膜生物反应器连续发酵生产胞外灵芝多糖

Continuous Fermentation of Ganoderma lucidum Exo-polysaccharide in a Membrane Bioreactor

产物灵芝多糖在间歇深层发酵稳定期存在浓度下降现象.采用膜生物反应器系统能够及时分离产物,控制产物的积累,有效防止灵芝多糖的消耗.而灵芝菌丝体在反应器中不断循环,浓度得到进一步提高,并不断分泌灵芝胞外多糖,可延长产多糖时间,从而提高了胞外多糖的总产量.研究了不同稀释率0～0.24hr－1下连续发酵的多糖生成和菌丝体生长状况; 连续发酵时发酵液中灵芝多糖的浓度比间歇发酵要低,并随稀释率的增大而下降,菌丝体浓度则随稀释率的增大而增大.总的菌丝体干重可比间歇发酵增加20%以上,多糖总产量可达到间歇发酵的5倍以上.连续发酵也有利于灵芝多糖与菌丝体的分离.结果表明利用膜生物反应器进行液体连续发酵是生产和分离胞外灵芝多糖的一条有效途径, 并可为其它真菌胞外多糖的深层发酵生产提供借鉴.

It was observed that the concentration of exo-polysaccharide (EPS) produced by Ganoderma lucidum fermentation decreased during stationary phase in batch culture. In this work, a membrane bioreactor system was applied in the fermentation of G. lucidum in order to decrease the loss of EPS. In the system, EPS and G. lucidum mycelia were separated by micro-pore membrane according to there size, mycelia were recycled back into fermentor and could reach a high density, and in the same time exo-polysaccharide secreted continuously. On the other hand, the effluent of membrane apparatus containing EPS was harvested and fresh media were added to the bioreactor to maintain constant volume. With this system, the loss and degradation of EPS could be well controlled. The yield of exo-polysaccharide and growth of G. lucidum mycelia were investigated at different dilution rates ranging from 0 to 0.24 h-1. Although the concentration of EPS in the effluent in continuous fermentation was a little lower than that in batch fermentation and decreased with the increase of dilution rate, the weight of mycelia increased 20% and the total amount of harvested EPS increased by 500% comparing with those in batch culture. Moreover, the process was beneficial for EPS separation by the effluent broth without mycelia. The result showed that it was an effective process to produce EPS in a membrane bioreactor system, and perhaps, can be applied for other fungi to produce EPSs in high yield.