Production and optimization of Polyhedroxialkonate (poly (3-hydroxybutyrate-co-3-hydroxyhexanoate)) by Aeromonas sp. EBA 118 isolated from soil using one factor at a time methodology

In this study, the PHAs producing bacteria were isolated from soils of Mashhad countryside. Using, staining methods, Black Sudan B and Acridine Orange, the suitable isolates have been separated. To increase the polyhydroxyalkanoate production, optimizing has been done in two stages. In the first stage, different nitrogen resource, glucose density, pH, temperature and aeration have been optimized in order to increase the biomass. In the second stage, the ratio of carbon to nitrogen, pH, temperature and amount of aeration have been optimized in order to increase polyhydroxyalkanoate production. Among the 31 isolates, 20 isolates have been recognized as the polyhydroxyalkanoate producer. Aeromonas sp. EBA 118 by producing the highest amount of the polyhydroxyalkanoate polymer has been chosen as the selected object. Yeast extract 7g/l, glucose 5g/l, pH=8, temperature of 20ºC and 75% aeration were the optimal conditions for the highest production of biomass. The optimal conditions in the second stage aiming the increase of the polyhydroxyalkanoate polymer production were the ratio of carbon to nitrogen 0.35, pH=7, temperature of 37ºC and 80% aeration. The results of FT-IR spectroscopy showed that the polymer produced by EBA118 isolate is not the kind of the pure polyhedroxybutirate, but is probably a kind of copolymer PHBHHx.