Effect of different limitations in chemostat cultures on growth and production of exocellular protease byBacillus licheniformis
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Maximal molar growth yields (Ysubmax) and protease production ofBacillus licheniformis S 1684 during NH4+-, O2-, and NH4++O2-limitation with either glucose or citrate as carbon and energy source and during glucose-, and citratelimitation in chemostat cultures were determined. Protease production was repressed by excess ammonia when glucose served as C/E-source. Glucose and citrate repressed protease production during NH4+-limitation. A low oxygen tension enbanced protease production at low μ-values. It was concluded that, besides ammonia repression, catabolite flux and oxygen tension influence protease production, indicating that the energy status of the cell is important for the level of protease production.Ysubmax-values were high during glucose-limitation and indicate a high efficiency of growth caused by a highYATPmax. During NH4+-, O2-, and NH4++O2-limitation with glucose as C/E-values were lower than during glucose limitation. The lowerYsubmax-values were due to a lower efficiency of energy conservation.Ysubmax-values during limitations with citrate as C/E-source were lower than during limitations with glucose as C/E-source.
specific growth rate (h-1)
growth yield per mol substrate (g biomass/mol)
maximal molar growth yield corrected for maintenance requirements (g biomass/mol)
- Ymax (corr)
Ymax corrected for product formation (g biomass/mol)
maintenance requirements (mol/g biomass·h)
- msub (corr)
maintenance requirements corrected for product formation (mol/g biomass·h)
maximal specific rate of protease production (E440/mg DW·h)
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