Pilot-scale production of bacterial cellulose by a spherical type bubble column bioreactor using saccharified food wastes

−Bacterial cellulose (BC) was produced by Acetobacter xylinum KJ1 in a modified airlift-type bubble column bioreactor, which had a low shear stress and high oxygen transfer rate (kLa). Saccharified food wastes (SFW) were used as the BC production medium due to its low cost. An aeration rate of 1.2 vvm (6 L/min) was tentatively determined as the optimal aeration condition in a 10 L spherical type bubble column bioreactor, by analysis of the oxygen transfer coefficient. When 0.4% agar was added, the BC production reached 5.8 g/L, compared with 5.0 g/L in the culture without the addition of agar. The BC productivity was improved by 10% in the addition of 0.4% agar into the SFW medium. Then, by conversion of a linear velocity of 0.93 cm/sec, from the relationship between the linear velocity and oxygen transfer rate, 1.0 vvm (30 L/min) was determined as an optimal aeration condition in a 50 L spherical type bubble column reactor. Using SFW medium, with the addition of 0.4% agar, and air supplied of 1.0 vvm, 5.6 g/L BC was produced in the 50 L spherical type bubble column bioreactor after 3 days of cultivation, which was similar to that produced in the 10 L bioreactor. In conclusion, the addition of agar, a viscous polysaccharide, into SFW medium is effective for the production of BC, and this scale-up method is very useful for the mass production in a 50 L spherical type bubble column bioreactor by decreasing the shear stress and increasing the kLa.