation), enzymes (cellulase and amylase) and antimicrobial compounds against 3 potent human pathogens- E. coli, Staphylococcus sp. and Vibrio sp. The majority of the isolated endophytes produced the phytohormone - IAA (ranging 2-45μg/ml), and 1 endophyte solubilized phosphate and fixed N2. All the fungal endophytes possessed cellulase and amylase activity. In the preliminary screening, 4 bacterial and 4 fungal endophytic isolates extract showed antagonistic activity against the 3 potent human pathogens which are known causative agents of urinary tract, skin and gastrointestinal tract infections, respectively. The endophytes of A. paniculata exhibiting broad and specific antimicrobial activity make them ideal candidates in medical purposes. SAARC J. Agric., 19(2): 157-170 (2021)