title: [Effects of pellet characteristics on L-lactic acid fermentation by Rhizopus oryzae].
abstract: OBJECTIVE
  Effects of pellet morphology, diameter, density, and interior structure on L-lactic acid fermentation by Rhizopus oryzae were characterized for different inoculum sizes and concentrations of peptone and CaCO3.
  
  
  METHODS
  Different initial spore concentrations were inoculated in the preculture medium with different peptone and CaCO3 concentrations, and cultivated at 30 degrees C for 36 h. Representative pellets were chosen for interior structure analysis and L-lactic acid production.
  
  
  RESULTS
  Inoculum size was the most important factor determining pellet formation and diameter. Peptone concentration had the greatest effect on pellet density. L-lactic acid production depended heavily on pellet density but not on pellet diameter. Low-density pellets formed easily under conditions of low peptone concentration and often had a relatively hollow structure. This structure greatly decreased production. The production of L-lactic acid increased until the density reached a certain level (50 - 60 kg/m3) , which the compact part distributed homogeneously in the thick outer layer of the pellet, and loose in the central layer. Homogeneously structured, denser pellets limited mass transfer. CaCO, concentration only had a slight influence on pellet diameter and density.
  
  
  CONCLUSIONS
  This work provides the insight into pellet structure and its relationship with productivity.
authors.forename: Huating
authors.initials: H
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
authors.forename: Yongqian
authors.initials: Y
authors.lastname: Fu
mesh_terms: D002119:Calcium Carbonate / Q000032:analysis / Q000378:metabolism; D003470:Culture Media / Q000032:analysis / Q000378:metabolism; D005285:Fermentation; D019344:Lactic Acid / Q000378:metabolism*; D012233:Rhizopus / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003470:Culture Media; D019344:Lactic Acid; D002119:Calcium Carbonate