When a Monascus isolate, a producer of Monascus pigments, was cocultured with either Saccharomyces cerevisiae or Aspergillus oryzae in a solid sucrose medium, there were significant morphological changes in Monascus culture. Cocultures exhibited cell mass increases of 2 times and pigment yield increases of 30 to 40 times compared to monocultures of Monascus. However, enhanced cell growth, an increase in pigment production, and morphological change did not occur in coculture with Bacillus cereus. Saccharomyces cerevisiae was more effective at enhancing pigment production than Asp. oryzae. Enhanced cell growth and increased pigment production occurred only in conjunction with morphological changes. Culture filtrates of S. cerevisiae were also effective in inducing morphology change in Monascus, similar to culture broths of S. cerevisiae. The hydrolytic enzymes produced by S. cerevisiae, such as amylase, and chitinase, are thought to be the effectors. The commercial enzymes α‐amylase and protease from Asp. oryzae both caused a morphological change in Monascus and were effective in enhancing pigment production. However, lysozyme, α‐amylase and protease from Bacillus species, protease from Staphylococcus, and chitinase from Streptomyces were not effective. The hydrolytic enzymes which cause a morphological change of Monascus culture and enhancement of pigment production are thought to be capable of degrading Monascus cell walls. An approximate 10‐fold increase in pigment production was observed in liquid cocultures with S. cerevisiae. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 576–581, 1998.

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Yarrowia lipolytica KCCM50506, which transforms isobutyric acid to L-b-hydroxy isobutyric acid (L-b-HIBA), was screened. Chemostat cultures were carried out in jar fermentors at dilution rates of 0.02 h A1 to 0.12 h A1 . L-b-HIBA fermentation-regulating factors were determined to be speci®c growth rate, and concentrations of glucose and isobutyric acid in fermentor from analysis of steady-state data. The speci®c productivity of L-b-HIBA increased as the speci®c growth rate increased, apparently as a growth-associated type of product formation. A fedbatch culture was carried out under optimum conditions where the concentrations of glucose and isobutyric acid in the fermentor were maintained at 23 g l A1 and 9 g l A1 , respectively. The concentrations of cells and L-b-HIBA obtained at the end of fermentation were 20 g l A1 and 49 g l A1 , respectively, corresponding to 2.0 and 2.7 times more than concentrations in batch culture.

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