Efficient Production of L-(+)-Lactic Acid Using Mycelial Cotton-like Flocs of Rhizopus oryzae in an Air-Lift Bioreactor

Abstract

L-(+)-Lactic acid production was enhanced in a culture of Rhizopus oryzae by induction of a mycelial flocs morphology. By conventional culture the morphology of R. oryzae is that of a pellet-like cake; however, when mineral support and poly(ethylene oxide) are added to the culture, the morphology of R. oryzae takes on a cotton-like appearance. The formation of these cotton-like mycelial flocs was induced by the addition of 5 ppm poly(ethylene oxide) into a 12-14 h culture containing 3 g/L of the mineral support before the formation of the conventional pellet morphology. The cotton-like flocs were also formed in cultures grown in an air-lift bioreactor. This morphology allowed effective mass transfer inside the flocs and effective fluidity of culture broth in an air-lift bioreactor. L-(+)-Lactic acid concentration produced by mycelial flocs in an air-lift bioreactor, with the support and poly(ethylene oxide), was 104.6 g/L with a yield of 0.87 using 120 g/L of glucose as the substrate; for this culture without both, the concentration was 43.2 g/L. These results demonstrate that cotton-like mycelial flocs are the optimal morphology for use in the air-lift bioreactor culture of R. oryzae.

Organic Acid Production by Filamentous Fungi

“…These studies have taken two basic approaches, immobilization of cells (Hang et al, 1989;Tamada et al, 1992;Hamamci and Ryu, 1994;Dong et al, 1996;Xuemei et al, 1999), and promotion of mycelial or pellet morphology (Yang et al, 1995;Kosakai et al, 1997;Du et al, 1998;Park et al, 1998;Yin et al, 1998;Zhou et al, 2000). The term pellet morphology can be the source of some confusion in the discussion of optimal fungal morphology, since pellets of less than about one millimeter are associated with high production rates and yields, whereas larger pellets are not.…”

Improved oxygen transfer and increased l-lactic acid production by morphology control of Rhizopus oryzae in a static bed bioreactor

“…Because immobilization of whole cells provides the way for the entrapment of multi-step and cooperative enzyme system present in the intact cells, repetitive use, and improved stability, it is feasible for long-term production [14][15][16][17][18][19][20][21]. Due to several advantages of immobilization, it has been applied in many bioreactors used in submerged filamentous fungal cultures including air-lift bioreactor, drum contactor, reciprocating jet bioreactor, tower fermentor, and hollow fiber bioreactor [22][23][24][25][26][27][28].…”

Efficient Production of l -Lactic Acid from Xylose by Pichia stipitis

“…The zygomycete fungus Rhizopus oryzae also can ferment glucose to lactic acid (26,50). The bacterial fermentation process is rapid and efficient, but complex fermentation media are used since lactic acid bacteria require complex nitrogen sources and vitamins in the medium, which increases the cost of the process (25,42,47).…”