Hori Katsutoshi, Marsudi Sidik, Unno Hajime
Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Biotechnol Bioeng. 2002 Jun 20;78(6):699-707. doi: 10.1002/bit.10248.
The feasibility of the simultaneous production of polyhydroxyalkanoates (PHAs) and rhamnolipids, as a novel approach to reduce their production costs, was demonstrated by the cultivation of Pseudomonas aeruginosa IFO3924. Fairly large amounts of PHAs and rhamnolipids were obtained from the bacterial cells and the culture supernatant, respectively. Decanoate was a more suitable carbon source than ethanol and glucose for the simultaneous production, although glucose was suitable for cell growth without an induction period under pH control. The kind of carbon source affected PHA monomer composition markedly and PHA molecular weight slightly. Monorhamnolipids and dirhamnolipids were included in the rhamnolipids extracted from the culture supernatant using decanoate, glucose, or ethanol as the carbon source. Both PHAs and rhamnolipids were synthesized after the growth phase. PHA content in the cell reached a maximum when the carbon source was exhausted. After exhaustion of the carbon source, PHA content decreased rapidly, but rhamnolipid synthesis, which followed PHA synthesis, continued. This resulted in a time lag for the attainment of maximum levels of PHAs and rhamnolipids. The reusability of the cells used in rhamnolipid production was evaluated in the repeated batch culture of P. aeruginosa IFO3924 for the simultaneous production of PHAs and rhamnolipids. High concentrations of rhamnolipids in the culture supernatant were attained at the end of both the first and second batch cultures. High PHA content was achieved in the resting cells that were finally harvested after the second batch. Simultaneous production of PHAs and rhamnolipids will enhance the availability of valuable biocatalysts of bacterial cells, and dispel the common belief that the production cost of PHAs accumulated intracellularly is almost impossible to become lower than that of cells themselves.
通过铜绿假单胞菌IFO3924的培养，证明了同时生产聚羟基脂肪酸酯（PHA）和鼠李糖脂作为降低其生产成本的新方法的可行性。分别从细菌细胞和培养上清液中获得了相当大量的PHA和鼠李糖脂。癸酸盐比乙醇和葡萄糖更适合用于同时生产的碳源，尽管在pH控制下葡萄糖适合细胞生长且无诱导期。碳源的种类对PHA单体组成有显著影响，对PHA分子量影响较小。使用癸酸盐、葡萄糖或乙醇作为碳源从培养上清液中提取的鼠李糖脂中包含单鼠李糖脂和双鼠李糖脂。PHA和鼠李糖脂均在生长阶段后合成。当碳源耗尽时，细胞中的PHA含量达到最大值。碳源耗尽后，PHA含量迅速下降，但在PHA合成之后的鼠李糖脂合成仍在继续。这导致PHA和鼠李糖脂达到最大水平存在时间滞后。在铜绿假单胞菌IFO3924的重复分批培养中评估了用于鼠李糖脂生产的细胞的可重复使用性，以同时生产PHA和鼠李糖脂。在第一批和第二批分批培养结束时培养上清液中均获得了高浓度的鼠李糖脂。在第二批最终收获的静止细胞中实现了高PHA含量。同时生产PHA和鼠李糖脂将提高细菌细胞有价值的生物催化剂的可用性，并消除关于细胞内积累的PHA生产成本几乎不可能低于细胞本身成本的普遍看法。
