인산염 제한하에서 Alcaligenes eutrophus의 유가식 배양에 의한 Polyhydroxyalkanoates의 대량생산과 축적특성
Mass Production and Accumulation Characteristics of Polyhydroxyalkanoates by Fed-batch culture of Alcaligenes eutrophus under Phosphate Limitation
For mass production of polyhydroxyalkanoates (PHA), high cell density cultures of Alcaligenes eutrophus by fed-batch culture under phosphate-limitation condition has been investigated. PHA accumulation by the regulation by the regulation of initial phosphate concentration could be automatically induced, and high density cell culture above 200 g/L also could be successfully produced. The production of Poly-β-hydroxybutyrate (PHB) and dry cell weight increased with increasing the initial phosphate concentration. When the initial concentrations of phosphate were in the ranges of 1.5~4.5 g-PO4/L, PHB and dry cell weight obtained were 83~266 g/L and 61~216 g/L, respectively, and PHB productivity was in the ranges of 1.35~3.10 g/L.h. When a mixture of glucose and propionic acid is used as carbon sources, poly(3-hydroxybutyrate-co-poly-3-hydroxyvalerate), P(3HB-co-3HV), could be also successfully produced under phosphate limitation condition. When the mole ratio of propionic acid to glucose in the feeding solution is 0.22, a final dry cell weight of 150 g/L and a P(3-HB-co-3HV) of 90 g/L were produced. Morphological changes and size distribution of PHB granules synthesized in A. eutrophus under phosphate-limitation condition are determined by TEM during the course of fed-batch. Mean granule diameters of PHB produced are in the range of 0.36~0.39 μm, and mean cell size was elongated from 0.54~0.59 μmx 1.3~1.5 μm to 0.83~0.89 μm x2.0~2.3 μm. Phosphate concentration in media did not affect size distribution of PHB granule and cell.