title: Optimization of lactic acid production by pellet-form Rhizopus oryzae in 3-L airlift bioreactor using response surface methodology.
abstract: The influence of two key environmental factors, pH and oxygen transfer coefficient (k(L)a), was evaluated on the lactic acid production as the main answer and, on the size of cell pellets of the fungal strain Rhizopus oryzae KPS106, as second dependant answer by response surface methodology using a central composite design. The results of the analysis of variance and modeling demonstrated that pH and k(L)a had a significant effect on lactic acid production by this strain. However, no interaction was observed between these two experimental factors. pH and k(L)a had no significant influence on the pellet size. Optimal pH and k(L)a of the fermentation medium for lactic acid production from response surface analysis was 5.85 and of 3.6 h(-1), respectively. The predicted and experimental lactic acid maximal values were 75.4 and 72.0 g/l, respectively, with pellets of an average of 2.54 +/- 0.41 mm. Five repeated batches in series were conducted with a mean lactic acid production of 77.54 g/l. The productivity was increased from 0.75 in the first batch to 0.99 g/l h in the last fifth batch.
authors.affiliation: Department of Microbiology, Faculty of Science, Kasetsart University, Jatujak, Bangkok 10900, Thailand.
authors.forename: Thanapoom
authors.initials: T
authors.lastname: Maneeboon
authors.forename: Wirat
authors.initials: W
authors.lastname: Vanichsriratana
authors.forename: Chaiyaporn
authors.initials: C
authors.lastname: Pomchaitaward
authors.forename: Vichien
authors.initials: V
authors.lastname: Kitpreechavanich
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D018929:Cell Culture Techniques / Q000379:methods; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology / Q000379:methods*; D019344:Lactic Acid / Q000378:metabolism*; D012233:Rhizopus / Q000378:metabolism*
chemical_list: D019344:Lactic Acid