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Improvement of vitamin B12 production by anaerobic ecosystem

通过厌氧生态系统提高维生素 B12 的产量

基本信息

批准号：
05453112
负责人：
NISHIO Naomichi
金额：
$ 5.06万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

Although vitamin B12 has been purified from the cells of Propionibacterim spp.after fermentation of sugars, it is difficult to get a high cell concentration due to strong growth inhibition by propionate and acetate prouced. Acetogens produce acetate from methanol/CO2 as substrates and have a high B12 content in the cells. But acetate also inhibits the bacterial growth.Therefore, we attempted to improve these bacterial cultivations to get high concentration of B12 by using microbial ecosystem which can utilize these acids under anaerobic condition. The results were as follows.1.Cultivation of Propionibacterium freudenreichii in coculture with Paracoccus denitrificans or Rhodobacter sphaeroides under denitrification.(1) .In mixed culture with P.denitrificans, B12 concentration could increase ca.2-fold due to the selective utilization of propionate and acetate by P.denitrificans even in the presence of glucose.(2) .In mixed culture with R.sphaeroides, propionate and acetate were also util … More ized and N2 was produced. Therefore, B12 production increased 4-fold. But the cell concentration of P.freudenreichii was still 10 g/l due to imcomplete utilization of these acids by R.sphaeroides.2.Cultivation of Acetobacterium sp.in coculture with a methanogen, Methanothrix sp.(1) .Although B12 content in the cells of Acetobacterium sp.used was very high (5 mg/g cell) , acetate exhibited strong growth inhibition (Kp=270 mM) .(2) Coculture with Methanothrix sp.was carried out in separate bioreactor system, since growth rate of the methanogen was 10 times lower than Acetobacterium. First, a fixed bed reactor of the methanogen was set up, where polypropyrene/ceramic mixture was packed to adhere the methanogen cells. Then, this reactor was conected to the chemostat culture of Acetobacterium with liquid recycling. By using this combined reactor system where Methanothrix cells consumed acetate, acetate level in the chemostat culture could be kept almost zero and B12 productivity reached to 20 mg/l/day. Less

虽然丙酸杆菌发酵糖后已从细胞中提纯了维生素B12，但由于丙酸和乙酸酯对细胞生长抑制作用较强，很难获得较高的细胞浓度。乙酸菌以甲醇/二氧化碳为底物产生醋酸酯，细胞中B12含量很高。但醋酸盐也会抑制细菌的生长，因此，我们试图通过利用微生物生态系统在厌氧条件下利用这些酸来改进这些细菌的培养，以获得高浓度的B12。研究结果如下：1.在反硝化条件下，弗氏丙酸杆菌与反硝化副球藻或球形红假单胞菌共培养。(1)与反硝化丙酸杆菌混合培养时，由于反硝化丙酸杆菌选择性地利用丙酸和乙酸酯，B12的浓度可提高约2倍。(2)在与球形副球藻混合培养中，丙酸和乙酸乙酯也能被…利用。粉化程度更高，生成氮气更多。因此，B12的产量增加了4倍。2.甲氧基乙酸杆菌与产甲烷菌共培养，虽然乙酸菌中B12的含量很高(5 mg/g细胞)，但乙酸盐对细胞的生长有很强的抑制作用(Kp=270 mm)。(2)由于甲氧基乙酸菌的生长速度比醋酸菌低10倍，所以与甲氧基乙酸菌共培养。首先，建立了产甲烷菌固定床反应器，填充聚丙烯/陶瓷混合物黏附产甲烷菌细胞。然后，将该反应器用于醋酸菌的液体循环恒温培养。利用这种甲藻细胞消耗乙酸盐的组合反应器系统，恒化器中的乙酸盐水平可以保持在几乎为零的水平，B12的产量达到20 mg/L/天。较少